Preprosthetic Surgery

Evaluation of Supporting Bony Tissue

Examination of the supporting bone should include visual inspection, palpation, radiographic examination, and, in some cases, evaluation of models. Abnormalities of the remaining bone can often be assessed during the visual inspection; however, because of bony resorption and location of muscle or soft tissue attachments, many bony abnormalities may be obscured. Palpation of all areas of the maxilla and mandible, including the primary denture-bearing area and vestibular area, is necessary.

Evaluation of the denture-bearing area of the maxilla includes an overall evaluation of the bony ridge form. No bony undercuts or gross bony protuberances that block the path of denture insertion should be allowed to remain in the area of the alveolar ridge, buccal vestibule, or palatal vault. Palatal tori that require modification should be noted. Adequate posttuberosity notching is necessary for stabilization of the posterior denture and peripheral seal.

The remaining mandibular ridge should be evaluated visually for overall ridge form and contour, gross ridge irregularities, tori, and buccal exostosis. In cases of moderate to severe resorption of alveolar bone, ridge contour cannot be adequately assessed by visual inspection alone. Muscular and mucosal attachments near the crest of the ridge may obscure underlying bony anatomy, particularly in the area of the posterior mandible, where a depression can frequently be palpated between the external oblique line and mylohyoid ridge areas. The location of the mental foramen and mental neurovascular bundle can be palpated in relation to the superior aspect of the mandible, and neurosensory disturbances can be noted.

Evaluation of the interarch relationship of the maxilla and the mandible is important and includes an examination of the anteroposterior and vertical relationships, as well as any possible skeletal asymmetries that may exist between the maxilla and the mandible. In partially edentulous patients, the presence of supraerupted or malpositioned teeth should also be noted. The anteroposterior relationship must be evaluated with the patient in the proper vertical dimension. Overclosure of the mandible may result in a class III skeletal relationship but may appear normal if evaluated with the mandible in the proper postural position. Lateral and posteroanterior cephalometric radiographs with the jaws in proper postural position may be helpful in confirming a skeletal discrepancy. Careful attention must be paid to the interarch distance, particularly in the posterior areas, where vertical excess of the tuberosity, either bony tissue or soft tissue, may impinge on space necessary for placement of a prosthesis that is properly constructed ( Fig. 13.2 ).

Proper radiographs are an important part of the initial diagnosis and treatment plan. Panoramic radiographic techniques provide an excellent overview assessment of underlying bony structure and pathologic conditions. Radiographs should disclose bony pathologic lesions, impacted teeth or portions of remaining roots, the bony pattern of the alveolar ridge, and pneumatization of the maxillary sinus ( Fig. 13.3 ).

Cephalometric radiographs may also be helpful in evaluating the cross-sectional configuration of the anterior mandibular ridge area and ridge relationships ( Fig. 13.4 ). To evaluate the ridge relationship in the vertical and anteroposterior dimensions, it may be necessary to obtain the cephalometric radiograph in the appropriate vertical dimension. This often requires adjusting or reconstructing dentures to this position or making properly adjusted bite rims to be used for positioning at the time the radiograph is taken.

More sophisticated radiographic studies, such as computed tomography scans, may provide further information. Computed tomography scans are particularly helpful in evaluating the cross-sectional anatomy of the maxilla, including ridge form and sinus anatomy. The cross-sectional anatomy of the mandible, including the configuration of basal bone, the alveolar ridge, and the location of the inferior alveolar nerve, can be evaluated more precisely.

Evaluation of Supporting Soft Tissue

Assessment of the quality of tissue of the primary denture-bearing area overlying the alveolar ridge is of utmost importance. The amount of keratinized tissue firmly attached to the underlying bone in the denture-bearing area should be distinguished from poorly keratinized or freely movable tissue. Palpation discloses hypermobile fibrous tissue that is inadequate for a stable denture base ( Fig. 13.5 ).

The vestibular areas should be free of inflammatory changes such as scarred or ulcerated areas caused by denture pressure or hyperplastic tissue resulting from an ill-fitting denture. Tissue at the depth of the vestibule should be supple and without irregularities for maximal peripheral seal of the denture. Assessment of vestibular depth should include manual manipulation of the adjacent muscle attachments. By tensing the soft tissue adjacent to the area of the alveolar ridge, the dentist can note muscle or soft tissue attachments (including frena) that approximate the crest of the alveolar ridge and are often responsible for the loss of peripheral seal of the denture during speech and mastication.

