Pre-prosthetic procedures in maxillofacial surgery: A review of literature

Maxillary tuberosity reduction

The maxillary tuberosity may be excessive either vertically or laterally. Excess vertical space prevents proper placement of the occlusal plane and teeth, while lateral excess complicates the path of insertion and restricts the thickness of the buccal flange of the denture between the tuberosity and the coronoid process. It is essential to examine the mounted diagnostic cast to determine the extent of the required reduction. A thorough radiographic evaluation is necessary to rule out sinus perforation. The reduction procedure begins with an elliptical incision and mucoperiosteum reflection to expose the tuberosity. Bone is then removed using rongeurs or burs, the area is smoothed with a bone file, and irrigated liberally with saline solution. The wound is typically closed afterward.

Tissue reapproximated with continuous suture technique

E-Cross-sectional view of posterior tuberosity area, showing vertical reduction of bone and re-apposition of mucoperiosteal flap. (In some cases removal of large amounts of bone produces excessive soft tissue, which can be excised before closure to prevent overlapping.

Prominent mylohyoid ridge reduction

The mylohyoid ridge becomes pronounced due to resorption in the height of the posterior mandible's ridges, which restricts the expansion of the denture in this area. This often leads to discomfort for denture wearers. Additionally, the tonicity of the mylohyoid ridge can cause issues with denture retention. According to Gillies,11 (1956) the mylohyoid ridge should be reduced whenever it is found to be at the same level or higher than the alveolar process.

Exostoses and tori

Buccal exostoses are typically found on the buccal side of the higher ridge. These bony outgrowths prevent proper fitting of the flanges and border seal, complicate the positioning of the teeth, and hinder the proper shaping of the flange. Surgical reduction is required to address these issues.

The palatal torus is a benign, slowly expanding growth formed by the palatine processes of the maxillae and sometimes the horizontal plates of the palatine bones. The exact cause of the palatal torus is unknown, but possible etiological factors include heredity, superficial trauma, malocclusion, and a functional reaction to mastication. It is often composed of cortical bone, though some may contain cancellous bone. Surgical excision is necessary when the palatal torus completely fills the palatal vault and extends beyond the palate.

Mandibular tori are removed in three situations:

Reduction of genial tubercles

As the jaw resorbs, the region where the genioglossus muscle connects to the anterior part of the mandible may become more prominent. In some cases, the tubercle can serve as a shelf for denture construction, but often, reduction is necessary to effectively create the prosthesis. Before deciding to eliminate this prominence, it is important to consider the possible augmentation of the front section of the mandible rather than reducing the genial tubercle. If augmentation is chosen, the tubercle should be left in place to support the graft in this area. Appropriate anaesthesia should be achieved using bilateral lingual nerve blocks and local anaesthetic infusion.

Soft tissue procedures

Frenectomy

A high attached frenum can lead to a loss of border seal, preventing the upper denture from staying in place. The deep labial notch created to accommodate such a prominent frenum can weaken the denture and increase the risk of midline fracture. The issue can be addressed using techniques such as Z-plasty, V-Y advancement, or diamond excision.

A prominent lingual frenum can cause lower denture instability. To test tongue function, the patient should be able to touch their upper lip with the tip of their tongue without moving the lower denture. If they cannot, a frenectomy is recommended. After a frenectomy, the lower denture is used as a stent to prevent postoperative recurrence.

A large buccal frenum, being flexible and flaccid, rarely hampers denture function.

Epulis fissuratum

Epulis fissuratum is the hyperplasia of the sulcular epithelium brought on by a denture that fits poorly or has settled as a result of resorption causing chronic discomfort. The sulcus between the two outer and inner folds, which make up the hyperplasia, may be ulcerated.

Papillary hyperplasia

Papillary hyperplasia can be caused by factors such as a low-grade Candida infection, an ill-fitting denture, or a palatal relief chamber in the denture. These conditions result in soft, polypoid masses with numerous papillary projections that are highly red. With proper oral hygiene, care of the dentures, and attention to oral tissues, most lesions will resolve on their own. However, if the lesions persist, they need to be surgically removed. Treatment options include electrocautery, sharp excision, cryosurgery, laser excision, laser ablation, and curettage with large rotary burs.

