Effect of a second injection of botulinum toxin on lower facial contouring, as evaluated using 3-dimensional laser scanning

BACKGROUND Botulinum toxin type A (BoNT-A) is widely used to improve the lower facial contour. OBJECTIVE To determine the difference in the changes in the lower facial contour achieved with 1 and 2 sessions of BoNT-A injections using 3-dimensional (3D) laser scanning. MATERIALS AND METHODS Twenty volunteers were randomly divided into 2 groups. Group I (n = 10) received a single injection, whereas Group II (n = 10) received 2 sessions of injections, the second being administered 4 months after the first. Each injection comprised of 25 U of BoNT-A and was administered to the masseter muscle bilaterally. Evaluation of the effect of BoNT-A injection was performed using 3D laser scan images obtained before the injection and 6months thereafter in Group I, and before the first injection and 6months thereafter in the Group II. RESULTS The mean changes in the volume and thickness in Group I were 21,186 mm3 and -1.52 mm, respectively; the corresponding changes were 24,072 mm3 and -3.84 mm in Group II. The reductions were significantly greater in Group II than in Group I. CONCLUSION The administration of a second BoNT-A injection is effective for better aesthetic results for the lower facial contour.