The lingual aspect of the mandible should be inspected to determine the level of attachment of the mylohyoid muscle in relation to the crest of the mandibular ridge and the attachment of the genioglossus muscle in the anterior mandible. The linguovestibular depth should be evaluated with the tongue in several positions because movement of the tongue accompanied by elevation of the mylohyoid and genioglossus muscles is a common cause of movement and displacement of the lower denture.

Treatment Planning

Before any surgical intervention, a treatment plan addressing the patient's identified oral problems should be formulated. The dentist responsible for prosthesis construction should assume responsibility for seeking surgical consultation, when necessary. Long-term maintenance of the underlying bone, soft tissue, and prosthetic appliances should be kept in mind at all times. When severe bony atrophy exists, treatment must be directed at correction of the bony deficiency and alteration of the associated soft tissue. When some degree of bony support remains despite alveolar atrophy, improvement of the denture-bearing area may be accomplished by directly treating the bony deficiency or by compensating for it with soft tissue surgery. The most appropriate treatment plan should consider ridge height, width, and contour. Several other factors should also be considered: in an older patient in whom moderate bony resorption has taken place, soft tissue surgery alone may be sufficient for improved prosthesis function. In an extremely young patient who has undergone the same degree of atrophy, bony augmentation procedures may be indicated. The role of implants may alter the need for surgical modification of bone or soft tissue.

Hasty treatment planning, without consideration for long-term results, can often result in unnecessary loss of bone or soft tissue and improper functioning of the prosthetic appliance. For example, when there appears to be redundant or loose soft tissue over the alveolar ridge area, the most appropriate long-term treatment plan may involve grafting bone to improve the contour of the alveolar ridge or support endosteal implants. Maintenance of the redundant soft tissue may be necessary to improve the results of the grafting procedure. If this tissue were removed without any consideration of the possible long-term benefits of a grafting procedure, the opportunity for improved immediate function and the opportunity for long-term maintenance of bony tissue and soft tissue would be lost. If bony augmentation is indicated, maximum augmentation frequently depends on availability of adjacent soft tissue to provide tension-free coverage of the graft. Soft tissue surgery should be delayed until hard tissue grafting and appropriate healing have occurred. This is especially true for conservation of gingiva and keratinized soft tissues, which provide a better implant environment. Therefore it is usually desirable to delay definitive soft tissue procedures until underlying bony problems have been adequately resolved. However, when extensive grafting or other more complex treatment of bony abnormalities is not required, bony and soft tissue preparation sometimes can be completed simultaneously.

Simple Alveoloplasty Associated With Removal of Multiple Teeth

The simplest form of alveoloplasty consists of the compression of the lateral walls of the extraction socket after simple tooth removal. In many cases of single tooth extraction, digital compression of the extraction site adequately contours the underlying bone, provided no gross irregularities of bone contour are found in the area after extraction. When multiple irregularities exist, more extensive recontouring often is necessary. A conservative alveoloplasty in combination with multiple extractions is carried out after all of the teeth in the arch have been removed (see Chapter 8 ). The specific areas requiring alveolar recontouring are obvious if this sequence is followed. Whether alveolar ridge recontouring is performed at the time of tooth extraction or after a period of healing, the technique is essentially the same. Bony areas requiring recontouring should be exposed using an envelope type of flap. A mucoperiosteal incision along the crest of the ridge, with adequate extension anteroposterior to the area to be exposed, and flap reflection allow adequate visualization and access to the alveolar ridge. Where adequate exposure is not possible, small vertical-releasing incisions may be necessary.

The primary objectives of mucoperiosteal flap reflection are to allow for adequate visualization and access to the bony structures that require recontouring and to protect soft tissue adjacent to this area during the procedure. Although releasing incisions often create more discomfort during the healing period, this technique is certainly preferred to the possibility of an unanticipated tear in the edges of a flap when inadequate exposure could not be achieved with an envelope flap. Regardless of flap design, the mucoperiosteum should be reflected only to the extent that adequate exposure to the area of bony irregularity can be achieved. Excessive flap reflection may result in devitalized areas of bone, which will resorb more rapidly after surgery, and a diminished soft tissue adaptation to the alveolar ridge area.

