The Segmental Mandibular Critical Size Defect in the Rat

Abstract

Objective: Advances in tissue engineering offer potential alternatives to current mandibular reconstructive techniques. However, prior to clinical translation of this technology, a relevant animal model must be used to validate possible interventions. This study aims to establish the critical size segmental mandibular defect that does not heal spontaneously in the rat. Method: Thirty rats underwent creation of 1 of 4 segmental mandibular defects: 0 mm, 2 mm, 3 mm, and 5 mm. All mandibular wounds were internally fixated with 1-mm microplates and screws. Rats were allowed to heal for 12 weeks, and then all mandibles were analyzed with micro-computed tomography (CT). Results: One rat was exsanguinated intraoperatively, and 1 mandible was fractured by the drill and the animal was euthanized. This resulted in 7 animals per group. No 5-mm segmental defects successfully healed, whereas all 0-mm and 1-mm defects had continuous bony growth across the original defect on micro-CT. Three of the 3-mm defects had bony continuity, and 3 had no healing of the bony wound. Conclusion: The rat animal model cannot heal a 5-mm segmental mandibular defect. Successful healing of 0-, 1-, and 3-mm defects confirms adequate stabilization of bony wounds with internal fixation with 1-mm microplates. The rat segmental mandibular critical size defect provides a clinically relevant testing ground for translatable mandibular tissue engineering efforts.