Preprosthetic Surgery


Hard Tissue Recontouring

Current Trends in  Alveolar Preservation

As  dental implants continue to grow in popularity and play a major role in prosthetic reconstruction, the need for traditional bony recontouring at the time of extraction has been de-emphasized. Current trends tend to lean toward preservation of alveolar bone and overlying periosteal blood supply, which enhances and preserves future bone volume. Alternatives to traditional alveoloplasty have emerged in an effort to maintain bone height and volume for the placement of implants to provide a stable platform for prosthetic reconstruction. Such alternatives include orthodontic guided tooth/root extraction, conservative extraction techniques using periosteotomes to maintain alveolar continuity, immediate grafting of extraction sites, relief of undercuts using bone grafts or hydroxylapatite (HA) augmentation, and guided tissue regeneration.

In  cases where bony abnormalities or undercuts require attention, selective alveolar recontouring is indicated.

Advances in implant technology have placed a greater emphasis on planning for alveolar ridge preservation. Beginning at the initial consultation, all extraction sites should be considered for implant reconstruction. Regardless of the reason for extraction (ie, pulpal disease, periodontal disease, or trauma), every effort should be made to maintain alveolar bone, particularly buccal (labial) and lingual (palatal) walls. However, even with alveolar bone maintenance, there can be unpredictable resorption in a short period of time.

Multiple adjacent extractions may also contribute to extensive alveolar bone loss precluding implant reconstruction.

Historically, techniques for alveolar ridge preservation were developed to facilitate conventional denture prostheses.

HA materials were the first materials not plagued by host rejection and fibrous encapsulation. Previously, the use of polymethyl methacrylate, vitreous carbon, and aluminum oxide had led to poor

results. Root form and particulate HA both were adapted and successful in preserving alveolar ridge form.

The obvious limitation with nonresorbable materials is that they preclude later implant reconstruction. Tricalcium phosphate is a resorbable ceramic that was originally thought would solve this problem, but it

proved not to be truly osteoconductive as it promoted giant cell rather than osteoclastic resorption.

This resulted in limited osteogenic potential. Another alloplast that has been used for this purpose is

bioactive glass, which consists of calcium, phosphorus, silicone, and sodium, but, again, the biologic behavior of the replacement bone was never felt to be satisfactory for implant reconstruction.

The gold standard for use for bony reconstruction anywhere has always been autogenous grafts. The dilemma with autogenous grafts involves donor site morbidity: whether from an intraoral or extraoral

source, the additional surgery and inconvenience to the patient has precluded its general use. To avoid the use of a donor site, various allogeneic bone preparations have been advocated. Stringent tissue bank regulations have provided the public with greater confidence in the use of these materials. Anorganic bone has most recently been adapted for use in alveolar ridge preparation. Two products are currently available commercially. The first is a xenograft derived from a bovine source.

The main advantage of this type of material is that it is available in an almost unlimited supply and is chemically and biologically almost identical to human bone.

Minimal immune response is elicited because of the absence of protein; however, the resorption rate of bovine cortical bone is slow. In both animal and human studies, remnants of nonvital cortical bone have been shown to be present 18 months or longer in the grafted site.

A second product, derived from human bone, is processed by solvent extraction and dehydration.Animal studies have shown that there is near complete remodeling with little or no remnant of the human anorganic bone left in the specimen.

Both the deproteinized bovine bone and the solvent dehydrated mineralized human bone appear to have great potential in alveolar ridge preservation. These materials take a long time to resorb, so a ridge form is maintained over an extended period of time, and are resorbed and remodeled via an osteoclastic process that results in bone ideally suited for implant placement.

The technique for alveolar ridge preservation at the time of extraction has been described by Sclar.

Atraumatic extraction is essential. Preservation of buccal or labial bone may be facilitated by the use of microosteotomes, and, whenever possible, buccal or labial mucoperiosteal elevation is to be avoided or limited. The socket should be gently curetted and irrigated, and in the presence of periodontal infection, topical antibiotics may be helpful. Tetracycline powder mixed with the deproteinized bovine bone or the solvent dehydrated mineralized human bone may allow for the use of either of these types of bone in almost

any clinical situation. It is not essential that the graft have complete watertight mucosal coverage. Collagen membrane is used to prevent spillage of the material from the socket, particularly in maxillary extractions.

