IMPROVING THE PATIENTS DENTURE BEARING AREAS AND RIDGE

RELATIONS

Dr. Rajat Dang

INTRODUCTION A thorough examination of the mouth prior to the

construction of complete dentures is necessary to identify potential problem areas. A determination of whether surgery is necessary is an essential part of that examination and plays an important role in successful patient management.

The vast majority of patients for whom complete

denture therapy is prescribed have already been wearing dentures. There is a risk in wearing dentures for prolonged periods. This risk, or biologic price, manifests itself in a number of adverse changes in the denture foundations. Consequently, several conditions in the edentulous mouth should be corrected or treated before the construction of complete dentures. Often patients are not aware that tissues in the mouth have been damaged or deformed by the presence of old prosthesis.

Other oral conditions may have developed that must be altered to increase the chances for the success of the new dentures. The patient must be cognizant of these problems, and a logical explanation by the dentist, supplemented by radiographs and where required, diagnostic casts, usually will convince the patient of the necessity for the suggested treatment.

The methods of treatment to improve the patient’s denture foundation and ridge relations are usually either non-surgical or surgical in nature, or a combination of both methods. A treatment plan calling for surgical correction should be made only after alternate non-surgical approaches have been considered and evaluated. A patient who presents with deformed, abused pathologic tissues from an existing denture should first undergo non-surgical approach.

It is always hoped that the results of the preprosthetic surgery are acceptable both surgically and prosthodontically. In this vein, the services of an oral and maxillofacial surgeon may be required, especially as the surgical preparation becomes more complicated. In these instances, a team approach is needed with the surgeon and the prosthodontist serving as equal members of the team.

Since the support, retention, and stability of a denture base depend on the quantity and quality of the denture bearing area and border seal, every effort is to be made to preserve the alveolar bone. The goal of pre-prosthetic surgery is to modify the denture bearing areas to render it free of disease and to make its form (and possibly its function) more compatible with the requirements of complete denture wearing.

Some of the characteristics of this ideal form which provide for maximum support and stability and minimum interference with function are:

• Adequate bone support for dentures.• Bone covered by adequate soft tissue.• No undercuts or overhanging protuberances.• No sharp ridges.• Adequate buccal and lingual sulcus.• No scar bands to prevent normal seating of denture.• No muscle fibers or frenula to interfere with the

periphery of the prostheses.• Satisfactory ridge relationship between the maxilla and

the mandible.• No soft tissue folds or hypertrophies on the ridge or

sulci.• A ridge free of neoplastic disease.

NON-SURGICAL METHODS

• Non-surgical methods of edentulous mouth preparation include:

• Rest for denture supported tissues.

• Occlusal and vertical dimension correction of old prostheses.

• Good nutrition

• Conditioning of the patient’s musculature

Rest for denture supporting tissues:

Rest for the denture supporting tissues can be achieved by the removal of the dentures from the mouth for an extended period or the use of temporary soft liners inside the old dentures. Regular finger or toothbrush massage of denture bearing mucosa, especially of those areas that appear edematous and enlarged is also beneficial.

Tissue abuse caused by improper occlusion can be made to disappear by,

• Withholding the faulty denture from the patient.

• Adjusting/correcting the occlusion and/or refitting the denture by means of a tissue conditioner.

• Substituting properly made dentures.

In these cases, it is necessary to allow the soft tissues to recover by removing the dentures for 24-48 hours before the impressions are made for the construction of new dentures. However, it generally is not feasible to withhold the patient's denture for an extended period while the tissues are recovering. Therefore, temporary soft liners have been developed as tissue treatment or conditioning materials. These soft liners maintain their softness for several days while the tissues recover.

Occlusal correction of old prostheses:

An attempt should first be made to restore an optimum vertical dimension of occlusion to the dentures presently worn by the patient by using an interim resilient lining material. This step enables the dentist to prognosticate the amount of vertical facial support that the patient can tolerate, and it allows the presumably deformed tissues to recover. The decision to create room inside the denture depends on its fit and the condition of the tissues. The tissue treatment material also permits some movement of the denture base so its position becomes compatible with the existing occlusion, apart from allowing the displaced tissue to recover their original form.

Consequently, ridge relations are improved and this improvement facilitates the dentist's eventual relation registration procedures. It also facilitates the occlusal adjustments intraorally and extraorally, i.e., on an articulator.

It may also be necessary to correct the extent of tissue coverage by the old denture base so all usable supporting tissue is included in the treatment. This correction can easily be achieved by use of one of the resin border-molding materials combined with a tissue conditioner.

Good nutrition:

A good nutritional program must be emphasized for each edentulous patient. This program is especially important for the geriatric patient whose metabolic and masticatory efficiency have decreased.

Conditioning the patient's musculature:

The use of jaw exercises can permit relaxation of the muscles of mastication and strengthen their coordination as well as help prepare the patient psychologically for the prosthetic service. If at the initial appointment the dentist observes that the patient responds with difficulty to instructions of relaxation and coordinated mandibular movements, a program of mandibular exercises may be prescribed. Such a program may be beneficial and the subsequent clinical appointment stages of registration of jaw relations facilitated.

