Duration of bite force reduction following a single injection of botulinum toxin in the masseter muscle bilaterally: A one‐year non‐randomized trial

Abstract

Background Previous studies concerning the effect of botulinum toxin in masseter muscle have mainly reported effects observed through inspection of facial features or differences in pain levels. One systematic review of studies utilizing objective measurements reported that long‐term muscular effect of botulinum neurotoxin injections into masseter muscle was inconclusive. Objective To evaluate the duration of reduced maximal voluntary bite force (MVBF) after botulinum toxin intervention. Methods The intervention group was comprised of individuals seeking aesthetic treatment for masseter reduction (n = 20), the reference group (n = 12) comprised of individuals with no intervention. Intervention through 25 units of Xeomin® (Merz Pharma GmbH & Co KGaA, Frankfurt am Main, Germany) botulinum neurotoxin type A injected into the masseter muscles bilaterally (totalling 50 units). A reference group did not receive any intervention. MVBF was measured in Newtons using a strain gauge meter at the incisors and first molars. MVBF was measured at baseline, at 4 weeks, 3 months, 6 months, and after 1 year. Results Both groups were similar in terms of bite force, sex and age at baseline. MVBF remained similar compared to baseline in the reference group. At 3 months, a significant reduction at all measurement points was observed in the intervention group; at 6 months, this reduction was no longer significant. Conclusion A single intervention of 50 units of botulinum neurotoxin results in a reversible MVBF reduction of at least 3 months, although a visually discernable reduction may be more long‐lasting.

Comparative Study on the Duration and Efficacy of Various Botulinum Toxin Type A Injections for Reducing Masseteric Muscle Bite Force and Treating Facial Wrinkles

“…These findings align with previous studies on the efficacy of BoNT/A for facial wrinkle treatment, where a similar pattern was observed [20][21][22]. The peak in MVBF reduction was typically observed at 2-4 weeks after the intervention, consistent with previous studies showing that the effects of BoNT/A peaked during this timeframe and lasted approximately 12 weeks after injection [23,24].…”