When temporary restorations are employed at the time of surgery, an ovate pontic provisional restoration helps to support the adjacent mucosa during soft tissue maturation. In selected instances immediate placement of implants in the extraction site can be done in conjunction with the use of these

deproteinized bone preparations. Because of the slow resorptive nature of both of these bone preparations, they may be ideally suited for buccal or labial defects that would otherwise be grafted with autogenous cortical bone.

Alveoloplasty

Often hard and soft tissues of the oral region need to undergo recontouring to provide a healthy and stable environment for future prosthetic restorations. Simple alveolar recontouring after extractions consists of compression and in-fracture of the socket; however, one must avoid over compression and over-reduction of irregularities. Current trends endorse a selective stent-guided approach to site-specific

bony recontouring, eliminating bony abnormalities that interfere with prosthetic reconstruction or insertion. Multiple irregularities produce undercuts that are obstructions to the path of insertion for

conventional prosthetic appliances. These obstructions need a more complex alveoloplasty to achieve desired results. In many cases the elevation of mucoperiosteal flaps using a crestal incision with vertical releases is necessary to prevent tears and to produce the best access to the alveolar ridge. During mucoperiosteal flap resection, periosteal and Woodson elevators are the most appropriate tools to prevent excess flap reflection, devitalization, and sequestrum formation. These conditions increase pain and discomfort for the patient and increase the duration needed before prosthetic restoration can proceed.

The use of a rongeur or file for advanced recontouring is preferred to rotary instruments to prevent over-reduction. For large bony defects, rotary instrument recontouring is preferred. Normal saline irriga-

tion is used to keep bony temperatures < 47˚C to maintain bone viability.

Owing to the physiology of bone and current restorative options available, interseptal alveoloplasty is rarely indicated. The main disadvantage of this procedure is the overall decrease in ridge thickness, which results in a ridge that may be too thin to accommodate future implant placement.

Removal of interseptal bone eliminates endosteal growth potential, which is necessary for ridge preservation.

Therefore, if this technique is to be used, one must be cognizant of ridge thickness and reduce the labial dimension only enough to lessen or eliminate undercuts in areas where implants are not anticipated.

After hard tissue recontouring, excessive soft tissue is removed to relieve mobile tissue that decreases the fit and functional characteristics of the final prosthesis. Closure with a resorbable running/lock-stitch

suture is preferred because fewer knots are less irritating for the patient.

Treatment of Exostoses

Undercuts and exostoses are more common in the maxilla than in the mandible. In areas requiring bony reduction, local anesthetic should be infiltrated. This produces adequate anesthesia for the patient as well as an aid in hydrodissection of the overlying tissues, which facilitates flap elevation. In the mandible an inferior alveolar neurovascular block may also be necessary. A crestal incision extending approximately 1.5 cm beyond each end of the area requiring contour should be completed. A full mucoperiosteal flap is reflected to expose all the areasof bony protuberance. Vertical releasing incisions may be necessary if adequate exposure cannot be obtained since trauma of the soft tissue flap may occur. Recontouring of exostoses may require the use of a rotary instrument in large areas or a hand rasp or file in minor areas. Once removal of the bony protuberance is complete and visualization confirms that no irregularities or undercuts exist, suturing may be performed to close the soft tissue incision. If nonresorbable sutures are used, they should be removed in approximately 7 days.

In  areas likely to be restored with implants or implant-supported prostheses, irregularities and undercuts are best treated using corticocancellous grafts from an autogenous or alloplastic source. This can be done using a vertical incision only adjacent to the proposed area of grafting.

A subperiosteal dissection is used to create a pocket for placement of the graft material. Visual inspection and palpation of the area should be done at the conclusion of the procedure to verify the relief of the defect. The incision can be closed with resorbable sutures. In areas that require a large amount of graft material, scoring ofthe periosteum can assist in closure of soft tissue defects. In addition, the use of a resorbable collagen membrane can be used to prevent tissue in growth into the surgical site.

