3D Assessment of Mandibular Margin Morphological Change after BTX-A Injection for Masseter Hypertrophy: A Retrospective Study.

[BACKGROUND] Some facial morphological changes may occur in some patients after botulinum toxin A (BTX-A) injection for the treatment of masseteric hypertrophy. The aim of this study was to investigate the morphological changes that occurred on mandibular margin.

[METHODS] This retrospective analysis included 43 patients (86 lateral cases) who received BTX-A injections for masseter hypertrophy. To assess the morphological changes in the mandibular margin after treatment, the sharpness of the mandibular margin was evaluated before and after the injections using an established grading system. Additionally, 3D scanning technology was used to measure both the therapeutic effect of the BTX-A injections and the extent of soft tissue sagging in the mandibular margin area.

[RESULTS] Grading: The grade of mandibular margin sharpness change occurred in 41 lateral cases post-procedurally.

[EVALUATION] Based on the measurement results, statistically significant differences were observed before, 1 month, and 3 months post-procedurally in subjects' positive lower face width representing the therapeutic effect of BTX-A injection and the extent of sagging soft tissue at sagittal section B and section C (p < 0.05), but not in section A (A: outer canthus, B: midpoint of the eyelid margin, and C: inner canthus) (p > 0.05).

[CONCLUSION] After receiving a BTX-A injection for masseteric hypertrophy, the mandibular margin may develop an unclear mandibular margin and sagging soft tissue in mandibular margin area. EBM Level: IV LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.