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

Abstract Purpose The effect of Botulinum toxin-A (BTX-A) on fracture healing of long bones, is controversial, and there is no controlled clinical or experimental study investigating 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. Animals and Methods Forty-eight male New Zealand white rabbits were used. Ten units of BTX-A were injected into each masseter muscle of the animals in the BTX-A group and saline was injected to the animals in the control group. A unilateral osteotomy and fixation with a microplate was performed. Bone healing was evaluated by radiodensitometric, biomechanical, histological 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=0.038). The mean failure load and the bending modulus values were significantly higher in the BTX-A group compared to the control group (p=0.032 and p=0.005, respectively). The mean histological bone healing scores, bone volume/total volume and trabecular diameter values were significantly higher in the BTX-A group compared to the control group (p=0.001, p=0.001 and p=0.026, respectively). Conclusion BTX-A application into the masseter muscles improves bone healing of a unilateral mandibular fracture in rabbits.