Tuberosity Reduction

Excesses in the maxillary tuberosity may consist of soft tissue, bone, or both. Sounding, which is performed with a needle, can differentiate between the causes with a local anesthetic needle or by panoramic radiograph. Bony irregularities may be identified, and variations in anatomy as well as the

level of the maxillary sinuses can be ascertained. Excesses in the area of the maxillary tuberosity may encroach on the interarch space and decrease the overall freeway space needed for proper prosthetic function.

Access to the tuberosity area can be obtained easily using a crestal incision beginning in the area of the posterior tuberosity and progressing forward to the edge of the defect using a no. 12 scalpel blade. Periosteal dissection then ensues exposing the underlying bony anatomy. Excesses in bony anatomy are

removed using a side-cutting rongeur. Careful evaluation of the level of the maxillary sinus must be done before bony recontouring is attempted in the area of the tuberosity.

Sharp undermining of the overlying soft tissue may be performed in a wedge-shaped fashion beginning at the edge of a crestal incision to thin the overall soft tissue bulk overlying the bony tuberosity. Excess overlying soft tissue may be trimmed in an elliptic fashion from edges of the crestal incision to allow a tension-free passive closure (Figure 9-12). Closure is performed using a nonresorbable suture in a running fashion. Small sinus perforations require no treatment as long as the membrane remains intact. Large perforations must be treated with a tension free tight closure as well as antibiotics, preferably a penicillinase-resistant penicillin such as an amoxicillin/clavulanate potassium preparation or a second-generation cephalosporin. The patient is instructed to take sinus medications including antihistamines and decongestants for approximately 10 to 14 days and not to create excessive transmural pressure across the incision site by  blowing his or her nose or sucking through straws.

Genial Tubercle Reduction

The genioglossus muscle attaches to the lingual aspect of the anterior mandible. As the edentulous mandible resorbs, this tubercle may become significantly pronounced. In cases in which anterior mandibular augmentation is indicated, leaving this bony projection as a base for subsequent grafting facilitates augmentation of mandibular height.During conventional mandibular denture fabrication, this bony tuberosity as well as its associated muscle attachments may create displacement issues with the overlying prostheses.

In these cases it should be relieved. Floor of-mouth lowering procedures should also be considered in cases in which genioglossus and mylohyoid muscle attachments interfere with stability and function of conventional mandibular prostheses.

Bilateral lingual nerve blocks in the floor of the mouth are necessary to achieve adequate anesthesia in this area. A crestal incision from the midbody of the mandible to  the midline bilaterally is necessary for proper exposure. A subperiosteal dissection exposes the tubercle and its adjacent muscle attachment. Sharp excision of the muscle from its bony attachment may be performed with electrocautery, with careful attention to hemostasis. A subsequent hematoma in the floor of the mouth may lead to airway embarrassment and life threatening consequences if left unchecked.

Once the muscle is detached, the bony tubercle may then be relieved using rotary instrumentation or a rongeur. Closure is performed using a resorbable suture in a running fashion. The genioglossus muscle is left to reattach independently.

Tori Removal

The etiology of maxillary and mandibular tori  is unknown; however, they have anincidence of 40% in males and 20% in females.

Tori may appear as a single or multiloculated bony mass in the palate or on the lingual aspect of the anterior mandible either unilaterally or bilaterally.

In the dentate patient they are rarely indicated for removal. Nevertheless, repeated overlying mucosal trauma and interference with normal speech and masticatory patterns may necessitate treatment. In the patient requiring complete or partial conventional prosthetic restoration, they may be a significant obstruction to insertion or interfere with the overall comfort, fit, and function of the planned prosthesis.

In the maxilla, bilateral greater palatine and incisive blocks are performed to achieve adequate anesthesia. Local infiltration of the overlying mucosa helps with hemostasis and hydrodissection that facilitates flap elevation. A linear midline incision with posterior and anterior vertical releases or a  U-shaped incision in the palate followed by a subperiosteal dissection is used to expose the defect. Rotary instrumentation with a round acrylic bur may be used for small areas; however, for large tori, the treatment of choice is sectioning with a cross-cut fissure bur. Once sectioned into several pieces, the torus is easily removed with an osteotome. Care must be taken not to over-reduce the palate and expose the floor of the nose. Final contouring may be done with an egg-shaped recontouring bur (Figure 9-13).

