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

Quantitative Ultrasonographic Assessment of Masseter Muscle Changes Following Botulinum Toxin Injection in Patients With Bruxism: A Prospective Pilot Study

This prospective pilot study aimed to evaluate short-term clinical and ultrasonographic changes in the masseter muscle following botulinum toxin injection in patients with bruxism. Clinical assessments included pain evaluation using the Visual Analog Scale (VAS), while ultrasonographic evaluation included measurement of masseter muscle thickness and quantitative texture analysis using fractal dimension and histogram parameters. Measurements were performed at baseline, 14 days, and 90 days after treatment. The study aimed to assess both macroscopic and microstructural changes in the muscle tissue.

Study Overview

• Status: Completed
• Conditions: Bruxism; Myofascial Pain; Masseter Muscle Hypertrophy
• Intervention / Treatment: Drug: Botulinum Toxin A (Botox )

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 17
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Choose A State
    • Kahramanmaraş, Choose A State, Turkey (Türkiye), 46000
      • Kahramanmaraş Sütçü İmam University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Botulinum Toxin Group; Participants received bilateral botulinum toxin injections into the masseter muscle using a standardized injection protocol. Clinical and ultrasonographic assessments were performed at baseline, 14 days, and 90 days post-treatment.	Drug: Botulinum Toxin A (Botox ); Botulinum toxin A was injected bilaterally into the masseter muscle using a standardized injection protocol. Injections were administered at three points in the most prominent region of the muscle. Clinical and ultrasonographic evaluations were performed at baseline, 14 days, and 90 days after injection.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Masseter Muscle Thickness	Change in masseter muscle thickness measured in millimeters using ultrasonography at baseline, 14 days, and 90 days following botulinum toxin injection.	Baseline, Day 14, Day 90

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain Intensity (VAS Score)	Change in pain intensity measured using the Visual Analog Scale (VAS) ranging from 0 (no pain) to 10 (worst imaginable pain) at baseline, 14 days, and 90 days after botulinum toxin injection.	Baseline, Day 14, Day 90
Fractal Dimension of Masseter Muscle	Change in fractal dimension values derived from ultrasonographic images using region-of-interest (ROI)-based analysis to assess microstructural complexity at baseline, 14 days, and 90 days post-intervention.	Baseline, Day 14, Day 90
Ultrasound Echotexture (Histogram Analysis)	Change in grayscale histogram parameters obtained from ultrasound images of the masseter muscle, reflecting echotexture characteristics, at baseline, 14 days, and 90 days after treatment.	Baseline, Day 14, Day 90

Collaborators and Investigators

• Sponsor: Kahramanmaras Sutcu Imam University

Study record dates

Study Major Dates

• Study Start (Actual): September 30, 2025
• Primary Completion (Actual): February 15, 2026
• Study Completion (Actual): February 15, 2026

Study Registration Dates

• First Submitted: April 16, 2026
• First Submitted That Met QC Criteria: April 16, 2026
• First Posted (Actual): April 22, 2026

Study Record Updates

• Last Update Posted (Actual): April 22, 2026
• Last Update Submitted That Met QC Criteria: April 16, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Botulinum Toxin A; Ultrasonography; Fractal Analysis; bruxism; Muscle Thickness; Masseter Muscle; Histogram Analysis
• Additional Relevant MeSH Terms: Stomatognathic Diseases; Tooth Diseases; Behavior; Habits; Bruxism; Masticatory Muscles, Hypertrophy of; Amino Acids, Peptides, and Proteins; Proteins; Biological Factors; Hydrolases; Enzymes; Enzymes and Coenzymes; Botulinum Toxins; Metalloendopeptidases; Endopeptidases; Peptide Hydrolases; Metalloproteases; Bacterial Proteins; Bacterial Toxins; Toxins, Biological; Botulinum Toxins, Type A
• Other Study ID Numbers: MasseterMuscle

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No