Japanese Journal of Clinical Oncology

Preparation of Multi-Bracket Appliance

First, the extent of the mandibular excision was estimated. Standard edgewise brackets (0.018 × 0.025 inch slot) were bonded to the teeth in the maxilla and in the remaining mandible, and dental impressions were taken. Rectangular wires (0.017 × 0.022 inch) passively fitted with the brackets were made on a dental model and hooks for maxillo-mandibular fixation were soldered. An acrylic bite plate to determine the maxillo-mandibular relationship was also fabricated on the same dental model in two of the three cases. Prior to surgery, the fabricated arch-wire was ligated to the brackets after some adjustment in the outpatient room. Orthodontists performed these procedures.

Intraoperation

After mandibular resection, the occlusion of the remaining teeth was replicated precisely. Wires for maxillo-mandibular fixation were then applied and the bite plate was placed between the maxillary and mandibular dentition in two cases. The harvested bone was then contoured to replicate the bone defect and then carefully fixed with miniplates to maintain the occlusion.

Postsurgical Treatments

Wires for maxillo-mandibular fixation were removed 4 weeks after surgery when bone union was recognized by roentgenography. The multi-bracket appliance was worn for a further 3 months when the wound contraction became mild. A plate type-retainer was used after removing the multi-bracket appliance.

Case 1

A 45-year-old woman presented with recurrent adenoid cystic carcinoma of the right sub-mandibular gland (Figs 2a and 2b). The planned mandibular resection approach was from above the right angle to the right lateral incisor. She had lost her maxillary incisors and she used removable partial dentures. Brackets and arch-wires were applied to the proposed residual teeth according to the protocol and an orthodontic plate with four artificial anterior teeth was also fashioned to maintain the occlusion of the remaining dentition (Fig. 2c). Resection of the mandible from above the right angle to the right canine including the sub-mandibular soft tissue and skin, and right radical neck dissection were carried out. The facial skin and mandibular defects were reconstructed using a fibula osteoseptocutaneous flap from the left lower leg (Fig. 2d). The mucosal defect was directly sutured. As the remaining mandible was rigidly fixed to the maxilla, the fibula was fixed accurately without any shift of the mandible. The wires for maxillo-mandibular fixation were removed 4 weeks after the operation, and the multi-bracket appliance was worn for a further 3 months. One year later, she was satisfied with her facial appearance and demonstrated stable occlusion of the residual teeth (Figs 2e and 2f). Removable partial dentures were worn in the reconstructed mandible and maxilla (Fig. 2g). She was able to eat all foods without difficulty.

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Figure 2. (a) Preoperative frontal view. (b) Preoperative coronal MRI showing adenoid cystic carcinoma in the submandibular gland (arrows). (c) Preoperative occlusal situation. The patient lost her maxillary incisors and used removable partial dentures. Brackets and arch-wires were applied to the proposed residual teeth and an orthodontic plate with four artificial anterior teeth was also fashioned. (d) After the maxillo-mandibular fixation, the fibula was fixed to the mandible with miniplates. Then, the peroneal vessels were anastomosed. (e) Postoperative frontal view one year after surgery. (f)The patients shows a 30 mm opening.(g)Postoperative occlusal situation. Removable partial dentures were worn in the maxilla.

Case 2

A 44-year-old man presented with left mandibular malignant schwannoma (Figs 3a and 3b). A segmental mandibulectomy from above the left angle to the midline was planned. Brackets and arch-wires were applied to the proposed residual teeth. Resection of the mandible from above the right angle to the right lateral incisor and right radical neck dissection were carried out. The defects of the mandible and oral mucosa were reconstructed using a fibula osteoseptocutaneous flap from the right lower leg (Fig. 3c). One year after the operation, he demonstrated good mastication and was able to consume a completely normal diet (Figs 3d and 3e).