Copious irrigation is necessary throughout the procedure. Closure is performed with a resorbable suture. Presurgical fabrication of a thermoplastic stent, made from dental models with the defect removed, in combination with a tissue conditioner helps to eliminate resulting dead space, increase patient comfort, and facilitate healing in cases in which communication occurs with the nasal floor. Soft tissue breakdown is not uncommon over a midline incision; however, meticulous hygiene, irrigation, and tissue conditioners help to minimize these complications.

Mandibular tori are accessed using bilateral inferior alveolar and lingual nerve blocks as well as local infiltration to facilitate dissection. A generous crestal incision with subsequent mucoperiosteal flap elevation is performed. Maintenance of the periosteal attachment in the midline reduces hematoma formation and maintains vestibular depth. Nevertheless, when large tori encroach on the midline, maintenance of this midline periosteal attachment is impossible. Careful flap elevation with attention to the thin friable overlying mucosa is necessary as this tissue is easily damaged. Small protuberances can be sheared away with a mallet and osteotome. Large tori are divided superiorly from the adjacent bone with a fissure bur parallel to the medial axis of the mandible and are out-fractured away from the mandible by an osteotome, which provides leverage (Figure 9-14).

The residual bony fragment inferiorly may then be relieved with a hand rasp or bone file. It is not imperative that the entire protuberance be removed as long as the goals of the procedure are achieved. Copious irrigation during this procedure is imperative, and closure is completed using a resorbable suture in a running fashion. Temporary denture delivery or gauze packing lingually may be used to prevent hematoma formation and should be maintained for approximately 1 day postoperatively. Wound dehiscence and breakdown with exposure of underlying bone is not uncommon and should be treated with local irrigation with normal saline.

Mylohyoid Ridge Reduction

In cases of mandibular atrophy, the mylohyoid muscle contributes significantly to the displacement of conventional dentures. With the availability of advanced grafting techniques and dental implants, there are fewer indications for the reduction of the mylohyoid ridge. In severe cases of mandibular atrophy, the external oblique and mylohyoid ridges may be the height of contour of the posterior mandible. In these cases the bony ridge may be a significant source of discomfort as the overlying mucosa is thin and easily irritated by denture flanges extending into the posterior floor of the mouth. As a result, reduction of the mylohyoid ridge may accompany grafting techniques to provide greater relief and comfort for subsequent restorations.Historically, this procedure has been combined with lowering of the floor of the mouth; however, with the advanced armamentarium available today, there are few, if any, indications for these procedures alone or in combination.

Anesthesia is achieved with buccal, inferior alveolar, and lingual nerve blocks. A crestal incision over the height of contour is made, erring toward the buccal aspect to protect the lingual nerve. Subperiosteal dissection along the medial aspect of the mandible reveals the attachment of the mylohyoid muscle to the adjacent ridge. This can be sharply separated with electrocautery to minimize muscle bleeding. Once the overlying muscle is relieved, a reciprocating rasp or bone file can be used to smooth the remaining ridge. Copious irrigation and closure with particular attention to hemostasis is completed. Placement of a stent or existing denture may also aid in hemostasis as well as inferiorly repositioning the attachment. Again, these procedures are rarely indicated and are included here essentially for historic reference, not for routine use.

Soft Tissue Recontouring

With the eventual bony remodeling that follows tooth loss, muscle and frenum attachments that initially were not in a problematic position begin to create complications in prosthetic reconstruction and to pose an increasing problem with regard to  prosthetic comfort, stability, and fit.

Often these attachments must be altered before conventional restoration can be attempted. As dental implants become commonplace in the restoration of partially and totally edentulous patients, surgical alteration of these attachments is indicated less often. Nevertheless, inflammatory conditions such as inflammatory fibrous hyperplasia of the vestibule or epulis, and inflammatory hyperplasia of the palate must be addressed before any type of prosthetic reconstruction can proceed. Obviously, any lesion presenting pathologic consequences should undergo biopsy and be treated accordingly before reconstruction commences. In keeping with reconstructive surgery protocol, soft tissue excesses should be respected and should not be discarded until the final bony augmentation is complete. Excess tissue thought to be unnecessary may be valuable after grafting or augmentation procedures are performed to increase the overall bony volume.

