1

Handbook of Implant Dentistry Compiled by Souheil Hussaini BDS, MS

WWW.ID-SC.COM

Chapter 1

History of Dental Implants

2

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.

3

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.

4

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

5

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

6

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.

7

Bar Retainers Bar retainers are screwed directly onto the implants and support dentures by clip mechanism. Two types are well-known: Dolder® and Hader®.

8

Chapter 2

Diagnosis for Dental implant

9

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)?

10

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.

11

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

12

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

13

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:

14

- 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

15

- 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)

16

- 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.

17

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

18

- 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

19

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)

20

- 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.

21

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.

22

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),

23

- 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.

24

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

25

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.

26

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.

27

- 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.

28

- 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

29

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.

30

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.

31

- 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.

32

- 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,

33

- 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

34

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

35

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.

36

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-

37

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.

38

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,

39

- 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:

40

- 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.

41

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).

42

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.

43

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).

44

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

45

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.

46

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

47

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.

48

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.

49

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

50

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.

51

Chapter 3

Essential requirements for dental implant

52

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 )

53

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 )

54

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)

55

Chapter 4

Types and material of dental implant

56

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

57

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.

58

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

59

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

60

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.

61

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

62

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.

63

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,

64

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.

65

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

66

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.

67

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

68

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

69

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).

70

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.

71

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:

72

- 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

73

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).

74

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-

75

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.

76

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

77

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

78

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:

79

- 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

80

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

81

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)

82

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)

83

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

84

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

85

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.

86

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.

87

Chapter 5

Anatomic basis of implantology

88

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.

89

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.

90

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.

91

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).

92

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.

93

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).

94

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.

95

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.

96

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

97

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).

98

Conditionally favorable:

Maxillary region up to the site of the 2nd

premolar.

Unfavorable:

Posterior region of the maxilla, including the maxillary

retromolar tuberc

99

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.

100

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).

101

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

102

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

103

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

104

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

105

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

106

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

107

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.

108

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.

109

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

110

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.

111

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.

112

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.

113

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

114

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.

115

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

116

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

117

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.

118

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.

119

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).

120

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:

121

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

122

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.

123

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.

124

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

125

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.

126

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:

127

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

128

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

129

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

130

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

131

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

132

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.

133

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

134

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

136

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

138

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

139

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

140

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

141

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.

143

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.

145

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

146

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.

148

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.

149

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.

151

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

153

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)

154

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:

155

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

156

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.

157

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.

158

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.

160

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.

161

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.

162

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.

163

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.

168

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.

170

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.

173

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

179

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

180

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

181

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.

182

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

183

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.

184

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).

186

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.

188

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.

193

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.

194

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.

197

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:

198

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.

199

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.

201

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.

251

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

CChhaapptteerr 1111

PPoosstt--ssuurrggiiccaall MMeeddiiccaattiioonn,, AAddvviiccee aanndd PPrreeccaauuttiioonnss

295

PPoosstt--ssuurrggiiccaall MMeeddiiccaattiioonn,, AAddvviiccee aanndd PPrreeccaauuttiioonnss

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

302

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

303

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.

304

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.

305

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.

306

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.

307

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.

308

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.

309

CChhaapptteerr 1122::

EEvvaalluuaattiioonn ooff SSuurrggeerryy

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

311

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

312

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.

313

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

314

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.

315

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.

316

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

317

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.

318

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

320

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.

321

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.

323

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.

324

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,

325

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

326

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;

327

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

328

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

329

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

330

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.

331

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.

332

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.

333

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.

335

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

336

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.

337

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

338

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

339

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.

341

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

343

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.

344

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.

346

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.

347

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

349

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

350

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.

351

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.

352

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.

357

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)

360

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.