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Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition
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Modeling rabbit temporomandibular joint torques during a power stroke
C G Widmer1, A W English, D I Carrasco
1Department of Orthodontics, University of Florida, College of Dentistry, Gainesville 32610-444, USA. widmer@dental.ufl.edu
The Angle Orthodontist
|August 10, 2002
Summary
Changes in mandibular form after orthognathic surgery can significantly alter temporomandibular joint (TMJ) torques. Modeling reveals that even a 20% change in jaw dimensions impacts muscle forces, particularly yaw torque.
Area of Science:
- Biomechanics
- Orthodontics
- Anatomy
Background:
- Limited understanding of how orthognathic surgery-induced mandibular form changes affect temporomandibular joint (TMJ) torques.
- The masseter muscle comprises subregions with distinct mechanical actions, influencing jaw movement and TMJ loading.
Purpose of the Study:
- To model torques generated about the working side TMJ by rabbit masseter muscle compartments.
- To investigate the impact of variations in mandibular dimensions (width, length, height) on these torques.
Main Methods:
- Utilized published electromyographic data to model torques from specific masseter muscle compartments.
- Calculated torques based on forces from stimulated muscle compartments and measured mandibular lever arms relative to the TMJ center.
- Extended previous models to incorporate 20% increases in mandibular width, length, and height.
Main Results:
- Working and balancing side masseter compartments acted as synergists for pitch torque but antagonists for roll and yaw torques.
- A 20% increase in mandibular dimensions resulted in non-uniform changes in compartment-generated torques.
- The posterior superficial masseter compartment exhibited the largest increase in yaw torque.
Conclusions:
- Mandibular form alterations can produce greater effects on TMJ torques than previously predicted by simpler force models.
- These findings highlight the complex interplay between jaw morphology and TMJ biomechanics following orthognathic surgery.