Hypermobile Tissue

When excess mobile unsupported tissue remains after successful alveolar ridge restoration, or when mobile tissue exists in the presence of a preserved alveolar ridge, removal of this tissue is the treatment of choice. Usually infiltrative local anesthesia can be performed in selected areas. Sharp excision parallel to the defect in a supraperiosteal fashion allows for removal of mobile tissue to an acceptable level.

Beveled incisions may be needed to blend the excision with surrounding adjacent tissues and maintain continuity to the surrounding soft tissue. Closure with resorbable suture then approximates residual tissues. Impressions for prosthesis fabrication should proceed after a 3- to 4-week period to allow for adequate soft tissue remodeling. In cases in which denture flange extension is anticipated, the clinician must be careful to preserve the vestibule when undermining for soft tissue closure.

Granulation is a better alternative if residual tissues cannot be approximated because it maintains the vestibule and increases the width of the attached keratinized mucosa.

Fibrous Inflammatory

Hyperplasia

Fibrous inflammatory hyperplasia is often the result of an ill-fitting denture that produces underlying inflammation of the mucosa and eventual fibrous proliferation resulting in patient discomfort and a decreased fit of the overlying prosthesis.

Early management consists mainly of adjustment of the offending denture flange with an associated soft reline of the prosthesis. When there is little chance of eliminating the fibrous component, surgical excision is necessary. In most cases laser ablation with a carbon dioxide laser is the method of choice. When the treatment of large lesions would result in significant scarring and obliteration of the vestibule, sharp excision with undermining of the adjacent mucosa and reapproximation of the tissues is preferred. Again, maintenance of a supraperiosteal plane with repositioning of mucosal edges allowing for subsequent granulation is preferred over approximation of wound edges that results in the alteration of vestibular depth. This is accomplished with local anesthetic infiltrated into the proposed tissue bed, which is closed only if necessary with resorbable sutures.

Inflammatory Papillary

Hyperplasia

Once thought to be a neoplastic process, inflammatory papillary hyperplasia occurs mainly in patients with existing prosthetic appliances.

An underlying fungal etiology most often is the source of the inflammatory process and appears to coincide with mechanical irritation and poor hygiene practices. The lesion appears as multiple proliferative nodules underlying a mandibular prosthesis likely colonized with Candida. Early stages are easily treated by an improvement of hygiene practices and by the use of antifungal therapy such as nystatin tid alternating with clotrimazole troches intermittently. Nocturnal soaking of the prosthesis in an antifungal solution or in an extremely dilute solution of sodium hypochlorite helps decrease the overall colonization of the prosthesis.

In proliferative cases necessitating surgical treatment, excision in a supraperiosteal plane is the method of choice.

Many methods are acceptable, including sharp excision with a scalpel, rotary débridement, loop electrocautery as described by Guernsey, and laser ablation with a carbon dioxide laser.

Because of the awkward access needed to remove the lesions, laser ablation is the method we employ. Treatment proceeds supraperiosteally to prevent exposure of underlying palatal bone. Subsequently, placement of a tissue conditioner and a denture reline is helpful to minimize patient discomfort.

Treatment of the Labial and Lingual Frenum

Labial Frenectomy

Labial frenum attachments consist of thin bands of fibrous tissue covered with mucosa extending from the lip and cheek to  the alveolar periosteum. The height of this attachment varies from individual to individual; however, in dentate individuals frenum attachments rarely cause a problem. In edentulous individuals frenum attachments may interfere with fit and stability, produce discomfort, and dislodge the overlying prostheses.

Several surgical methods are effective in excising these attachments. Simple excision and Z-plasty are effective for narrow frenum attachments (Figures 9-15 and  9-16). Vestibuloplasty is often indicated for frenum attachments with a wide base.

