Ameloblastoma is a rare benign odontogenic neoplasm of the jaws that is found most often in the mandible (80%), in the region of the molars and the ramus. Ameloblastomas represent 1% to 3% of all cysts and tumors of the oral and maxillomandibular region. The multicystic/solid ameloblastoma is the most common type, comprising 91% of all the ameloblastomas.1 They usually progress slowly but are locally invasive and may cause significant morbidity. Four distinct growth variants of ameloblastoma are recognized in the current 2005 WHO classification for head and neck tumors: peripheral, unicystic, solid/multicystic, and desmoplastic.2 There have been controversies regarding the treatment of ameloblastomas: enucleation/curettage versus resection with wide margins. Solid ameloblastoma shows a high recurrence rate (60% to 90%) with conservative enucleation. A recent meta-analysis revealed that the risk of recurrence was 3.15-fold greater with conservative treatment in comparison to resective treatment.3 A segmental resection with a 1 to 2 cm margin has therefore been favored for the solid or multicystic-type ameloblastoma.4,5
Several options exist for reconstruction of the resulting defect. Restoration of function and an acceptable cosmetic result are the primary objectives of mandibular reconstruction. Vascularized or nonvascularized bone grafts, bone morphogenic protein, and distraction osteogenesis (DO) are options that have been previously described.6–8 Involvement of the temporomandibular joint (TMJ) adds another level of complexity since a functional and stable joint must also be reconstructed.9 Segmental defects involving the TMJ are challenging and limited evidence-based information is available regarding their management. The TMJ can be restored using iliac crest grafts,10,11 costochondral grafts,12–14 DO,15,16 microvascular-free bone flaps,17–20 metallic condylar head attached to a reconstruction plate,21–23 and alloplastic TMJ prosthesis.6,24–29
Following mandibular reconstruction, functional oral rehabilitation can be achieved with dental implants and restorative dentistry. The aim of this report is to describe 3 patients with large ameloblastomas in the mandible also involving the TMJ. These patients were treated by partial mandibulectomy and simultaneous reconstruction with a custom-made Zimmer-Biomet TMJ prosthesis and concomitant-free bone graft harvested from the iliac crest. Inferior alveolar nerve (IAN) repair was also undertaken either with direct repair or using human allograft.
REPORT OF 3 PATIENTS
This patient has been previously published by the main author.29
A healthy 55-year-old man was referred in 2011 with a recurrent lesion in the left posterior mandible. The referring surgeon had removed the primary lesion in 2005, which was diagnosed histologically as unicystic ameloblastoma, intramural type. A subsequent recurrence had also been treated in 2007 by enucleation and curettage. Thus, the patient was presenting with a second recurrence.
Extraoral examination was in the limits of normal. Intraoral examination revealed fullness of the left posterior buccal vestibule and tenderness to palpation extending to the left coronoid process. The patient was edentulous in the maxilla, and partly dentate in the mandible. Maximum interincisal opening was limited to 33 mm.
Panoramic tomography revealed a large multilocular radiolucent lesion in the left mandibular ramus (Fig. 1). Computed tomography (CT) showed significant expansion of the medial and lateral cortices in the coronoid process region with perforation of the cortical plates (Fig. 2). Magnetic resonance imaging demonstrated fluid within the lesion and no invasion into the surrounding soft tissues, despite cortical perforation.
A segmental resection of the left mandible, including 1.5 cm margins, was planned with simultaneous mandibular and TMJ reconstruction. Three-dimensional CT imaging and computer-assisted design (Medical Modeling, Denver, Colorado) were used to plan the surgical resection and to design the custom prosthesis. The 3-dimensional CT images show the lesion in the left native mandible (Fig. 3A) and the planned resection margins (Fig. 3B). A virtual model of the prosthesis was designed using dedicated software. The device was composed of a metallic (titanium alloy) mandible–condylar component and an ultra-dense, high molecular weight polyethylene glenoid fossa (Fig. 4). The mandibular body portion of the prosthesis included screw holes for simultaneous stabilization of an autogenous bone graft, which would facilitate later placement of dental implants. Mirroring software was used to shape the inferior border of the prosthesis to optimize the planned cosmetic contour. The device was manufactured by Zimmer-Biomet Microfixation (Jacksonville, FL) using computer-aided design/computer-aided manufacturing technology.
