OP039: Anatomic basis for inverse planning for mandibular reconstruction

Abstract

Purpose This study aims to determine the ideal position of mandibular basal bone and the alveolar bone that forms the basis for comprehensive mandibular reconstruction and dental rehabilitation. Materials and methods The mandibular bone position and morphology of 10 patients with normal profile was evaluated with contrast enhanced computed tomographic scans (CT) profile with 1 mm slice thickness. The bone morphology in the symphysis region and first molar region was evaluated. The alveolar bone region of mandible is defined as crest of the alveolar bone till the root apex. The basal bone is that part of mandible below the mandibular teeth apices. At the symphysis region antero-posterior relationship of mid point of the basal bone to mid-point of alveolar bone was determined by dropping perpendicular line from sella-nasion line. At the first molar region, the medio-lateral relationship at first molar teeth were determined by dropping a perpendicular from the inferior orbital rim. Inter-alveolar vertical dimension was determined by measuring distance from maxillary alveolar crest to mandibular alveolar crest. A surgical guide aligned on the maxillary teeth was used to inset the fibula flap used for the reconstruction. Bone insetting to a pre-adapted reconstruction plate was used to reconstruct the basal bone. Another segment of fibula bone was used in a double-barrel fashion to reconstruct the alveolar bone, which was aligned based on the surgical splint aligned to the maxillary teeth. Results At the first molar region the mean difference of the mid-alveolar and mid-basal bone was 0.45 cm. In the symphyseal region this difference was 0.67 cm. The average intermaxillary alveolar crest distance was 1.58 cm in the first molar region and 0.77 cm in the symphyseal region. Conclusion This concept establishes a functional relation of the basal and alveolar bone in the reconstructed mandible with the maxilla and attains an ideal functional position for the implant placement that enables a harmonious occlusion.