Effect of Botox injection in the anterior belly of digastric on skeletal relapse following mandibular advancement surgery. Randomized controlled trial

Purpose: to test whether Botox injection in the anterior belly of the digastric muscle in sagittal split osteotomy for mandibular advancement could reduce the tendency of postoperative relapse in comparison to the same surgery without Botox injection in bimaxillary orthognathic surgery. Methods: A total of 24 patients indicated for mandibular advancement bi-maxillary orthognathic surgery were randomly assigned to 2 equal parallel groups; 12 patients were injected with Botulinum toxin type A before surgery (Intervention group), and 12 patients were treated without injection (Control group). The relapse was evaluated by the differences in cephalometric variables at 1 week and 6 months postoperatively. The evaluated cephalometric variables are 3 angular measurements (SNB, ANB, and ArGo-SN) and 2 linear measurements (Pog and B point) concerning Frankfort Horizontal and coronal planes on CBCT image. Results: There was a statistically significant difference between the Botox and control groups in Pg/coronal horizontal measurement. The Botox group showed a statistically significant lower increase (lower relapse) in Pg/coronal measurement than the Control group. In comparison between the two groups, there was no statistically significant difference in B and Pg concerning the FH plane, B point about the coronal plane, and all angular measurements: SNB, ANB, and Ar-Go/SN. Conclusion: Botulinum toxin type A injection into the anterior belly of the digastric muscle is an easy and effective approach to decrease relapse following mandibular advancement orthognathic surgery.