Effect of botulinum toxin injection into the masseter muscle in patients with bruxism: a single-arm, institutional-based prospective clinical study

The aim of this study was to evaluate the effect of botulinum toxin injection into the masseter muscle in patients with bruxism, focusing on pain, maximum mouth opening, occlusal bite force, and masseter muscle thickness.Thirty patients with bruxism (21 females, 9 males; mean age 32 ± 10 years) were injected with 10 IU of botulinum toxin into each masseter muscle. Evaluations were conducted at baseline and at 4, 8, and 12 weeks post-injection to assess pain, maximum mouth opening, occlusal bite force, and masseter muscle thickness.Pain scores significantly declined from 6.8 ± 1.2 to 3. 4± 1.1 at 4 weeks. Mouth opening showed a significant improvement, increasing from 38.2 ± 3.9 mm to 41.3 ± 4.0 mm at 4 weeks. Bite force was significantly reduced from 500.5 ± 45.2 N to 422.0 ± 39.2 N at 4 weeks. Masseter muscle thickness also significantly decreased, from 13.4 ± 1.6 mm to 11.8 ± 1.5 mm at 4 weeks. A positive correlation was observed between the reduction in masseter muscle thickness and the decrease in bit force.Botulinum toxin injection was safe and effective in reducing pain, masseter muscle thickness, and bite force, as well as in improving mouth opening in patients with bruxism.