In August 2011, the lesion was accessed via submandibular, submental, and preauricular incisions. The entire mandible posterior body and ramus to the left mental foramen was resected (Fig. 5).
The IAN was partly decompressed, sectioned, and released from the proximal mandible, the specimen was removed. The nerve was withdrawn out through the mandibular foramen. Biopsy and quick section showed the nerve to be free of tumor. Repair of the IAN was achieved by re-anastomosis with microsurgical repair. The oral mucosal dehiscence was repaired with primary closure and then re-enforced with a free temporalis fascia graft sutured in place. Fibrin sealant was also used as a 3rd layer creating a barrier between the wound and the oral cavity (Fig. 6).
The histopathologic assessment confirmed a diagnosis of recurrent multicystic ameloblastoma. A corticocancellous block bone graft was harvested from the right anterior iliac crest. The alloplastic system was installed with screw fixation. The block bone graft was then screwed directly to the lingual aspect of the mandibular prosthesis (Fig. 7). Postoperative panoramic tomography (Fig. 8A) and anteroposterior cephalometric radiographs (Fig. 8B) revealed a smooth mandibular contour mirroring that of the right mandible.
The postoperative course was uneventful. The patient showed good facial symmetry, and quick return to good mandibular function. Sensory function in the lower lip and chin had returned to normal by 6 months after surgery. After 5 years, his mouth opening was 40 mm.
In March 2015, 2 implants (teeth 35–36) were placed (Fig. 9A). The postoperative healing was uneventful, and the patient was sent to his dentist for restorative dentistry (Fig. 9B).
A healthy 22-year-old female patient was referred in 2015 for a recurrent lesion in her right mandible. The patient had her wisdom tooth number 48 removed by another surgeon in October 2009. The tooth was associated with a cystic lesion. A biopsy suggested features of ameloblastoma in the cyst lining. The subsequent surgery was a marginal resection of the lesion and the extraction of the tooth number 47. The patient had an uneventful follow-up every year until December 2013. She came back with no symptoms but some new radiolucencies on the panoramic tomography. Extraoral and intraoral examinations were in the limits of normal. A CT scan revealed several new lesions in the mandibular body as well as in the right condyle (Fig. 10).
A new incisional biopsy in April 2014 came back as recurrent ameloblastoma. The proposed treatment included a right partial mandibulectomy with immediate custom TMJ reconstruction with concomitant autogenous corticocancellous free bone graft from the iliac crest. Surgery was planned and the prosthesis designed virtually as in patient 1.
In December 2014, teeth 45 and 46 were removed in preparation for the resection surgery to facilitate the creation of an intact oral mucosal cover over the area of the future prosthesis.
In August 2015, under general anesthesia, the patient underwent a right partial mandibulectomy. Submandibular, submental, and preauricular approaches were used. Resection included the TMJ, ramus, and body of the mandible to the 45 area (Fig. 11)
A nerve allograft (Avance Nerve Graft; AxoGen, Alachua, FL) was used for the IAN reconstruction (Fig. 12). An autogenous corticocancellous block bone graft harvested from the anterior iliac crest was attached to the mandibular prosthesis with screw fixation. Figure 13 demonstrates attachment holes designed within the prosthesis to facilitate suture placement between the fossa prosthesis and the condylar prothesis to prevent “condylar sag.”
The histopathology confirmed multicystic ameloblastoma.
