Comparative Botulinum Toxin Injection Strategies Beyond the Masseter for Bruxism: A Scoping Review.

Abstract

Background: Botulinum toxin type A is used to reduce excessive masticatory muscle activity in bruxism, but whether extending injection beyond the masseter provides additional benefit remains uncertain. This scoping review aimed to map comparative evidence on expanded botulinum toxin muscle targeting for bruxism and assess whether available studies provide evidence of incremental clinical benefit beyond masseter-only injection. Methods: PubMed, Scopus, the Cochrane Central Register of Controlled Trials, and the World Health Organization International Clinical Trials Registry Platform were searched from inception to 3 August 2026. Eligible studies directly compared botulinum toxin injection strategies differing in the muscles targeted. Data were charted and synthesized descriptively. The protocol was prospectively registered with INPLASY (INPLASY202680008). Results: Five small randomized trials involving 133 participants were included, of whom 116 contributed to the comparative analyses. Expanded strategies added the temporalis, anterior digastric, lateral pterygoid, or medial pterygoid. Additional clinical benefit of broader targeting was not clearly demonstrated, although some studies reported greater reductions in activity of the additionally injected muscle. In all studies, the masseter dose was held constant while additional muscles were injected, resulting in higher total toxin doses and preventing separation of anatomical targeting effects from dose escalation. Safety evidence was insufficient because reporting was limited and heterogeneous, and the small overall sample precluded adequate characterization of the safety profile. Conclusions: The available evidence is preliminary and insufficient to determine whether routinely extending botulinum toxin injection beyond the masseter provides additional clinical benefit. Future adequately powered, dose-controlled trials should prioritize patient-important outcomes and distinguish the effects of anatomical targeting from total toxin dose.