Report of Multidisciplinary Treatment of an Extensive Mandibular Ameloblastoma With Free Iliac Crest Bone Flap, Dental Implants, and Acellular Dermal Matrix Graft

Ameloblastomas are benign odontogenic tumors, constituting 1% and 9%–11% of all oral and odontogenic tumors, respectively. Presenting an aggressive nature in progression, ameloblastomas can cause orofacial swelling, sensitivity, occlusal disorders, and periodontal attachment loss.^1–3  Although the literature reports various treatment alternatives for ameloblastomas based on the extent of the lesion,^4–8  more radical procedures including radical resection and hemimandibulectomy are performed for extensive tumors.⁹  To overcome esthetic and functional disabilities caused by radical resective treatment of extensive tumors, several surgical techniques for reconstruction of the orofacial region have been proposed.¹⁰  Recently, free bone flaps, in which bone grafts can be adapted to the deficient site with sufficient intact blood supply, have been shown to be superior in bone volume gain and resistance when compared with other techniques.^9,11 

Although free bone flaps resolve the bone deficiencies caused by resective surgeries, for complete restoration of the life quality, problems associated with loss of dentition have to be managed. Conventional prosthesis presents a low success rate due to the disrupted morphology of bone and soft tissues, diminished salivary flow rate, and adverse effects of radiotherapy. By providing accurate rehabilitation of the supporting bone and dentition, dental implants allow stabilization of prosthesis and thereby have a considerable place in restoring functional deformities and esthetics in patients with maxillofacial defects.^12,13 

This case presents the multidisciplinary rehabilitation of a patient diagnosed with extensive ameloblastoma using dental implants and acellular dermal matrix grafts following reconstruction with free iliac crest bone flap.

A 29-year-old female patient with pain and orofacial swelling was referred to the Department of Periodontology in January 2010 by the Department of Plastic Reconstructive and Aesthetic Surgery. Radiographic and clinical examinations revealed extensive ameloblastoma occupying the symphysis and part of the right-sided body of the mandible (Figures 1 and 2). A multidisciplinary treatment approach including resection of the tumor via segmental mandibular resection, reconstruction with free iliac crest bone flap, and rehabilitation of the dentition with dental implant-supported fixed restorations were planned. The patient was informed about the surgical and dental procedures in detail, and informed consent forms were obtained prior to the procedures.

Under general anesthesia, segmental mandibulectomy was performed, and the lesion was removed with a resection margin of at least 1 cm of normal bone beyond the tumor mass (Figures 3 and 4). The immediate reconstruction was performed with microvascular free iliac bone flap, 7.0 × 3.0 cm, harvested from right iliac crest region and based on deep circumflex iliac artery and vein. The fixation of the flap to the mandible is achieved with a reconstruction plate and screws (Figures 5 through 7). The postoperative follow-up was uncomplicated, and the patient was discharged 10 days after the operation.

Six months after reconstructive surgical procedures, computerized tomography scans were obtained to determine the healing process and amount of bone formed. After evaluation of radiographic and clinical data, 7 endosseous 2-stage dental implants (Tapered Swiss Plus, Zimmer Dental, Carlsbad, Calif, 3.7 and 4.8 mm in diameter, 14 mm in length) were placed into the mandibula according to the manufacturer's instructions (Figures 8 and 9). To avoid postoperative complications, antibiotics and analgesics were prescribed. The healing was uneventful and sutures were removed 10 days after surgical procedures.

Seven months after insertion of dental implants, clinical evaluation revealed a mucogingival problem associated with a lack of keratinized tissue at the surgical site (Figure 10). To avoid the possible problems associated with mucogingival deformity, prior to the second-stage uncovery surgery, a 2 × 4 cm acellular dermal matrix graft (Alloderm, Life Cell Corp, The Woodlands, Tex) prepared in 2 equal pieces (1 × 2 cm each) was performed at the site (Figure 11). Sutures were removed 15 days after the surgical procedure with uneventful healing. Following a healing period of 3 months, second-stage surgeries were performed using the custom-designed abutments due to the increased tissue interface following resective and reconstructive surgeries (Figures 12 and 13). One month after the completion of surgical procedures, fixed mandibular prosthesis was delivered (Figure 14).

