Vertical Facial Morphology and Occlusal Force Changes After Masseter Botulinum Toxin Injection in Bruxism

Influence of Vertical Facial Morphology on Occlusal Force Changes After Masseter Botulinum Toxin Injection in Bruxism: A Prospective T-Scan Study

This study investigated whether the shape of the face affects how jaw muscles respond to botulinum toxin injections in people who grind their teeth (bruxism). Participants were divided into two groups based on their facial structure: low-angle (shorter face height) and normal-angle. Each participant received botulinum toxin type A injections into the masseter (jaw) muscle. Bite force measurements were taken before and 15 days after the injection using the T-Scan computerized occlusal analysis system. The study aimed to determine whether facial structure influences the early changes in bite force balance following the injection.

Study Overview

• Status: Completed
• Conditions: Bruxism; Occlusal Changes
• Intervention / Treatment: Biological: Botulinum Toxin Type A (BOTOX) Injection

• Study Type: Interventional
• Enrollment (Actual): 34
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Istanbul
    • Istanbul, Istanbul, Turkey (Türkiye), 34010
      • Department of Orthodontics, Faculty of Dentistry, Biruni University

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age 18-40 years
• Confirmed bruxism diagnosis through self-report and clinical signs
• Full permanent dentition excluding third molars
• Angle Class I molar relationship
• No previous BTX-A injection within 6 months
• GoGn/SN angle between 18° and 38° on lateral cephalometric radiograph

Exclusion Criteria:

• Systemic neuromuscular disorders
• Known allergy to botulinum toxin or its excipients
• Pregnancy or breastfeeding
• Active infection at the injection site
• Concurrent use of medications known to interact with BTX-A
• History of orthognathic surgery or prior temporomandibular joint surgery

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: Masseter BTX-A Injection (Low-Angle and Normal-Angle Subgroups); Patients with bruxism received bilateral masseter muscle injections of 25 units of botulinum toxin type A (Botox®, Allergan) per side. T-Scan occlusal force measurements were performed at baseline (T0) and day 15 post-injection (T1). Participants were stratified into low-angle and normal-angle subgroups based on GoGn/SN cephalometric angle.

Biological: Botulinum Toxin Type A (BOTOX) Injection; Botulinum toxin type A (Botox®, Allergan, Irvine, CA, USA) was injected bilaterally into the masseter muscle at a dose of 25 units per side (50 units total per patient). Injections were performed by a single experienced clinician under sterile conditions using a 30-gauge needle.; Other Names: botox

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Center of Force (CoF)	The Center of Force (CoF) represents the geometric center of the total occlusal force distribution, measured using the T-Scan Novus™ computerized occlusal analysis system (version 10.0.40; Tekscan, Inc., South Boston, MA, USA). CoF values closer to zero indicate greater bilateral occlusal balance. Within-group changes (T0 to T1) and between-group differences were assessed and compared between low-angle (GoGn/SN < 26°) and normal-angle (GoGn/SN 26-38°) subgroups.	Baseline (T0) and day 15 post-injection (T1)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Anterior and Posterior Force Percentage	Anterior force percentage is defined as the combined occlusal force distribution of the anterior teeth, and posterior force percentage as the combined force distribution of the posterior teeth. Both were measured using the T-Scan Novus™ system at baseline (T0) and day 15 post-injection (T1). Within-group changes and between-group differences in anterior-posterior force distribution were evaluated and compared between low-angle and normal-angle subgroups.	Baseline (T0) and day 15 post-injection (T1)

Collaborators and Investigators

• Sponsor: Biruni University
• Investigators: Study Chair: Esra Agaoğlu Mogul, Department of Orthodontics, Faculty of Dentistry, Biruni University

Study record dates

Study Major Dates

• Study Start (Actual): February 9, 2026
• Primary Completion (Actual): May 8, 2026
• Study Completion (Actual): May 8, 2026

Study Registration Dates

• First Submitted: June 23, 2026
• First Submitted That Met QC Criteria: June 23, 2026
• First Posted (Actual): June 29, 2026

Study Record Updates

• Last Update Posted (Actual): June 29, 2026
• Last Update Submitted That Met QC Criteria: June 23, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Stomatognathic Diseases; Tooth Diseases; Behavior; Habits; Bruxism; 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: BiruniU-2026-09

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared due to patient privacy and ethical restrictions. Data are available from the corresponding author on reasonable request.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No