Depending on the degree of irregularity of the alveolar ridge area, recontouring can be accomplished with a rongeur, a bone file, or a bone burr in a handpiece, alone or in combination ( Fig. 13.6 ). Copious saline irrigation should be used throughout the recontouring procedure to avoid overheating and bone necrosis. After recontouring, the flap should be reapproximated by digital pressure and the ridge palpated to ensure that all irregularities have been removed ( Fig. 13.7 ). After copious irrigation to ensure removal of debris, the tissue margins can be reapproximated with interrupted or continuous sutures. Resorbable sutures are usually used to approximate tissue and add tensile strength across the wound margins. The resorbable material is broken down by salivary proteolytic enzymes or hydrolysis over several days to weeks, eliminating the need for removal. If an extensive incision has been made, continuous suturing tends to be less annoying to the patient and provides for easier postoperative hygiene because of the elimination of knots and loose suture ends along the incision line. The initial soft tissue redundancy created with reduction of the bony irregularities often shrinks and readapts over the alveolus, allowing preservation of attached gingiva.

When a sharp knife-edge ridge exists in the mandible, the sharp superior portion of the alveolus can be removed in a manner similar to that described for simple alveoloplasty. After local anesthesia is obtained, a crestal incision is made, extending along the alveolar ridge approximately 1 cm beyond either end of the area requiring recontouring ( Fig. 13.8 ). After minimal reflection of the mucoperiosteum, a rongeur can be used to remove the major portion of the sharp area of the superior aspect of the mandible. A bone file is used to smooth the superior aspect of the mandible. After copious irrigation, this area is closed with continuous or interrupted sutures. Before removal of any bone, strong consideration should be given to reconstruction of proper ridge form using grafting procedures (discussed later in this chapter).

Intraseptal Alveoloplasty

An alternative to the removal of alveolar ridge irregularities by the simple alveoloplasty technique is the use of an intraseptal alveoloplasty, or Dean technique, involving the removal of intraseptal bone and the repositioning of the labial cortical bone, rather than removal of excessive or irregular areas of the labial cortex. This technique is best used in an area where the ridge is of relatively regular contour and adequate height but presents an undercut to the depth of the labial vestibule because of the configuration of the alveolar ridge. The technique can be accomplished at the time of tooth removal or in the early initial postoperative healing period.

After exposure of the crest of the alveolar ridge by reflection of the mucoperiosteum, a small rongeur can be used to remove the intraseptal portion of the alveolar bone ( Fig. 13.9 ). After adequate bone removal has been accomplished, digital pressure should be sufficient to fracture the labiocortical plate of the alveolar ridge inward to approximate the palatal plate area more closely. Occasionally, small vertical cuts at either end of the labiocortical plate facilitate repositioning of the fractured segment. By using a burr or osteotome inserted through the distal extraction area, the labial cortex is scored without perforation of the labial mucosa. Digital pressure on the labial aspect of the ridge is necessary to determine when the bony cut is complete and to ensure that the mucosa is not damaged. After positioning of the labiocortical plate, any slight areas of bony irregularity can be contoured with a bone file, and the alveolar mucosa can be reapproximated with interrupted or continuous suture techniques. A splint or an immediate denture lined with a soft lining material can then be inserted to maintain the bony position until initial healing has taken place.

This type of technique has several advantages: the labial prominence of the alveolar ridge can be reduced without significantly reducing the height of the ridge in this area. The periosteal attachment to the underlying bone can also be maintained, thereby reducing postoperative bone resorption and remodeling. Finally, the muscle attachments to the area of the alveolar ridge can be left undisturbed in this type of procedure. Michael and Barsoum reported the results of a study comparing the effects of postoperative bone resorption after three alveoloplasty techniques. In their study, nonsurgical extraction, labial alveoloplasty, and an intraseptal alveoloplasty technique were compared with evaluate postoperative bony resorption. The initial postoperative results were similar, but the best long-term maintenance of alveolar ridge height was achieved with nonsurgical extractions, and the intraseptal alveoloplasty technique resulted in less resorption than did removal of labiocortical bone for reduction of ridge irregularities.

