Bruxism is a recurrent jaw-muscle activity characterized by clenching or grinding of the teeth and/or bracing or thrusting of the mandible according to the International Classification of Sleep Disorders (ICSD), 3rd edition (Lobbezoo et al., 2013; Sateia, 2014). Bruxism is categorized into two distinct circadian manifestations: sleep bruxism and awake bruxism (Lobbezoo et al., 2013). Sleep bruxism is characterized by abnormal rhythmic or arrhythmic muscle activity during sleep. In contrast, awake bruxism is a muscular activity characterized by repetitive or sustained tooth contact and/or bracing or thrusting of the mandible, differing etiologically from sleep bruxism. The incidence of sleep bruxism is 20%–25% in children, 8%–10% in adults, and 3% in the elderly (Beddis et al., 2018; Cheifetz et al., 2005; Lobbezoo et al., 2013; Manfredini et al., 2013). Although emotional stress, neurological disorders, certain drugs, and occlusal interferences have been proposed as causes of bruxism, the exact cause and pathophysiology are still unknown (Beddis et al., 2018). The symptoms of bruxism include tooth abrasions and mobility, fracture of dental restorations, hypertrophy of the masseter muscle, and myalgia or arthralgia characteristic of temporomandibular disorders (Beddis et al., 2018; Klasser et al., 2015; Rodrigues et al., 2023). To relieve these symptoms, various modalities of management have been applied, such as occlusal stabilization splints, drugs such as clonazepam or clonidine, and cognitive-behavioral therapy, but none of these are completely effective (Beddis et al., 2018; Klasser et al., 2015; Memis, 2022; Vingender et al., 2023).

Botulinum toxin type A (BTX-A) is an exotoxin produced by the bacterium Clostridium botulinum, which blocks acetylcholine release from cholinergic nerve endings into the neuromuscular junction, thereby causing muscle inactivity. BTX-A is approved by the United States Food and Drug Administration (FDA) for the treatment of these conditions; cervical dystonia, severe primary axillary hyperhidrosis, strabismus, blepharospasm, hemifacial spasm, and glabellar wrinkles, and it is used both for its therapeutic and aesthetic effects (Kwon et al., 2019; Lang, 2004; Rauso et al., 2022). In recent years, there has been an increasing trend in the use of this drug to regulate the activity of bruxism; nevertheless, there is a lack of scientific data on the efficacy and safety of BTX-A on bruxism, as well as the optimum dose of BTX-A for the alleviation of bruxism in Asian populations. The purpose of this study was to establish the effectiveness and safety of a prabotulinumtoxin A (praBTX-A) injection in patients with nocturnal bruxism and masseter hypertrophy.