The patient was fully satisfied with the esthetic and functional results achieved. Following delivery of the prosthesis (prosthetic baseline), clinical and radiographic examinations were carried out after 3 and 6 months. Peri-implant tissue health was achieved and maintained during the follow-up period (Table 1). Radiographic analysis showed minimal bone loss for the 6-month follow-up period evaluated.

Ameloblastomas are benign odontogenic tumors that develop from the epithelial rests of Malassez, and although being slowly developing in nature, they have the capacity of aggressively infiltrating into trabecular bone that results in local hard and soft tissue deformities.¹⁴  The mandibula accounts for 80% of all ameloblastomas reported in the literature, and within the mandibula the most dominantly affected part is the molar region or the ascending ramus.⁹  Based on the extent of the lesion, 2 treatment strategies have been developed in clinical practice. While conservative treatment procedures are preferred in smaller lesions, more radical procedures are being performed in larger lesions due to the aggressive nature and ability of recurrence of the tumor.⁹  Despite presenting the most certain treatment alternative for larger ameloblastomas, resective treatment procedures result in deficiencies of orofacial function and esthetics that lead to psychological problems as well.^12,15–18  To manage the problems associated with these procedures and to restore the defects that occur following resective surgeries, several reconstructive treatment alternatives have been developed.¹⁰  In recent years, vascularized free bone grafts (free bone flaps) have been the method of choice in plastic and reconstructive surgery and accepted as the gold standard for mandibular reconstruction. Vascularized free bone grafts presents several advantages over other techniques such as the greater amount and durability of bone that can be obtained and maintained due to the intact blood supply conserved.¹⁹  Four major donor sites for free bone flaps have been introduced in the literature (fibula, ilium, scapula, and radius). Iliac crest presents higher reconstructive properties in the mandibula when compared to the other donor sites with its compatible morphology for mandibular reconstruction and ability to provide sufficient amount of good quality of bone in the reconstructed area.⁹ 

Although reconstruction of lacking hard and soft tissue support can be gained by these reconstructive surgical techniques, complete rehabilitation of function and esthetic can be achieved by restoring the dentition. For treatment of functional, esthetic, and phonetic deficiencies associated with the lack of dentition, dental implant-supported prostheses have been reported to provide the optimal prosthetic fundamental by presenting superior stability and function.^12,15  Several studies exist in the literature presenting successful rehabilitation of patients with maxillofacial defects reconstructed using nonvascularized/vascularized free grafts and dental implants.^9,12,14–31  In a case series, Wu et al¹⁶  reported 5-year clinical and radiographic outcomes for 117 dental implants performed in 29 patients reconstructed with vascularized free fibula grafts and revealed 95% and 87% cumulative success rates for 1 year and 5 years, respectively. In a clinical study, Blake et al¹⁸  reported peri-implant status of 216 dental implants performed in 43 patients reconstructed with vascularized free fibular/iliac crest bone grafts. They reported 34.4% occurrence of peri-implant mucositis and peri-implantitis for dental implants performed in iliac crest and 25.3% for vascularized free fibula grafts followed up for 8 to 10 years. In a recent case series,¹⁹  peri-implant clinical status and stability of dental implants performed following reconstruction with vascularized free iliac crest bone in 3 patients diagnosed with extensive ameloblastomas were reported. Twelve months of follow-up data revealed similar implant stability values for the whole follow-up period evaluated. In addition, although slight improvements for clinical peri-implant parameters were noted, probing depth (PD) showed increasing values during the follow-up period which is consistent with the literature.^{12,16,18,19,29,30}  In a similar study, Schultes et al²⁹  compared peri-implant status (PD/bleeding) and stability of 143 dental implants performed in patients reconstructed using vascularized free iliac crest and scapula grafts. When compared with the native mandibular bone, while dental implant stability values evaluated using Periotest presented the highest values for scapula (−3.3), decreased values for mandibula (−2.1) and iliac crest grafts (−0.7) were reported. In this case report, acceptable peri-implant health was achieved following rehabilitation with dental implant supported prosthesis, as well as the satisfactory functional and esthetic results obtained, which are consistent with the literature.

