Post on 14-Jul-2015
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Handbook of Implant Dentistry Compiled by Souheil Hussaini BDS, MS
WWW.ID-SC.COM
Chapter 1
History of Dental Implants
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History of Dental Implants over 1,350 years before Per Brånemark started working with titanium for dental Implants. In the late 1950s and 1960s, modern implantology was born. Metals such The earliest known examples of dental implants, endosseous implants date back as steel and implants of a blade design were said to integrate by the formation of a pseudo-periodontal ligament (in truth a connective tissue capsule). It was Brånemark who, in 1952, discovered that the titanium bonded irreversibly to the living bone tissue. He repeated the effect of fusing metal with bone and subsequently demonstrated that titanium could be shown at the histological level to structurally integrate with living bone, which could be achieved with a high degree of predictability. Brånemark called this phenomenon osseointegration, in which no long-term soft tissue inflammation, fibrous encapsulation, or implant failure were found.
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In 1965, the implantation of new titanium roots in an edentulous patient was the first practical application of osseointegration, which was followed 16 years later by a study published in the International Journal of Oral Surgery by Adell et al. ‘’Biotes’’ implants were the first commercial implants, characterized by their machined titanium surface, external hex joint, and thread pitch. Terminologies in implantology: Crown Crowns should approach the original teeth in biting surface properties and aesthetic features. The crown may be onsite (machined) or offsite (handmade). The final crown is either screwed or cemented onto an abutment.
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Abutment A crown is supported by an abutment, which acts as an interface between the crown and the implant. Lugs are shaped on the abutments stem that control the rotation or twist of the implant. Implant fixture An implant is screwed into the bone of the jaw, which provides the anchor or foundation for an abutment. Osseointegration occurs by bone tissue regenerating around the implant which minimizes the bone loss that might occur when natural teeth are lost. Impression Coping Impression copings are used to replicate the implant position in the patient’s mouth. The dentist screws the impression
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coping to the implant and then takes an impression of the dentition using either “open” or “closed” impression techniques. Open tray technique allows removal of the impression along with impression coping(s) which remain fixed in the impression material. The dentist then adds the analogue(s) to the copings prior to sending the impression to the lab. Closed tray technique allows removal of the impression from the patient’s mouth followed by unscrewing the impression coping(s) from the implant. The impression coping(s) are then placed back into position and the analogues are added. Analogue or Implant replica Laboratory technicians use analogues to replicate implants that are placed in the patient’s mouth. During casting the
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analogue, which is screwed onto the impression coping, is set into the plaster model fabricated from the patient’s dentition. Retentive Anchors Various designs of Retentive Anchors are available: -Ball Abutment -Magnetic Abutment -Tower Abutment They come in two main parts: The shaped abutment part and the Matrix which clips over it (female). The anchor abutments are screwed into the implants and full or partial dentures are clipped on them. This prevents unwanted movements of the prosthesis providing a very stable platform.
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Bar Retainers Bar retainers are screwed directly onto the implants and support dentures by clip mechanism. Two types are well-known: Dolder® and Hader®.
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Chapter 2
Diagnosis for Dental implant
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Initial workup for patient selection: The critical selection of patients and the critical application of endosteal dental implants are the two most important prerequisites for the treatment success that we’re all desire, LANNEY 1986. The three most basic principles that apply to all medical treatment are particular importance for implant therapy: - Nihil nocere (“do not harm”), - evaluate risks and benefits, - avoid over treatment. A brief review of the patient’s general physical health: - is the patient’s cardiovascular & renal system stable? - does the patient have any bleeding disorders? - is the patient immunocompromised? - does the patient have an uncontrolled endocrine disorder (e.g. diabetes)?
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A screening oral examination: - does the patient have an adequate oral hygiene? - is there sufficient soft and hard tissues for placing & restoring implants? Radiographs of the implant sites: - Periapical radiograph for individual implant sites - Panoramic radiograph for overview of anatomical structures - Tomographies in case of anatomic proximities, surgical templates etc. Photographs: - Pre-operative Intraoral and extra oral photographs of the selected patient.
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Medical History: Absolute contraindications: Absolute contraindications to implant rehabilitation include recent myocardial infarction and cerebrovascular accident, valvular prosthesis surgery within 6 months, immunosuppression, bleeding disorders, active treatment of malignancy, drug abuse, psychiatric illness, as well as bisphosphonate therapy for more than 5 years. Any of these conditions bar elective oral surgery, and require judicious monitoring by the physician as well as the dental provider. (Hwang D, Wang HL.2006) Relative medical contraindications: Systemic conditions and habits influence dental implant survival to varying degrees. Illnesses that impair the normal
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healing cascade compromise surgical success. The mere presence of a disease, however, does not necessarily preclude implant therapy or affect significantly long-term outcomes. Certain disorders, when controlled improve implant survival rates. Relative contraindications include adolescence, osteoporosis, smoking, diabetes, positive interleukin-1 genotype, HIV positive patients, cardiovascular disease, and hypothyroidism. Temporary limiting contraindications: Acute inflammatory diseases and infections: - Influenza, bronchitis, gastroenteritis, sinusitis and
inflammatory diseases of the urogenital tract
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Pregnancy: - Stress factors - Pregnancy gingivitis - Inability to take radiographs - Inability to prescribe medication Temporary consumption of certain medications: - Anticoagulant and immunosuppressant drugs
Physical and psychic stress situations: - Corporal conditions: physical disability - Psychosocial situations: unemployment, divorce and death of a family member Poor patient compliance:
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- Psychological or intellectual conditions modifying his co-operation
Alcohol and drug abuse:
- Unreliable co-operation and motivation, (poor oral hygiene) - Patients inadequately nourished, exhibiting a generally compromised immune response Neurosis, psychosis: - Complexity of psychological conditions, tendency to
recur, (absolute contra-indications)
Problem Patients: - Emotionally unstable patients
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- Treatment using the least invasive therapy to avoid subsequent conflict between the dentist and the patient General and nutritional conditions: - Cachetic and grossly obese patient (significant risk) - Age: biological situation more important than chronologic age Current medications: - Certain medications with their effect or their side effects can induce complications during the surgical procedure or long term difficulties (corticosteroids, immunosuppressive, long term antibiotic therapy); blood diluting drugs can cause bleeding in a very long time Metabolic disorders: - Juvenile diabetes type 1 (absolute contraindication)
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- Type 2 diabetes (relative contra indication) (ECKERT 1989, BOHLENDER 1988), - Major effects of hyperthyroidism including loss of physical (osteoporosis) and mental vigor Hematologic disorders: - Erythrocytes (anemia), (absolute contraindication) - Leukocytes (reduced host defence), (absolutecontra indication) - Blood clotting system (hemorrhagic diathesis), (absolute contra indication). Cardiac and circulatory diseases: - Surgery possible but associated with increased risk, - Absolute prerequisites: evaluation of circulatory parameters and knowledge of the cardiac disorder.
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Osseous metabolic disturbances: - Systemic and local osseous disorders, (absolute contraindications), (osteomalacia, ostitis deferments, osteogenesis imperfecta) - Post menopausal osteoporosis (25 % of women over age 60): evaluation of the risk to benefit ratio Collagen disorders: - Pathologic function of the immune system with inflammatory alterations of collagenous connective tissue (contra indications), (scleroderma, SJÖGREN syndrome, rheumatoid arthritis,) Dental implant as a potential bacterial focus: - High risk of bacteraemia with patients presenting heart valve prosthesis or history of bacterial endocarditic
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- Alloplastic vascular replacements (cardiac bypass surgery, pacemaker,): not serious risks Dental History: During a conversation on the topic with the patient, it is important to consider the patient’s general and dental knowledge, motivation and compliance with the treatment being provided. This awareness leads the patient to clean the peri-implant area, especially during the initial stages of healing after placement. Anatomical factors that may complicate implant placement are: - Nasal or sinus floors, - Inferior alveolar nerve, - Roots of adjacent teeth that cannot be moved orthodontically. - Impacted teeth
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Others factors may also include: - Diseases of the oral mucosa (lichen planus, etc) - Uncontrolled periodontitis, especially aggressive forms - Retained roots - Interarch distance: insufficient or too much implant crown ratio Intra oral contraindication: Unfavourable intermaxillary relationships: - Inadequate bone quantity - Problematic intermaxillary relationship: implants crown ratio Problematic occlusal and functional relationships: - Dysgnathia (gap between arches)
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- Functional or parafunctional disturbances: bruxism, Pathologic conditions in the alveolar bone: - Roots fragments, cysts, foreign bodies, granuloma, inflammatory reactions - Re-evaluation after appropriate treatment Radiation therapy in the jaw region: - Damage of cells and vascular elements in irradiated jaws - Danger of osteoradionecrosis with chronic ulceration of the bone Pathologic alterations of oral mucosa: - Leukoplakia or lichen planus, (absolute contra-indications), - Stomatitis.
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Xerostomia: - Age related saliva flow reduction (menopause), auto-immune disorders, long term drug therapies, - Reduced saliva flow does not exert a physiologic cleansing effect and so does not reduce sufficiently the bacteria (relative contra-indication) * Macroglossia: - Patients with long term partial or total edentulism that caused an enlarged tongue * Myxedema, *Acromegaly Unrestored teeth, poor oral hygiene: - Plaque retention, poor patient co-operation, bacterial risk.
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COMPREHENSIVE CLINICAL EXAMINATION: Extraoral clinical examination: - Facial asymmetries, - Soft / hard tissue pathology, - Temporomandibular joint disorders, Intraoral examination : Morphology of the alveolar ridges, intermaxillary relationship, condition of the oral mucosa, general condition of the remaining dentition, as well as level of oral hygiene are generally taken into consideration before placement of an implant, which can be subdivided into the following: - Dental caries, - Occlusal wear and patterns, - Restorations / prosthesis, - Pulpal diseases, - Cracked or fractured, - Mobility, - Occlusal habits, (bruxism, .etc),
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- Jaw relations (diagnostic casts): interarch distance, jaw relationships, tooth position and alignment. Periodontal or peri-implant tissues examination: - Pockets probing depths (6 per tooth or per implant), - Gingival recessions, - Disease activity (increasing in clinical attachment loss, bleeding on probing, suppuration), - Amount of inflammation, plaque, and / or calculus, - Color, contour, and consistency of gingival biotype, - Furcation involvements, - Levels of adjacent cementoenamel junctions to implant site, - Amount of keratinized gingiva, - Frenum pulls, - Depth of vestibule, - Width and height of osseous tissues (sounding, radiographs), - Thickness of gingiva, - Tooth mobility or migration.
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Evaluation of existing prosthesis: Inspection of the prosthesis that the patient may or may not be wearing can provide tips about special prosthetic problems, as well as the psyche of the patient. Evaluation of the intra and extra oral photographs: The importance of documenting and observing each tooth in a magnified image and surrounding area adds to the betterment of the treatment plan and maintenance phase. Evaluation of a radiograph: Prognosis of remaining teeth, proximity to vital structures, bone availability as well as the possible existence of any pathologic conditions. Evaluation of an articulated study casts: The exact measurement of mesiodistal space and intermaxillary arch space is more accurately performed on a
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cast than intraorally. Quantitative measurement of the amount of concavity in the alveolar ridge is needed for planning soft and hard tissue augmentation using the study casts. Indication for placement of implant: In early 1970’s, the edentulous, severely atrophied mandible represented to be one of main indication for implant supported prosthesis and in some situations it was considered to be the only indication. This is mainly because, the conventional complete dentures often proved to be unsatisfactory for patients with edentulous mandibles, whereas implant treatment achieved a significant improvement. The range of indications has increased in recent years; if the patient is healthy and the intraoral condition (bone availability) points toward successful osseointegration, implants can be indicated or to be the treatment of choice not only for edentulous and partially edentulous patients, but also for the replacement of a single tooth.
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Radiography: Pre-operative Radiography INTRA ORAL AND PANORAMIC RADIOGRAPHY: The radiographic technique of choice is the intra oral paralleling technique with projections perpendicular to the tangent of the dental arch in the areas of interest. The bisecting angle technique should be avoided because it distorts dimensions. When applied to the edentate regions: - The intra oral technique provides valuable information concerning the mesiodistal dimension of the region in which implants are considered and, thus about the number of implants that can be inserted.
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- Radiographs also provide information about the potentially available bone height relative to the mandibular canal, floor of the nose, mental foramen and floor of the maxillary sinus.. - It can dimensionally determine cases of the implant treatment that cannot be performed due to lack of available bone volume unless bone augmentation procedures are performed. Panoramic radiography can provide information that is necessary to determine whether implant treatment may be contemplated however its lack of detail often prohibits a sufficiently accurate diagnosis of tooth related diseases. In panoramic radiographs: - Distortions are frequently found, above all concerning horizontal dimensions (TRONJE 1982). This makes panoramic images less well suited for accurate estimates of the amount of bone available in the mesiodistal direction, particularly in the anterior parts of the jaws.
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- when anatomic conditions makes impossible to place in an intra oral films parallel to the vertical axis of the alveolar process, a better estimate of bone height can be made in panoramic radiographs. - It is important that due account is taken of the magnification in panoramic radiographs, as this can vary between panoramic units. It has been demonstrated recently that the use of templates with incorporated metal spheres of known diameter in situ when the radiograph is taken can effectively eliminate the distortion problems. The metal spheres appear radio-opaque in the final film; because their diameter is known, it is easy to calculate the true bone height (BEHNEKE 1986, SPIEKERMANN 1987). When implants will be inserted between the teeth, and the mental foramen, or between a tooth and the anterior border of
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the maxillary sinus, supplementary intra oral radiographs should always be obtained: - They should be taken with a direction of the X-ray beam perpendicular to the tangent of the alveolar arch. - Inaccurate horizontal angulation of the x-ray beam can easily make the distances of interest appear too small or, less frequently too large (GRÖNDAHL & al. 1996). An important objective of the preoperative radiographic evaluation of the implant patient is to determine the height and the width of the bone available for implant insertion. Ideally, the bone width should allow complete coverage of all implant threads 1mm – 2mm on both the buccal and the lingual sides. The available bone height must be estimated from the part of the alveolar bone in which a sufficient bone width is found to a site specific anatomic border in the vertical direction, e.g. the lower border of the nasal cavity, the lower border of the maxillary sinus, or the upper border of the mandibular canal.
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Sufficiently accurate estimations of bone width and height cannot be obtained without cross sectional tomography. To achieve ideal conditions for a successful integration of the implant with the surrounding bone, it is important that good images of the implant recipient site can be obtained during the diagnostic phase. The most important factor is the presence of a sufficient amount of cancellous bone ratio to compact bone 3:1 in which the implant can be anchored: - The compact bone at the marginal bone crest can provide stability of the marginal part of the implant. The cancellous can provide the cells and nourishment for the implant. - Stability in the anterior part of the mandible is obtained by anchoring the implant in a layer of cortical bone at the base of the mandible.
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- In the maxilla, the lower border of the nasal cavity or the maxillary sinus cannot provide the necessary ‘apical’ stability and hence the stability comes from the surrounding wall that is holding the implant in place. - If neither of these possibilities are at hand, stability of one of the surfaces of the implant can sometimes be achieved by placing it in a layer of buccal or more often lingual bone cortex and augmenting the missing wall. Often during the radiographic diagnosis stage a concavity is detected in the buccal surface, apically located to the cortical layer which makes it not suitable for anchoring: - A shorter implant can provide sufficient stability if the concavity is at the mid part, bone augmentation with intentional perforation of buccal plate of the bone is predictably performed instead of compromising the angulations of the implant.
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- A relatively narrow width of the jaw bone in combination with a thick, cortical marginal border may provide proper conditions for immediate implant stability and hence the stability comes from the surrounding wall that is holding the implant in place. - A narrow alveolar bone with a thin layer of compact bone at the alveolar crest often provides less than optimal conditions for implant treatment. Bone splitting prior to implant placement can maintain the 1mm-1.5mm cortical buccal bone. All the above situations should be analyzed with radiographic imaging. - The presence of thick trabeculae in the spongious bone can provide the necessary conditions for good primary stability (VAN DER STELT 1979, LINDH & al. 1996) - The trabecular pattern seen primarily reflects the conditions in the junctional area between compact and trabecular bone,
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- The presence of a trabecular pattern is no guarantee that bone trabeculae will be found in the interior part of the jaw bone; - The absence of such pattern strongly indicates a definitive absence of bone trabeculae. Radiographic measurements are neither so accurate nor so precise that they can be completely trusted (GRÖNDAHL & al. 1991, EKESTUBBE & GRÖNDAHL 1993, LINDH & al. 1996): - One must decrease the calculated distances by 1-2 mm; to avoid damages of the infra alveolar neurovascular bundle, a safety margin should be applied to the calculated distances between the marginal bone crest and the upper border of the mandibular canal; - Due accounts must also be taken of the fact that the drilling procedure which precedes the implant insertion goes .5mm – 1mm deeper than the implant itself. - One must also taken in account that the upper part of the implant cannot always be placed at the level of the marginal crest, e.g. in cases when an implant has to be placed buccal
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or lingual to the upper bone margin or when a narrow width of the marginal bone makes reduction of the bone height necessary. CROSS SECTIONAL TOMOGRAPHY: The horizontal dimension of an intended implant site can be determined from intra oral or panoramic radiographs. In curved parts of the dental arch, measurements in panoramic radiographs can be inaccurate due to distortions. Preliminary estimates of the bone can be made in intra oral radiographs, provided that a paralleling technique has been used, or in panoramic radiographs. Determination of actually available bone height is the best made in cross sectional tomograms in which the width of the jaw and also the bone can be determined and measured. Cross sectional tomography should be done perpendicular to the tangent of the dental arch and perpendicularly to a horizontal reference plane, the hard palate for maxillary
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examinations and the base of the mandible for mandibular examinations. To determine the distance between the mental foramen and an anteriorly positioned tooth, intra oral radiographs should be obtained with an X- ray beam direction perpendicular to the tangent of the dental arch. Cross sectional tomography in the mandible is needed to determine the distance between the marginal bone crest and the upper border of the mandibular canal as well as the presence of lingual concavities and the inclination of the alveolar process. The single implant case: The distance between opposing root surfaces is preferably measured in intra oral radiographs. Slight variations in patient positioning can make such a distance appear too small or too large in panoramic images.
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If tomography is considered necessarily, thin tomographic layers 1mm should be used to avoid disturbing ghost shadows. Tomography is recommended when a single implant is to be placed above the mandibular canal or any single implant where the available bone is in doubt. COMPUTED TOMOGRAPHY: Similar to tomographs, the exposures are made in single plane, with the help of a computer and special software that allows for multiplanar reformation of the image, planes of section in all three dimensions of space can be produced. The dentist has at his/her disposal cross-sectional panoramic and occlusal views of the actual osseous topography in 3D. Equipment from GENERAL ELECTRIC CORPORATION (DENTASCAN ®) employs the MSPA technique (maxilla-
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mandible shape pattern analysis). This provides transverse section images at 1 mm intervals from left to right around the entire dental arch in both mandible and maxilla. The other vital indication is to visualize and calculate the ratio between the cancellous bone and cortical for better treatment planning especially if bone augmentation procedures are indicated. Conebeem is a recent generation of CT (CBCT) which performed with patient sitting or standing in 30 seconds and equal radiation to a digital panoramic radiograph. Finding the (HU) housefield unit is also an additional information which a CT can provide.
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RISK FACTORS SUBJECT RISK: Cigarette Smoking: Cigarette smoking is a major preventable cause of human disease; it results in increased mortality and morbidity. (Around 50% of smokers died due to smoking related illnesses ;DOLL & al. 1994). Cigarette smoking is associated with impaired healing of surgical wounds (REES & al. 1984, SIANA & al. 1989, SILVERSTEIN 1992). Periodontal effects of cigarette smoking (TONETTI 1999): - Smokers present 3 to 7 times higher risk of developing periodontitis, - Smoking has been shown to explain up to 51% of the total attributable risk for periodontitis,
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- Smokers respond less well to periodontal therapy, - The treatment associated decrease in the risk of periodontal disease progression seems to be more limited in time. BAIN & MOY 1993 observed that a significantly greater % of implants failures occurred in smokers than in non smokers: - Smokers had an overall implant failure rate of 11.3 %, - Non smokers presented a failure rate of 4.8 %. - While failures rates decreased with increasing implant length, the failure rate for each implant length was consistently higher in smokers than in non smokers. Cigarette smoking was associated with significantly higher levels of marginal bone loss (HAAS & al. 1996, LINDQUIST & al. 1996), and soft tissue inflammation (HAAS & al. 1996, WEYANT 1994). LINDQUIST & al. 1997:
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- The extent of marginal bone loss around osseointegrated implants has been associated with the number of cigarettes smoked, - Both smoking and oral hygiene are associated with marginal bone loss. A recent prospective investigation has evaluated the effect of peri operative smoking cessation protocol on short term implant survival (BAIN 1996): - the protocol involved patient information of the increased risks of implant failure among smokers and involved complete smoking cessation for 1 week before and 8 weeks after surgery; - the results indicated that the displayed short term implant failure rates similar to those who had never smoked, and significantly lower than among the smokers who did not follow the protocol; - This initial indication of the short term benefits of a smoking cessation protocol is highly suggestive of a possible causal relationship between smoking and implant failure.
