Botulinum toxin type A for myogenic temporomandibular disorders: A scoping review of injection protocols, clinical outcomes, safety, and evidence gaps

Background Botulinum toxin type A (BoNT-A) has been increasingly investigated for persistent myogenic temporomandibular disorders (TMDs), particularly when conservative therapies provide insufficient symptom control. However, variability in patient selection, injection protocols, outcomes, and safety reporting complicates interpretation of its effectiveness. Objective To map and critically synthesize evidence regarding BoNT-A injection protocols, clinical outcomes, functional and physiological effects, safety, and methodological limitations in adults with myogenic TMD. Methods This scoping review followed PRISMA-ScR. PubMed/MEDLINE, Scopus, Web of Science Core Collection, and Embase were searched from inception to August 2026. Clinical studies involving adults with myogenic TMD, masticatory myalgia, or myofascial pain treated with intramuscular BoNT-A were included. Data on injection protocols, pain, function, physiological effects, and safety were charted, and risk of bias was appraised using design-appropriate tools. Results Of 1470 records identified, 770 remained after duplicate removal, and 20 clinical studies were included. Substantial heterogeneity existed in diagnostic criteria, formulation, dose, targeted muscles, injection techniques, comparators, outcomes, and follow-up. Pain and patient-reported outcomes frequently improved, particularly in uncontrolled studies, whereas placebo-controlled trials showed less consistent superiority. Pain improvement did not consistently parallel functional recovery. Objective assessments demonstrated reduced muscle thickness, electromyographic activity, bite force, and masticatory performance. No standardized protocol or optimal dose with an established benefit–risk profile was identified. Conclusions BoNT-A may provide symptomatic benefit in selected patients with persistent myogenic TMD, but evidence does not support routine first-line use. Standardized protocols, multidimensional outcomes, and longer-term randomized trials are needed.