Comparative effectiveness of injecting botulinum toxin type A in the masseter muscle with or without injection in the lateral pterygoid muscle in patients with bruxism: A randomized controlled trial.

[INTRODUCTION] Bruxism is a common problem defined by the involuntary grinding or clenching of teeth. This study aimed to compare the treatment outcomes of Botulinum toxin type A (BTX/A) injections into the masseter and lateral pterygoid muscles with injections into the masseter muscle only in patients with bruxism.

[MATERIALS AND METHODS] Thirty patients with bruxism aged 18-45 years were randomly divided into two groups. Group 1: Bilateral BTX/A injections in the masseter and lateral pterygoid muscle. Group 2: bilateral BTX/A injections in the masseter muscle only. Electromyography (EMG) of the muscles was measured before treatment (t0) and two weeks after treatment (t1). The bruxism questionnaire has four close-ended questions. Patients' answers were recorded five times: t0, t1, six weeks after (t2), three months after (t3), and six months after (t4).

[RESULTS] Regarding the bruxism questionnaire scores, group 1 was not superior to group 2 (p > 0.05), and there was an improvement over time (p < 0.05). Both groups were equally effective in improving the EMG scores in the masseter muscle (p > 0.05). However, group 1 outperformed group 2 in improving the lateral pterygoid muscle EMG scores (p < 0.05). indicating that injection of BTX/A in the lateral pterygoid muscle could benefit patients with bruxism.

[DISCUSSION] The bruxism scores were notably decreased when BTX/A was administered to the masseter muscle alone or in conjunction with the lateral pterygoid muscle. It suggests hyperactivity in the lateral pterygoid muscle may occur when the BTX/A is solely injected into the masseter muscle.