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Osteopenia and Osteoporosis: Low bone density at the site of implant placement (type 4 bone) has been associated with increased risk of implant failure in retrospective (JAFFIN & al. 1991) and prospective (HUTTON & al. 1995) investigations. The latter investigation indicated that patients with low quantity and low density of bone were at highest risk for implant loss. An investigation indicated that the prevalence of implant sites with type 4 bone was twice as high among heavy smokers as among people who had never smoked or light smokers. Smoking might therefore produce its negative effects on implant survival both directly and via a possible effect on jaw bone density. Systemic osteoporosis has also been mentioned as a possible risk factor for lack of success with osseointegration (DAO et. 1993, ROBERTS et. 1992).
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Concerning osteopenia, it was demonstrated that implant placed in lower quantities of bone were at higher risk of failure (HUTTON & al. 1995). Indirect evidence to support this notion also comes from the recognition that shorter implants in the past higher failure rates than longer ones in a given time period. Diabetes: Uncontrolled diabetes has been shown to be a risk factor for periodontal disease (EMRICH & al. 1991, NELSON & al.1990). A 1 year report of implant survival in non insulin dependent diabetics indicated a 7.3 % failure rate. This seems to indicate that osseointegration can be obtained in the majority of diabetic patients. Nevertheless, the medium to long term prognosis of implants placed in these subjects is currently unknown.
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Medications: A medical and medication history has been associated with an increased risk of implant loss (WEYANT 1994). Few isolated reports, Ibandronate ( Boniva) 2.5 mg PO qd and Alendronate (Fosamax) 70mg PO qwk have associated implant failure with the assumption of anti osteoporosis drugs and Diphosphonate in particular (STARK & al. 1995). These reports should caution to clinicians with regards to the potential impact of medication whose mode of action might interfere with the physiology of the bone remodelling process. Cause of Tooth Loss and Persistent Periodontal Infection: A case report showing loss of the endosteal osseointegrated implant placed in the dentition of a subject affected with a rapidly progressive early onset form of a periodontal disease has suggested a possible relationship between the cause of tooth loss and an increased risk of implant disease leading to implant failure (MALMSTRÖM & al. 1990).
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The concept that implants may be affected by the periodontal conditions comes from two indirect lines of evidence: - Similar microflora colonizing teeth and implants in partially edentulous patients (MOMBELLI & al. 1995, PAPAIOANNOU & al. 1996); - Identification of a hyperinflammatory phenotype in partially edentulous patients with peri-implantitis lesions (SALCETTI & al. 1997). Inadequate Oral Hygiene: An increase of implant failure (VAN STEENBERGHE & al. 1993), and an increased prevalence of soft tissue problems (WEYANT 1994), have been reported in subjects with suboptimal levels of oral hygiene. Others observations are reporting an increased prevalence of complications following oral and periodontal surgery
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procedures in plaque infected dentitions (LINDQUIST & al. 1997), has also suggested a possible synergistic effect of inadequate oral hygiene and cigarette smoking in the determination of marginal bone loss around successfully integrated implants. Elderly Patients: Questions concerning limitations vis à vis dental implant for older patients are relatively easy to answer. The important concern is the biological age and not the chronological age. A good rule of thumb is that a patient should have a life expectancy of at least 5 years from the time of implantation.
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Young Patients: More difficult is the question concerning how early in life dental implants may be placed. Numerous authors have stated that implants should not be placed before the 15
th to
16th year of life. This is based on the assumption that, for boys
and girls, jaw growth is complete by this time. Clinical studies have shown a continuation of facial growth into the late teens for women and into the twenties for men (BJÖRG 1963, SILMAN 1964, HUNTER 1966, BISHARA & al. 1984). More recently, there has been an increase in the number of authors, who warn against placement of dental implants during the growth period (ÖDMAN & al. 1991, LEKHOLM 1993, LEDERMANN & al. 1994). STÖCKLI 1984 demonstrated that the distance between implants placed into a still growing osseous bed remained the same despite the fact that the bone increased in size. This observation can be explained when one considers that newly formed bone in the peri-implant area serves as an
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isolating tissue despite the histologically similar structure functional growth of the jaw bone itself. The primary task of the peri-implant bone is to stabilize and circumscribe the implant. A similar process in connective tissue is the scar formation, which likewise does not take part in functional growth. Some have offered that the assumption of the osseous prerequisite (cessation of growth) for the placement of dental implants is achieved after age of 15 or 16. However, especially in the esthetically sensitive anterior segment of the maxilla, this assumption must be tempered by the fact that no definitive correlation exists between chronologic patient age and completion of jaw growth. Even the consideration of a hand radiograph as an additional diagnostic aid for dental implantology has its limitations because the growth of bone in the jaw regions continues later than the long bones.
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If the treatment plan includes the option of dental implants in the anterior region of a young patient (before age 15 to 16): - Serious consideration should be given to the possibility of subsequent esthetic complications if implants are placed, versus the temporary use of a Maryland bridge; - The latter may, of course, be associated with resorption of the labial bony wall of the edentulous space. Implant Site: Substancial experimental evidence has indicated that different intra oral sites are associated with different rates of implant survival. It is currently unclear whether the observed differences can be explained, at least in part, by the insertion of shorter implants in the posterior regions of the jaws and / or by lower bone density in these regions. Encroachment to vital structures could also alter the survival rate.
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Implant Device: Several investigations have indicated that shorter devices seem to be lost more frequently than longer ones (BAHAT 1993, BUSER & al. 1997). This observation can be interpreted in 2 ways: - the shorter implants offer the smaller surfaces for implant bone contact and may therefore be more prone to biomechanical overload of the implant device, - and / or a marginal peri-implant infection spreading apically along a shorter implant may require less time to cause resorption of a critical portion of the established osseointegration lead to loss of the device. Differences in implant surface have also been associated with increased risk of implant loss: hydroxyapatite coated implants have been found to be at higher risk for failure in a large independent medium term investigation (WEYANT 1994). This
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finding is no longer observed anymore (et al. 2008) with recent improved HA coated surfaces. Clinical Significance: Knowledge of subject risk should assist the clinician with determining the prognosis for the individual case and thus with patient selection. Improved understanding of subject based on risk for peri-implantitis and biomechanical overload combined with a careful preoperative assessment of implant based risk could be useful in determining number, location and type of implants as well as the design of the reconstruction.
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Chapter 3
Essential requirements for dental implant
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Essential requirements of dental implant
Dental implant should be:
1. Non-toxic*
2. Non-carcinogenic*
3. Non-allergenic*
4. Non-radioactive*
5. Biologically compatible ( A material is biocompatible if
it remains stable, at the same time does not elicits an
unwanted or undesirable tissue reaction inside the
living organism )
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6. Mechanically compatible (biomaterials must exhibit
adequate mechanical strength in order to distribute
the other physical properties of implant biomaterials
that constantly being improved to the forces into
implant bed for better esthetic and function )
7. Functional and Practical (The implant must provide
the desired clinical esthetics and easy oral hygiene
maintenance. Implant must be radio-opaque. All steps
of any implant procedure should be easy to perform,
reproducible both surgically and prosthetically; should
be possible to remove (if it is necessary). The
abutment should be sterilizable in office and implant
should be economically reasonable )
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8. Osseointegratable ( Implant should lead to
osseointegration and should not cause
fibroencapsulation )
9. (*: The most essential requirement for all biomaterials is that they should not cause any local or systemic abnormal reaction)
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Chapter 4
Types and material of dental implant
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Types and material of dental implant
Types of dental implants: Dental implants have been classified by a variety of categories: 1. Position. 1.1 Subperiosteal. This type is consisting of non osseointegrated framework that rests on the surface of the maxilla or mandible. This framework rests beneath the mucoperiosteum, with posts that penetrate the mucosa into the mouth, usually supporting an overdenture. 1.2 Transosseous. The most common form of this implant type is the transmandibular staple, which has a plate that fits against the lower border of the mandible at the symphysis and which has posts rising from it. Some of these posts pass into the jaw and others pass
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through it into the mouth, where they serve to stabilize a denture. 1.3 Endosseus. They are divided into two subcategories:
Root form implants:
They can be smooth, threaded, perforated, solid, hollow, or vented; can be coated or textured; and are available in submergible or non submergible forms in a variety of biocompatible materials.
There are two
primary types based on their design. Cylinder (or press-fit) root form implants depend on microscopic retention and/or bonding to the bone, and usually are pushed or tapped into a prepared bone site. Screw root forms are threaded into a bone site and have obvious macroscopic retentive elements for initial bone fixation. Combination root forms have features of both.
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Blade implants:
This form is flat and narrow in the facio-lingual dimension with the neck of the implant connects the implant body and permucosal abutment. 2. Material composition Many materials have been used for implants, including ceramics such as aluminum oxide and metals ranging from alloys of gold, titanium, and nickel-chrome-vanadium to commercially pure titanium (most commonly used dental implants today). Among the clinically tested implant materials, commercially pure titanium is recognized today as a material of choice, since it is not only characterized by excellent biological but it’s also good in mechanical properties (STEINEMANN, 1996). Alternative implant materials could not provide enough evidence for longevity and satisfying success
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rates. For example, Aluminum Oxide (Al2O3) implants completely disappeared from the market in the late 1980's, since it was not strong enough to withstand high masticatory forces and demonstrated an increased risk for fatigue fractures under long term function. The titanium bone interface can successfully transfer the compressive and shearing forces imposed in the oral cavity, but only if the surface configuration of the implant provides mechanical retention. Recently several all-ceramic implant systems have been increasingly manufactured. These commercially available one piece implants are mostly indicated for replacement of missing teeth in anterior region where aesthetic is critical, to avoid dark shadows of metallic dental implants. However due to its one piece angulation limitations its usage is limited to patients with adequate bone. To date, there have been no reports of allergic reactions. Recently they possess a
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flexural strength of 1200 MPa that comes in the form of Y-TZP (ytria tetragonal zirconia polycrystals). The main disadvantage is that it has a lower fracture resistance comparing to metallic implants. 3. Design characteristics Many endosseous implants conform more or less to the shape of a tooth root, being either in the form of a tapered cylinder or a true cylinder. There are different types, Threaded on the external surface, solid screws, smooth and plasma-sprayed surface, external fins rather than threads, and hollow cylinders with fenestrations, called baskets. Others are flat plates called blades. The most commonly used dental implants are, threaded, plasma-sprayed and smooth hydroxyapatite (HA) coated.
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Today, screw implants are highly preferred in implant dentistry, since threaded implants offer two major advantages compared with press-fit cylindrical implants. First advantage: The implant threads improve implant primary stability, which is important in avoiding micromovements of the implant until osseointegration is achieved. - This is primarily important for implants inserted in a non submerged fashion or in areas of low bone density. Second advantage: The threads seem to play an important role for the load transfer from the implant to the surrounding bone. - This aspect is not yet fully understood, but there is a striking observation that bone trabeculae under occlusal load most often point toward and attach itself
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on the edge of the threads which has been demonstrated by several histological studies. Endosteal root-form dental implants are by far the most commonly used dental implant today. An endosteal implant is an alloplastic material, an inert foreign body used for implantation into tissues, surgically inserted into a residual bony ridge primarily to serve as a prosthodontic foundation. The prefix endo means “within” and osteal means “bone”.. They are placed into the maxilla or mandible through an intra oral incision in the mucoperiosteum. These implants are used for restoring single, multiple teeth and complete edentulous patients. The predictability, reproducibility and success rate (85% in the maxilla - 99% in the mandible, after 15 years follow up) due to their potential for osseointegration have encouraged their use.
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Osseointegration as defined by Brånemark is “a direct
structural and functional connection between ordered, living bone and the surface of a load-carrying implant. Creation and maintenance of osseointegration, depends on the understanding of the [periimplant soft and hard] tissue’s healing, repair, and remodeling capacities”. To other authors osseointegration denotes at least some direct contact of living bone with the surface of an implant at the light microscopic level of magnification with the percentage of direct bone-implant contact being variable. It also has been defined simply as progressive biological anchorage mechanism. As more studies are in progress to investigate the process, mechanism and physiology of osseointegration, the understanding of this concept is also progressively changing. Hence these osseointegrated fixtures are directly united to living,
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remodeling bone without an intermediate soft-tissue layer. The implant functions as a mechanical part of, the incorporating hard tissue; thus, load is transferred directly to the anchoring bone. The crucial point is that bone and marrow must be made to heal as highly differentiated tissues and not allowed to develop into poorly differentiated scar tissue. The early bone-healing process, called primary callus response by McKibbin, is not affected by mobility. However, it has been experimentally verified that the bone cell differentiation process will become disturbed by prolonged (weeks) implant mobility later in the healing process. Therefore, loading of a dental implant before it has been stabilized by a sufficient amount of bone is a potential hazard for fibrous union.
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Alloplastic materials used commonly as endosseous root-form dental implants. 1. Commercially pure titanium or (CP) Ti: Titanium is a light metal that forms a tenacious and adherent layer of its oxide (primarily TiO2) on its surface. This oxide layer makes titanium inert and stable in the ambient environment, making it highly corrosion resistant and biocompatible (e.g.: Brånemark implant, Astra, BioHorizons, 3i etc.). It is also generally believed that the presence of this oxide layer is intimately involved in the process of osseointegration. Hanawa
demonstrated that after six
years of clinical loading, a retrieved implant showed a passive layer of titanium oxide which contained Ca, P and S in its composition, indicating it to be bioactive surface favoring uptake of mineral ions even though it was coated with a protein layer. Titanium has unique
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properties as an implant material for use in contact with mineralized tissue applications. Adell et al.
In a
15 year study of 2768 (CP) TI Brånemark implants reported the success rate of 81% of the maxillary and 91% of the mandibular fixtures remained stable, supporting bridges in the first 5-7 years. And 89% of the maxillary and 100% of the mandibular cases, the bridges were continuously stable thereafter. In the past titanium has also been used in plasma sprayed surface condition (e.g.: Life Core implant, IMZ, ITI, Bicon, etc.). Wheeler in an 8 year retrospective study of 1202 patients in which press-fit cylinder implants were placed; He reviewed 889 titanium plasma-sprayed and 313 hydroxyapatite-coated implants. The success rates were 92.7% for titanium plasma sprayed and 77.8% for hydroxyapatite-coated systems.
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2. Ti-4AL-6V alloy: The alloy is corrosion resistant and passive. It was designed to have improved strength properties. There may be differences in the characteristics of the passive oxide layer between this alloy and the (CP) Ti. A thickness of the proteinaceous film of 500 nm (nano meter) between the implant and the tissue has been reported for this alloy as compared to 20 nm for (CP) Ti. Patrick et al. have reported successful 5 year results with implants of this type. Young et al.
inserted
Ti-6Al-4V dental implants in monkey mandible and demonstrated, by histology and microradiography, that bone tissue was in immediate opposition to the titanium spheres, plasma-sprayed titanium balls, of the implants. There were no discernible fibrous tissue interposed in the bone-implant interface. This was demonstrated with and without occlusal loading by the same author in another study. Similar results were demonstrated by Brunski as well. The Core-Vent
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implant, the Bicon implant etc. are some examples of this type of implant systems. 3. Ceramic-coated titanium implants: Titanium or its alloy implants whose surfaces are coated with hydroxyapatite are commonly used. In the past these were called “bioactive” because of chemical bonds forming at the hydroxyapatite-bone interface, as reported in transmission electron
microscopy thick are (TEM) studies. The hydroxyapatite coatings of 50 – 100 microns are prepared by sintering or plasma spray deposition. The latter process involves the injection of powder into a hot plasma arc and rapid deposition of the molten material onto a relatively cool metal substrate. Marjorie et al.
in a 3 years retrospective and follow-up
study of 95 cases where the implants were placed in bone of less-than-optimal quality compared the hydroxyapatite-coated and uncoated implants. The
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success rates were 100% for hydroxyapatite-coated implants and 84% for uncoated implants. The Calcitek implant, Restore implant, Steri-Oss implant and Bicon implants were some examples of these types of dental implants.
IMPLANT SURFACE: The notion that surface properties of implants might influence the elaboration of a bone implant contact is relatively new. At earlier time, it was assumed that rough surfaces will improve adhesive strength compared with smooth ones. This assumption is now confirmed by numerous animal experiments that measured the push and pull out strength or removal torque values (CARLSSON & al. 1988, CARR & al. 1997, CLAES & al. 1976, JOHANSSON & al. 1987, THOMAS & al. 1987, WILKE & al. 1990).
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It was observed that a rough surface favors bone deposition and thus gradually increases the extent of the bone implant interface (BUSER & al. 1991). It is now supported by numerous experimental studies (GOTFREDSEN & al. 1991-95, WENNEBERG & al. 1995-96-97) that roughness can be further characterized by the shape and dimension of the surface irregularities in which the degree of mechanical interlock increases with the roughness of the substrate. At the same time the structure and function of the bone implant contact changes because: - A smooth surface only transmits compressive forces, with little resistance against shear and apparently not against traction. - A mild roughness (<10µm) augments the resistance against shear.
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Adhesion requires either a chemical bond or microporosity (20-50µm) that leads to micro-indentation between metal and bone. Macroporosity (roughness) favors bony ingrowth and it is widely used as porous coatings in orthopedic implants (BEREITER & al. 1989, BOBYN & al. 1983, CALLAGHAN 1993, CAMERON 1982, SCHENK 1995). Finally, the macro design or shape of an implant has an important bearing on the bone response. Hence, bone growth concentrates preferentially on protruding elements of the implant surface, such as ridges, crests, teeth, ribs or the edge of threads that apparently act as stress risers when load is transferred (SCHENK & al. 1989). At the present time different implant surfaces exists, but importantly the difference exist between:
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- Machined titanium surface (smooth) - Titanium plasma sprayed surface (Additive-rough) - Sandblasted- surface etched (Subtractive-rough) - Hydroxyapatite coatings (Additive-rough) - Aluminum oxide ceramic (rough) - Laser-etching (Subtractive-rough) - Anodic oxidation (Additive-rough) The two most documented titanium surfaces in implant dentistry which are not commonly used today are: - The machined titanium surface - The titanium plasma sprayed surface
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MACHINED TITANIUM SURFACE:
Current studies and researches identified that the surfaces, including its micro roughness is due to the machining procedure that has been modified over past 30 years. The research from the ALBREKTSSON’s team and others has shown that, both in vitro and vivo, even minute modifications of the surface characteristics can have dramatic effects on the interaction with bone cells and fibroblasts. Even the impurities within the oxide layer are a relevant factor. Screw type implants with a machined surface have demonstrated an increased failure rate for short implants and for implants inserted in sites with poor bone density (JAFFIN & al. 1991, JEMT 1993-96, QUIRYNEN & al. 1990).
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TITANIUM PLASMA-SPRAYED COATING:
Several attempts have been made to improve implant anchorage in jaw bone by modifying the surface characteristics of titanium implants. One of them was made by roughening titanium surfaces. Some of the titanium implants that are used today (I.T.I. STRAUMANN ®, Dens ply ®) were coated with titanium powder which is applied using a special plasma flame spraying technique. At the same time this creates a rough and enlarged surface of the implant body. The titanium plasma-sprayed surface was the first rough titanium surface introduced in implant dentistry more than 3 decades ago (SCHROËDER & al. 1976). It has demonstrated satisfying long term results in fully and partially edentulous patients (BABBUSH & al. 1986, CALLAGHAN 1993, LEDERMAN & al. 1996). Alternatively rough titanium can be produced by non-coating techniques such as sand or grit-blasting, TiO2-
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blasting, acid etching, laser etching or combinations of some of the above. There is scientific evidence that rough titanium surfaces offer significantly better bone anchorage than do machined titanium surfaces. This was evaluated both by histomorphometric evaluation of the bone implant interface and by biomechanical studies measuring either pull out, push out or removal torque forces (BUSER & al. 1991, CARLSSON & al. 1988, CARR & al. 1997, CLAES & al. 1976, COCHRAN & al. 1999, GOTFREDSEN & al. 1991-95, JOHANSSON & al. 1987, WENNEBERG & al. 1995-96-97, WILKE & al. 1990, WONG & al. 1995) . From a clinical point of view rough titanium surfaces offer a significantly better implant anchorage in bone with shorter healing period. The options that utilize these shorter implants also have a good long term prognosis.