Mental nerve repositioning

In patients with severe atrophy of the mandibular alveolar process, the mental foramen may be located at or near the crest of the residual ridge. This positioning can result in pressure on the mental nerve from the denture flange. Patients often experience pain similar to trigeminal neuralgia, including a dull, burning sensation or abrupt, sharp, severe pain that lasts briefly. Pain can be triggered by digital pressure on the mental foramen or during mastication, and some patients may also report lower lip pain and numbness.

For many patients, simply relieving the denture flange to alleviate pressure on the mental foramen is sufficient to resolve these symptoms. However, if this does not provide adequate relief, additional measures may be necessary. In such cases, surgical repositioning of the neurovascular bundles and enlargement of the mental foramina may be required to address the issue.

Ridge extension procedures

Vestibuloplasty is a surgical technique aimed at deepening the vestibule by lowering muscle attachments on the buccal, labial, and lingual aspects of the residual ridges to improve the alveolar ridge’s contour. In 1935, Kazanjian12 introduced a technique for deepening the vestibule by covering the newly exposed bone with a labial flap taken from the alveolar process, allowing the lip surface to re-epithelialize. A key drawback of this approach is the loss of vestibular depth due to scar contracture on the labial aspect.

To address this issue, Clark5 (1953) proposed a vestibuloplasty technique where the flap is pedicled off the lip rather than the alveolar process. Tortorelli13 (1968) recommended horizontally fenestrating the periosteum at the base of the newly created vestibule to prevent regression following Clark’s method. Howe (1965)14 and Kethley and Gamble (1978)15 described the "lip switch procedure," a variation of Kazanjian’s technique where an initial lip incision creates a labial mucosal flap extending to the crest of the ridge.

In 1959, Obwegeser16 introduced a submucosal vestibuloplasty technique, which raises the anterior vestibular area when there is sufficient mandibular height, enhancing denture stability and retention. This procedure is indicated when there is adequate vestibular depth on the lingual aspect of the mandible, inadequate facial vestibular depth from mucosal and muscular attachments in the anterior mandible, and at least 15 mm of anterior mandibular height. These methods often yield satisfactory results without requiring hospital stays, donor-site surgeries, or prolonged denture-free periods. However, the degree of vestibular depth relapse is unpredictable, and issues may arise with adjusting the denture's peripheral flange to the vestibule's depth.

On the lingual aspect of the mandible, the mylohyoid and genioglossus muscles, along with labial muscle attachments, can cause similar issues. Trauner17 addressed these problems by repositioning the mylohyoid muscles inferiorly and separating them from the mylohyoid ridge, thus deepening the floor of the mouth and reducing the mylohyoid muscle's impact on the denture. Clark’s supraperiosteal flap technique, labially pedicled, can be used for extending the labial vestibule. After these vestibular extension procedures, the denuded periosteum area may be covered with a skin graft.

Combining vestibular extension with split-thickness skin grafting, especially when there is at least 15 mm of mandibular bone height and insufficient alveolar ridge for denture support, is recommended. This approach provides a broad base of fixed keratinized tissue and eliminates mucosa and muscle attachment forces that can dislodge the denture. Prior to soft tissue procedures, any significant bony irregularities should be corrected with grafting or small-scale alveoloplasty to ensure the remaining bone contour is suitable for denture construction. The early covering of the exposed periosteal bed enhances patient comfort and allows for earlier denture construction, producing predictable long-term results.

Muscle and mucosal attachments that affect denture construction, stability, and retention are often a result of maxillary alveolar bone resorption. While the maxilla’s large denture-bearing area can often support adequate denture construction and stability after significant bone loss, additional soft tissue changes or modifications may be necessary alongside previous augmentation surgeries.