The patient's postoperative course was uneventful. Figure 14A demonstrates the smooth anatomic mandibular contour on the anteroposterior radiograph. Figure 14B is a 3-dimensional Cone Beam CT scan showing complete healing of the bone graft. In September 2016, the patient's mouth opening was 50 mm and her occlusion was stable (Figs. 15-16). She has return of feeling after nerve grafting though it is reduced.
In April 2017, 2 implants (teeth 45–46) were placed into type II bone (Fig. 17). The postoperative implant healing was uneventful, and the patient was sent to her dentist for restorative dentistry.
A healthy 20-year-old man had a previous marsupialization for a suspected keratocyst in his right mandible. The biopsy performed at the same time revealed histologic features of multicystic ameloblastoma. He was referred for definitive surgery.
Panoramic tomography in June 2015 revealed a large multilocular radiolucent lesion in the right mandibular ramus, associated with an impacted wisdom tooth.30 Extraoral and intraoral examinations showed buccal and lingual expansion in the posterior right mandible and communication of the cystic portion of the lesion through an opening in the oral mucosa. A CT scan performed later showed that the lesion expanded the anterior border of the ramus and coronoid notch. There was expansion of the lingual cortex and mild expansion of the buccal cortex (Fig. 18).
The size and extent of the lesion and condylar involvement lead to the recommendation for resection surgery and immediate alloplastic reconstruction with a custom prosthesis.
Teeth 44 to 47 were removed in April 2015 prior to the resective surgery to allow for the creation of an intact mucosal barrier over the planned area of reconstruction.
Virtual planning and prosthesis design were carried out as in the first 2 patients.
In September 2015, the patient underwent partial resection of his right mandible extending from condylar process to first bicuspid region (Fig. 19). A custom prosthesis was placed via a submandibular, submental, and preauricular approach. Reconstruction of the IAN was performed with nerve allograft (Avance Nerve Graft). A corticocancellous block bone graft from the anterior iliac crest was harvested for reconstruction of the right mandibular body and future implant placement with restorative dentistry (Fig. 20). The oral mucosal defect was repaired as in patient 1.
The postoperative recovery was uneventful. Postoperative panoramic tomography (Fig. 21A) and anteroposterior cephalometric radiographs (Fig. 21B) revealed a smooth mandibular contour mirroring the left mandible. The return to good oral function was quick.
A follow-up Cone Beam CT scan showed excellent healing of the bone graft (Fig. 22). On September 2016, his mouth opening was 50 mm and occlusion was stable (Fig. 23). In May 2015, 3 implants (teeth 45–46–47) were placed (Fig. 24). The postoperative implant period was uneventful, and the patient was sent to his dentist for restorative dentistry.
Maxillomandibular fixation was not used in any of the patients. Light guiding elastics were used for 3 to 4 weeks. These were removed starting postoperative day 1 for jaw stretching exercise, eating, and oral hygiene.
Treatment of ameloblastomas must be adapted to macroscopic and histologic characteristics of each tumor.31 Recurrence of ameloblastoma is directly related to the surgical approach. Recurrence with conservative treatment (enucleation) is high: from 60% to 90%. Resection with 1 to 2 cm. margin has been shown to result in lower recurrence rates but can be associated with greater morbidity, poor cosmetic, and functional outcomes.
