Effects of Dose and Injection Site on Gingival Smile Treatment with Botulinum Toxin Type A: A Prospective Study

Background: Botulinum toxin type A is an easy and efficacious treatment for gingival smile. However, the optimal dose and injection site are controversial. Objective: We compared the reduction in gingival exposure using two methods with different doses and injection sites. Methods: In this prospective self-controlled study, healthy participants with gingival smile (anterior gingival exposure of >3 mm) underwent two treatment methods. First, participants received a single-point injection of 2 U botulinum toxin type A per side (simplified method). After 8 months, the individualized method was performed with 2–5 U of botulinum toxin type A (total 4–10 U), which was injected at 1–2 sites according to pretreatment severity. Data were collected at baseline and at 4, 12, and 32 weeks of follow up. Results: Fifty-five participants were enrolled. Anterior gingival exposure and bilateral posterior gingival exposure were significantly reduced 4 and 12 weeks after botulinum toxin type A injection ( P ≤ 0.05) with both methods. These parameters returned to baseline by 32 weeks ( P > 0.05). Posttreatment anterior gingival exposure at 4 weeks and 12 weeks with the individualized method was significantly lower compared with the simplified method (both P ≤ 0.05). Patient satisfaction with the individualized method was preferred compared with the simplified method ( P ≤ 0.05). Few adverse events were observed with both methods without statistical significance. Conclusions: It is necessary to increase the injection dose and tailor the injection site according to the pretreatment severity of anterior gingival smile.