Several techniques can provide additional fixed mucosa and vestibular depth in the maxillary denture-bearing area. One effective method for correcting soft tissue attachments on or near the crest of the maxilla's alveolar ridge is the submucosal vestibuloplasty, as described by Obwegeser.18 This technique is particularly useful when there is sufficient bony maxilla remaining for adequate denture support. It involves either excising or repositioning the underlying submucosal tissue, allowing the labiovestibular mucosa to adhere directly to the periosteum of the remaining maxilla. Adequate mucosal length is needed to achieve vestibular depth without causing an abnormal appearance of the upper lip.

When there is insufficient labiovestibular mucosa and submucosal vestibuloplasty would result in lip shortening, alternative vestibular extension techniques should be considered. For these cases, mucosa pedicled from the upper lip can be sutured at the depth of the maxillary vestibule following a supraperiosteal dissection, as a variation of Clark's5 vestibuloplasty technique. The alveolar ridge’s denuded periosteum heals through secondary epithelialization. This approach typically requires a longer healing period of 6-8 weeks before denture construction, and moderate discomfort may be experienced during the postoperative phase.

Ridge augmentation

Augmentation of atrophic alveolar bone involves implanting graft materials, and the techniques used can significantly impact postsurgical morbidity. These methods range from basic subperiosteal tunneling to more extensive osteotomies. Techniques such as distraction osteogenesis, allografts, and bone grafts are employed to enhance the residual alveolar ridge. The choice of technique depends on patient compliance, the specific site, the amount of remaining alveolar bone, and the cause of bone resorption. For severe ridge deformities, autogenous bone grafts are often the preferred choice. Significant amounts of autogenous bone can be harvested from the iliac crest and calvarial bone in cases of severe atrophy. However, iliac onlay grafts, due to their different embryonic origins, tend to resorb more compared to calvarial grafts, with membranous bone maintaining its volume better than endochondral bone.

When severe mandibular resorption results in insufficient height and contour, leading to an increased risk of fracture, or when implant placement is planned in areas with inadequate bone width or height, superior border augmentation with a bone graft may be required. In 1948, Clementschitsch19 reported using autogenous corticocancellous blocks from the iliac crest for superior border augmentation. Today, these bone blocks are often secured to the mandible with small, rigid fixation screws to minimize graft mobility. Bone augmentation is frequently combined with membrane-guided tissue regeneration, and implants may sometimes be placed simultaneously with bone graft augmentation.

The inferior border augmentation technique for atrophic mandibles was first clinically applied by Sanders and Cox.20 Although rarely used today, this method involves augmenting mandibular bulk with iliac crest bone grafts secured with rigid fixation. This approach addresses both alveolar ridge atrophy and the prevention of atrophic mandibular fractures. However, it does not correct abnormalities in the denture-bearing regions caused by mandibular atrophy, such as the exposed position of the mental nerve, irregularities in the superior border, or increased interarch distance.

During a visor osteotomy, the mandible is split buccolingually, and the lingual cortical plate is moved superiorly. This horizontal osteotomy with interpositional graft aims to address the defect created by elevating the superior aspect of the ridge, allowing for grafting to achieve a predefined height. Grafts are typically sourced from the cancellous marrow and corticocancellous iliac crest. Corticocancellous blocks are shaped to a specific size and placed between the mandible and the pedicled bone for augmentation. Generally, two blocks are positioned in the cuspid regions, two in the molar regions, and one in the midline. Cancellous marrow and corticocancellous chips are packed into the space between the cortical struts and at the graft interface with the mandible.

A method for directly augmenting the maxilla with a contoured rib was described by Baker and Connole 21 in 1977. This technique involves an osteotomy to separate the superior and inferior dimensions of the residual jaw, followed by grafting bone into the osteotomy to create an interpositional bone graft. The initial documentation of interpositional augmentation for the atrophic maxilla was provided by Farrell et al.22 in 1976, Bell et al.23 in 1977, and Bell and Buckles24 in 1978. Bell and McBride25 described the Le Fort I osteotomy in 1977. When the palatal vault is well-formed but the ridge height is insufficient, interpositional bone grafting in the maxilla is indicated. This technique can also address transverse and anteroposterior discrepancies between the mandible and maxilla, producing stable and predictable outcomes while potentially eliminating the need for additional soft tissue procedures.