Local anesthetic infiltration is performed in a regional fashion that avoids direct infiltration into the frenum itself; such an infiltration distorts the anatomy and leads to misidentification of the frenum. Eversion of the lip also helps one identify the anatomic frenum and assists with the excision. An elliptic incision around the proposed frenum is completed in a supraperiosteal fashion. Sharp dissection of the frenum using curved scissors removes mucosa and underlying connective tissue leading to a broad base of periosteum attached to the underlying bone. Once tissue margins are undermined and wound edges are approximated, closure can proceed with resorbable sutures in an interrupted fashion. Sutures should encounter the periosteum, especially at the depth of the vestibule to maintain alveolar ridge height. This also reduces hematoma formation and allows for the preservation of alveolar anatomy.

In  the Z-plasty technique, excision of the connective tissue is done similar to that described previously. Two releasing incisions creating a  Z shape precede undermining of the flaps. The two flaps are eventually undermined and rotated to close the initial vertical incision horizontally. By using the transposition flaps, this technique virtually increases vestibular depth and should be used when alveolar height is in question.

Wide-based frenum attachments may be treated with a localized vestibulosty technique. A supraperiosteal dissection is used to expose the underlying periosteum. Superior repositioning of the mucosa is completed, and the wound margin is sutured used to the underlying periosteum at the depth of the vestibule. Healing proceeds by secondary intention. A preexisting denture stent may be used for patient comfort in initial postoperative period.

Lingual Frenectomy

High  lingual frenum attachments may consist of different tissue types including mucosa, connective tissue, and superficial genioglossus muscle fibers. This attachment can interfere with denture stability, speech, and the tongue’s range of motion.

Bilateral lingual blocks and local infiltration in the anterior mandible provide adequate anesthesia for the lingual frenulum excision. To provide adequate traction, a suture is placed through the tip of the tongue. Surgical release of the lingual frenulum requires dividing the attachment of the fibrous connective tissue at the base of the tongue in a transverse fashion, followed by closure in a linear direction, which completely releases the ventral aspect of the tongue from the alveolar ridge (Figure 9-17). Electrocautery or a hemostat can be used to minimize blood loss and improve visibility. After removal of the hemostat, an incision is created through the area previously closed within the hemostat. Careful attention must be given to Wharton’s ducts and superficial blood vessels in the floor of the mouth and ventral tongue. The edges of the incision are undermined, and the wound edges are approximated and closed with a running resorbable suture, burying the knots to minimize patient discomfort.

Ridge Extension Procedures in the Maxilla and Mandible

Submucous Vestibuloplasty

In 1959 Obwegeser described the submucous vestibuloplasty to extend fixed alveolar ridge tissue in the maxilla.

This procedure is particularly useful in patients who have undergone alveolar ridge resorption with an encroachment of attachments to the crest of the ridge.

Submucous vestibuloplasty is ideal when the remainder of the maxilla is anatomically conducive to prosthetic reconstruction. Adequate mucosal length must be available for this procedure to be successful without disproportionate alteration of the upper lip. If a tongue blade or mouth mirror is placed to the height of the maxillary vestibule without distortion or inversion of the upper lip, adequate labiovestibular depth is present (Figure  9-18).

If distortion occurs then maxillary vestibuloplasty using split-thickness skin grafts or laser vestibuloplasty is the appropriate procedure.

Submucous vestibuloplasty can be performed in the office setting under outpatient general anesthesia or deep sedation. A midline incision is placed through the mucosa in the maxilla, followed by mucosal undermining bilaterally. A supraperiosteal separation of the intermediate muscle and soft tissue attachments is completed. Sharp incision of this intermediate tissue plane is made at its attachment near the crest of the maxillary alveolus. This tissue layer may then be excised or superiorly repositioned (Figure 9-19). Closure of the incision and placement of a postsurgical stent or denture rigidly screwed to the palate is necessary to maintain the new position of the soft tissue attachments. Removal of the denture or stent is performed 2 weeks postoperatively. During the healing period, mucosal tissue adheres to the underlying periosteum, creating an extension of fixed tissue covering the maxillary alveolus. A final reline of the patient’s denture may proceed at approximately 1 month postoperatively.

Maxillary Vestibuloplasty

When a submucous vestibuloplasty is contraindicated, mucosa pedicled from the upper lip may be repositioned at the depth of the vestibule in a supraperiosteal fashion.