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From a physiologic point of view a rough implant surfaces has advantages over a smooth one when it comes to the behavior of newly formed bone. Rough surfaces exhibit better wettability and therefore improved adhesion. Especially in the immediate postoperative phase (accumulation and organization of the blood coagulum onto the implant surface) such physical phenomena are important for osteogenesis. Rough implant surfaces exhibit a measurable increase in the strength of the implant bone when compared to smooth surfaces (SCHMITZ 1991). Furthermore, through ingrowth of bony trabeculae into the micro-porosities there is improvement in force transmission to the bone and therefore improves the long term stability of the bond between implant and bone. The reaction of the bone to the implant is determined not only by the degree of porosity but also by the size of the individual pores. Porosities ranging in size from
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70 to 700 µm will be filled by mineralized bone (BOBYN 1980, KLAWITTER & al. 1976). The reaction of the epithelial tissue and connective tissue cell is also determined by the size of the individual pores. Procecikins ranging in size from 8-12 mm will be filled by epithelial cells, connective tissues and fibroblasts respectively.
SANDBLASTING - SURFACE ETCHING:
Sprayed plasma changes the smooth implant surfaces into a rough surface by adding material; it is also possible to roughen a smooth surface by subtracting material, for example by sandblasting, etching or special laser treatment. An important advantage of the latter techniques, in contrast to additive techniques, is that they avoid any possible contamination due to the technical procedures. In subtracting method, the risk of titanium particle loss during insertion of the implant would
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appear to be absent when compared with plasma flame spraying/HA additive technique. On the other hand, if aluminum Oxide which is a poisonous material (commonly used to spray the titanium surface) remains on the surface of implant, it can be a non osseointegratable spot. The etching technique implemented to remove aluminum oxide remnants has the disadvantage of removing and flattening of the initially rough surface. I.T.I. STRAUMANN ® implants used a Titanium Plasma Spray surface (T.P.S.) since the last 3 decades; they improved the surface to Sandblasted Large grit Acid etched (S.L.A.). Recently wetting the SLA surface has demonstrated a simple method to stabilize the oxide layer by immersing the implant into a container filled with isotonic sodium chloride solution. The ideas behind these roughened surfaces are:
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- Macro roughness created by sandblasting for ideal stability in bone - Micro roughness created by acid/laser etching increases cell activity on surface - Nano roughness created by anodic oxidation mimics human cancellous bone There are cases demonstrating that faster bone opposition to the implant leads to increased bone/implant contact, evidenced in greater removal torque values thus allowing earlier functional loading. Roughness reduces healing time to 6-8 weeks within which the patient would be with good bone quality and quantity in order to enable restoration.
HYDROXYAPATITE (HA) COATINGS:
Another attempt was made with a hydroxyapatite coating of titanium implants. This coating offers an improved bone adhesion as shown in several
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experimental studies (BUSER & al. 1991, COOK & al. 1992, THOMAS & al. 1987, WONG & al. 1995). Long term efficacy of hydroxyapatite (HA) coated implants has shown contrary results as follows: -Some publications (BIESBROCK & al. 1995, BUCHS & al. 1995-96) presented long term results are well comparable to results with threaded titanium implants -Other authors (JOHNSON 1992, PIATELLI & al. 1995, WEEHLER 1987) reported a clear increased failure rate for HA coated implants. Moreover other authors (WEINLANDER 1991, JOHNSON 1992) discouraged their clinical use due to sever complications. HA coated implants exhibit a bioreactive surface structure that leads to more rapid osseous healing in comparison with metal implants. On the other hand, precisely this feature of the implant surface appears to
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have negative effects over the mid - to long - term stability of HA particle. Explanted HA coated implants often exhibit cracks or even complete loss of the HA coating and have also shown heavier colonization of micro organisms (KRAUSER & al. 1991, RAMS & al. 1991). Due to these negative reports hydroxyapatite (HA) coated implants play only a minor role in implant dentistry today. In order to avoid the drawbacks of plasma-sprayed HA coatings, scientists have developed a new coating method inspired by the natural process of bio-mineralization. In this biomimetic method, the precipitation of calcium phosphate apatite crystals onto the titanium surface from simulated body fluids (SBF) formed a coating at room temperature. (L. Le Gu´ehennec & al 2005-2007)
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ALUMINIUM OXIDE CERAMIC:
Endosteal implants fabricated from aluminum oxide (BIOLOX ®, FRIALIT ®) consist of 99.7% AL2O3 and a residual amount of MgO. With regards to its mechanical properties aluminum oxide is fundamentally different from metals. It has an extremely high compressive strength (far exceeding metals) but a relatively low resistance to bending and tensile forces. These mechanical properties limit the size and shape of aluminum oxide implants and because of the danger in situ breakage, their use in implant dentistry today is very limited.
LASER-ECHING:
The 2 mm collar of implant surface has a precise cut of 8-12 µm. It encourages bone and connective tissue attachment while preventing apical migration of epithelium. (M. Nevins & al 2008)
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It improves the bone response and enhanced the bone formation rate. Surface chemistry and topography, either separately or together, play an important role in the bone response to implants (Guo Z & al 2010, Anders Palmquist
& al 2011)
ANODIC OXIDATION:
Micro- or nano-porous surfaces may also be produced by potentiostatic or galvanostatic anodization of titanium in strong acids (H2SO4, H3PO4, HNO3, HF) at high current density (200A/m2) or potential (100 V). The result of the anodization is to thicken the oxide layer to more than 1000nm on titanium. The anodization process is rather complex and depends on various parameters such as current density, concentration of acids, composition and electrolyte temperature. Two mechanisms have been proposed to explain this osseointegration; mechanical
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interlocking through bone growth in pores, and biochemical bonding. (L. Le Gu´ehennec & al 2005-2007) Clinical results showed that the anodized surface reduces the healing time for 4 weeks and presents better results among other surface treatment (C.N.Elias 2010) PRIMARY STABILITY AND ADEQUATE LOAD: The tissue response to a freshly installed implant depends on the mechanical situation. As in direct fracture healing, it requires perfect stability if bone is expected to be formed. In a fracture, a stable fixation is obtained by exact adaptation and compression of the fragments. The primary stability of implants depends on their appropriate design and precise press fitting at surgery. Primary stability must counteract all forces that could create micro-motion between the implant and the surrounding tissues. In
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other words, it should build up enough preload to compensate for functional load. It thus determines not only the size but also the direction of the forces that are considered to remain adequate. All these parameters must be specified and this explains why immediate functional loading may be possible for such systems with bar-connected screws whereas others require a prolonged unloaded healing period, before a supraconstruction can be installed. IMPLANT PLACEMENT MODALITIES: Two modalities for implant placement are known in implant dentistry:
Submerged approach
Non submerged approach
Today, it is generally accepted that both modalities are applicable in implant patients and offer predictable bone and soft tissue integration; as demonstrated both in animal (BUSER & al. 1992, ERICSSON & al.
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1996, GOTFREDSEN & al. 1991, WEBER & al. 1996) and in clinical studies (BECKER & al. 1997, BERNARD & al. 1995, BUSER & al. 1996, ERICSSON & al. 1994). Most recently, a strong trend towards a non submerged implant placement is apparent, since it helps the clinician to avoid a second surgical procedure and to reduce the treatment time and related costs. However, in esthetic zone this concept remains a challenge. With the use of healing abutments during surgery where augmentation is required, this issue has been partially solved. The micro gap between the healing abutment and the implant is still a concern.
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Chapter 5
Anatomic basis of implantology
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TOOTH AXIS:
Maxillary teeth axis lies oblique to and not aligned with the
vertical axis of the cranium. Consequently, roots in the dental
arch of the maxilla are more closely spaced than the crowns of
the teeth, which usually have the appearance of tilting slightly
outwards.
The axis of the mandibular teeth is inclined inwards relative to
the vertical axis of the cranium, such as their crowns on
opposite sides of the jaw lie closer together than the roots.
With regards to the alveolar wall, this means that the cortical
bone is thicker lingually than bucally.
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RELATIONSHIP OF THE MAXILLARY TEETH TO THE
MAXILLARY SINUS AND NASAL CAVITY:
In 70 % of cases, the floor of the maxillary sinus lies below
the level of the nasal floor and is often concave with a smooth
wall.
The base of the maxillary sinus is represented by the alveolar
recess. The root tips of the 2nd
molar and also those of the 1st
molar exhibit the smallest distance from the maxillary sinus.
The alveolar wall of these two teeth can arch anteriorly over
the floor of the maxillary sinus, such as the latter is more or
less completely compartmentalized.
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The sinus exhibit lobulations that are rarely symmetrical
bilaterally and the deepest point are usually observed in the
region of the 1st molar and rarely in both maxillary premolar
area.
In all stages of maxillary atrophy the base of the sinus may
approach the alveolar crest; after loss of teeth not only does
atrophy of the alveolar wall occur but the sinus floor also sinks
downwards such that several years after tooth loss only a
paper thin bony lamella separates the floor of the empty
alveolus from the maxillary sinus. On the contrary the
maxillary premolar region has sufficient bone height available
anterior to the sinuses for implant placement.
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A very important clinical question may arise i.e. to what extent
encroachment on the maxillary sinus can be tolerated during
implant placement. As a general rule, implants can be placed
till the base of the maxillary sinus; beyond which subsequent
implant removal and replacement with a shorter implant would
be necessary otherwise it can represent a risk of infection if
peri-implantitis occurs. On the other hand, some authors have
reported no complications after raising the sinus 5-10mm
during implant bed preparation (Tatum) or even penetration of
the implant itself into the sinus by 1-2 mm (WATZEK 1988,
BRÅNEMARK & al. 1984).
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Valsalva* maneuver should be done to detect any oro-antral
communication.
* The Valsalva maneuver is performed by exhaling against a
close airway. The technique is named after Antonio Mario
Valsalva, the 17th century physician and anatomist from
bologna, Italy. He described the Eustachian tube and
maneuver to test its patency.
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MANDIBULAR CANAL:
The mandibular canal is:
closest to the inferior border of the mandible
in the region of the 1st permanent molar as it
descends from the mandibular foramen (ULM
& al. 1990).
close to the lingual compact bone at the angle
of the mandible (approximately 80 % of its
course) and between the 1st and the 2
nd
premolars it again occupies space in the
middle of the mandible (MATEIKA & al. 1988,
HÄRLE 1989).
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located further mesialy than its suggested by
the position of the mental foramen where the
orifice is often cranially and distally targeted
(REICH 1980).
The distance from the mandibular canal to the dental alveoli
can be as little as:
3-4 mm in the region of the 3rd
molar.
About 8 mm in the region of the 1st molar.
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INCISIVE CANAL:
Between the 1st and 2
nd premolars the canal deviates sharply
towards the buccal side and exits the mandible as the mental
foramen. Close to this opening a small curved canal located
in the center of the cancellous bone deviates in the frontal
caudal plane. This is the incisive canal which contains nerves
and vessels for the canine and incisor teeth. It is safer to allow
a distance of at least 5 mm for any implant placed mesial to
the mental foramen. This also depends upon the severity of
bony atrophy that could shorten the canal. Generally, a buccal
concavity is observed in this region.
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CLASSIFICATION OF THE POTENTIAL IMPLANTATION
SITES
The condition of the mucous membrane plays an essential
role:
Favorable: thick, attached and keratinized mucous
membrane
Unfavorable: mobile and thin mucous membrane
From the description of anatomic structures and topographic
relationships, one recognizes at this stage that physiological
restrictions are imposed upon implantology within:
Bone layout
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Bone structure
Vascular and nerve supply to the various regions of
the jaw
The topographic relationship of the maxillary teeth to
the nasal cavity and the maxillary sinus
Favorable:
Anterior mandible (between the two mental foramina)
Mandibular region near posterior teeth, as forward as
natural dentition exists. (If implants are being
considered only after several years of total tooth loss,
then the posterior mandibular region is usually no
longer a suitable site).
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Conditionally favorable:
Maxillary region up to the site of the 2nd
premolar.
Unfavorable:
Posterior region of the maxilla, including the maxillary
retromolar tuberc
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ANATOMIC PREREQUISITES:
Resorptive processes:
Every tooth extraction leads to remodeling of the alveolar
bone, including osteoclastic resorption of the residual alveolar
ridge especially the labial wall as well as bone deposition
within the extraction socket.
The rate of bone resorption is the highest during the first 3
months with significant slowing after 6 months.
Remodeling is generally complete and stabilized after 1-2
years.
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The average rate of resorption in the mandible (approximately
0.2 mm / year) is 3-4 times higher than the maxilla
(TALLGREN 1972).
Bone resorption in the mandible occurs primarily lingually in
the premolar areas and bucally in the molar segments. In the
maxilla resorption of the alveolar ridge occurs mainly on the
buccal aspect. This type of primarily centripetal atrophy leads
to a maxilla that is relatively smaller than the mandible and
leads to change of the intermaxillary relationships (HÄRLE
1989).
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PPeerrii--iimmppllaanntt TTiissssuuee
For implants to be successful and functional for extended
period of time there has to be an effective biological
compatibility between the implant material and the tissues of
the jaws. Recently, many authors have studied just this role of
the biologic tissues and its connection with the implant and
begun to realize how important this tissue-implant biological
seal really is. Using light microscopy and electron
microscopy it has been seen that the gingival epithelium
regenerates a series of epithelial cells after surgery similar to
those seen in the natural tooth sulcular epithelium and
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junctional epithelium zones. Other reports have shown a
basal lamina like structure that is assumed to help create a
positive attachment between the gingival epithelium and
implant surface.
The importance of this gingival structure in implant dentistry is
great, as all dental implants have a coronal portion that is
supported by a post which passes through the submucosa
and overlying stratified squamous epithelium covering into the
oral cavity. The seal between the implant and biologic tissues
becomes an essential factor in maintaining implant longevity
by helping prevent the ingress of bacterial plaque, toxins and
oral debris. Surrounding tissues are likely to become inflamed
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if this seal is breached, which in turn will lead to more critical
deleterious effects such as chronic resorption of the
supporting bone. If degenerative changes are allowed to
progress continuing loss of bone will lead to increasing
mobility of the implant and finally acute inflammation with pain
until a point where implant failure occurs. Also if such
extensive bone loss takes place that the implant becomes
impractical subsequent placement of implants or other
restorative procedures may be compromised.
Bone, composed of 75% inorganic calcified matrixes is the
principal load bearing organ for the implant. It responds in
different ways to different implant types. For example, for
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endosteal implants that are placed within the bone, the bone
must first be drilled or trephined to allow a site in which to
place the implant. Over heating of the bone during this
procedure will cause excessive cell destruction, and possibly
compromise the healing after placement of the implant. It has
also been seen in some cases that after prosthetic loading of
the implant, there is slight bone resorption as the load is
transferred to the bone. This may mean that the recently
healed bone after surgery is now being resorbed under
pressure from the prosthetic device and is being replaced by
fibrocellular connective tissue. The process does not stop
here however as ossification may also begin in the
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fibrocellular stroma, leading once again to a mature bone-
implant interface.
Bone response to subperiosteal implants is slightly different as
they do not require the drilling of a receptor site. The
elevation of a full thickness muco-periosteal flap although
does disturb the nutrient supply to the osteoblastic cells and
the outer surface of the cortical bone which may lead to
necrosis of the osteocytes. This may cause focal areas of the
bone to become non-vital and eventually be resorbed by
phagocytic cellular activity. To balance out this bone reaction
in response to the surgical manipulation of soft tissue the
osteoblasts lining the endosteal surfaces of the jaw bone
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become active and deposit new bone. The thickness and
quantity of alveolar bone remain approximately stable.
Therefore the method by which load transfer takes place from
implant to bone has been a topic of much discussion. Two
main theories exist as to how this occurs:
1) Through the development of an ankylotic-like
relationship between the implant and bone
2) The development of an intermediate ligamental system
Most authors agree with the ankylotic state theory, also
referred to as osseointegration. However in ankylosis there is
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no space between the tooth and the bone but in
osseointegration space exists. The bone will not resorb
around an ankylosis tooth but it will resorb around an implant.
SOFT TISSUE CONDITION:
In addition to bony atrophy after tooth loss redundant soft
tissue (scar) forms and there is a simultaneous reduction in
the expense of attached gingiva (TETSCH 1991). Bony
atrophy and loss of attached gingiva are correlated.
It is important to bear in mind that the bone is healed by
regeneration as opposed to soft tissue which is healed by
repair.
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AVAILABLE BONE:
One of the most significant factors in every implant case is the
amount of available bone in the area where implants have to
be placed.
According to MISCH 1990, available bone can be determined
using diagnostic aids (radiographs, study models, etc) with
regards to height, width, length and shape. Prior to the
treatment implant-crown ratio should be anticipated,
estimated and considered within the treatment plan.
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BONE HEIGHT:
The vertical extent of bone available for implantation is defined
by the distance between the alveolar crest and opposing
anatomic boundaries (maxillary sinus, mandibular canal, floor
of the nose, etc).
Implants should be placed with a safety margin of 1-2 mm
from certain structures and 8 mm is the accepted minimal
length for cylinder or screw type implants. Exceptions may
apply if compact bone is very thick (the mandibular symphysis
region of a severely atrophied mandible). Whenever possible
longer implants should be used to increase the bone implant
contact surface area. Overheating the bone during osteotomy
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with longer drills to prepare more than 13mm is generally not
desirable. The 5 mm short implants have proved to be
successful in many clinical cases where specific systems and
protocols have to be followed according to individual case by
case basis.
BONE WIDTH:
The width of a bone is measured in area of the planned
implant placement site as the distance between the oral
(lingual / palatal) and the buccal osseous walls at the level of
alveolar ridge.
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For screw form and cylinder implants a width of about 5 mm
bone is required and about 2.5 mm for blade implants. After
surgical placement at least 2 mm of bone should remain on
each of the oral (palatal/lingual) and buccal implant aspects
and if not possible to preserve the 2mm of bone an expansion
is preferable than osteotomy or a narrower diameter implant
can be used. Since post operative resorption occurs always,
the 2mm of bone existing on the implant at the time of surgery
might resorb having unseen implant threads exposed under
the soft tissue.
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IMPLANT CROWN RELATIONSHIP:
The relationship between the endosteally anchored implant
and the height of the prosthetic crown is having significant
influence on the functional loading of the implant and the peri-
implant bone. The crown / implant ratio should be as close to
1 / 1 as possible but connecting multiple implants could alter
this ratio. Although this ratio is logically acceptable, 5mm
implants restored with 10 mm crown have been clinically
successful for more than 10 years.
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BONE SHAPE (CONTOUR):
The shape and contour of the alveolar segment destined to
receive a dental implant can be viewed as favorable if the
static occlusion as well as functional and esthetic demands of
the prosthesis loaded by the implant is designed with axial
loading. However non-axial loading has demonstrated a very
high success rate in the maxillary canine region.
BONE IMPLANT DISTANCE:
The minimum distance as measured from axis to axis between
two 4mm-diameter implants is 7 mm, depending upon the
implant diameter this corresponds to a minimum 3 mm
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distance between implants. However, this 3 mm distance can
be reduced by 0.5 mm in platform switching type implants
without compromising bone integrity. The minimum distance
between an implant and a natural tooth should be about 1.25
mm (ÖHRNELL & al. 1992).
QUANTITATIVE BONE AVAILABILITY:
During all stages of alveolar ridge atrophy the resulting
anatomical shape, representing quality and quantity of the
bone, can alter the treatment plan due to the resorptive
process.
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A classification of alveolar resorption has therefore proven to
be useful during planning case discussions. Each class
demands special implant measures. This is particularly
important when the quantity of the bone is considered in
addition to the severity of resorption.
ATWOOD 1971-79 was the first to describe precisely the
characteristics of the shapes in the edentulous mandible.
Common features of all stages of resorption are:
The progressive loss of height of the alveolar bone
The resulting decreases in the distance
between the alveolar crest and the mandibular
canal
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CLASSIFICATIONS:
A classification presented by LEKHOLM & ZARB 1985
describes the various degrees of atrophy for both the
mandible and the maxilla. Numerous variations are derived
from the combination of resorptive stages and the four bone
qualities (Types I- IV) cited by these authors.
In 1987 MISCH & JUDY provided a classification for the
partially edentulous (Classes I - IV) as well as the completely
edentulous (Class V) jaw.
The basis of their classification is the amount of available
bone for endosteal implantation with regards to the bone
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height, width and length of the bony alveolar ridge. The
system is applicable for cylinder, screw type and blade form
endosteal implants.
