A Case of Familial Oligodontia Treated with Anteroinferior Maxillary Distraction Osteogenesis Using Internal Distractors

Congenital absence of teeth （hypodontia） is one of the developmental abnormalities frequently seen in the craniofacial region. Non-syndromic hypodontia includes different phenotypes ranging from hypodontia of one tooth excluding third molars to oligodontia and anodontia. We report a case of familial oligodontia with anterior-posterior and vertical undergrowth of the maxilla. The patient was a male with the chief complaint of malocclusion and mandibular protrusion, and was aged 15 years and 3 months when the active treatment started. The patient had a facial profile with midfacial concavity and short face. Cephalometric analysis showed severe skeletal class Ⅲ due to the retruded maxilla with short vertical height （ANB angle, −7.9°）. Intraoral examination revealed anterior crossbite and deep bite. The maxillary second premolars, first molars, and second molars were congenitally missing bilaterally. We planned anterior-inferior movement of the maxilla using a pair of internal distractors and set-back of the mandible to improve skeletal disharmony via surgical orthodontics, followed by wearing a partial denture to restore the occlusion of missing teeth. After preoperative orthodontic treatment, Le Fort І osteotomy and fixation of internal distractors were performed. Following a one-week consolidation period, maxillary distraction osteogenesis was performed for 10 days at the rate of 1mm per day. The direction and location of installation of the distractors were simulated in advance on a three-dimensional model and accurately positioned on the maxilla; however, the direction of the distractors changed posteriorly possibly due to the occlusal force during the distraction osteogenesis. Since the maxillary advancement was insufficient, the maxillary position was modified concomitant with the mandibular set-back during the secondary surgery, resulting in the desirable facial profile and an acceptable occlusion. The bone-borne distractor seems to be suitable for patients with oligodontia for preventing the adverse movement of teeth. However, since the available space and the direction of the internal distractor are limited, careful consideration for the direction and fixation of the distractor and monitoring of the device’s deformation due to the patient’s occlusal force are necessary.