SURGICAL METHODS

Frequently, certain conditions of the denture bearing tissues require edentulous patients to be treated surgically. These conditions are the result of unfavorable morphologic variations of the den ture bearing area, or more commonly may follow long term wear of ill-fitting dentures.

Correcting conditions that preclude optimal prosthetic function

( Hyperplastic ridge, Epulis fissuratum, Papillomatosis.)

The premise underscoring surgical intervention is that mobile tissues (e.g., a hyperplastic ridge), tissue that interfere with optimal seating of the denture (eg epulis), or tissues that readily harbor microorganisms (a papillomatosis

are not conducive to firm healthy foundations for complete dentures. Whenever possible, these tissues should be rested, massaged, and / or treated with an antifungal agent prior to their surgical ex cision. If the patient's health precludes surgical in tervention, the impression technique and design of the denture base have to be modified.

Frenular attachments and pendulous maxillary tuberosities. Frena, or fibrous bands of tis sue attached to the bone of the mandible and maxillae, are frequently superficial to muscle at tachments. If the frenum is close to the crest of the bony ridge, it may be difficult to ob tain the ideal extension and border of the flange of the denture.This tissue can be removed surgically. Frena often become prominent as a re sult of reduction of the residual ridges. If muscle fibers are attached close to the crest of the ridge when the frenum is removed, they usually are de tached and elevated or depressed to expose the amount of desired ridge height.

The frenectomy can be carried out before prosthetic treatment is begun, or it can be done at the time of denture insertion when the new denture can act as a surgical template.

Pendulous fibrous maxillary tuberosities are frequently encountered. They occur uni laterally or bilaterally and may interfere with denture construction by excessive encroachment on or obliteration of the interarch space. Surgical excision is the treatment of choice, but occasionally maxillary bone must be removed. Care must be used to avoid opening into the maxillary sinus.

Bony prominences, undercuts, spiny ridges, and nonparallel bony ridges.

Mandibular tori are usually removed to avoid undercuts and to make possible a border seal beyond them against the floor of the mouth. They generally occur so close to the floor of the mouth that a border seal cannot be made. On the other hand, maxillary tori are infrequently removed. Satisfactory dentures can be made over most of them.

The indications for the removal of maxillary tori are as follows:

• An extremely large torus that fills the palatal vault and prevents the formation of an adequately extended and stable maxillary denture.

• An under cut torus that traps food debris, causing a chronic inflammatory condition; surgical excision is necessary to create optimal oral hygiene.

• A torus that extends past the junction of the ard and soft palates and prevents the devel opment of an adequate posterior palatal seal.

• One that causes the patient concern (be cause of a cancerphobia)

Bony exostoses may occur on both jaws but are more frequent on the buccal sides of the posterior maxillary segments. They may create discomfort if covered by a denture and usu ally are excised. It must be emphasized that routine excision of mandibular exostoses is not recom mended because all alveolar ridge surgery is accompanied by varied, but often dramatic residual ridge reduction. Frequently the denture can be relieved to accommodate the exostosis, or a permanent soft liner can be employed.

Sometimes, the genial tubercles are extremely prominent as a result of advanced ridge reduction in the anterior part of the body of the mandible. If the activity of the genioglossus muscle has a tendency to displace the lower denture or if the tubercle cannot tolerate the pressure or contact of the denture flange in this area, the genuial tubercle is removed and the genioglossus muscle detached. If it is clinically necessary to deepen the alveololingual sulcus in this area, the genioglossus muscle is sutured to the geniohyoid muscle below it.

Residual alveolar ridge undercuts are rarely excised as a routine part of improving a pa tient's denture foundations. Usually, a path of inser tion and withdrawal of the prosthesis can be deter mined together with careful adjustment of a den ture flange, which enable the dentist o use the un dercuts for extra stability.

Discrepancies in jaw size. Impressive ad vances in surgical techniques of mandibular and maxillary osteotomy have enabled the oral sur geon to create optimal jaw relations for prosthetic patients who have discrepancies in jaw size. The prognathic patient frequently places considerable stress and unfavorable leverages on the maxillary basal seat. This may cause excessive reduction of the maxillary residual ridge. Such a condition is even more conspicuous when some mandible teeth are still present. A mandibular osteotomy in these cases can create a more favorable arch alignment and improve cosmetics as well. However, changes in the soft tissues of the face tend to be accentuated by such a procedure.

Usually an adjunctive face-lifting procedure in this type of patient produces impressive results.

Pressure on the mental foramen. If bone resorption in the mandible has been extreme, the mental foramen may open near or directly at the crest of the residual bony process. When this happens, the bony margins of the mental foramen usually are more dense and resistant to resorption than the bone anterior or posterior to the foramen is. This causes the margins of the mental foramen to extend and have very sharp edges 2 to 3 mm higher than the surrounding mandibular bone. Pressure from the denture against the mental nerve exiting the foramen and over this sharp bony edge will cause pain. Also pressure against the sharp bone will cause pain because the oral mucosa is pinched between the sharp bony margin of the mental foramen and the denture.