For secure anchoring of endosteal implants one requires not
only adequate bone quantity (height, width and shape) but
also density and therefore the bone quality is important.
With increasing age (after 45) osteoporotic alterations occur in
the jaw bones. This is a physiological reduction of the
trabecular density occasioned by the hormonally induced
insufficiency of the osteoblasts.
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Osteoporosis with aging usually takes a more rapid course in
women than in men (BALOGH & al. 1962).
Typical signs include internal resorption resulting in a thinner
cortical plate (centrifugal osteolysis), an increase in the bone
marrow component and a simultaneous loss of osseous
trabeculae.
In most cases the quality of the bone is determined only
during the surgical procedure. An experienced surgeon will
recognize the bone quality as soon as the pilot hole has been
drilled.
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JAFFIN et al. 1991 have reported increased failure rates with
implants placed in Type IV bone quality. DAO et al. 1993,
KÖNDELL et al. 1988 have demonstrated the lack of any
correlation between the patient’s age, sex and subsequent
implant loss. On the other hand the development of
osteoporosis is clearly correlated with patient’s age and sex.
Even if there’s good medical evidence of the existence of
osteoporosis in some other region of the body (e.g. hip), the
same pathologic symptoms may not be presented in the jaw
region (WAKLEY et al. 1988).
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BONE QUALITY - SURGICAL IMPLANT PLACEMENT:
Once the cortical bone is penetrated, drilling of the bony bed
for cylinder implants is performed using reduced rpm and cool
saline with pumping motion. The final implant bed preparation
is carried out in a single stroke with a continuous motion and
out from the same axis. This precludes unfavorable widening
of the implant bed especially in implants with press fit
anchorage.
In Type I bone, care is required to avoid complications such
as:
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implant carrier fracture
bone cracks
distortion of implant-carrier connection
stress concentration in the bone-implant interface
accelerating bone remodeling leading to bone
resorption and eventual loss of implant
narrow type implant fracture.
Any of the above could occur during implant placement
without using the thread cutting tap into the bone with
insufficient osteotomy. In certain systems that do not provide
the thread cutting tap, using the final drill for a longer period of
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time to slightly enlarge the osteotomy site diameter is
required.
In spongy bone (Classes III, IV) self tapping implants therefore
have certain advantages.
MISCH (1990) acknowledged the fact that structural
differences of the bone can influence treatment planning. The
clinical success with each degree of bone quality of his
classification is topographically based and described from the
clinical point of view, with regards to its importance and the
problems it may present in implantology.
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BONE QUALITY - PRIMARY PROSTHETIC LOADING:
Another classification of the various bone qualities was
proposed by LEKHOLM & ZARB (1985) and is used in
combination with the classification of bone resorption also
proposed by these authors. For example:
The situation with resorption Class B and quality
Class 2 would be viewed as a favorable initial
condition
An unfavorable situation is represented by
resorption Classes D-E / qualities 1-4 in the
maxilla or resorption class B / quality 1 in the
mandible.
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Based upon above classification of alveolar bone quality into
classes D1-D4, MISCH recommended “progressive bone
loading” because bone possesses the capacity for functional
adaptation, i.e. bone responds to changes in loading with a
remodeling of internal structure.
From clinical point of view “progressive bone loading” is a
process whereby intervals of time are inserted intentionally
between the individual prosthodontic treatment steps.
One of the possibilities in order to respect this “progressive
bone loading” is the use of temporary prosthesis allowing the
bone adaptation and maturation to occur during occlusal
vertical loading. Because we are not sure when the
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osteointegration is ready to receive shear stresses avoid
tightening the abutment screw to 30N at earlier period of
healing in 6 weeks.
This protocol is recommended:
As soon as the patient feels pain during the abutment screw
tightening, set the hand wrench to 15 Ncm first and gradually
increase the torque to the manufacturer’s recommendation by
observing the patients facial expression. This can save the
practitioner an implant failure at the last steps of restoration.
The shear load issue during prosthetic phase does not apply
to one-piece implant systems.
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COMPLEXITY BASED CLASSIFICATION - IMPLANT
POSITION IN THE MOUTH
A classification presented in 2000 by the Implant Dentistry
Study Consortium describes a complexity based classification
which will provide the dentist with treatment options other than
existing anatomical limitations and categorizes the diagnostic
tools required during procedure.
-Numeric part, clarifies the complexity of the case:
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Level I: Dental implant in the maxillary premolar area or
mandibular anterior inter-foramina region. This level is the
safest category due to absent of vital structures and good
accessibility. It requires the least time to complete the
procedure (7-30 minutes/implant). Auxiliary procedures
commonly not needed (e.g. grafting and splitting), post
operative recovery is fast (3 days) and it’s highly Successful
(97%)
Minimum radiography required before and during procedure
(IOPA, OPG), length of the implant is not an issue; CT scan &
Tomography generally won’t be used. Sever concavities are
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generally not observed. Immediate loading and flapless
procedures are very common.
Level II: Dental implant in the mandibular posterior area
(premolar & Molar). Due to the vital structures such as Inferior
alveolar nerve, sub lingual depression, mental foramen rise
and loop this level will be less safe and requires more time to
complete the procedure compare to level I. CT scan or
Tomography generally required. Increased pain sensation
post operatively can be expected. Bone splitting commonly
performed. Length of implant is limited and angulation of
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implant during placement could be slightly altered by the
Shape of bone.
Level III: Dental implant in the maxillary anterior area. Esthetic
zone dictates soft and hard tissue augmentation, angulation
correction, soft tissue management, temporization and skilled
laboratory technician. Vital structures to be considered in this
level are Incisive canal and Floor of the nose. Time require to
complete this level is more compare to previous levels due to
the additional restoration procedure and surgical template is
mandatory. CT scan or Tomography generally required in this
stage. There will be more pain and swelling sensation post
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operatively compares to level I and II. Bone spreading and
less splitting is commonly performed. Esthetic success is
always a challenge and esthetic prognosis after 5 years is the
worst of all levels. Length of implant is limited due to the labial
concavity. Angulation of implant is commonly dictated by the
Shape of the bone. Implant position is the most accurately
demanding and soft tissue maturation is an issue.
Level IV: Dental implant in the maxillary molar area. Vital
structures to be considered are maxillary Sinus and its artery
supply. Due to the D4 bone quality of the area increases, post
operative healing time should be expected. Sinus complication
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such as perforation and infection can increase the risk. It’s the
least successful level amongst the all and requires more time
to complete the surgical procedure compare to level I, II, and
III; due to the least accessibility, bone and membrane has to
be available, PRP can be useful, augmentation is the
maximum in quantity, more equipment to be used and
repeated radiographs to be taken during surgery is common.
Surgical dexterity and patience is required. CT scan or
Tomography generally to be taken. Maximum pain and
swelling post operatively. Bone spreading is commonly
performed, functionally and biomechanically demanding and
nasal drops are generally required. Prognosis after 8 years is
the worst of all levels. Length of implant is limited due to the
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sinus floor, angulation of implant placement could partially be
dictated the previously resorbed buccal bone. Angulating the
implant to avoid the sinus is commonly done in which cases
prosthetic challenges emerge. Implant placement in relation to
the sinus membraneis so delicate and common cold or
sinusitis could delay the procedure.
-Alphabetic part, categorizes the equipment and material
require during surgery:
B: Bone block; when any bone Block is added to the surgery,
anywhere in the mouth, the letter B is added to the
Classification.
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b: Bone particles and membrane
S: Open sinus lift; when a lateral window open sinus lift is
added to the surgery the letter S is added to the Classification.
s: Internal sinus lift
M: Mixed; Multiple implants in different areas of the mouth with
various levels
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Chapter 6
Osseointegration of dental implant
135
OOSSSSEEOOIINNTTEEGGRRAATTIIOONN OOFF DDEENNTTAALL IIMMPPLLAANNTTSS
Osseointegration clearly belongs to the category of direct or
primary healing. Originally it was defined as ‘direct bone
deposition on the implant surface’ (BRÅNEMARK et al.
1997) a fact also called ‘functional ankylosis’ (SCHROËDER
et al. 1981).
Osseointegration is also characterized as ‘direct structural and
functional connection between ordered living bone and the
surface of a load bearing implant’ (LISTGARTEN et al. 1991).
A fundamental difference exists between osseointergration
and direct fracture healing; osseointegration can be compared
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with direct fracture healing in which the fragment ends
become united by bone without intermediate fibrous tissue or
fibrocartilage formation, whereas, osseointegration unites not
to bone but to an implant surface, a foreign material. Thus
the material plays a decisive role for the achievement of the
union.
Orthopedic joint replacement and dental implants share many
common features such as material surface configuration and
measures for primary stabilization. Dental implants face the
main complication by piercing the mucosa thereby evoking the
risk of infection. In joint replacement the articulating surfaces
137
are subjected to wear and the resulting particles may cause
foreign body reactions and possibly aseptic loosening. The
tissue response to both categories of implants is modified by
the structure of the surrounding bone. The bulky components
of artificial joints are mainly supported by cancellous bone and
the initial contact with cortical bone is marginal. In contrast,
the jaw bone and the coronal part of the dental implants
become firmly anchored within compact bone whereas the
apical segment is exposed to cancellous bone and bone
marrow.
These local differences influence profoundly by the
histological aspects of osseointegration in all stages. The most
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pragmatic way of understanding and testing the degree of
osseointegration is to relate it to mobility, the more mobility the
less the osseointegration.
THE BONE IMPLANT INTERFACE:
The space between an implant and its osseous bed should be
narrow in that case bone formation is comparable to primary
healing after bone fracture since no callus forms. Direct
bridging via lamellar bone occurs at a rate of 1 µm/day.
Healing of implants with a wide space around them is
comparable to a secondary healing of a bone fracture as the
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bone formation occurs via formation of a fibrous and bony
callus at about 50-100 µm/day.
The temporal sequence is woven bone with subsequent
remodeling into lamellar bone. New bone formation can occur
directly in the vicinity of the implant depending upon the
degree of its stability. Bone grows only upon solid
foundation. Implant stability influences cell differentiation and
therefore also bone formation.
Experiments have demonstrated:
A positive correlation between the degrees of initial
implant mobility
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The development of cartilage or connective tissue in
the peri-implant space
The absolute requirements for all types of bone growth are
therefore:
Mechanical stability
Adequate blood supply
Once activated osseointegration follows a common
biologically determined program that is subdivided into
3 stages:
Incorporation by woven bone formation
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Adaptation of bone mass to load (lamellar and parallel-
fibered bone deposition)
Adaptation of bone structure to load (bone
remodeling)
INCORPORATION BY WOVEN BONE FORMATION:
The first bone tissue formed is woven bone. It is often
considered as a primitive type of bone tissue and
characterized by a random felt-like orientation of its collagen
fibrils, numerous irregularly shaped osteocytes and at the
beginning a relatively low mineral density.
142
Woven bone is the ideal filling material for open spaces and
for the construction of the first bony bridges between the bony
walls and the implant surface.
It usually starts growing from the surrounding bone towards
the implant except in narrow gaps where it is deposited
simultaneously upon the implant surface. Woven bone
formation dominates the scene of the first 4 to 6 weeks after
surgery.
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ADAPTATION OF BONE MASS TO LOAD:
(Deposition of lamellar and parallel-fibered bone)
Starting in the second month the microscopic structure of
newly formed bone changes either towards lamellar bone or a
modification called parallel-fibered bone.
Lamellar bone is the most elaborate type of bone tissue
packing of the collagen fibrils into parallel layers
with alternative course (comparable to plywood) gives it the
highest strength. Parallel-fibered bone is an intermediate
between woven and lamellar bone. The collagen fibrils run
144
parallel to the surface but without a preferential orientation in
that plane.
Another important difference is found in the linear apposition
rate:
For human lamellar bone this amount is only 1-1.5µm
/ day
For human parallel-fibered bone it is 3 times larger
As far as the growth pattern is considered, both types cannot
form a scaffold like woven bone but merely grow by apposition
on a preformed solid base.
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Considering above fact, 3 surfaces are qualified as a solid
base for deposition of parallel-fibered and lamellar bone:
Woven bone formed in the first period of
osseointegration
Pre-existing or pristine bone surface
The implant surface
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ADAPTATION OF BONE STRUCTURE TO LOAD:
(Bone remodeling)
Bone remodeling characterizes the last stage of
osseointegration. It starts around the third month and after
several weeks it will increase to the highest activity then slows
down again throughout life.
In cortical as well as in cancellous bone remodeling occurs in
discrete units often called a bone multicellular unit (FROST
1963-66). Remodeling starts with osteoclastic resorption
followed by lamellar bone deposition. Resorption and
apposition are coupled in space and time.
147
Cyclical load stimulates cortical remodeling. Functional
adaptation of cancellous bone however is based on shape-
deforming, uncoupled or unbalanced resorption and formation.
Its control and regulations are still an unsolved problem.
Remodeling in the third stage of osseointegration contributes
to an adaptation of bone structure to load in two ways:
It improves bone quality by replacing pre-
existing necrotic bone and/or initially formed
more primitive woven bone with mature viable
lamellar bone.
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It leads to a functional adaptation of the bone
structure to load by changing the dimension
and orientation of the supporting elements.
It has been mentioned previously that bone remodeling
continues throughout life and thus becomes important for the
longevity of implants.
Continuous replacement from old bone to a new bone
prevents accumulation of micro damage and fatigue as one
possible cause of aseptic implant loosening.
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THE INTERFACE BETWEEN THE MUCOSA AND THE
IMPLANT:
The mucosa that surrounds a dental implant is different from
the gingiva and the bone tissue that enables osseointegration;
it hardly contains any periodontal structure.
The characteristics of the transmucosal passage junctional
epithelium and connective tissue attachment of the implant are
established when healing of the ridge mucosa following
implant surgery is in progress.
In this context the essential role of epithelium in wound
healing is to cover any connective tissue surface that is
150
severed such as during surgery. Thus the epithelial cells at the
periphery of the mucosal wound produced at implant
installation are coded to divide and migrate across the injured
part until epithelial continuity is restored.
The epithelial cells also have the ability to stick to the implant
surfaces, synthesize basal lamina as well as
hemidesmosomes and establish an epithelial barrier that has
features in common with a junctional epithelium.
Equally important is the capacity of a normal, uninflamed
connective tissue to form an attachment to the titanium
surface below the epithelium and in a more superficial location
to support the junctional epithelium.
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The maintenance of normal connective tissue is critical
importance for normal turnover of the epithelial and connective
tissue in attachments to the titanium implant.
152
STRUCTURE OF GINGIVA AND PERI-IMPLANT MUCOSA:
One study of VAN DRIE et al. 1991 using the beagle dog
model observed that the junctional epithelium following
abutment connection never reached the bone crest but
consistently terminated about 1 mm above the bone.
The findings from the studies (BERGLUNDH et al. 1991, VAN
DRIE et al. 1991) referred to indicate that:
During wound healing an interaction occurs between
titanium dioxide on the implant surface and the apical
part of the supra alveolar connective tissue
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This zone of interaction is not recognized as a
wound. Consequently once the interaction is
established there is no further epithelial
migration.
THE INTERFACE:
As per HANSON et al. 1983:
The lining epithelium facing the implant surface
harbored hemidesmosomes (like an epithelium tooth
interface)
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Concerning the connective tissue interface cells
(fibroblasts and macrophages) and collagen fiber
bundles were consistently separated from the
titanium oxide by a 20 µm wide proteoglycan layer.
As per LISTGARTEN et al. 1992:
Light and electron microscopic analysis of demineralized and
undemineralized sections revealed that the intact connective
tissue implant interface of the peri-implant mucosa was
characterized by collagen fibers aligned in a direction more or
less parallel to the implant surface.
BERGLUNDH et al. 1994:
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Reported that no vascular plexus existed close to the implant
that could compensate for the lack of a periodontal ligament
plexus.
Also reported that the gingiva around teeth and the mucosa
around implants (made of commercially pure titanium) have
some characteristics in common but differ in:
The composition of the connective tissue
The alignment of the collagen fiber bundle
The distribution of vascular structures in the
compartment apical of the junctional
epithelium
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BIOLOGICAL DIMENSION:
A study by BERGLUNDH & LINDHE 1996 using the beagle
dog model observed that:
The clinically healthy peri-implant mucosa was
attached to the implant surface through a 2 mm long
junctional epithelium and a zone of connective tissue
that was about 1 mm high.
At the sites were the mucosa-implant-attachment
prior to abutment connection was made short (2 mm),
wound healing consistently resulted in bone
resorption to establish a mucosa-implant- attachment
and it was about 3 mm high.
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BREAK-UP OF THE MUCOSAL ATTACHMENT:
The mucosal attachment that followed implant installation is
established to the titanium or ceramic abutment surface is
severed if the abutment is removed.
The problem that arises from repeated abutment shift or
change was studied in a dog experiment by ABRAHAMSSON
et al. 1997:
If the original attachment is severed a de novo wound healing
process is initiated.
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In this wound healing there is an additional epithelial
migration that involves the zone previously occupied by the
connective tissue portion of the attachment in order to allow
for a new connective tissue attachment of genetically
determined dimension. This process could lead to marginal
bone resorption.
FUNCTION OF GINGIVA AND PERI-IMPLANT MUCOSA:
LILJENBERG et al. 1997 using BRÅNEMARK ® system,
studied the characteristics of the ridge mucosa before/after
implant installation and 6 months after abutment connection
demonstrated that:
159
The ridge mucosa as well as the peri-implant mucosa
harbors a well keratinized oral epithelium and a
connective tissue composition which is similar in
terms of collagen cells and vascular structures.
The peri-implant mucosa also included a junctional
epithelium which allowed the penetration of products
from the oral cavity.
As a result of this penetration of bacterial products,
the healthy peri-implant mucosa housed also a small
inflammatory cell infiltrate lateral to the junctional
epithelium.
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TONETTI et al. 1985 concluded that:
Healthy keratinized mucosa around osseointegrated
dental implants shares functional similarities with a
normal gingiva.
The local immune response in the peri-implant
mucosa is an important prerequisite for long term
clinical success of osseointegrated implants.
ADONOGIANAKI et al. 1995, suggested that:
The inflammatory and immune events are similar in
the peri-implant mucosa and gingiva.
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The production of peri-implant crevicular fluid and
gingival crevicular fluid is governed by similar
mechanisms.
PROBING GINGIVA AND PERI-IMPLANT MUCOSA:
It has been demonstrated that the tip of a periodontal probe in
a pocket depth measurement at a tooth site fails to reach the
apical cells of the junctional epithelium and the gingiva
becomes compressed in apical direction.
On the implant site however the probe passes beyond the
apical cells of the junctional epithelium, also the peri-implant
mucosa during probing is displaced mainly in the lateral
direction rather than apical.
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If we compare the findings of two studies (ERICSSON &
LINDHE 1993, LANG et al. 1994) it becomes apparent that:
In comparison to tooth sites, probing depth and
probing attachment level, meaningful measurements
at implant sites can be obtained only if the force light
is about 0.2 N.
If a higher probing force is utilized, the attachment
between the mucosa and the implant surface may be
compromised, the mucosa dislocated in lateral-apical
direction and the probe tip allowed ending close to
the bone level.
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In this context it should be realized that the probing
force most commonly used by different professional
groups as high as 0.44 N (FREED et al. 1983).
PREREQUISITES FOR OSSEOINTEGRATION
- A precise fitting (anatomical reduction),
- A primary stability (stable fixation),
- An adequate loading during the healing period
- A bioinert or bioactive material
164
- A surface configuration that is attractive for bone
deposition (osteophilic).
Albrektsson et al. presented information on a series of
background factors that needed control for a reliable
osseointegration of an implant to work. These factors
involved:
- Biocompatibility (metals),
- Implant design,
- Surface conditions of the implant,
165
- Status of the host bed,
- Surgical technique at insertion,
- loading conditions applied afterwards;
166
Chapter 7
Surgery
Preparing the operating site Bone grafting
167
Pre-prosthetic surgery is an important part of implant dentistry
concerning patients with severely atrophic maxillary or
mandibular alveolar bone. Techniques to increase the
alveolar portion of the jaws are various, including:
Use of bone grafts
Autogenous bone from the rib or iliac have been used in the
past to increase alveolar ridge height and width, these are not
used widely today because clinical results show that the graft
resorbes within 1-3 years after placement.
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Use of Particulate Ceramic Bone Grafts ( Alloplast )
Attempts to restore ridge height and width were also made
using non-living bone substitute such as hydroxyapatite (HA).
After placement of these grafts, it was seen that fibrous tissue
surrounded these particles, so that the mass was subject to
macro and micro movements, hence not proving to be a good
support for the implant, and also causing discomfort,
dysesthesia and paraesthesia.