However, a drawback of this approach is the need to harvest bone from the iliac crest donor site, which may necessitate further soft tissue surgery. Additionally, inadequate bone support and the extension of the maxillary sinuses into the alveolar ridge can complicate implant placement in the posterior maxillary area. In such cases, a sinus lift procedure can be performed to augment the alveolar ridge by inserting graft material into the sinus. This involves carefully lifting the sinus lining from the bony floor by creating an incision in the lateral aspect of the maxillary wall. Graft materials for this procedure can include autogenous bone, allogeneic bone, or a combination of both.

For patients with a well-formed palatal vault but insufficient anterior and posterior bone, total maxillary osteotomy with interpositional bone grafting should be considered. This approach is also suitable for patients with maxillary transverse deficiency and bone loss presenting a relative Class III deformity. Various surgical techniques can be employed to achieve palatal vault osteotomy and elevation, including total maxillary osteotomy with palatal vault elevation. Both techniques rely on pseudo-augmentation of the alveolar ridge to enhance stability and depth of the palatal vault. If desired, interpositional bone grafting can be integrated with the total maxillary osteotomy with palatal vault elevation. The palatal vault osteotomy was first described by Charest and Goodyear.26

Implants

Implant-supported prostheses have become a prominent alternative to conventional restorations for the dental rehabilitation of edentulous patients, offering significant improvements in masticatory function and overall well-being. For optimal implant success, several factors are ideal: a normal maxilla-mandibular relationship, healthy peri-implant soft tissues, and residual bone height and width of at least 10 mm and 6 mm, respectively. The use of autogenous bone grafts in conjunction with osseointegrated implants has been shown to significantly reduce bone resorption.

Lasers

Today’s lasers are more advanced and versatile than ever, thanks to a range of technologies, materials (such as gases, solids, semiconductors, and colorants), and wavelengths. These advancements have made lasers a simple, safe, and effective tool in modern oral surgery. The ability of lasers to evaporate soft tissues without causing bleeding leads to wound healing without scarring or altering the healed site. Additionally, lasers eliminate the need for sutures, a significant advantage in preprosthetic surgery as it prevents vestibule length loss associated with sutures. This capability makes lasers particularly suitable for preparing soft tissues in patients.

Alveolar distraction osteogenesis

Alveolar distraction osteogenesis is an alternative approach for reconstructing larger bone and soft tissue defects. The technique involves distracting bone along a vector transverse to its long axis, which promotes the formation of new bone. Initially applied to the human mandible, recent clinical reports have shown that severe alveolar ridge atrophy can be effectively treated using this method.

One of the key benefits of distraction osteogenesis is that it eliminates the need for additional surgery at the donor site. Additionally, the coordinated elongation of both bone and surrounding soft tissues is a significant advantage. To achieve favorable outcomes, it is crucial to extend and widen both hard and soft tissues. Alveolar distraction osteogenesis is particularly effective for elongating soft tissues in malfunctioning alveolar regions, enabling the restoration of soft tissues with appropriate quality and volume, especially in cases of moderate to severe defects.

Tissue engineering

Tissue engineering, the science of cultivating living human tissue for transplantation, is opening new possibilities for medical treatments and advancing preprosthetic surgery. Cell culture technology has revolutionized oral reconstructive surgery, initially applied to cultured skin and mucosal grafts. A major advantage of cell culture is its ability to expand a small biopsy specimen into large, transplantable mucosal tissues within weeks.

For example, gingival mucosa has been successfully replaced with cultured palatal mucosa. Studies have shown that after 4 months, these grafts developed well-differentiated, keratinizing mucosa similar to the palatal mucosa in situ. Although research into creating ex vivo intraoral skin/mucosal grafts has shown promising results, the complexity, duration, and cost of this process are significant when compared to simpler autogenous grafting methods. The most notable benefit of ex vivo produced grafts is the absence of donor-site morbidity.