In individuals with myofascial temporomandibular-disorder pain, a single injection of Botulinum toxin type A may provide long-term pain-relieving effects.

In order to determine the long-term impact of Botulinum toxin type A (BoNT-A) on muscle thickness, pain sensibility, and subjective pain in people with myofascial temporomandibular disorder pain (MFP-TMD), a controlled clinical trial was conducted.

BoNT-A therapy in various doses (30U-75U for masseter muscle and 10U-25U for temporalis muscle) was given to 14 female individuals with chronic MFP. In a single session, the anterior temporalis and masseter muscles were bilaterally injected with the medication. Self-perceived pain (Visual analog scale [VAS]), muscle thickness (ultrasonography) and pain sensibility (Pressure-Pain Threshold [PPT]) were all clinically measured.

VAS and PPT were followed up on 1, 3, 6, and 72 months following therapy, whereas ultrasonography was followed up on 1, 3, and 72 months. Non-parametric repeated measures comparisons among the assessment times were analyzed statistically using the Bonferroni test and the Friedman test for multiple comparisons as a post hoc test. In all tests, a probability level of 5% was deemed significant.

Over the course of the trial, VAS values showed a considerable decline. PPT values showed a substantial rise when baseline data was contrasted with post-intervention follow-ups, and muscle thickness showed a substantial decline when baseline values were contrasted with the 1- and 3-month evaluations, but there were no differences in the comparison between baseline data and 72-months follow-up.

A single injection of BoNT-A showed a decrease in subjective pain after the 1st month of examination (which persisted until the 6-year assessment) and reversibility of adverse events on masticatory-muscle thickness in individuals with chronic MFP-TMD.