Use of Particulate Ceramic Bone Grafts together with
Autogenous Cancellous bone
This method was seen to be quite successful clinically as
compared to particulate ceramic implants alone, as it
169
produced a more lamellated bone structure at the ridge site.
Such lamellated or cortical bone structure resists resorption.
Use of xenografts
Als the use of a porous xenogenic bone graft, obtained from a
bovine source has been successful. Some resorption of the
material does take place, but this is a chronic process that is
taking place over years. During this time, as the graft
material resorbs, there is a favorable remodeling and bone
rebuilding response, thus the alveolar ridge is maintained.
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Use of Endosteal Implants (Immediate Placement)
A very recently introduced method, placing endosteal implants
into recent bone defects aims to preserve the remaining bone
and ridge. This application of endosteal implants has led
to studies and discussions of osseous repair and the response
of host bone to the insertion of titanium metal implants as a
graft material.
All bone augmentation materials act on bone via one of
three mechanisms:
1. Osteoconduction
2. Osteoinduction
3. Osteogenesis
171
Osteoconduction
Osteoconduction takes place in the presence of bone or
differentiated mesenchymal cells, as it is the growth of bone
by apposition, from and on existing bone. All osteoconducive
materials are biocompatible. An example of this would be the
healing of bone around an osteointegrated implant.
Osteoinduction
Osteoinductive materials induce the transformation of
undifferentiated cells into osteoblasts or chondroblasts, and
are contributory to bone formation during the remodeling
172
process. The most common example of an osteoinductive
material would be a bone allograft.
Osteogenesis
Osteogenic graft materials are composed of living bone cells,
and so are capable of forming bone even in the absence of
mesenchymal cells. At present, the only osteogenic material
available is autogenous bone, however collecting stem cells
aspirate from the patient’s hip is also practiced today.
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Dental Implants and esthetic demands vs. possible
solutions - Golden proportion
An organized and systematic approach is required to evaluate,
diagnose and resolve esthetic problems predictably. Our
ultimate goal as clinicians is to achieve a pleasing composition
in the smile to create an arrangement of the various esthetic
elements to proper proportion or relation according to known
principles. Any clinical case will be demonstrating different
factors of esthetic composition which can be simply and
effectively applied to the smile of that particular case. The
serve principles to assist the clinician in determining adequate
174
tooth display, tooth size, tooth arrangement, and orientation to
the face during esthetic diagnosis and treatment.
The “golden” or “divine proportion” concept in the arch and
tooth evaluation states that: for objects to be in esthetic
harmony, they should exist in the ratio of 0.618 to 1. In
dentistry, certain groups of teeth are theoretically
proportionate to each other in this ratio.
In calculating the most esthetic arrangement of the maxillary
arch from the labial approach, it is essential to understand that
the golden proportion is in two dimensions rather than three.
When you include this simple mathematical equation in your
practice, you make it easier to diagnose various esthetic
problems and arrive at the best solution. Mathematical formula
175
of the golden proportion is: S/L=L/S+L=2/1+√5=0.618.
However, many more formulas have to be considered for each
case scenario.
Preparing the operating room
Getting the OR ready for the surgery refers to many different
topics, such as:
Environmental control
Setting up the sterile field
Opening sterile supplies
Surgical team scrubbing
Preparing the patient for the surgery
176
The topics of asepsis and aseptic practices are paid special
attention to in this chapter as they have a greatest direct
impact upon the surgical team in helping to reduce patient risk
to surgical site infection. The principles of surgical asepsis,
which have been developed by the Association of Peri-
Operative Registered Nurses, will be discussed. All of them
are based on scientific facts and should be used as guidelines
to provide information and directions which can serve as the
basis of developing policies to be followed in a practice
setting.
Environmental control in the OR is usually taken for granted,
although OR requires meticulous housekeeping to prevent
cross-contamination. Cross contamination is the transmission
of microorganisms between patients, healthcare workers and
patients, and between inanimate objects and patients. Traffic
177
patterns, air exchange and ventilation system, temperature
and humidity control, and cleaning are all the environmental
controls which we have to keep in mind.
OR traffic patterns depend on the surgical suite design and
ideally traffic flow should move from entrance (clean area) to
exit (dirty area). The surgical suite can be divided into:
1. Unrestricted area, where street clothes are acceptable and
traffic is not limited:
Entrance
Exit
Patient holding area
Supply receiving area
Offices
178
Locker rooms
2. Restricted area, where surgical attire and hair covers are
required: (Masks should be worn when sterile supplies are
open or scrubbed personnel are present)
OR is usually located in the part of the hospital which
is free from
contaminated particles, dust, noise, and radiation.
Sterilizing area
Scrub sinks
According to the Centres for Disease Control and Prevention
(CDC), the microbial level in the OR is directly proportional to
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the number of people moving about. So traffic in this area is
limited to authorised personnel only.
3. Semi-restricted area, where surgical attire is required, and
traffic is limited to authorised personnel and patients:
Access corridors to OR
Sub sterile areas
Air exchange and ventilation system
There should be a minimum of 15 completely filtered air
changes per hour with 3 fresh air changes. Air should enter
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the OR at the ceiling level and exhaust near the floor level. Air
in the OR should be maintained at a positive pressure with
respect to adjacent areas so it will force air out into the
hallway, preventing contaminated air entering the OR. The
doors to the OR should always remain closed.
A standard air filtration system comprises of two filters: first
one with the efficiency of more or equal to 30% and second
one, more or equal to 90%. Filters should be checked and
cleaned (changed) routinely.
Temperature and humidity
The ideal temperature is 22-24 degrees Celsius with humidity
50-55% (to inhibit bacterial growth which occurs at 37 degrees
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Celsius and humidity over 60%). The temperature can be
slightly increased for paediatric patients.
Cleaning
It is done before, during and at the end of the operating day.
Before the surgery, damp dusting of all horizontal surfaces is
done using disinfectants. This reduces viable microbial
contamination from air and other sources by 90-99%.
Disinfection
Is a process that is less lethal than sterilization. It eliminates
virtually all recognizable micro-organisms, but not necessarily
all microbial forms. It is a method of preventing cross-
contamination when sterilization is not possible.
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There are three levels of disinfection:
1. High level: kills some, but not necessarily all bacterial
spores; it is tuberculocidal, and sometimes sporicidal.
2. Intermediate level: kills Mycobacterium tuberculosis,
hepatitis B virus, and HIV, it may not be capable of
killing the bacterial spores.
3. Low level: kills most bacteria, some fungi, and some
viruses, it does not kill M. tuberculosis or bacterial
spores.
A disinfectant is acceptable for dentistry if the solution is
registered with the Environmental Protection Agency (EPA) or
approved by ADA. Disinfectants must be used according to
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the manufacturer’s instructions with regards to the personnel
protection, mixing, dilution, method and duration
of application, reuse, and shelf life.
At the end of each procedure, wet vacuuming is advisable (if
wet mopping is done, the mop head and solution should be
disposed of).
And at the end of the day, the furniture should be moved;
horizontal surfaces cleaned; walls, lights, doors spot cleaned
and floors wet vacuumed.
Ceilings, walls, ventilation grills, sterilizers are cleaned on
weekly basis.
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Cleaning equipment should be disassembled and disinfected
routinely.
Surgical instruments after the surgery should be:
1. Rinsed under running water to remove most blood,
bodily fluids and tissue.
2. Soaked in the water with enzymatic detergent added
for 10 min. to prevent organic matter from sticking to
the instruments.
3. Rinsed under running water.
185
4. Disinfected with EPA approved disinfectant for
appropriate period of time for safe handling by the
personnel.
5. Rinsed again.
6. Cleaned: placed into the special sink under the water
to which neutral pH (7) enzymatic detergent can be
added and brushed with a brush (not wire or steel
wool as it will damage the instruments) under the
surface of the water. Instruments should be
disassembled and thorough brushing should be done
of any teeth, grooves, and hinges. It is preferable to
clean the instruments in the ultrasonic cleaner.
7. Rinsed under running water (Pay attention to clean
the joints properly).
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8. Air or towel dried, inspected and arranged either in
the cassettes or packed individually.
Instrument processing is potentially hazardous and wearing a
mask, protective eyewear, rubber utility gloves, and gown is
necessary.
Scrubbed persons function within the sterile field:
All the members of the surgical team wear scrub attire which
usually consists of pants, suit, mask, head cover and shoes
with shoe canvas. Scrubbed personnel work directly in the
surgical field, non-scrubbed personnel work in the periphery.
Masks are worn at all times in the OR to minimize the airborne
contamination. They should be tight fitting and cover the
187
mouth and nose completely. Laughing, sneezing, coughing
and unnecessary talking should be avoided because they
deposit additional organisms on to the mask. Masks are
changed at minimum in between patients, or hourly, as they
loose their filtration ability with time. They should be either on
or off (they must not be allowed to hang around the neck).
During removal, only the strings are handled to prevent
contamination of the hands.
Head covers should completely cover the hair so that single
hair strands, pins, clips, particles of dandruff and dust do not
fall on the sterile field, OR attire should be changed when wet
or soiled.
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All the members of the surgical team should be in good
health: colds, sore throats, skin lesions must be excluded as
these are the sources of pathogenic microorganisms.
Jewellery, makeup and nail polish are not allowed in the OR
and nails should be cut short.
Scrubbed personnel should prepare themselves in the
following manner:
1. Make sure you have the shoe covers on or use slippers
dedicated for the OR.
2. Put on the head cover.
3. Put on the mask and pinch it over the nose for tight fitting.
4. Open the provided sponge and place within reach.
189
5. Check the water temperature.
6. Wash hands and follow the initial washing using antiseptic
soap.
7. Remove the stick from the sponge package and clean
under the nails under running water.
8 .By using the sponge apply the scrub generously and start
by scrubbing the nails with the brush side (20 strokes).
9. When scrubbing the fingers always start with the thumb.
Imagine that each finger has three sides, use 5 strokes for
each side and be certain to scrub between the fingers.
10. Proceed to your hands and palms (20 strokes).
11. Finish with your forearms to the level 2 inches above the
elbows.
190
12. Rinse with water and be sure that the level of your fingers
is always higher than the elbows.
13. Dry with a sterile towel then scrub with a skin antiseptic
solution for a minimum 3 minutes and dry with a sterile towel
again starting with the fingers, palms, then forearms. From this
time onward, the hands are sterile and should not touch any
unsterile object. Then scrubbed personnel should put on the
sterile surgical gown and gloves. The scrub nurse will do hers
by herself, but the surgeon will be assisted by the nurses. The
scrub nurse extends the gown in front of the surgeon; he/she
will put his/her hands through the sleeves and the gown will be
tightened at the back by a circulating nurse. Then the
scrubbed nurse will extend the gloves, first right then left, the
surgeon will put his hands in, and the gloves will be pulled up
over the cuffs. Surgical gown sterility after dawning is limited
191
to the gown front, from chest to sterile field level and the
sleeves from 2 inches above the elbow to the cuff.
Wearing gloves does not diminish the importance of cleaning
hands because statistically one quarter of the gloves are
perforated during the surgery. Considering the risk of HIV and
hepatitis double gloving is becoming a routine, at least in
trauma surgery, where sharp bone fragments are present.
Goggles are worn when the surgical wound is irrigated or
bone drilling is performed.
Sterile drapes are used to create a sterile field:
Only the scrubbed personnel should handle sterile drapes.
They should be placed on the patient, furniture and equipment
192
included in the sterile field except the incisional site. The
incision site should be draped from the centre to periphery.
Once positioned, drapes should not be moved. Only the
surface of the draped area is considered sterile. Wet or
punctured drapes should be replaced.
All items used within the sterile field must be sterile:
All sterile items should be inspected for package integrity and
sterilization process indicators (indicator tape or biological
indicators). Sterilization is the process which kills or destroys
all types and forms of microorganisms, including viruses,
bacteria, fungi, and spores. Four methods of sterilization are
generally accepted in dentistry.
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1. Autoclaving under 121 C at 15 psi for 20 min. depending
on the type of the autoclave.
2. Chemical (vapour) sterilization (heat, water, chemical
agent) under 132 C at 30 psi for 20 min.
3. Dry heat sterilization under 160 C for 2 hours.
4. Glutaraldehyde solutions: immersion of instruments in fresh
2% solution for 1 hour, reimmersion in fresh 2% solution for 3
hours, rinsing with sterile water and drying aseptically.
Ethylene oxide gas, UV light, microwave, and other forms of
radiation are effective but have limited use in dentistry.
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Maximum storage time of the sealed instrument is considered
one month. All sterile items should be inspected for package
integrity and sterilisation process indicators before opening.
Fluid and air can contaminate a packed sterile object if it
becomes wet or is dropped on the floor.
All items introduced into a sterile field should be opened,
dispensed and transferred by methods that maintain sterility
and integrity. A nonsterile person presents the sterile item
directly to the scrubbed personnel or places it securely on the
sterile field.
When opening wrapped supplies, the nonsterile person should
open the top wrapper flap away first, then the sides and the
195
last wrapper flap towards herself (so she will not reach over
the sterile item) then secure the flaps to prevent them from
flipping and contaminating the contents. The inside of the
wrapper and its contents are considered sterile with the
exception of the 1 inch outer edge of the wrapper.
When opening the peeled package, the nonsterile person
opens the package by rolling the wrapper over his hands and
presenting the contents to the scrubbed personnel. The inner
edge of the heat seal is considered as the line between the
sterile and nonsterile.
For solutions, only the top rim of the bottle and its contents are
considered sterile. The container is held by the scrubbed
196
personnel or placed at the edge of the sterile table covered
with waterproof drape. For non-alcohol and nonantiseptic
solutions, some of the contents should be poured out first to
wash the edge of the bottle, and then the contents are poured
slowly in the sterile container in a cautious manner to prevent
splashing. The remaining fluid and the bottle should be
discarded.
Instruments are laid out with their handles pointing out
towards the operator in order that they will be used. The
instruments should not be wet.
Any equipment entering from outside to the OR must be damp
dusted with germicidal solutions.
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Sterile fields should be maintained and monitored
constantly:
If there is any doubt about the item’s sterility, consider it is
nonsterile.
Sterile fields should be prepared as close as possible to the
time of use. If there is a delay in starting the surgery the table
should be covered with a sterile drape. Usually the operating
trolley is considered sterile for 6 hours.
All personnel moving within or around a sterile field
should act in a manner to maintain the sterile field:
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Scrubbed personnel should move only within sterile areas.
They should maintain a safe distance from each other and
always pass each other turning either face- to- face or back-
to- back.
Scrubbed personnel should remain in the same position
during the surgery. If you started the surgery sitting, then
continue and finish it in a sitting position; if it was started
standing then it should be continued standing. Arms and
hands should be kept within the sterile field. A safe distance
(30cm) must be maintained when approaching nonsterile
personnel or equipment.
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Nonsterile personnel should remain in nonsterile areas and
contact only nonsterile objects. They should always face the
sterile field on approach and never walk between two sterile
fields.
Patient preparation:
The patient undergoing an implant surgery is prepared in a
manner similar to other patients undergoing any form of
surgery. The surgical team has to prepare for surgery in
aseptic conditions. This includes surgical scrubbing for the
200
doctor and assistant, an intra-oral and extra-oral scrub of the
patient with Betadine or Chlorhexidine, followed by gowning
and draping. Even a healthy mouth is contaminated with
microorganisms of many types. Fortunately oral tissues have
the ability to cope successfully with autogenous infections, but
they are more vulnerable to the microorganisms introduced
from outside. It is quite impossible to render the mouth sterile
although the number of microorganisms can be reduced
considerably by attention to oral hygiene and scaling the teeth
a week or two prior to the surgery.
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The patient should be dressed in the OR attire before entering
the operatory. Face should be washed with soap, mouth
rinsed with the solution of 0.5% chlorhexidine gluconate in
70% alcohol. Shaving is not recommended; hair trimming
should be used instead. The area around the mouth should
be scrubbed with skin disinfectant, and proper draping should
be done.
Finally, according to the ADA Council on Dental Therapeutics,
using aseptic techniques will:
1. Reduce the number of pathogenic microbes to the
level where normal body resistance mechanism can
prevent infection
202
2. Eliminate cross-contamination.
3. Protect the patient and personnel from infection.
4. Protect all dental personnel from the threat of malpractice.
203
Chapter 8
Dental implant Armamentarium
204
Implant Surgery Armamentarium
TOPICAL ANESTHESIA
STERILE COTTON BUDS
SUTURE 03 and 04 SILK & VICRYL
NEEDLE HOLDER
SCISSORS
PERIOSTEAL ELEVATOR
TWO STERILE TOWELS
STERILE SHEET FOR TABLE
SALINE (2) PER PATIENT
SYRINGES 20 ML. (4)
205
CHLORHEXIDINE
SALINE CUPS (2)
BLADE no. 15, 12, 11
BLADE HOLDER
DENTAL SYRINGE
ANESTHESIA 2% and 4% CARPULE
DIAZEPAM TABLETS, BRUFEN TABLETS
3EMPTY STAINLESS STILL CUPS
(CHLORHEXEDINE, SALINE, ALCOHOL)
KIDNEY TRAY
SURGICAL MOTOR + HANDPIECE
HEAD COVER
206
STERILE GLOVES
ICE PACK
SURGICAL SUCTION
CHEEK RETRACTORS FOR PHOTOGRAGHY
RETRACTORS FOR SURGERY
SINUS LIFT INSTRUMENTS(4)
DISH FOR BONE COLLECTION
STERILE GOWNS
BASIN TO SCRUB
CORSODYL OR ANY CHLORHEXEDINE MOUTH
WASH FOR PATIENT AFTER SURGERY
GAUZE
207
CURETTES FOR EXTRACTION SOCKETS
STRAIGHT HANDPIECE
BURS
ALGINATE IMPRESSION
STUDY CASTS FOR ALL PATIENTS
I.V. TUBE FOR SALINE TO CONNECT TO THE
MICRO MOTOR
PATIENT’S DIGITAL X-RAY FILM
DEMONSTRATED ON A X3 MONITOR
INTRAORAL DIGITAL X-RAY MACHINE
PANAROMIC DIGITAL X-RAY MACHINE
208
Chapter 9
Guided bone regeneration
209
Guided Bone Regeneration
Guided bone regeneration (GBR) describes the use of
membranes to direct bone growth to fill boney defects. This
concept was derived from guided tissue regeneration (GTR),
which was first described by KARRING, LINDHE, NYMAN and
others in periodontology. In implantology, however, GBR
better describes the therapeutic goal of membrane application
(BUSER et al., 1993). When applied in combination with
endosteal dental implants, the GBR technique can be used
with either primary or secondary osseous defects.
- Primary usage in case of inadequate bone availability:
210
Two step procedure:
o Initially GBR membranes are employed to
create sufficient bone availability for
implantation. The implants are then placed
in the newly formed bone during the second
surgical procedure after the healing period
of 3-6 months.
One step procedure:
o GBR membranes are used to augment peri-
implant bone during the healing phase.
Membranes and implants are placed during
one surgical appointment.
211
-Secondary usage in case of inadequate bone availability:
GBR membranes are used in the treatment of
peri-implantitis to induce re-ossification (re-
osseointegration) of peri-implant boney defects.
The concept of GTR was developed from studies on wound
healing following periodontal surgical procedures. The initial
studies were based on the assumption that during the
periodontal healing process the various cell types in the
vicinity of the wound would exhibit various rates of migration
into the area. Relatively GTR & GBR procedures are
performed due to the fact that cell types, such as epithelial
212
cells and connective tissue cells, show an elevated
proliferation rate in comparison with the cells that form
cementum, periodontal ligament, or bone.
The introduction of special membranes between bone and
overlying soft tissues prevents the invasion of undesired
epithelial cells and fibroblasts into the wound area thus
enhancing colonization of the periodontal defect with cells
capable of forming the desired new tissues (periodontal
ligament, bone). Even in situations involving advanced bone
loss this mode of therapy permits the formation of new
attachments to the tooth, including new cementum, new
213
connective tissue fibers and new bone (GOTTLOW et al.,
1986; NYMAN et al., 1982; KARRING et al., 1986;
PONTORIERO et al., 1988).
GTR has been successfully employed clinically and in
experimental animal studies in implantology. The goal, using
membranes, has been to prevent the immigration of epithelial
and connective tissue cells into primary or secondary osseous
peri-implant defects while simultaneously permitting re-
ossification of the peri-implant area by the more slowly
immigrating bone-forming cells. In recent years, the GBR
technique has been used with extremely encouraging results
214
also in human clinical trials (DAHLIN & al., 1990; SEIFERT &
al., 1990; BECKER & al., 1990; BUSER & al., 1990;
JOVANOVIC & al., 1992-93).
