Effect of Botulinum Toxin Type A on Mandibular Fracture Healing: An Experimental Study in Rabbits

Purpose: The effect of botulinum toxin type A (BTX-A) on fracture healing of the long bones is controversial, and no controlled clinical or experimental study has investigated the effect of BTX-A on mandibular fractures. The purpose of this study was to investigate whether BTX-A injection into the masseter muscles affects bone healing by reducing the displacing forces in an unfavorable mandibular fracture model. Materials and Methods: Forty-eight male New Zealand white rabbits were used. Ten units of BTX-A was injected into each masseter muscle in the animals in the BTX-A group, whereas saline solution was injected in the animals in the control group. A unilateral osteotomy and fixation with a microplate were performed. Bone healing was evaluated by radiodensitometric, biomechanical, histologic, and histomorphometric methods after 21 days. Results: The mean bone mineral density in the fracture area was significantly higher in the BTX-A group (P =.038). The mean failure load and bending modulus values were significantly higher in the BTX-A group than in the control group (P =.032 and P =.005, respectively). The mean histologic bone healing scores, bone volume-total volume values, and trabecular diameter values were significantly higher in the BTX-A group than in the control group (P =.001, P =.001, and P =.026, respectively). Conclusions: BTX-A application into the masseter muscles improves bone healing of a unilateral mandibular fracture in rabbits. (C) 2020 American Association of Oral and Maxillofacial Surgeons