## 4 Discussion
Mouth opening is frequently restricted in TMD patients, and botulinum toxin therapy helps relax the nearby masticatory muscles, reducing muscle inflammation and improving mouth opening. Nevertheless, approximately 10% of TMDs patients develop a disorder associated with chronic orofacial pain [30]. [PERSON] et al. [31] reported that BoNT-A is at least as effective as occlusal splints for persistent orofacial pain, thus conservative treatments such as occlusal devices should be the first option for the management of orofacial pain related to TMDs. The authors [31] suggested employing low doses of BoNT-A in patients who do not obtain considerable pain relief from conservative treatments. These findings are in accordance with other two RCTs [22; 23] included in this study. On the other hand, most of the included studies [25; 26; 28; 31; 32; 33] comparing BoNT-A and saline solution showed significant differences favoring the BoNT-A group regarding pain intensity reduction and changes in maximum occlusal force. Differently, only one RCT by [PERSON] et al. [29], comparing BoNT-A and saline solution, reported there were no significant changes after treatment in most of the evaluated outcome measures, with the exception of pain on palpation. Bite forces and electromyographic activity are both significant factors in assessing the performance of the masticatory muscles. [PERSON] et al. supported previous findings concerning the significant decrease in electromyographic activity and bite force values after BoNT-A injections, showing a recovery of electromyographic activity occurring by 33 weeks and bite force by 25 weeks after a moderate dose of BoNT-A [30]. BoNT-A injections are not recommended for patients who are growing because it is known that reduced muscular power and activity lead to bone loss, and that the biochemical and biomechanical interactions are particularly significant during the growth period of masticatory structures [30]. Despite this, low doses of BoNT-A, such as a total dose of 50U, are proposed not to be dangerous because the grade and duration of the adverse effects are dose-dependent [17]. Furthermore, according to some clinical trials, bigger doses are not likely to get more therapeutic benefits when treating pain conditions [11; 17; 34]. The available research on bruxism and botulinum toxin is inconclusive and there is no evidence that bruxism can be cured with injections of BoNT-A. The repetitive activity of the masticatory muscles known as bruxism, which can show in either sleep bruxism (SB) or awake bruxism (AB), is defined by the tightness or grinding of the teeth. In addition to tooth abrasions and mobility, dental restoration fractures, hypertrophy of the masseter muscle, and mylgia or arthralgia typical of temporomandibular disorders, it is a frequent condition with an adult prevalence. The cause and pathophysiology of bruxism are still unknown, despite the fact that etiological factors such emotional stress, neurological illnesses, certain medicines, and occlusal interferences have been hypothesized. Occlusal splints, medications such as benzodiazep or L-dopa, and cognitive-behavioral therapy are just a few of the treatment modalities that have been researched for the management of bruxism. However, these methods have not been proven to be completely effective because they only appear to address the symptoms of patients rather than the underlying cause, limiting the damaging effects of bruxism on anatomical structures. At present, it has been shown that botulinum toxin is effective for treatment of bruxism associated with TMDs [19; 34; 35; 36]. A systematic review of [PERSON] et al., analyzing 68 studies, reported that treatment with BoNT-A is a safe and effective clinical option in patients affected by bruxism, underlining that injections of BoNT-A give better outcomes than traditional treatment [36]. Furthermore, this systematic review showed that application of BoNT-A should be considered in daily clinical practice, especially for patients affected by severe bruxism [36].