Existing bone is the origin for the cells capable of forming new
bone. The oxygen and nutrition requirements of the cells are
supplied by the blood vessels from the adjacent bone marrow
penetrating the coagulum present in the osseous defect. The
coagulum functions as an osteoconductive matrix wherein pre-
osteoblast cells can differentiate to become osteoblasts,
permitting normal osteogenesis to proceed.
Controlled experiments have exhibited only minimal osseous
regeneration when defects were treated without membranes.
215
Furthermore, clinical studies have demonstrated that the rate
of resorption of newly formed bone after membrane removal is
somewhat elevated during the first year, but afterwards
remains stable (DAHLIN & al., 1991; JOVANOVIC & al.,
1992).
Recommended steps for clinical application of GBR in
implantology:
Use paracrestal incision to assure complete soft
tissue coverage.
216
Remove all soft tissue residues from the bone
surface.
Confirm that there is sufficient space between
the bony defect and the membrane.
Create perforations in the bony defect to allow
filling of the osseous wound with blood.
Provide a material to fill the defect (autograft,
allograft, alloplast or xenograft bone material)
for stabilization of the blood coagulum and for
membrane support.
Ensure complete closure of the margins of the
defect via tight adaptation of the periphery of
the membrane on the surrounding bone (may
217
require stabilization using fixation screws or
pins).
Create tension free primary wound closure via
mattress sutures or interrupted sutures.
Adhere to at least a 6-month, or preferably a
9-month healing period with the membrane in
situ (KENNEY & al., 1993).
Remove the membrane immediately if a soft
tissue dehiscence occurs (membrane
perforation).
218
The use of decalcified freeze dried bone (NEVINS & al. 1992)
or hydroxyapatite (WATCHEL & al. 1991) have been
recommended (MASTERS 1988) in addition to autologous
bone transplants for the stabilization of the blood coagulum
and membrane support. From purely the biological
standpoint, the use of autologous bone is advantageous in
attempts to regenerate bony defects instead of applying
exogenous bone replacement materials. The resorption rate of
autologous bone is very high however, and hence a
combination mixture is commonly used. Small bone chips to
fill peri-implant boney pockets can usually be obtained from
the same site during the drilling procedure. If greater amounts
of cortical or spongy bone transplant material are required,
219
appropriate donor sites are the tuberosity region, retromolar
area, or the chin. To eliminate the necessity of a second
surgical procedure to remove nonresorbable membranes,
resorbable membranes made of collagen or synthetic
materials have been advocated for use in regeneration
of osseous defects in recent years (SCHULTZ et al., 1990;
BALSHI, 1991). These membranes are completely resorbed
6-8 weeks after surgical placement in humans.(ZAPPA 1991).
While biologically resorbable membranes have definitive
clinical advantages when used in periodontal defects (no
second surgical procedure is required to remove them), this
220
particular advantage does not always exist in implantology.
With the exception of non-submerged implants and the
treatment of peri-implantitis, the surgical site must be re-
opened in any case of submerged implants.
The membranes developed particularly for the treatment of
osseous defects in reconstructive oral surgery (Gore-Tex
Augmentation Material GTAM®) are not resorbable and are
made of expanded polytetrafluoroethylene (e-PTFE).
Membranes must fulfill the following requirements
(MELLONIG et al., 1993):
221
Be bioinert, to ensure tissue integration without
complications.
Serve as a physical barrier to preclude penetration by
cells.
Be sufficiently stiff to ensure the creation of a
hollow space in the area of the bony defect;
on the other hand, be sufficiently flexible to
completely cover the defect and close off its
margins.
Exhibit a certain roughness to enhance their role as a
matrix to promote the proliferation of bone cells.
The membrane should extend 2-3 mm beyond
the defect borders.
222
Stabilization should be achieved by the in
growth of the connective tissues.
INDICATIONS FOR THE GUIDED BONE REGENERATION
TECHNIQUE:
Bony Dehiscences
Fenestrations
Immediate or delayed immediate implant placement
Ridge augmentation
Peri-implantitis treatment
223
SURGICAL PROCEDURE:
PRIMARY INCISION:
Primary healing of the soft tissues is completely dependent
upon an adequate blood supply from the soft tissue flap
because the blood supply from the subjacent bone is
precluded. The incision should be beveled in relation to the
crest of the ridge. During the periosteal reflection a partial
thickness flap is first created that becomes a full thickness flap
near to the bony ridge. Any necessary vertical releasing
incisions should be made approximately one tooth width from
the anticipated margin of the membrane to prevent any
disturbances of wound healing.
224
MEMBRANE PLACEMENT:
The chances of clinical success are good when the membrane
technique is used to cover peri-implant osseous defects. In
rare cases the membrane can be secured without mobility by
means of the cover screw creating a secure cavity of sufficient
size with blood coagulum beneath the membrane. There are
two disadvantages to this technique: the first is the space
created underneath the cover screw after the membrane
resorbs could be a route for food entrapment; the second
being that the membrane, if exposed, cannot be removed
without disturbing the implant at a critical healing period.
225
To guarantee stabilization of the coagulum and to prevent the
membrane from collapsing it is always helpful to fill the bony
defect with autologous trabecular bone. The size of the defect
can be attributed to cases of failure to achieve complete
osseous regeneration (inadequate migration rate of the bone
forming cells), and also to premature removal of the
membranes (JOVANOVIC et al., 1992).
226
AUTOLOGOUS BONE AND BONE
REPLACEMENT MATERIALS:
Autologous bone transplants are superior for filling osseous
defects because of their osteogenic potential. Proteins
commonly found in the bone (Bone Morphogenic Protein /
BMP; URIST & al., 1980) are primarily responsible for the
activation of osteoblasts. In recent years, allogenic,
heterologous and alloplastic materials themselves have been
recommended for use as bone replacements materials, either
in combination with autologous bone or alone. Newly
introduced allopastic bone substance materials, uses a liquid
glue (BioLinker™ n-methyl-2-pyrrolidone-solution) at the time
227
of application, which hardens the material and substitutes the
membrane. This material when mixed hardens in minutes to
form a solid but porous body within the defect which prevents
the invasion of undesired epithelial cells and fibroblasts into
the wound area.
228
Type Definition Examples
Autologous (autogenous)
Materials
Autoplastic
(from the same
organism)
Transplantation of impacted teeth,
re-implantation of teeth, bone
transplants
Homologous (allogenic)
Materials
Homoplastic (from
another individual of
the same species)
Banked bone (lyophilization)
Heterologous (xenogenic)
Materials
Heteroplastic (from
an individual of
another species)
Devitalized, deproteinated bone
(Kiel bone chips), collagen, gelatin
Alloplastic Materials Alloplastic(foreign
substances)
Metals, ceramics, plastics
229
SUTURE TECHNIQUE:
In order to ensure that the membrane remains free of
complications, two important factors should be noted:
-Tender handling of the soft tissue during the surgical
procedure.
-Creation of a wound closure that is absolutely free of
tension.
To obtain complete coverage of the membrane, the soft tissue
flaps must be sufficiently mobilized and in some cases may
require severing the periosteum. Intra oral wound closure is
230
normally performed via horizontal mattress sutures for fixation
of the periosteum over the membrane, and then individual
interrupted sutures are employed. A very simple yet common
cause of complication is aspiration of the soft tissue region
(instead of the saliva) for a long period of time resulting in cell
dehydration.
POSTOPERATIVE CARE:
Patients must not wear any prosthesis during the first 2-3
weeks after the surgery. Later, the prosthesis can be relieved
in the area of the wound and worn as usual.
Recommendations during the first 2 postoperative weeks:
231
Use of chlorhexidine and hyloronic acid gels to
prevent infection and enhance healing.
Application of cold packs and systemic
administration of non-steroidal anti-
inflammatory drugs to prevent swelling.
No alcohol based mouth rinses should be
used for the first week.
232
BONEY DEHISCENCES / FENESTRATIONS:
An implant dehiscence is defined as an exposure of the
implant surface from the top of the implant head to the point
where the implant is totally covered by bone. An implant
fenestration, or window of exposed implant surface, results
from either insufficient buccolingual alveolar width or
inadvertent misdirection of implant placement.
In a prospective multicenter study (DAHLIN et al., 1995)
implant dehiscences and fenestrations were evaluated 3 years
following alveolar bone augmentation therapy:
233
Cumulative survival rates after 2 years: maxilla 85%,
mandible 95%.
Cumulative survival rates after 3 years: maxilla 76%,
mandible 83%.Augmenting bone at exposed implant
threads may involve additional risk factors for the
longevity of the implants placed.
234
Chapter 10
Ridge Augmentation
235
RIDGE AUGMENTATION
ENLARGEMENT OR AUGMENTATION OF
ALVEOLAR RIDGES:
In areas with a partially resorbed alveolar ridge, the bone
volume is often insufficient to contain an implant. Therefore,
enlargement of the alveolar ridge is frequently necessary prior
to the placement of an implant, guaranteeing the maintenance
of the secluded space into which exclusively osteogenic cells
may proliferate. Such an augmentation would first have to be
236
created for the enlargement of atrophic jaw bone crest prior to
implant placement.
Minor augmentation might be needed after tooth extraction
incase of immediate implant placement when the socket size
and the implant diameter does not match. In these cases
primary stability is compromised.
Frequently crystal part of implant could require minor
augmentation simultaneously with Implant placement when
few threads of implant are exposed.
237
As opposed to a self-contained jaw bone defect created during
osteotomy, bone-implant contact is so tight that there is
inadequate space for epithelial penetration.
Using the GBR technique excellent treatment results (new
bone formation) can be achieved if the following prerequisites
are fulfilled:
The implant must exhibit primary stability in bone.
From the prosthetic point of view, the implant must
exhibit a favorable position and axis orientation
despite the limited bone availability.
238
The peri-implant osseous defect must not be
excessively large (the extent of the dehiscence should
not exceed 5mm).
Autologous bone should be placed beneath the
membrane to serve as a space maintainer
and as a matrix for new bone formation.
The surgical procedure must be performed
gently so as not to impair the blood supply to
the soft tissue flaps, which is critical for wound
healing.
If, after reflecting the flaps, the primary stability of the implant
in a prosthetically acceptable position and axis orientation is
239
questionable or risky, and it is clear that an expansive peri-
implant bony defect will be present after implant placement, it
is wiser to deal first with the necessary ridge augmentation,
and to place the implants during a second subsequent surgical
procedure.
Whenever a two-step procedure is elected, the membrane
must be well stabilized and beneath the membrane there must
be a secure hollow space for the anticipated new bone
formation. For support, chips of cortical and spongy bone are
placed into the defect in such a way that the trabecular portion
faces the bleeding bony surface, while the cortical portion
240
faces outward. Other types of allografts, xenografts, and
alloplasts have also revealed very successful results.
Clinically:
The membrane should be adapted and stabilized
using fixation screws and if possible a modified
horizontal mattress suture technique.
Surgical experience has shown that the
membrane should first be trimmed and affixed
with screws apically followed by the placement of
bone transplant material in the defect.
At the end, the membrane is lifted and closed over
the transplanted bone. This ensures good adaptation
241
of the membrane and the bone transplant within the
defect.
Numerous clinical studies have shown that it is possible using
the two-step GBR technique to create sufficient new bone for
surgical placement of implants. The technical difficulties, as
well as the risk of subsequent perforation of the wound
margins by the sharp edges of the membrane during initial
healing phase, must be viewed as disadvantages of this
method (Buser et al., 1990-93).
242
ONE STAGE AND TWO STAGE PROCEDURES:
One Stage implant systems were designed to have a smooth
collar, 1-3 mm in height, corresponding to the connective
tissue height surrounding the neck of the implant above the
bone and below the crown margin (biological width). The
philosophy behind this design claims that if the implant
abutment connection is kept above the bone level, it results in
less bone resorption at the neck of the implant. After 30 years
of clinical evidence, this hypothesis is no longer valid. The
bone stability around the implant neck is more related to
surface treatment (e.g. surface roughness) and morphology
(e.g. platform switch) rather than having the per-mucosal part
243
as single piece (one stage) or two pieces, where healing
abutment can be tightened manually to the fixture at the time
of the surgery and removed at the time of uncovery.
The occurrence of similar attachment characterized between
the mucosa and the titanium surface, i.e. a junctional
epithelium and a zone of collagen-rich connective tissue, was
also reported from studies using:
- One stage dental implant systems (Buser et al. 1989-
92, Schroëder et al. 1981),
- Or a combination of two stage and one stage dental
implants systems (Astra Tech
244
Implants ®, Brånemark System ®, I.T.I. Straumann ®).
Weber et al. 1996, using an animal model with titanium
plasma sprayed implants, demonstrated that:
-The junctional epithelium in an initially submerged implant
consistently terminated at a higher level than the case for the
non submerged implants.
- The marginal bone level was found to be similar for the two
groups of implants.
245
- Provided, stability is secured for the osseointegrated part of
the implant following insertion, either in a one or two stages of
procedure, soft tissue healing and the resulting formation of a
mucosal attachment to the titanium surface are features that
apparently are independent whether the implant is initially
submerged or not.
One of the disadvantages of one stage implant is that, if bone
augmentation is required soft tissue primary closure is often
not possible, which could jeopardize the healing of the
augmented material.
246
Immediate Implantation / Delayed Immediate
Implantation
Post extraction Healing
Following tooth extraction, the first 24 hours are characterized
by the formation of a blood clot and the start of hemolysis.
Within 2-3 days the blood clot is contracting and replaced by
the formation of granulation tissue with the blood vessels and
collagen fibers. After 4 days an increased density of
fibroblasts is visible in the clot and the proliferation of
epithelium from the wound margins is apparent. Remodeling,
247
including bone resorption, of the sockets begins with the
presence of osteoblasts. One week after extraction, the
socket is characterized by granulation tissue consisting of a
vascular network, young connective tissue, and osteoid
formation in the apical portion and epithelium coverage over
the wound. Three weeks following the extraction, the socket
is characterized by a dense connective tissue overlying the
residual sockets, which are now filled with granulation tissue.
A trabecular pattern of bone starts emerging and wound
coverage by epithelium is complete. Two months following
the extraction, bone formation in the socket is complete. The
bony height of the original sockets has not yet been reached
and the trabecular pattern is still undergoing remodeling.
248
Placement of implants at the time of tooth extraction is called
‘immediate implant placement’. Implants that are placed
immediately following tooth loss (trauma) or tooth extraction
are likely to succeed if the following prerequisites are fulfilled:
Sufficient bone must be available at the time
of implant placement, i.e. the implant must
achieve primary stability and must be
anchored at least 4 mm in bone from its apical
end.
Sufficient soft tissue mobilization must be
achieved (the wound will heal by primary
249
intention) (WERBITT et al., 1992; WILSON,
1992).
No evidence of periapical infection.
The initial osseous situation will be favorable for immediate
implants if immediately after tooth extraction the alveolus
defect is narrow, corresponding to the diameter of the implant
(e.g. after extraction of mandibular anterior teeth; TOLMAN et
al., 1992).
Reducing the height of the alveolar process is usually not
indicated to achieve adequate width for the placement of
dental implants. Doing so can lead to esthetic problems,
especially in partially edentulous patients because of the
250
resultant disturbed implant-crown relationship. Primary soft
tissue closure is often extremely difficult to achieve following
immediate implant placement. The wound margins have to be
freed up so they can be mobilized to completely cover both
the implant and the membrane with absolutely no tension.
Prerequisites for the placement of 2 stage submerged
implants placed immediately into extraction sockets:
Preservation of the bony margins of the alveolus
during extraction to provide the necessary
support for the membrane barrier.
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Primary implant stability by precise preparation of
an implant bed in the apical portion or along the
walls of the socket.
Tight circumferential adaptation of a barrier
membrane around the implant neck, extending
over the borders of the alveolus by 3-4 mm.
Careful management of the soft tissue flap and
close flap adaptation to the neck of the implant. If
the latter cannot be achieved, the extraction socket
should be left to heal for 1 month to obtain soft
tissue coverage of the wound. The implant may
then be placed into the extraction site (WILSON &
WEBER, 1993).
252
Meticulous plaque control for the entire healing
period of approximately 6 months. This is achieved
by postsurgical antibiotic coverage, daily oral rinses
with hyloronic acid and daily application of
chlorhexidine gel under the base of the temporary
restoration.
A review of the literature reveals that complications can be
expected in up to 50% of cases when dental implants are
placed immediately after tooth loss and the GBR technique is
used. The most common problem is the disturbance of wound
healing, which may be delayed until the 6th-20
th postoperative
253
week. Most often, this is related to the perforation of the
membrane (BROSE et al., 1989; BARZILAY, 1993).
Another problem with immediate implantation is that the
inflammatory infiltrate, which may persist after tooth extraction,
can disturb wound healing (OHRNELL et al., 1992).
The tendency today is to move toward ‘immediate delayed
implantation’. This means that implants are placed only after
soft tissue healing occurs over extraction wounds, which
generally takes between 6 to 8 weeks (JOVANOVIC et al.,
1992).
254
G.B.R. COMPLICATIONS (membrane exposure):
If the membrane perforates the mucosa at some time after the
procedure, no effort should be made to close this opening
surgically (BECKER et al., 1990; WATCHEL et al., 1991;
JOVANOVIC, 1992; BUSER et al., 1993). All membranes are
porous so bacteria will quickly colonize the partially exposed
membrane surface. The patient must be advised to apply
bacterial chlorhexidine and hyloronic acid gels topically
several times daily using an extra soft tooth brush (or the
patient’s own finger gently).
If the membrane is resorbable, the time of resorption will be
reduced, and if this exposure appears early after surgery,
255
sometimes the reduced time of resorption will not be sufficient
to produce a minimum of bone regeneration. If the membrane
is non resorbable, it must be removed no later than 6 weeks
after the perforation. As the membrane is removed, it is
important not to disturb the already regenerated tissue, which
at this time is normally not yet calcified. The internal surface
of the flap should be freed of epithelial remnants so the wound
can again be closed securely. Afterward, the common GBR
technique healing time of 6-9 months is observed. Antibiotics
need only be prescribed if there is an obvious infection.
256
Bone Splitting and Bone Spreading
There are two types of osteotomes used complementary with
a mallet in these procedures:
Chisel shaped: These are flat and thin chisels that
comes in different angels and widths.
Conical shaped: Approximately 50mm in length
angeled and straight comes in 4 tips: sharp, convex,
concave and flat.
There is another type of osteotome used complementary with
a ratchet or a hand piece used in these procedures:
257
This type is available in a series of 4 conical none cutting
shaped threads ranging from 1mm-4mm by rotation via ratchet
or hand piece at slow speed (10-50 NCm)
In cases of a narrow alveolar ridge, bone splitting is indicated
only if:
There is a buccal and palatal layer of spongiosa.
The alveolar ridge still has sufficient height
(since maximally 2/3 of the implant may
spread the bone to ensure optimum primary
stability).
258
In the lower jaw, the denser bone structure of the mandible
requires a more cautious spreading due to fracture possibility.
Previously, vertical incisions in bone used to be performed
with a diamond-separating disk. Opening the alveolar ridge
vertically, in half, during bone splitting used to be performed
using bone chisels (osteotomes), straight for the maxilla and
curved for the mandible. This procedure allowed the increase
in width (bucco-palatal/lingual) of the alveolar ridge when this
distance was at minimum 2.5-3 mm and when the minimal
vertical length was 6-10 mm. Today, piezosurgery has
replaced the diamond-separating disks and the chisels in most
circumstances.
259
Spreading is commonly done by using a series of conical none
cutting shape threads ranging from 1mm-4mm by rotation via
ratchet or hand piece at slow speed (10-50 NCm)
corresponding to the diameter of implant. Spreader diameter
is generally 0.9mm smaller than the final implant to be placed.
After spreading the bone, the cortical lamellas can be fixed
with the last spreader in order to facilitate the filling of the
space created between the two cortical lamellas using
autogenous or other bone materials. Some cases require
both implant placement and augmentation simultaneously by
using bone splitting and spreading techniques. In some
instances where primary stability cannot be achieved bone
splitting and spreading is only done intended for bone
260
augmentation. Fracturing the bone wall during bone spreading
can be avoided through complementary splitting of the
alveolar ridge. This is achieved by making an intentional
vertical cut using the piezo tip far from the implant position
where the stress will be transferred. This area should be
augmented in order to prevent granulation tissue penetration.
At the end of the surgery, it is recommended to use a
membrane in order to protect the bone graft during its healing
time. It is also very important to obtain a complete closure of
the flap.
261
Surgical procedure for raising the sinus floor using bone
splitting and spreading techniques:
Stage 1: pilot drilling of 1 mm diameter into the cortical
base of the sinus, just short of the sinus floor.