The main disadvantage of this technique is the decrease in ridge thickness that obviously occurs with this procedure. If the ridge form remaining after this type of alveoloplasty is excessively thin, it may preclude placement of implants in the future. For this reason the intraseptal alveoloplasty should reduce the thickness of the ridge in an amount sufficient only to reduce or eliminate undercuts in areas where a plan to place endosteal implants does not exist. Methods for preservation of alveolar width with simultaneous grafting into the extraction site are addressed later in the chapter.

Maxillary Tuberosity Reduction (Hard Tissue)

Horizontal or vertical excess of the maxillary tuberosity area may be a result of excess bone, an increase in the thickness of soft tissue overlying the bone, or both. A preoperative radiograph or selective probing with a local anesthetic needle is often useful to determine the extent to which bone and soft tissue contribute to this excess and to locate the floor of the maxillary sinus. Recontouring of the maxillary tuberosity area may be necessary to remove bony ridge irregularities or to create adequate interarch space, which allows proper construction of prosthetic appliances in the posterior areas. Surgery can be accomplished using local anesthetic infiltration or posterosuperior alveolar and greater palatine blocks. Access to the tuberosity for bone removal is accomplished by making a crestal incision that extends up the posterior aspect of the tuberosity area. The most posterior aspect of this incision is often best made with a No. 12 scalpel blade. Reflection of a full-thickness mucoperiosteal flap is completed in the buccal and palatal directions to allow adequate access to the entire tuberosity area ( Fig. 13.10 ). Bone can be removed using a side-cutting rongeur or rotary instruments, with care taken to avoid perforation of the floor of the maxillary sinus. If the maxillary sinus is inadvertently perforated, no specific treatment is required, provided that the sinus membrane has not been violated. After the appropriate amount of bone has been removed, the area should be smoothed with a bone file and copiously irrigated with saline. The mucoperiosteal flaps can then be readapted.

Excess, overlapping soft tissue resulting from the bone removal is excised in an elliptical fashion. A tension-free closure over this area is important, particularly if the floor of the sinus has been perforated. Sutures should remain in place for approximately 7 days. Initial denture impressions can be completed approximately 4 weeks after surgery.

In the event of a gross sinus perforation involving an opening in the sinus membrane, the use of postoperative antibiotics and sinus decongestants is recommended. Amoxicillin is usually the antibiotic of choice, unless contraindicated by allergy. Sinus decongestants such as pseudoephedrine, with or without an antihistamine, are adequate. The antibiotic and the decongestant should be given for 7 to 10 days postoperatively. The patient is informed of the potential complications and cautioned against creating excessive sinus pressure such as nose blowing or sucking with a straw for 10 to 14 days.

Buccal Exostosis and Excessive Undercuts

Excessive bony protuberances and resulting undercut areas are more common in the maxilla than in the mandible. A local anesthetic should be infiltrated around the area requiring bony reduction. For mandibular buccal exostosis, inferior alveolar blocks may also be required to anesthetize bony areas. A crestal incision extends 1 to 1.5 cm beyond each end of the area requiring contouring, and a full-thickness mucoperiosteal flap is reflected to expose the areas of bony exostosis. If adequate exposure cannot be obtained, vertical-releasing incisions are necessary to provide access and prevent trauma to the soft tissue flap. If the areas of irregularity are small, recontouring with a bone file may be all that is required; larger areas may necessitate use of a rongeur or rotary instrument ( Fig. 13.11 ). After completion of the bone recontouring, soft tissue is readapted, and visual inspection and palpation ensure that no irregularities or bony undercuts exist. Interrupted or continuous suturing techniques are used to close the soft tissue incision. Denture impressions can be completed 4 weeks postoperatively.

Although extremely large areas of bony exostosis generally require removal, small undercut areas are often best treated by being filled with autogenous or allogeneic bone material. Such a situation might occur in the anterior maxilla or mandible, where removal of the bony buccal protuberance results in a narrowed crest in the alveolar ridge area and a less desirable area of support for the denture, as well as an area that may resorb more rapidly.