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Figure 3. (a) Preoperative frontal view.(b)Preoperative CT showing malignant schwannoma (arrows).(c)The mandible was fixed to the maxilla by wires through arch-wires. Then, the fibula was trimmed to match to the defect of the mandible and transferred. (d) Postoperative frontal view one year after surgery.(e) Postoperative panoramic radiograph one year after surgery.

Case 3

A 13-year-old boy presented with left mandibular myxofibroma (Figs 4a and 4b). Similar to the other two cases, brackets and arch-wires were applied to the proposed residual teeth (Fig. 4c). Segmental mandibulectomy from above the left angle to the left canine was performed. Bone defect was reconstructed with a fibula flap from the left lower leg. There were no skin defects and a small mucosal defect was directly sutured. One year after the operation, he was very satisfied with his facial appearance. He also demonstrated stable and good occlusion. (Figs 4d, 4e and 4f).

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Figure 4. (a) Preoperative frontal view.(b)Preoperative CT showing mandibular myxofibroma (arrows).(c)Preoperative occlusal situation.(d)ostoperative frontal view one year after surgery. (e) Postoperative panoramic radiograph one year after surgery.(f)Postoperative occlusal situation.

DISCUSSION

Despite the small sample size, the present results from mandibular reconstruction using a multi-bracket appliance are very encouraging. This technique offers two major advantages over the conventional dental arch-bar.

First, the multi-bracket appliance keeps the original dental arch form firmly. Brackets are bonded to the individual teeth directly without any loosening. Rectangular arch-wires control the individual tooth position three-dimensionally and have considerable stiffness to counter the external pressure. These properties are helpful in maintaining occlusion of the remainig dentition accurately in bone grafting procedure as well as protecting against postsurgical wound contraction. On the other hand, the dental arch-bar is attached to teeth by ligature wires and often loosens in maxillo-mandibular fixation. Furthermore, this appliance does not demonstrate sufficient mechanical strength. In contrast, the dental arch-bar, when used for mandibular fracture, enables accurate fixation of the mandible. This is due to the lack of bony and soft tissue defects. Thus, the arched shape of the mandible can be perfectly restored which preserves the rigid maxillo-mandibular fixation. Baurmash reports that there is little difference in the strength of attachment if one is dealing with a full dental arch, but the difference in strength is evident when only a small number of anchorings are available (4).

In the case of mandibular resection following tumor ablation, the tissue defect is generally large and the number of remaining teeth is small. Initially horseshoe-shaped mandibles are divided into two relatively straight sticks. A small number of circumdental wires is considered to be insufficient to hold the arch-bars rigidly which results in considerable movement of the mandibles, even under maxillo-mandibular fixation. Therefore, holding the mandibles in position precisely during bone grafting procedure is difficult. Furthermore, as the teeth elongate during maxillo-mandibular fixation, circumdental wires tend to loosen a few weeks after surgery and the supporting teeth move toward the reconstructed direction. Re-tightening of the wires is often required which sometimes leads to periodontal injury (5). We have occasionally experienced deterioration of occlusion after the removal of the arch-bars due to wound contraction and resultant bone remodeling which continue for several months after surgery. The multi-bracket appliance appears to solve these problems, but the contribution of the acrylic plate should also be considered.

The multi-bracket appliance also keeps the oral cavity clean. This appliance is designed for long-term use in orthodontic treatment while avoiding periodontal injury. Thus, long-term use of this appliance maintains the occlusal relationship against wound contraction. In contrast, arch-bars occasionally cause gingival infection around the circumdental wires and early removal of these appliances is unavoidable. The wound contracture progresses after removal and deviation of the remaining mandible occurs, resulting in destruction of occlusion. In the present series, multi-brackets were applied for 3 months without any complications.

The goals of mandibular reconstruction are the restoration of aesthetic contour and oral function including mastication, speech, and swallowing. Although multi-brackets require the cooperation of orthodontists, and it is time-consuming to articulate the dental models and apply the multi-bracket appliance, this appliance provides improved functional dental rehabilitation.