Stage 2: insertion of a bone spreader tip from
#1 to #4, which corresponds to a 1mm -
3.1mm diameter. This is followed by placing a
cone shaped convex tip osteotome into the
bone cavity with light pressure or blows with a
mallet, depending on the cortical strength, to
create a green-stick fracture and lift the
262
SCHNEIDER’S membrane in the maxillary
sinus.
Once the desired diameter has been reached, the
augmentation material (autogenous or synthetic) is
condensed under the maxillary sinus with a bone
carrier.
When reaching the adequate height, the implant is
inserted, (implants with a rounded tip and self
cutting screws are suitable).
Osseointegration will take 4 to 7 months,
depending on the blood supply and the
quantity of the augmentation material used to
elevate the alveolar ridge. Cellular infiltration
263
occurs at a rate of 1mm a month in a 3
dimensional mode.
The application of the bone spreading technique requires an
accurate assessment of the bone quantity and quality; the
bone density can only be assessed intra-operatively. For the
bone spreading technique, the alveolar ridge should be at
least 5 mm in height and 3 mm in width. The use of ratchet-
controlled spreaders has often replaced the mallet driven
ones. The previously described procedure can be applied
anywhere in the mouth except in the mandible where a
safety zone of 2 mm short of the inferior alveolar canal is
required.
264
This procedure is indicated for:
Closed sinus elevation
Thin alveolar ridge
265
Sinus elevation and bone grafting
The posterior maxilla is the least predictable area for implant
survival in long term. A number of reasons for this have been
suggested, including inadequate bone height, poor bone
density and high occlusal forces. Past attempts to place
implants in this region have been compromised because of
the presence of the maxillary sinus, and the attempt to avoid
perforating it.
The maxillary sinus acts as a limiting anatomic factor to
implant length. If adequate bone is not available below the
sinus, sinus elevation can be performed. This is usually
266
indicated when 8-10 mm of bone is present, and the dentist
desires to use 12 mm implant to improve implant survival.
An alternative case scenario exists when there isn’t enough
available bone beneath the maxillary sinus (less than 5mm of
bone is present between the crest of bone and floor of the
sinus). In this case, a sinus lift can be done along with sub-
antral augmentation. The area will then be allowed a 4-9
months healing period before implants are placed.
267
SINUS FLOOR ELEVATION (LIFT) PROCEDURE:
In the maxillary posterior segments, sufficient vertical bone is
often not available for risk free placement of implants of at
least 10 mm in length. Various augmentation techniques to
improve the anatomic situation in such cases have been
proposed:
Onlay type maxillary ridge augmentation
o Pieces of transplanted bone block are
positioned upon the crest of the ridge and
affixed using the dental implants. This method
can lead to restorative difficulties because it
changes the shape of the ridge and reduces
268
the interocclusal space considerably.
However, this procedure is ideal when vertical
augmentation is required.
Inlay type maxillary ridge augmentation
o Particulate autologous, homologous,
heterologous or alloplastic augmentation
materials are placed into the maxillary sinus
after lifting the buccal bony plate (open sinus
lift). Using this technique, the mucosa of the
floor of the sinus is not severed and the
intraoral configuration of the alveolar ridge
remains unchanged.
269
Lateral condensation of crestal bone right after
splitting it, in case of low bone density (type 4).
o The quality of bone can be improved from
type 4 to type 3 or even 2 by compressing or
condensing the existing intra-alveolar bone
towards the buccal and palatal plates via
bone condensers or spreaders.
o In order to guarantee an adequate primary
stability of the implant, the bone below the
sinus floor should be at least 5.0 mm, with
the intrasinus augmentation height amounting
to 10 mm or more.
270
o The lateral condensation, after splitting the
ridge in two, depends on the bone density. If
the existing bone type is 1 (mostly cortical),
the implant can only be placed in the middle
of the existing ridge, and no condensation is
possible. However, it is possible to improve
the bone quality by condensation and
spreading expansion in type 3 & 4. Moreover,
in type 4 bone, implant can be placed in a
more ideal position than type 1 bone due to
the fact that bone spreading and expansion
can provide a leeway to guide the osteotomy.
This procedure can be followed with an
271
augmentation on the lateral plate to replace
the deficient buccal soft and hard tissues. The
spaces created by splitting should be
preferably filled with bone substitutes and
protected with a membrane.
Both techniques can be combined when needed.
INDICATIONS FOR SINUS LIFTING:
Generally sinus lift procedures are performed in free end
situations in the maxilla, where insufficient bone height is
available or in totally edentulous maxillae with a low sinus
floor. Prior to short implants, reports state that the success
272
rate for most implant systems of minimal bone height must
have been 10mm. Today, more than 10% of practitioners find
that 5mm is still workable to avoid open sinus lift. At this
moment there must be a clear indication for lateral window
open sinus lift surgery in the first place. If, for example, the
available bone is 5mm and crown:implant ratio is 1:2, the
surgeon can opt for implant placement without raising the
sinus expecting a high success rate. If the condition of
remaining dentition is not debatable or if a partial removable
denture is used in the maxilla where the inter occlusal space
273
has been maintained, the patient is not necessarily a
candidate for an open sinus pre-implant surgery. Hence, a
few millimeters of the sinus floor are raised simultaneously
while the implants are placed. Debatable teeth have to be
extracted and the residual bone is used for better anchorage
of the implants rather than depending on grafted bone.
SURGICAL PROCEDURE:
The commonly practiced technique for sinus lifting is attributed
to TATUM, who modified the CALDWELL-LUC procedure
(opening of the maxillary sinus via the canine fossa).
In 1986, TATUM suggested:
274
A top hinge door is made in the lateral sinus wall
using a large round diamond bur, while keeping the
integrity of the SCHNEIDER’S membrane intact.
However, piezo-surgery today has replaced the
round diamond bur for safer membrane perforation
incidences.
After turning this trap door inward and upward
(optional, or removing the door and keeping it a side
to close the window with it later) together with the
sinus mucosa in a horizontal position at the bottom of
the sinus, the newly created space underneath the
trap door and lifted membrane is filled with bone graft
material. Different combinations, except blocks, have
275
proved successful (e.g. alloplast, allograft, xenograft,
and autograft). The failure with block grafts in the
sinus can be contributed to less blood supply inside
the graft itself.
Dental implants can usually be placed after a
healing time of 4 to 6 months during a second
surgical procedure.
Recently, modifications to this classic surgical
procedure have been proposed which deal primarily
with:
o The temporal sequence of the surgery
(immediate implant placement)
276
o The type of augmentation material to be
employed, or the use of a resorbable
membrane in order to protect the healing
of the site (Boyne et al., 1980; Kent et
al., 1989; Sailer et al., 1989; Jensen et
al., 1990; Howald et al., 1992).
If there is at least 4 to 5 mm of bone height between
the crest of the ridge and the floor of the sinus to
ensure primary implant stability, the implants may be
placed during the same surgical procedure as the
sinus lift.
o The advantages of this technique are:
277
the direct view of the implant body
and tip that is anchored in the sinus,
less time consuming,
Reduced surgical steps
Sinus floor stability by the implant
tips, where commonly 20 % of bone
height is lost in 6 months of healing
phase without implants.
Usually amoxicillin antibiotics are administrated for a
period of 7 days (MISCH, 1987). The use of
metronidazole in liquid form mixed with bone graft has
shown good results as well.
278
A predictable vertical bone gain of 1-3 mm at the
crestal resorbed area can be augmented
simultaneously if required.
CONTRA-INDICATIONS FOR SINUS LIFTING:
Previous sinus surgeries, like the CALDWELL-
LUC operation, often leaves scar tissue instead of
the normal ciliated mucosa lining of the maxillary
sinus i.e. pseudo stratified ciliated columnar
epithelium. Absorbable collagen membranes that
seal the perforation (which often occurs) prior to
particulate base placement normally suffice. This
279
perforation can be diagnosed using the valsalva
maneuver test.
Maxillary sinus diseases such as tumors, chronic
polypous sinusitis or strong allergic conditions
require an ENT specialist multidisciplinary
treatment.
The presence of boney septa or severe sinus
floor convolutions. If a usual trap door
preparation is made it will block the door and
prevent it from being turned inward and
upward. Then the regions anterior and
posterior to the septum should be augmented
280
simultaneously and separately according to
the need.
Extremely narrow sinuses.
AUGMENTATION MATERIALS USED FOR SINUS
LIFTING:
When the sinus lift procedure is performed bilaterally, large
amounts of augmentation material must be available. It is
usually not possible to obtain enough autologous bone from
intra oral sources (tuberosity, chin, etc) to suffice the
need. Even though one of the least recommended sources
today is the retrieval of autologous bone from the inner portion
281
of the hip. It used to be a standard procedure, but it requires
additional surgery as well as general anesthesia and
hospitalization. A disadvantage is the postoperative pain felt
by the patient. Also, this procedure depends on the quality of
the donor bone which is sometimes too spongious. The main
consequence is then postoperative resorption of this grafted
bone or lack of primary stability if implants placed
simultaneously. Never the less this bone remains ideal bone
since it contains the maximum amount of stem cells available
for harvesting. If these stem cells are combined with CaSO4
and TCP, they can give more favorable results.
282
In recent years, efforts have been made to use bone
replacement materials (allograft, xenograft, alloplast) either
alone or in combination with autologous bone. Non-
resorbable hydroxyapatite can be used due to its inert quality
(Smiler et al., 1987; Dielert et al., 1990) as well as freeze dried
demineralized bone by itself or in combination with resorbable,
porous hydroxyapatite and TCP materials (Hotz, 1992;
Streckbein et al., 1987; Higushi et al., 1993). A long-term
study presented by MISCH (1987) and LOSADA et al. (1993)
showed high success rates. However, non-resorbable
hydroxyapatite alone is not commonly used successfully today
contrary to the above literature.
283
COMPLICATIONS:
The 1st most common complication is the perforation of the
SCHNEIDER’S membrane (approximately 35 % of the cases).
If the perforation is very small (0.5mm-1mm), there is no great
chance of losing the graft material into the sinus. If the
perforation is larger (2mm or more), it can be covered with a
resorbable membrane, in case the perforation is too large
(5mm or more), the sinus lift must be postponed to preferably
2-3 months later.
The 2nd
complication is an infection involving the maxillary
sinus, causing sinusitis. The inflammation is treated with
antibiotics (amoxicillin 500mg four times daily for 7 days).
284
Another complication may be the loss of graft into the sinus,
which will also lead to sinusitis; or loss of an inserted implant
due to insufficient bone quantity as a result of graft loss or
atrophy. Severe pain is not common but if it doesn’t reduce in
7-10 days an ENT specialist should be consulted for an
intranasal approach for clearing the sinus. Constant dull pain
for more than 3 weeks could mean that the implant did not
osseointegrate and the body is rejecting the implant. The
same dull pain also might commonly occur if a block graft was
used in the sinus and it is being rejected. At times, rejection of
some of the bone particles is seen on the surface of the
buccal soft tissue. This has to be removed for the soft tissue
to heal.
285
Transpositioning of the Inferior Alveolar and Mental
Nerves
INDICATIONS AND ADVANTAGES OF INFERIOR
ALVEOLAR NERVE LATERALIZATION OR DISTALIZATION
OF THE MENTAL NEUROVASCULAR BUNDLE in less that
6mm bone hight cases:
Replacing removable prosthetic appliances with
implants in the posterior region and stabilizing the
anterior residual dentition.
Stabilizing the temporomandibular joint and muscle
balance or tone overall, as there is reconstruction of
286
the total stomatognathic system with posterior
mandibular teeth restoration.
Reducing the rate of alveolar ridge atrophy, as implant
placement procedures are prophylactic or preventive
in nature for bone resorption to continue.
LIMITING FACTORS OF INFERIOR ALVEOLAR NERVE
LATERALIZATION AND / OR DISTALIZATION OF THE
MENTAL NEUROVASCULAR NERVE:
It is a difficult procedure, which needs clinical
experience, knowledge of the anatomy, and ability to
treat intra-operative or post-operative complications.
287
The risk of nerve damage can be permanent, each
patient should be warned that there is a chance of
transient nerve deficit postoperatively, or a chance for
permanent nerve deficit, which may range from
anesthesia to paresthesia, dysesthesia or
hyperesthesia.
Risk of fracture of the mandible is minimal but
possible as the vast majority of these patients have
severe advanced degrees of atrophy in this area of
the mandible and without the benefit of the CT Scan,
this procedure would be difficult if not impossible to
carry out. Comparing the benefits and risks of this
288
procedure indicates higher risks of complications
which overthrows its benefits.
It is also not indicated to place any type of granular
allograft and/or any one of the alloplast materials in
this area, as it could upon contact it irritates the
exposed neurovascular bundle.
In most instances, the residual bone from the
osteotomy site is not sufficient to place an implant at
the termination of the procedure. However, if
sufficient, then it would be necessary to thin down the
medial aspect of the cortical plate when repositioning
the implant, as it would then prevent excessive
289
pressure or crushing of the nerve against the surface
of the implant(s).
Procedures such as onlay or saddle grafting can be
offered to the patient as an alternative to these nerve-
repositioning procedures. However, a second surgical
site is then required as well, thus increasing treatment
time and the number of procedures for the patient.
Lastly, adequate soft tissue coverage over the graft is
often difficult, if not impossible to achieve.
290
Dental Implants in the posterior mandible
The main limitations when performing implant surgery in the
posterior mandibular region are anatomical. Concavities may
exist on the buccal and the lingual mylohybrid aspect of the
bone, making perforations possible, and more importantly, the
risk of penetrating the mandibular canal are high. This can
result in hemorrhage, impaired visibility and increased
chances of fibrous tissue formation at the surface of the
implant. For the patient, a persistent altered nerve feeling will
be present, such as anesthesia, paraesthesia or
hyperesthesia. To avoid this from occurring, with a help of a
CT scan a safety zone of 2mm can be set above the
291
mandibular canal, which should not be violated during
surgery.
Concerning radiographs, the mandibular canal is often difficult
to identify on peri-apical and panoramic radiographs alone.
The mental foramen was seen in only 50% of peri-apical
radiographs taken, and although it is always seen on
panoramic views, its position is not always accurate. Studies
have shown that its position is more inferior than it actually
appears. Nevertheless, panoramic radiographs are still used
to determine the amount of vertical bone available above the
mandibular canal for implant placement.
292
Another factor to be considered, in any crestal osteoplasty
done during surgery in order to increase the width of residual
bone, is that the amount removed should be decreased from
the calculated height of the bone available during radiographic
evaluation.
An additional method that has been suggested to help avoid
perforation of the mandibular canal is to use no block
injections; instead, infiltration anesthesia only in the
surrounding soft tissues is used. The bone can then be
prepared without pain, as few sensory fibers exist in this area,
with the exception of the inferior alveolar nerve in the
mandibular canal. The patient should be asked to notify the
293
dentist when he/she feels pain or discomfort, as this will
indicate the close proximity to the mandibular canal. This is
not a very reliable method though, as patient apprehension or
misinterpretation of pressure as pain can produce false
results. However it can save the practitioners from severe
permanent complications.
294
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295
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Some amount of pain, bleeding and inflammation frequently
occur after surgery. Home care instructions should address
all of these three main concerns:
Measures to control/reduce pain:
Concerning post-operative medication for pain, the most
commonly prescribed drugs are:
296
Non-opioid Analgesics:
1. Mefenamic acid (Ponstan Forte ): A non steroidal anti-
inflammatory drug used for mild to moderate pain .
Dose of 500mg/tablet tds (when required)
2. Ibuprofen: To treat mild to moderate pain and has
proven to significally reduce postoperative dental pain
in clinical studies, it’s as safe as acetaminophen while
achieving better analgesia with less nausea and
cramping. Dose from 600mg tds (when required)
297
3. Acetaminophen: Used as an alternative to Aspirin.
Dose of 500mg/tablet tds (when required)
4. Diflunisal (dolobid): It’s a more potent form of aspirin.
It’s a NSAID with a duration of action of twelve hours
or more.
Dose of 500mg/tablet tds (when required)
5. Aspirin: It has analgesic, anti-inflammatory and anti-
pyretic properties. However at analgesic doses its
relative risk for G.I. complication is high. Aspirin is not
a drug of choice in the management of dental implant
surgical patients because of its very significant
298
antiplatelet effects. Due to its mechanism of altering
normal homeostasis it is the least desirable. Dose of
325mg/tablet tds (when required)
Opioid analgesics:
These would be indicated in cases of severe pain. The
dentist should be aware of any other drugs that the patient
might be taking for other present systemic problems, as
drug interactions will have to be considered before any
medicine is prescribed. For example, the depressant
effect of narcotics can be increased by the concomitant
administration of alcohol, barbiturates, antihistamines and
benzodiazepines.
299
Dexamethasone is a potent synthetic member
of the glucocorticoid class of steroid drugs. It
acts as an anti-inflammatory and
immunosuppressant. It is given usually starting
with five tablets of 4mg decreased gradually to
one tablet for 5 days after an operation.
Measures to Control bleeding:
Slight seeping from the wound edge is to be expected for at
least the first 12 hours. If heavy persistent bleeding occurs,
patients are advised to call for instructions. For those
patients who have had soft tissue grafts, and are wearing a
plastic STENT on the roof of the mouth, it is important to
300
keep this in for the first 24 hours. Following this period, the
STENT can be removed, cleaned, and replaced as needed.
Patient should be told to bite on the gauze pack
placed over the surgical area with light pressure, until
the bleeding is controlled.
A moist tea bag wrapped in gauze may also help slow
bleeding if it does not stop with simple pressure, due
to the tannic acid content of the tea.
The patient should also be advised not to exercise or
use physical force for the first 24 hours after surgery.
If the bleeding is still continuous after 3-4 hours, the
patient should contact the dentist for further assistant.
301
Measures to control/reduce swelling:
A slight amount of swelling and even discoloration is not
unusual following surgical procedures, and usually
disappears within four to five days. If significant swelling and
discoloration persists for more than five (5) days, the
patients should seek advice. Ice packs should be used for
10 minutes on and 10 minutes off for the first 24 hours.
Following the first 24 hours, moist warm packs can be used
if needed.
The swelling can be expected to stay for 3 days to several
weeks, depending upon the extent of the surgery. Several
authors have also studied the effects of glucocorticoids on
post-operative swellings. Patients treated with glucocorticoids
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had half the pain and half the trismus compared to control
groups.
IMMEDIATE POST-SURGICAL CARE
1. IMPLANT PATIENTS:
The patient undergoing an implant surgery is prepared in a
manner similar to other patients undergoing any form of
surgery. The surgical team is recommended to prepare for
surgery in aseptic conditions. This includes surgical scrubbing
for the doctor and assistant, an intra-oral and extra-oral scrub
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of the patient with Chlorhexidine, followed by gowning and
draping.
For those patients who have received dental implants, the
doctor may have advised them not to wear the present
denture for 7-10 days till the sutures are removed. It is
important that they don’t attempt to place the denture until
your first postoperative visit.
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2. SMOKING:
Smoking plays a significant role in the progression of gum
disease and associated bone loss. Patients, who smoke
following surgery will often experience, delayed healing and
greater discomfort, strongly advise the patients to refrain
from smoking.
3. MEDICATIONS:
It is important that they follow the instructions written on their
prescriptions. If unfavorable reactions occur (nausea,
vomiting, headache, rash, etc.) Discontinuation of the
medication should be advised.
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Patients who take oral contraceptives (birth control pills) are
advised that the antibiotics prescribed for their treatment may
inactivate their birth control pill, and render it ineffective. If
alternate means of birth control are not practiced, they may
have an increased risk of pregnancy while taking antibiotics.
If they have been given a prescription for Corsodyl mouth
rinse, they may find increased staining during its use. These
stains will be polished off at their postoperative visits. Do not
prescribe this rinse if they have white plastic fillings
(Composites) as they may permanently discolor. Alternatively
applying Vaseline on the teeth and fillings and/or applying a
chlorhexidine gel locally on surgical site will reduce the
staining.
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4. CLEANING THE MOUTH:
For the day prior/following the day of surgery, warm salt
water rinses can be used. The dorsum of the tongue should
be brushed that day. Patients should not attempt to brush
the surgery site for 24 hrs. The next day, they can brush and
floss normally. If they have been given a prescription for a
mouth rinse, remind the patient, it should not contain
alcohol. Chlorhexidine gel (0.5%) and hyaluronic acid gel
(0.2%) are adequate to substitute other home care methods.
