LAUSR

BACKGROUND Over the years, demand for less invasive procedures for treating gummy smile, such as botulinum toxin A injections, has substantially increased. Meanwhile, the optimal injection site for botulinum toxin A injection is still debatable. OBJECTIVE To investigate the efficacy of botulinum toxin A injection at the Yonsei point for treating gummy smile. METHODS In this double-blind single-site randomized clinical trial, healthy participants with a gummy smile (anterior gingival exposure of ≥3.0 mm) were enrolled and randomized (1:1 ratio) into two groups. The experimental group was administered with 6 units (U)(a single-site injection of 3 U was given to the right Yonsei point and 3 U to the left Yonsei point), while the control group received the same dose in the bilateral levtor labii superioris alaeque nasi (LLSAN) muscle sites. The patients were assessed at baseline and 4, 12, 24, and 48 weeks after the first injection by a digital vernier caliper. RESULTS A total of 49 participants were enrolled. Anterior and bilateral posterior gingival exposure were reduced at 4, 12, and 24 weeks (P ≤ 0.05) and returned to baseline at 48 weeks in both groups; there was no difference between the groups at these time points. The increase in satisfaction among patients was significant, and few adverse events were observed in both groups. CONCLUSIONS Both the Yonsei point and the LLSAN muscle site could be used as botulinum toxin A injection sites for treating gummy smiles.