Local anesthetic infiltration is generally sufficient when filling in buccal undercut areas. The undercut portion of the ridge is exposed with a crestal incision and standard dissection, or the undercut area can be accessed with a vertical incision made in the anterior maxillary or mandibular areas ( Fig. 13.12 ). A small periosteal elevator is then used to create a subperiosteal tunnel extending the length of the area to be filled in with bone graft. Autogenous or allogeneic material can then be placed in the defect and covered with a resorbable membrane. Impressions for denture fabrication can be taken after tissue healing 3 to 4 weeks after surgery. A modification of this technique is also discussed in Chapter 15 .

Lateral Palatal Exostosis

The lateral aspect of the palatal vault may be irregular because of the presence of lateral palatal exostosis. This presents problems in denture construction because of the undercut created by the exostosis and the narrowing of the palatal vault. Occasionally these exostoses are large enough that the mucosa covering the area becomes ulcerated.

Local anesthetic in the area of the greater palatine foramen and infiltration in the area of the incision are necessary. A crestal incision is made from the posterior aspect of the tuberosity, extending slightly beyond the anterior area of the exostosis, which requires recontouring ( Fig. 13.13 ). Reflection of the mucoperiosteum in the palatal direction should be accomplished with careful attention to the area of the palatine foramen to avoid damage to the blood vessels as they leave the foramen and extend forward. After adequate exposure, a rotary instrument or bone file can be used to remove the excess bony projection in this area. The area is irrigated with sterile saline and closed with continuous or interrupted sutures. No surgical splint or packing is generally required, and the apparent redundant soft tissues will adapt after this procedure.

Mylohyoid Ridge Reduction

One of the more common areas interfering with proper denture construction in the mandible is the mylohyoid ridge area. In addition to the actual bony ridge, with its easily damaged thin covering of mucosa, the muscular attachment to this area often is responsible for dislodging the denture. When this ridge is extremely sharp, denture pressure may produce significant pain in this area. (Relocation of the mylohyoid muscle to improve this condition is discussed later in this chapter.) In cases of severe resorption, the external oblique line and the mylohyoid ridge area may actually form the most prominent areas of the posterior mandible, with the midportion of the mandibular ridge existing as a concave structure. In such cases, augmentation of the posterior aspect of the mandible, rather than removal of the mylohyoid ridge, may be beneficial. However, some cases can be improved by reduction of the mylohyoid ridge area.

Inferior alveolar, buccal, and lingual nerve blocks are required for mylohyoid ridge reduction. A linear incision is made over the crest of the ridge in the posterior aspect of the mandible. Extension of the incision too far to the lingual aspect should be avoided because this may cause potential trauma to the lingual nerve. A full-thickness mucoperiosteal flap is reflected, which exposes the mylohyoid ridge area and mylohyoid muscle attachments ( Fig. 13.14 ). The mylohyoid muscle fibers are removed from the ridge by sharply incising the muscle attachment at the area of bony origin. When the muscle is released, the underlying fat is visible in the surgical field. After reflection of the muscle, a rotary instrument with careful soft tissue protection or bone file can be used to remove the sharp prominence of the mylohyoid ridge. Immediate replacement of the denture is desirable because it may help to facilitate a more inferior relocation of the muscular attachment; however, this is unpredictable and may actually be best managed by a procedure to lower the floor of the mouth.

Genial Tubercle Reduction

As the mandible begins to undergo resorption, the area of the attachment of the genioglossus muscle in the anterior portion of the mandible may become increasingly prominent. In some cases the tubercle may actually function as a shelf against which the denture can be constructed, but it usually requires reduction to construct the prosthesis properly. Before a decision to remove this prominence is made, consideration should be given to possible augmentation of the anterior portion of the mandible rather than reduction of the genial tubercle. If augmentation is the preferred treatment, the tubercle should be left to add support to the graft in this area. Local anesthetic infiltration and bilateral lingual nerve blocks should provide adequate anesthesia. A crestal incision is made from each premolar area to the midline of the mandible. A full-thickness mucoperiosteal flap is dissected lingually to expose the genial tubercle. The genioglossus muscle attachment can be removed by a sharp incision.

Smoothing with a burr or a rongeur followed by a bone file removes the genial tubercle. The genioglossus muscle is left to reattach in a random fashion. As with the mylohyoid muscle and mylohyoid ridge reduction, a procedure to lower the floor of the mouth may also benefit the anterior mandible.