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5. PREPARATION OF NUTRITIOUS FOODS:
1. Eggs (in all forms). 2. Soups, bouillon, and chowder. 3. Soft meats, such as meat loaf, canned tuna, salmon,
potted meat, finely ground boiled chicken. 4. Soft pureed vegetables (potatoes, peas, beans, carrots,
asparagus, etc ). Things to avoid: Yogurt, citrus fruits and juices, tooth
pastes containing Peroxide.
5. Eat or drink only cold or room temperature foods until the numbness subsides.
Patients should be advised to eat three (3) meals daily and
drink at least six (6) to eight (8) glasses of water per day,
particularly in the immediate postoperative period.
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The following is a prescription sample handed over to patients
after implant surgery:
Antibiotic: AMOXICILLIN 500mg - 3 x daily for 7 days
Analgesic (for pain): Ponstan Forte- 3 x daily for 3 days
(If not available) BRUFEN 600mg-3 x daily for 3
days
ELUGEL ( clorhexidene gel 0.5% )- Three times a day for
2 weeks
GINGIGEL (Hyaluronic Acid 0.2%)- Three times a day for
2 weeks.
The Patient can rinse with warm Saline the next day, after
SurgeryPlease remove the sutures in 2 weeks.
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310
EEvvaalluuaattiioonn ooff SSuurrggeerryy::
Exactly what constitutes success or failure in implant dentistry
is difficult to describe, as there are yet no specific definition of
clinical success. The primary factors to be assessed in order
to judge implant quality are pain and mobility, although
evaluation of a number of other factors have been suggested
by various authors. These include:
1. Rigid fixation
Rigid fixation is the absence of clinical mobility of the
implant under vertical or horizontal forces of 1 to 500g.
It suggests that a portion of the implant is in direct
contact with bone. Any implant with more than 1 mm
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horizontal or vertical mobility should be taken out of
function, to prevent further bone loss.
2. Probing depth
Probing depths of up to 3mm are indicative of a healthy
periodontium for a normal tooth. In implants however,
pocket depths of up to 6mm have been reported with
stable, rigid fixated implants. Depths of 6mm are also
more conducive to gram-negative organism growth,
which is why 3mm has been suggested as an ideal for
implant sulcus depth, especially when esthetic is not
the main concern. Increasing probing depths suggest
bone loss—making it an easy and quick method for
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assessing potential deleterious changes in the peri-
implant tissues. Probing depths should be assessed
every 6 months for the first year after the surgery and
once annually for 5 years.
3. Bone Loss
The level of the peri-implant bone is judged using
radiographs, and compared to the levels of bone at the
initial placement of the implant. Ideally, minimum bone
loss should be seen. If more than one third of the
implant height of bone has been lost, the implant is at
significant risk of failure.
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Possible mechanical causes contributing to bone loss
include:
occlusal forces
cantilever
material strength
implant quality
Possible Parafunctions and biological causes including:
deep pockets
subgingival screw access open margin
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smoking
hormonal imbalance
uncontrolled systemic diseases like diabetes.
4. Bleeding Index
One of the indicators of implant health is a bleeding
index. During the first year after surgery, bleeding on
probing, peri-implant tissue color, form and consistency
should all be assessed and recorded. Bleeding on
probing is seen to be correlated with radiographic bone
loss and increased pocket depths. Care should be
taken while probing, as excessive forces may provoke
bleeding, producing false results.
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5. Peri-implant disease
The presence of peri-implantitis should be suspected if
exudate is seen. Peri-implantitis leads to bone loss,
which in turn may lead to secondary occlusal trauma
and further worsening of the condition. Antibiotic
treatment, use of chlorhexidine and aggressive soft
tissue care both by the dentist and patient are indicated
in such cases. If the exudates still persists after 1-2
weeks of treatment, laser therapy followed by surgical
management is most likely needed.
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6. Pain
Perhaps the worst prognosis of all is when the patient
complains of pain, as this condition rarely improves and
requires removal of the implant, even if there is no
mobility present. The implant may also be tender to
percussion - implying a more advanced stage of
complication for the implant. If tenderness is the only
complaint however, the underlying cause should be
evaluated and addressed, as it may be possible to treat
it. Most often removal of stresses placed on the
prosthesis for a period of 2 weeks will eliminate the
problem. Occlusion and parafunctional habits should
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also be assessed. If the nerve is been triggered it might
disappear in few months.
Ideally after initial surgery and the healing process, one
should expect a rigidly fixed implant with no crestal bone
loss, adequate zones of attached gingiva, a soft tissue
thickness of less than 3 mm and no tenderness or
discomfort under vertical or horizontal forces, if a
successful prognosis is to be made. These criteria can
be directly evaluated at the second stage surgery, when
both soft and hard tissue conditions can be assessed
and also corrected if necessary before the fabrication of
the final prosthesis.
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Chapter 13
Uncovery
319
At this stage the patient is prepared for surgery similar to the
original stage I procedure. In general discomfort, swelling, and
risk of infection occurs to a lesser degree than at the original
surgery.
Soft tissue incision:
A tissue punch may be used to uncover the implant when
there is 1.5mm or more of attached keratinized tissue facial to
the implant site.
The periosteal elevators should not be levered against the
endosteal implant body or first stage cover screw during this
procedure. Instead, the lingual or palatal bone is used for
leverage, and the facial tissues are gently pulled off the healed
implant site. Adequate reflection of the soft tissue completely
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exposes the crestal bone around the implant site and allows
repositioning of the attached tissue at the conclusion of the
procedure.
In case the healing cover screw became exposed during the
healing phase, the primary crestal incision is made along the
lingual aspect of the healing cover, and a sulcular incision is
placed around the rest of the implant. A mucoperiosteal flap is
then reflected in a fashion similar to that previously described.
A lack of attached tissue is common on the facial aspect of the
implant when it becomes exposed during initial healing and
may require a tissue graft or acellular tissue graft on the facial
to restore attached or immobile tissue.
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Chapter 14
Prosthetic Phase - Impression Procedure
322
Prosthetic Phase - Impression Procedure
The esthetics of an implant-supported fixed restoration
partially depends on the presence of an ideal soft tissue
environment. One of the goals of a restoration is to maintain a
healthy interdental papillae and a natural cervical line. The
provisional prosthetic phase is extremely important to achieve
this goal. Any of the following options can be selected for
bone-level or infra-bony implants. If the implant is a tissue-
level or a one-piece, the soft tissue healing period is omitted.
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1. Placing a healing abutment (Trans-mucosal Healing
Cap), and waiting for a period of 1-3 weeks, followed
by the final impression procedure.
2. Placing a temporary abutment with a provisional
prosthesis: for complete healing and maturation of the
newly constituted tissue formed at the surgical site, it
is histologically ideal to wait for a period of 2-3 months
prior to the impression phase. The laboratory can then
fabricate an ideal and cleansable margin. The main
advantage of this protocol is to know where the tissue
settles. This healing process should not be physically
or mechanically disturbed.
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3. Since the 2-3 month wait period may not be practical
in most instances, it is possible for an impression to
be made at stage II (uncovery) surgery. The following
criteria are to be strictly followed:
The crestal bone level around the implant is to
be considered as the baseline by making a
bitewing radiograph;
A 3 mm height should be calculated from the
bone coronally for the future biological width
to form, unless the neighboring gingival tissue
is less than 3 mm where the crown margin
should be at gingival level not below/above to
minimize impinging on the biological width,
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In this 3 mm zone the crown-abutment joint
should not be present. Above this point the
abutment finish line will be milled. The ideal
surface treatment is a laser-etched abutment
collar for this zone.
An abutment which has a finish line 1-1.5 mm
apical to the anticipated gingival margin is
selected from a range of pre-fabricated or
custom-made ones.
If the patient opts for the first option due to his personal, work
and social life until the final impression is made in 1-3 weeks,
the patient could wear removable over-denture prosthesis
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while the healing cap is in place. Wearing a removable
denture always requires adaptation, not only on a functional
but also on an emotional level. A psychological study done by
Hogenius et al. reviewed problems associated with removable
prostheses in 473 patients, who were treated with
osseointegrated implants. The study showed that the patients
were found to be more depressed than average.
Impression during stage I (Surgery) can also be made and has
the following advantages;
The patient’s life is not affected physically or
psychologically during the healing period;
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Produces less discomfort during uncovery;
Reduces cost and chair time;
Allows for immediate loading;
Allows more time for progressive loading;
Esthetically, the final results will be more predictable
as this procedure allows for creation of an ideal
provisional design to build a healthy peri-implant soft
tissue environment.
Several methods for fabrication of the impression template
during stage I (surgery) are available. However, these
procedures are most applicable to the partially edentulous
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patients where the template can be adequately stabilized by
fitting over or around enough teeth in the jaws.
The various impression techniques include:
1. Indirect (Closed Tray) Hex-Engaging
2. Direct (Open Tray) Hex-Engaging
3. Indirect (Closed Tray) Non Hex-Engaging
4. Direct (Open Tray) Non Hex-Engaging
Abutment Level Impression Techniques
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1. Indirect (Closed Tray) Non Hex-Engaging
2. Direct (Open Tray) Non Hex-Engaging
Optional Implant Overdenture Impression Techniques
1. Multipurpose Abutment Indirect (Closed Tray) Impression
2. O-Ring Attachment Indirect (Closed Tray) Impression
3. ZAAG® Attachment Chairside Impression/Overdenture
Processing
4. ZAAG® Attachment Closed Tray Entrapment Impression
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Implant Level Impression Techniques
Closed and open tray Impressions
Closed Tray
1. Impression posts are screwed onto implant bodies
with the 0.050” (commonly) hex drive seating tool
(screw driver).
2. Screws are placed which match the height of the
impression posts.
3. Block-out wax is placed to cover the holes on the top
of the screw to prevent impression material from
entering.
4. The impression posts are recorded onto implant
bodies with stiff material.
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5. The impression posts are unscrewed from the
implants and the implant body analogs are attached to
the same screw.
6. The impression posts are placed with the attached
analogs back into the impression material.
Open Tray
1. long impression posts are screwed onto implant bodies with
the 0.050” (commonly) hex drive seating tool (screw driver).
2. A custom tray is used and holes are prepared which line up
with the impression posts.
3. The impression is recorded. The long screws will protrude
through the holes created in the impression tray.
4. With the impression tray still in place, the impression post
screws are unscrewed from the implant bodies.
5. The implant body analogs are connected to the impression
posts which are still in the impression.
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6. The impression posts are screwed to the analogs with the
long impression post screws.
7. The analogs are held in place to help prevent rotation of the
impression post. The analogs are connected by block-out light
cure resin to prevent the effect of setting expansion on analog
positions. The impression is now ready to be sent to the lab.
Note: a combination of open and close-tray techniques has
been developed by fabricating a two-piece impression post
with an advantage over the close-tray technique in that the top
part of the impression post will remain in the impression
material reducing the inherent handling error caused by the
close-tray technique.
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Chapter 15
Restoration Options (Prosthetic Designs)
334
Restoration Options (Prosthetic Designs)
Traditional dentistry provides a restoration design that is
directly related to the existing oral condition. On the other
hand, implant dentistry can modify the existing oral condition
by providing additional abutments and bone augmentation in
both partially and completely edentulous patients, and thus
positively affecting the final prosthetic design.
It is the final restoration, not the implants, that accomplishes
the optimum goal of implant dentistry, i.e. replacement of
missing teeth to normal contour, function, esthetics, speech,
and health. Therefore, to satisfy patient’s needs and desires,
the prosthesis should be designed first.
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A number of restoration options are available to most partially
and fully edentulous patients, nevertheless, not all patients
should be treated with the same restoration type or design.
Prosthesis Design in the Completely Edentulous
The restoration type depends on various factors such as the
anatomical needs, predictability, personal desires, and cost.
However, in the completely edentulous patients a removable
implant-supported prosthesis offers several advantages over a
fixed-implant restoration:
Facial esthetics enhanced with labial flanges
Nocturnal parafunction manageable upon removal of
prosthesis
Fewer implants placed
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Less bone augmentation needed before implant
insertion
Shorter treatment if no bone augmentation is required
Less expensive
Easier daily home care
On the other hand, a fixed-implant prosthesis has some
benefits, the psychological advantage being the major one.
The edentulous patients often feel the implant teeth are better
than their own, which proves a significant improvement over
removable restorations. In addition, fixed prostheses often last
longer than implant-supported overdentures because
attachments do not require replacement and acrylic denture
teeth wear faster than porcelain to metal.
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Prostheses Design in the Partially Edentulous
The fewer natural teeth missing, the better the indication for
an implant-supported fixed partial denture. Advantages of
fixed restorations in the partially edentulous include:
A more natural feel (psychological)
Less food entrapment
No attachments to change or adjust (less
maintenance)
Lasts the life of the implants (longevity)
Prosthetic Options for Implant Dentistry (Misch, 1989)
FP-1: Fixed prosthesis; replaces only the crown; looks
like a natural tooth
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FP-2: Fixed prosthesis; replaces the crown and a
portion of the root; crown contour appears normal in
the occlusal half but is elongated or hypercontoured in
the gingival half
FP-3: Fixed prosthesis; replaces missing crowns and
gingival color and portion of the edentulous site;
prosthesis most often uses denture teeth and acrylic
gingiva, but maybe porcelain to metal
RP-4: Removable prosthesis; overdenture supported
completely by implant
RP-5: Removable prosthesis; overdenture supported
by both soft tissue and implant
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Abutment types
Abutments
An abutment is the portion of the implant that supports and
retains a prosthesis or implant superstructure.
340
Classification of all abutments
In the two piece implant system, abutments are the
components of implant system that screw directly onto the
implant. They will eventually support the prosthesis. For screw
retained restorations, they accept the retaining screw of
prosthesis. For cement retained restorations, they may be
shaped like a conventional crown preparation.
In implant systems which incorporate anti rotational features,
the abutments have two components that move independently
of each other, one engages the anti rotational feature, and the
other secures the abutment within the implant fixture.
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i) According to the type of manufacturing:
Preformed (stock) Abutments: Straight abutments
Angled abutments
Anatomical abutments
Standard abutments
Conical (tapered) abutments
Millable abutments
Ball abutments (for complete denture retention)
Custom made abutments: Castable abutments (UCLA abutments)
342
CAD-CAM abutments
ii) According to the number of parts: Single piece abutments
Two piece abutments
iii) Based on the method of retention of the prosthesis to the abutment:
Abutment for screw retention
Abutment for cement retention
Abutment for attachment
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iv) Based on the axial relationship of the implant and the abutment:
Straight abutment
Angled abutment
V) Based on the material
Titanium: either fully silver colored or electroplated with
gold color; the collar is either smooth or rough.
Zirconium: either fully zirconium or zirconium with titanium
intaglio surface.
Castable (plastic): either fully plastic or plastic with gold
intaglio surface.
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Preformed Abutments
The preformed abutments take many forms. Their walls
are usually smooth, polished, and straight-sided titanium
or titanium alloy. Their length ranges from 1-10mm. In non
esthetic areas, not more than 1-2mm of titanium should be
allowed to penetrate the soft tissue to maximize the
patient’s ability to clean the prosthesis. In esthetic areas,
generally more than 2mm of porcelain can be allowed to
be carried subgingivally for optimum esthetics.
345
Straight abutments
An intermediate component placed between the cement
retained prosthesis and the implant.
Angled abutments
A straight abutment with angled 15 or 30 to the implant
long axis. They are commonly used in upper anterior teeth
to correct divergently placed implants.
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Standard abutments
An intermediate component placed between the implants
and metal framework/restoration, providing support and
retention for the fixed-removable restoration. It is excellent
for bar overdentures.
Tapered abutments
An intermediate component placed between the implants
and the restoration for a fixed-removable restoration. The
abutment is cone shaped for maximum esthetics.
Excellent for screw retained fixed prosthesis.
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All ceramic Abutments
All ceramic abutments are designed to fit directly into the
fixture. They can be used in highly esthetic areas.
One piece vs. two piece abutments
There are two general types of abutments for cement
retention used in implant dentistry.
The two-piece abutment for cement retention has one
component to engage the anti-rotational hex of implant
body and the other component (abutment screw) to fixate
the abutment in implant body together. The one piece
abutment that is not engaging the anti-rotational hex but
fixed to the implant platform is used in multiple implants
receiving a bridge restoration.
348
Advantages of one-piece abutment
They are stronger
No screw loosening
Easily complete sitting
Less expensive
Thicker walls to allow great freedom of preparation
In deep subgingivally placed fixtures
Disadvantages of one-piece abutment
Only for multiple abutments
Not for angled abutments
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Advantages of two-piece abutments
Anti rotational under shear forces
Angled abutments
Disadvantages of two-piece abutments
Screw loosening
Abutment loosening under restoration
Torque and counter torque devices needed for preload
Proper sitting with radiograph must be checked
Thinner walls limit freedom of preparation
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Custom made abutments
There are times when an implant system have be
used that does not have an angled abutment (one
piece implants), or when an implant has been placed
in such a manner that the available angled abutments
will not satisfy the needs for proper orientation. It is
necessary to fabricate a custom abutment by making
impressions or preparing direct resin patterns. To
fabricate a desired emergence profile which is
triangular, oval or rectangular in natural teeth, a
custom-made abutment may deem necessary. A
common path of insertion is desired when a multi-
implant restoration is to be made of non-parallel
implants.
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UCLA abutment
It is a custom cast non-segmented implant crown
bypassing the abutment portion by using plastic
sleeve directly waxed to the implant analog in the
master cast. It may be necessary when soft tissue
thickness is less than 2mm. It is the treatment of
choice for posterior single crowns due to its
retrievability potential.
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Cementation
There is a trend in implant restorations to produce cementable
implant-supported prosthesis. Procedures for cementable
prosthesis are proclaimed to be superior for variety of
reasons. The most common rationale is that dentists are
familiar with crown and bridge procedures therefore
cementable implant prosthesis requires less time.
Depending upon the type of prosthesis, single or multiple, the
type of cementation will depend on clinician’s judgment.
Ideally, the trend is to go for provisional cementation for the
initial few weeks followed by a definitive cementation.
353
Provisional cementation:
Zinc oxide eugenol with EBA is the cement of choice
Definitive cementation:
Various cements are available but Zinc phosphate is the
cement of choice
354
Provisional cementation
Very often it is important to evaluate the occlusion, the soft
tissue health, and hygiene at a follow up appointment so that
the fixed implant prosthesis is often cemented with temporary
cement.
Temporary cement often used as definitive cement which
permits easy retrieval of the prosthesis if intermediate or long-
term complications develop.
The most common cement used with the least hardness for
the definitive restoration is a Zinc oxide eugenol (Tempbond).
355
Definitive cementation
Final cementation for implant prosthesis should be done in a
dry environment.
The cement most often used in implant prosthesis includes:
Glass ionomer: It is the cement of choice for definitive cementations for implant. It is technique sensitive as it needs a dry field for setting.
Zinc phosphate cement: It is as commonly used as GIC. It has good compressive and tensile strength. It requires a cold glass slab for mixing and has the longest working time.
356
Reinforced zinc oxide eugenol (IRM): It provides an excellent seal, but it exhibits lowest compressive strength and high solubility.
Zinc polycarboxylate cement: It is not used often on implant abutment as definitive cement. It maybe used as stronger provisional cement when zinc oxide eugenol appears insufficient.
Composite resin: Has the highest compressive and tensile strengths and it is used when the intent is not to remove the restoration in the future, and when the abutment height is below 4mm. In other instances, it is used in cementing the crowns with access holes to the abutments, which are screw retained to the implant.
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Chapter 16
Hygiene and Maintenance
358
To ensure optimum peri-implant health after the surgery, it is
important to eliminate all plaque. 0.12% concentration of
Chlorhexidine Gluconate has demonstrated almost
100% elimination of bacteria in the oral cavity for 6-12 hours.
It acts by interacting with the negative charges on the bacterial
cell wall, affecting its permeability, and thereby causing
leakage of intra-cellular components and cell death.
The importance of maintaining oral hygiene should be
stressed to the patient. The use of an interdental brush or a
359
rotary unitufted brush, with instructions on how to properly use
them, can be advised.
It would be prudent to keep the patient on recall intervals of 1
year until the effectiveness of oral hygiene and integrity of the
implant is noted. Periodic intraoral radiographs could also be
taken in the recall visits to assess osseous changes.
The maintenance visit includes:
1) scaling, polishing (with fluoride application) of the teeth
especially around the implant (with prophy cups, Superfloss)
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2) standardized x-ray to see and compare the level of the
bone height to the previous year and
3) 0.8% Hyaluronic Acid application. Hyaluronic acid is the
most physiologically important proteoglycan found naturally in
the mucosal extracellular matrix where it interacts with other
components of connective tissue to provide the strength and
elasticity essential for good oral health, and act as a barrier to
the penetration of micro-organism and other toxins which are
likely to contribute to the etiology of periodontal disease.