The treatment for repair of fractures of the severely atrophic and edentulous mandible is difficult. In many cases, the miniplates or reconstructive plates are used to fix bone fragment [3]. There is no consensus on the best treatment, especially in cases with a vertical height of less than 10 mm [5]. When the fixation was not done appropriately, it causes malunion and nonunion [4]. Also, considering denture-bearing area and the position of the plate is very important to avoid the infection and/or the plate exposure [6]. In our case, miniplate was fixed at the inferior margin side in the mandible to avoid infection and exposure of the miniplate due to the maxillary teeth against the mandible residual ridge. Therefore, the first fracture surgical procedure was selected extraoral approach without the intraoral incision lines.

A miniplate was selected as fixing device because of the large bone contact surface in the fracture site of mandibular median and the need for dental implant placement after this fracture surgery. The use of a reconstructive plates was thought to result in further fracture induced by the large screws and the contacts of dental implant bodies to be placed and screws of reconstructive plates. In this case, eight dental implant bodies could be placed without contact between dental implants bodies and screws of miniplate after restoration of the first mandibular median fracture.

The second mandibular fracture occurred after taking an impression of a dental implant superstructure. The fracture site had the smallest bone height diameter in the left side mandible. It was difficult to fixate the new fracture site with a miniplate or a reconstructive plate after removal of the existing miniplate in the midline of the mandible. External fixation of mandible fractures is a useful when an open surgery is difficult because of extensive comminution, bone or soft tissue loss and infection [7]. In particular, external fixation adopted to the mandible fracture by gunshot provides many advantages owing to its versatility and simplicity of use [8]. Transmucosal fixation is one strategy for the treatment of edentulous mandibular fracture using external fixation principles within the oral cavity [9]. There is a report of good healing results using this intraoral locking plate fixation technique for fractures of the edentulous mandible. Similar to these concepts, the mandibular fragment was fixed by attaching the superstructure to the residual dental implants in our case. Since the superstructure had already been created before the second fracture, it was possible to restore the mandible to its original position by attaching the superstructure. In addition, patients were able to chew from soft foods. It was reported that the duration of the external fixator usually varies from 8 to 12 weeks, sufficient time for bone repair and remodeling [10]. In our case, the complete bone union of fracture site was confirmed by CT about 1 year after seating of the superstructure. The patient was managed regularly with attention to peri-implantitis. Four years have passed since the superstructure was mounted, but the clinical progress is good. Further follow-up is required.