Facial volume reduction and masticatory function after masseter botulinum toxin injection: a prospective study

Abstract

BACKGROUND: Botulinum toxin type A (BTX-A) is widely used for masseter reduction to improve lower facial contour. While its esthetic effects are well established, the potential impact on masticatory function remains unclear, particularly in healthy individuals. This study aimed to evaluate changes in facial volume, patient satisfaction, and perceived chewing function following BTX-A injection. METHODS: A quasi-experimental clinical trial was conducted in 24 healthy adults who received bilateral masseter injections of BTX-A (50 units total). Lower face volume was assessed using 3D stereophotogrammetry at baseline and at 4, 8, and 12 weeks post-injection. Patient satisfaction was measured using the FACE-Q™ questionnaire, and masticatory function was assessed with the Chewing Function Questionnaire (CFQ) and visual analog scale (VAS). Friedman and Wilcoxon signed-rank tests were used for statistical analysis. RESULTS: Significant reductions in lower face volume were observed at all follow-up time points (p < 0.05), with the greatest change occurring by week 12. Satisfaction scores with facial appearance and treatment outcome significantly increased. Masticatory function remained stable, with no significant changes in CFQ or VAS scores. Participants reported no perceived decline in chewing ability throughout the study period. CONCLUSION: Our results suggest that botulinum toxin injection into the masseter muscle may reduce lower face volume and improve patient satisfaction without compromising perceived masticatory function in healthy adults. These findings provide preliminary evidence for the esthetic application of BTX-A and may contribute to future investigations into its potential roles in areas such as bruxism management and prosthodontic planning. TRIAL REGISTRATION: TCTR20240617001. Registered on June 17th, 2024.