The exposed periosteum can then be left to epithelialize secondarily. Split-thickness skin grafts may be used to help shorten the healing period. In addition, placement of a relined denture may minimize patient discomfort and help to mold and adapt underlying soft tissues and/or skin grafts.

Another option in this situation is laser vestibuloplasty. A carbon dioxide laser is used to resect tissue in a supraperiosteal plane to the depth of the proposed vestibule. A denture with a soft reline is then placed to maintain vestibular depth.

Removal of the denture in 2 to 3 weeks reveals a nicely epithelialized vestibule that extends to the desired depth (Figure 9-20).

Lip-Switch Vestibuloplasty

Both lingually based and labially based vestibuloplasties have been described.

In  the former an incision in the lower lip and submucosa undermining to the alveolus is followed by a supraperiosteal dissection to the depth of the vestibule (Figure 9-21).

The mucosal flap is then sutured to the depth of the vestibule and stabilized with a stent or denture. The labial denuded tissue is allowed to epithelialize secondarily.

In  the transpositional vestibuloplasty, the periosteum is incised at the crest of the alveolus and transposed and sutured to the denuded labial submucosa. The elevated mucosal flap is then positioned over the exposed bone and sutured to the depth of the vestibule (Figure 9-22).

These procedures provide satisfactory results provided that adequate mandibular height exists preoperatively. A minimum of 15 mm is acceptable for the above procedures. Disadvantages include unpredictable results, scarring, and relapse.

Mandibular Vestibuloplasty  and Floor-of-Mouth Lowering

Procedures

As with labial muscle attachments and soft tissue in the buccal vestibule, the mylohyoid and genioglossus attachments can preclude denture flange placement lingually. In a combination of the procedures described by Trauner as well as Obwegeser and MacIntosh, both labial and lingual extension procedures can be performed to effectively lower the floor of the mouth (Figure 9-23).

This procedure eliminates the components involved in the displacement of conventional dentures and provides a broad base of fixed tissue for prosthetic support.Again, adequate mandibular height of at least  15 mm is required. Split-thickness skin grafting is used to cover the denuded periosteum and facilitate healing.

Today, with the incorporation of endosteal implants and the fabrication of implant-borne prostheses, lingual and buccolabial flange extensions to stabilize mandibular prostheses are not necessary.

Consequently, attention is directed toward preservation or preparation of the alveolus for implants rather than extension of the fixed tissue attachments. As a result, these procedures are rarely used today.

Hard Tissue Augmentation

As  stated previously, the overall goals of reconstructive preprosthetic surgery are to provide an environment for the prosthesis that will restore function, create stability and retention, and service associated structures as well as satisfy esthetics and prevent minor sensory loss. There are many classification systems of rigid deficiencies associated with many treatment options; nevertheless, each patient must be evaluated individually. When atrophy of the alveolus necessitates bony augmentation, undercuts, exostoses, and inappropriate tissue attachments should be identified and included in the overall surgical plan prior to prosthetic fabrication.

Maxillary Augmentation

In  the past, vestibuloplasties were the procedure of choice to accentuate the alveolus in the atrophic maxilla. Unfortunately, poor quality and quantity of bone combined with excessive occlusal loading by  conventional prostheses continued to accelerate the resorptive process. Either augmentation or transantral implant cross-arch stabilization must be considered when anatomic encroachment of the palatal vault or zygomatic buttress and loss of tuberosity height affect overall fit and function of a conventional prosthesis. This section discusses conventional augmentation procedures of the maxilla to  restore acceptable alveolar form and dimensions.

There is a fourfold increase in resorption in the mandible compared with that in the maxilla, combination syndromes not withstanding.When severe resorption results in severely atrophic ridges (Cawood and Howell Classes IV–VI), some form of augmentation is indicated.

Onlay, interpositional, or inlay grafting are the procedures of choice to reestablish acceptable maxillary dimensions.

Ridge Split Osteoplasty Ridge-splitting procedures geared toward expanding the knife-edged alveolus in a buccolingual direction help to restore the crucial endosteal component of the alveolus that is associated with preservation and response to transligamentary loading and maintains the alveolus during the dentate state. Replacement of this tissue allows for dental implant stimulation of the surrounding bone that can best mimic this situation and preserve the existing alveolus and possibly stimulate future bone growth. Adequate dimensions, however, should exist that allow for a midcrestal osteotomy to separate the buccal and lingual cortices (Figures 9-24 and 9-25).