The most suitable way of managing this is to alter the denture so pressure does not exist. However, in rare instances it may be necessary to trim the bone to relieve the mental nerve of pres sure. Pressure on the mental nerve is reduced by increasing the opening of the mental foramen downward toward the inferior border of the body of the mandible. Such a change permits the men tal nerve to exit the bone at a point lower than it had previouslv, thereby taking pressure off the nerve.A lack of parallelism between the maxillary and mandibular ridges can be encountered and, on occasion, may require surgical repair. This lack of parallelism may be caused by a lack of trimming of the tuberosity and ridge behind the last maxillary tooth when it is removed or may be the result of defects, unequal ridge reduction, or abnormalities of growth and development. Most clinicians favor parallel ridges for their denture foundations, because the resultant forces generated are directed in a way that tends to seat the denture rather than dislodge it.

Virtually all the surgical procedures described necessitate the use of a surgical template. The patients old dentures can usually be modified with a soft treatment resin to function as such. The use of a lined template protects the operated area from trauma and enables the patient to continue wearing the dentures. It must be understood that extensive surgical preparation of the edentulous mouth is rarely necessary, infact clinical experience indicates that careful prosthetic technique and design will frequently preclude a surgical intervention. When essential, any required surgical procedure should be as conservative as possible.

ENLARGEMENT OF DENTURE BEARING AREAS (VESTIBULOPLASTY) The reduction of alveolar ridges is frequently accompanied by an apparent encroachement of muscle attachments on the crest of the ridge. These so called high (mandibular) or low (maxillary) attachments serve to reduce the available denture bearing areas and to undermine denture stability. The anterior part of the body of the mandible is the sight most frequently involved: the labial sulcus is virtually obliterated and the mentalis muscle attachment appear to migrate to the crest of the residual ridge. This usually results in the dentist arranging the teeth more Lingually than the position of the former an terior teeth. Such lingual crowding may not be tolerated by the patient; and when the absent sulcus is accompanied by little or no at tached alveolar mucosa in this area, it is virtually impossible for a lower denture to be retained.

Myoplasty accompanied by sulcus deepening has been carried out in an attempt to improve denture retention. This enables the prosthodontist to in crease the vertical extensions of the denture flanges. When horizontal bony shelving is present in the mentalis muscle region, the surgical procedure is less successful and its relative efficacy is at tributable to the modification of the powerful mentalis muscles activity. A wide and deep sulcus is not essential for success and the vestibuloplasty can be restricted to the premolar region because the buccinator muscles are not a major cause of the problem. Although a lingual vestibuloplasty can provide for a major denture dimensional increase, the procedure is traumatic, particularly in frail and elderly patients and therefore not frequently recommended.

The use of acrylic resins template or the modified previous dentures to support vestibuloplasty in the mandible is essential. These templates must be fastened to the mandible with circum mandibular wires for atleast one week. Carefully designed splints will reduce inflammation, reduce post operative scarring and maintain muscles in the desired positions thereby improving the result.

One other result of excessive alveolar bone loss or reduction is obliteration of the hamular notch.This anatomical cul-de-sac, with its potential for displacement, makes it an important part of the posterior palatal seal of the maxillary denture. Its absence can severely undermine retention of the

• denture, and a small localized deepening of the sulcus in this area may be indicated. The patient's old denture or a surgical template is employed after the surgery to help retain the patencv of the newly formed sulcus, or notch.

Ridge augmentation. For many years surgeons have attempted to restore mandibular bulk by plac ing onlay bone grafts from an iliac or rib source above or below the mandible. Unfortunately, fol low-up reports suggest that the result generally leaves much to be desired with respect to ridge height and minimal morbidity as a treatment out come. Other methods of dimensional increase of the mandible also have been proposed. However, it is a formidable undertaking for elderly patients.

REPLACING TOOTH ROOTS BY OSSEOINTEGRATED DENTAL IMPLANTS. Complete dentures are not the only method available for treating edentulous patients. Recent research has provided irrefutable evidence of the desirability and feasibility of osseointegrating tooth replicas or analogues in edentulous jaws. This scientific advance has ushered in a new era in the treatment of edentulism by virtue of the fundamental change in its applied concept of pre prosthetic surgery. In this technique, a number of cylindrically shaped screws, made of specific materials and confirming to specific designs are buried inside the selected host bone sites.

They are left to heal in situ for 4 to 6 months while osseointegration occurs. The screws or tooth root analogues are uncovered at a second surgical procedure, when an elective removable fixed bridge is attached to the implants. The technique also improves the scope for use of supporting over dentures and is widely regarded as having completely eclipsed the previously mentioned pre prosthetic surgical methods.