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.

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