A labial incision originates just lateral to the vestibule and continues supraperiosteally to a few millimeters below the crest of the alveolus. A subperiosteal flap then originates exposing the underlying crest. Copious irrigation accompanies an osteotomy circumferentially anterior to the maxillary sinus from one side to the other.Mobilization of the labial segment can be achieved with careful manipulation with an osteotome, taking care to maintain the labial periosteal attachment. An interpositional cancellous graft can then be placed in the resulting defect, replacing the lost bony mass. Closure of the incision is away from the graft site and usually requires suturing of the flap edge to the periosteum with subsequent granulation of the remainder of the exposed tissue bed.

Endosteal implants can be placed approximately 3 to 4 months later; waiting this length of time has been shown to increase overall long-term implant success.

Onlay Grafts When clinical loss of the alveolar ridge and palatal vault occur (Cawood and Howell Class V), vertical onlay augmentation of the maxilla is indicated. Initial attempts at alveolar restoration involved the use of autogenous ribgrafts; however, currently corticocancellous blocks of iliac crest are the source of choice.

In  a similar approach to that described above, the crest of the alveolus is exposed and grafts are secured with 1.5 to 2.0 mm screws. Studies show increased success with implant placement in a second stage procedure rather than using them as sources of retention and stabilization of the graft and alveolus at the time of augmentation. Implant success ranges from > 90% initially and falls to 75% and 50%, respectively, at 3 and 5 years postoperatively.

Implant success may be directly proportional to the degree of graft maturation and incorporation at the time of implant placement. As a result, 4 to 6 months of healing is an acceptable waiting period when longterm implant success may be affected.

Interpositional Grafts

Interpositional grafts are indicated when adequate palatal vault height exists in the face of severe alveolar atrophy (Cawood and Howell Class VI) posteriorly, resulting in an increased interarch space. Because this method involves a Le Fort I osteotomy, true skeletal discrepancies between the maxilla and mandible can be corrected at the time of surgery. The improvement of maxillary dimensions as a result of interpositional grafts may obviate the need for future soft tissue recontouring to provide adequate relief for prosthetic rehabilitation (Figure 9-26). Although early studies entertained the simultaneous placement of dental implants at the time of augmentation, recently several authors have demonstrated better success rates for implants placed in a second-stage procedure; this alleviates the need for excessive tissue reflection for implant placement and allows for a more accurate placement at a later date.

A relapse of 1 to 2 mm has been demonstrated in interpositional grafts using the Le Fort I technique with rigid fixation.

More data are needed to determine long-term overall success and relapse with these procedures.

Sinus Lifts and Inlay Bone Grafts

Sinus lift procedures and inlay bone grafting play a valuable role in the subsequent implant restoration of a maxilla that has atrophied posteriorly and is unable to accommodate implant placement owing to the proximity of the maxillary sinus to the alveolar crest. Incisions just palatal to the alveolar crest are created, followed by subperiosteal exposure of the anterior maxilla. A cortical window 2 to 3 mm above the sinus floor is created with the use of a round diamond bur down to the membrane of the sinus. Careful infracture of the window with dissection of the sinus membrane off the sinus floor creates the space necessary for graft placement; the lateral maxillary wall is the ceiling for the subsequent graft (Figure 9-27).

Corticocancellous blocks or particulate bone may be placed in the resulting defect. Tears in the membrane may necessitate coverage with collagen tape to prevent extrusion and migration of particulate grafts through the perforations. Although implant placement can proceed simultaneously when 4 to 5 mm of native alveolus exists, we have found few cases where the alveolus meets these requirements and therefore elect to place implants approximately 6 months later. Block and Kent have reported an 87% success rate with sinus-grafting procedures. They also have stated that in the literature there is an overall success rate ranging from 75 to 100%.

As these procedures gain popularity and are routinely incorporated into mainstream preprosthetic surgery treatment plans, more accurate data and longterm follow-up will be available.

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