Biomechanical analysis of teeth movement during the repair of mandibular defects using transport disk distraction osteogenesis.

Introduction: Teeth movement or rotation is one of the complications of mandibular defect repair using transport disk distraction osteogenesis (TDDO). However, the mechanical reasons are not clearly understood.

Material and methods: To evaluate the biomechanical factors associated with teeth movements during mandibular defect repair with TDDO, a finite element model created from computed tomographic images of the human mandible was adopted to evaluate teeth displacement and the Von Mises stress distribution on the periodontal ligament resulting from the transport disk for teeth subjected to TDDO loading.

Results: Under a displacement of 0.5 mm to the fixed arm of the transport disk, the teeth on the disk moved away from the distraction. The stress on the periodontal ligament was highest (60 KPa) around the distal neck. Upon the application of 150 g of resistance, the entire tooth moved in the same direction and the isoline gradient was almost parallel to the long axis of the tooth. Although the stress was distributed similarly; it decreased to 0.117 KPa geometrically.

Discussion: When mandibular defects are repaired with TDDO, the transport disk and anti-distraction forces contribute to the reversal movement or rotation of the teeth, which may become immobility when antagonistic forces are applied in the same direction.