Factors Influencing the Effectiveness of Botulinum Toxin Therapy in Bruxism Management.

A total of 304 patients with bruxism (206 women, 98 men; mean age: 52.5 years) received 25 units of botulinum toxin injected into the bilateral masseter muscles; the changes in various clinical symptoms and their contributing factors were analyzed 2 months after treatment. The mean masseter muscle electromyographic amplitude (189 μV) and maximal bite force (618.4 N) significantly decreased after botulinum toxin therapy compared to that at baseline (55.4 μV, 527.3 N, respectively; < 0.001). Maximal mouth opening (44 mm), sleep quality (visual analog scale: 5.3), shoulder and neck stiffness (6.7), and headache (5.4) significantly improved after the injection (47.3 mm, 6.6, 4.7, and 2.6, respectively; < 0.001). Multivariate analysis revealed that the mean masseter electromyographic amplitude reduction rate was significantly affected by age, sex, and baseline amplitude (all < 0.001); the maximal bite force reduction rate was influenced by age ( < 0.001), sex ( = 0.007), and baseline bite force ( = 0.008). Age, sex, and muscle activity may affect the therapeutic effects. A more effective outcome for bruxism can be achieved using a tailored approach involving dose adjustment, thereby preventing the side effects attributed to excessive dosage.