The TMJ can be restored using iliac crest grafts, costochondral grafts, DO, microvascular-free bone flaps, metallic condylar head attached to a reconstruction plate, and alloplastic TMJ prosthesis. The most widely used autogenous graft for TMJ reconstruction is the costochondral graft.32 Possible and not infrequent complications associated with costochondral grafts include fracture, unpredictable cartilage growth, ankylosis, and donor site morbidity like pneumothorax.33–36 The TMJ reconstruction with an alloplastic device appears to be a more predictable option than a costochondral graft.37 The use of a metallic condylar head attached to a reconstruction plate placed directly into the glenoid fossa (with or without retention of the TMJ disc) has been associated with erosion into temporal fossa and middle cranial fossa, plate exposure, and plate fracture.38 Reports using DO to reconstruct the TMJ are rare. The DO has been effective in some clinical reports but the treatment duration is much longer, incorporating the necessary latency, distraction, and consolidation phases. The patient must live with the implanted distractor device for more than 3 months and device failure, graft resorption, and nonunion have been reported.32 Controlling the curvilinear complex mandibular segmental defect in 3 dimensions with DO can be challenging. A second procedure is required for device removal. By contrast, the use of mirroring technology in the planning software used in the patients presented in this report facilitated a predictable restoration of good mandibular contour. Rigid fixation of the device obviated the need for maxillomandibular fixation allowing immediate postoperative jaw opening physiotherapy. No secondary surgery was required.
Another popular technique to reconstruct the TMJ after ablative surgery is the free vascularized fibula graft.7,30 These grafts are ideal for patients who have received, or will receive, radiation therapy.32 Successful healing is commonly reported though the return to good oral function is slower and the donor site morbidity potential is not inconsequential, especially in young, athletically active patients. The available bone volume for subsequent dental implant placement can be variable.
More recently, the use of recombinant human bone morphogenic protein type 2 associated or not with a collagen carrier and allogenic bone graft for restoration of large mandibular defects has been described with good success.39–41 The BMP-2 is an expensive material and as such can still have limited availability in some hospital facilities. Containment of the graft and healing time are other variables that could extend treatment timing. Nevertheless, the use of BMP may well be an interesting future modification to the technique presented in this paper as it could obviate the need to harvest autogenous tissue altogether.
The authors have used alloplastic custom fitted devices coupled with autogenous-free iliac bone grafts. The early results in these 3 patients demonstrate excellent and quick return to good facial form and function. Extensive autogenous tissue harvest (rib and fibula) was avoided. Maxillomandibular fixation was not required, allowing early return to normal oral function. This corroborates with successful results in previously published clinical reports.6,24–28,42,43
Currently available alloplastic TMJ total joint devices (metal head articulating with ultra dense high molecular weight polyethylene fossa) have been in use for over 20 years. Numerous long-term studies have demonstrated their predictability and durability.44–46 These devices are indicated for ankylosis, congenital disorders, condylar fractures, avascular necrosis, failed autogenous grafts, severe inflammatory, and degenerative TMJ disease and tumors requiring extensive resection.47
In the 3 patients presented in this paper, patients underwent TMJ and partial mandibular reconstruction with a hybrid custom alloplastic device coupled with an autogenous-free bone graft. The use of nonvascularized bone grafts provided ample bone volume. This facilitated the subsequent placement of dental implants for restoration of the lost teeth.
Ameloblastoma is a rare tumor with a well-documented propensity for local and regional invasion and a high risk of recurrence. Recent literature suggests that the initial surgical approach and histologic growth patterns are the most important prognostic determinants in ameloblastomas. Tumors involving the TMJ pose an additional challenge for reconstruction. In those patients, a total joint replacement with a custom prosthesis can provide a reliable alternative for the reconstruction. Excellent facial form and oral function can be achieved. Maxillomandibular fixation can be avoided. Treatment can be carried out as a single surgery. The use of concomitant nonvascularized bone graft facilitated optimum future dental restoration with less morbidity than a fibula-free flap or costochondral graft.
The 1 drawback to the presented technique may be the costs associated with the manufacture of the custom device though these costs are conceivably offset by the potential for significantly shorter hospital stays and earlier return to normal life for the patient. Our patients left the hospital after 3 to 4 nights.
Further future study with a larger number of similar patients will be appropriate to confirm the initial favorable results seen in these 3 patients. Future studies should also compare and contrast this technique with the alternative procedures looking at such factors as total cost, hospital length of stay, time to return to normal oral function, and patient satisfaction.
The authors thank to the engineers at Medical Modelling and Zimmer Biomet Microfixation for their role in these patients.
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