Ultrasonographic Evaluation of Masseter Muscle Changes After Botulinum Toxin Injection in Bruxism Patients

This study investigated the short-term effects of botulinum toxin injection on the masseter muscle in patients with bruxism using quantitative ultrasonographic methods. All participants received bilateral botulinum toxin injections into the masseter muscle using a standardized technique. Ultrasonographic examinations were performed using a high-frequency linear probe. Masseter muscle thickness was measured at a standardized anatomical location during maximal clenching.

For quantitative texture analysis, a fixed-size region of interest (ROI) was placed in the central intramuscular portion of the masseter muscle while avoiding fascia, bone, and artifacts. Fractal analysis was performed using the box-counting method to assess structural complexity, while histogram analysis was used to evaluate grayscale pixel distribution reflecting echotexture characteristics.

Clinical and ultrasonographic measurements were recorded at baseline, 14 days, and 90 days post-injection. The study aimed to determine whether botulinum toxin induces not only functional and morphological changes but also microstructural alterations in muscle tissue.

Inclusion criteria

Adults aged 18-60 years Clinically diagnosed with bruxism Scheduled for botulinum toxin injection into the masseter muscle Willing to participate and provided written informed consent Completed all follow-up visits (baseline, Day 14, and Day 90)

Exclusion criteria

Previous botulinum toxin injection to the masseter muscle Presence of neuromuscular disorders affecting masticatory muscles History of temporomandibular joint surgery Pregnancy or breastfeeding Presence of trauma, infection, or mass in the masseter region Any condition that may interfere with ultrasonographic evaluation Failure to complete follow-up visits