One of the most challenging conditions that make both performing and maintaining dental implant-supported prosthetic rehabilitations in patients with maxillofacial defects reconstructed with vascularized bone and dental implants is the lack of keratinized soft tissue in the peri-implant area.^{12,16,18,19,29,30}  According to the preliminary studies of Lang and Loe,³²  to achieve and maintain periodontal health, 2 mm of keratinized gingiva of at least 1 mm attached must be present. When the differences in tissues around dental implants and natural teeth are taken into account,³³  although the same concept cannot be directly accepted, it has been well documented in the literature that keratinized tissues around dental implants help to maintain patient comfort and resistance to mechanical trauma during oral hygiene procedures, and also keratinized tissues avoid tissue prolapses while attaching or removing components during prosthetic rehabilitations, and help in forming peri-implant tissue attachments.^34,35  It has been reported that for perfusion of surgically transferred free bone flaps, a thick muscle layer also has to be transferred to achieve favorable healing. Following the healing period, the transferred muscle layer results in an increased distance between the bone and oral mucosa, which leads to lack of keratinized tissues and deepened peri-implant pockets around dental implants.³⁶  To maintain peri-implant health performed at these thick and muscular tissues, the protective role of keratinized tissue becomes more pronounced for facilitating prosthetic and oral hygiene procedures.

To increase keratinized tissue around teeth and dental implants, several techniques have been proposed in the literature.^37–40  Recently introduced acellular dermal matrix (ADM) graft is harvested from human dermis and to avoid possible immunogenic tissue reactions, all of its cellular components were removed without losing its structure—proteins, collagen, elastin, proteoglycans, and basement membrane. It has many clinical advantages such as the unlimited supply of the donor tissue and need for less invasive surgical procedures like the secondary surgical site at the donor site.³⁷  Due to these advantages, ADM grafts have been widely used for increasing the width of gingiva around teeth and dental implants with high success rates, long-term stability, and increased postoperative patient comfort.^41–47  In this case report, acellular dermal matrix graft was chosen to increase keratinized tissues based on its major advantage of decreased postoperative complications and patient discomfort when compared to other soft-tissue grafting techniques requiring a second surgical donor site. The postoperative healing was acceptable, and approximately 2-mm gain in keratinized tissue was observed. The keratinized tissue formed around dental implants provided ease in both performing prosthetic stages and in facilitating dental implant maintenance.

Based on the results of this case report, it can be concluded that extensive ameloblastomas can be successfully treated with a multidisciplinary treatment approach including radical resection, reconstruction of the mandibular segment by transferring a free iliac crest bone flap, and dental implants. By this approach, significant improvements can be gained in the life quality of patients at both esthetic and functional aspects. Due to the muscular nature of soft tissues formed around the surgical area, frequent maintenance periods including clinical and radiographic evaluations are suggested to detect early inflammatory changes in peri-implant tissues. Furthermore, for long-term success and maintenance of dental implants placed in reconstructed sites, increasing the keratinized tissue can be considered to facilitate prosthetic procedures and to effectively maintain dental implants. Further controlled studies including more patients are needed to clarify the effect of keratinized tissues on peri-implant health and to determine additional procedures to increase the success and long-term stability of dental implants performed in reconstructed sites.

Abbreviations

ADM

acellular dermal matrix

PD

probing depth