Evaluation of the Efficacy of Low-Dose Botulinum Toxin Injection Into the Masseter Muscle for the Treatment of Nocturnal Bruxism: A Randomized Controlled Clinical Trial

Introduction Botulinum toxin (Botox®) is considered an effective treatment for nocturnal bruxism when injected into the masseter muscle. Several studies have used different dosages of Botox for this purpose. The objective was to determine whether 10 MU of botulinum toxin type A (BTXA) injections into the masseter muscle could lessen nocturnal bruxism. Material and methods The sample consisted of 22 patients who suffered from pain in the masseter muscle and sensitivity of the teeth as a result of its wear due to nocturnal bruxism. The sample was randomly divided into two groups. The Botox (BO) group included 11 patients injected with 10 MU of BTXA, and the placebo (PL) group included 11 patients who received a sham intervention. Pain perception was assessed on visual analogue scales, whereas muscle activity was recorded by electromyography (EMG) to evaluate the effectiveness of this treatment protocol on nocturnal bruxism. Results A total of 20 patients entered data analysis with one dropout from each group. The differences in the perceived pain values between the BO and the PL groups before and after the injection were statistically significant (p<0.05). In the BO group, the changes in the perceived pain values over time were statistically significant (p<0.05). The pain levels significantly decreased at two weeks, one month, and three months following the injection. However, the levels increased again at the fourth- and sixth-month assessment times with statistically significant differences (p>0.05). The differences in the EMG recorded values were statistically significant between the two groups (p<0.05). Conclusions Within the current study's limitations, injecting 10 MU of BTXA into the masseter muscle reduced muscular activity in this muscle, resulting in decreased muscle spasms and pain symptoms associated with nocturnal bruxism for about three months before symptoms gradually relapsed.