Human temporomandibular joint eminence shape and load minimization

Area of Science:

• Biomechanics
• Orthodontics
• Dental Anatomy

Background:

• Previous research suggested temporomandibular joint (TMJ) eminence shapes develop to minimize joint loads.
• This hypothesis requires further investigation, particularly concerning the influence of TMJ disc displacement on eminence morphology.

Purpose of the Study:

• To test the hypothesis that TMJ eminence shapes ideally develop to minimize joint loads.
• To compare predicted optimal eminence shapes with measured shapes in individuals with and without TMJ disc displacement.

Main Methods:

• Nineteen participants (9 female, 8 male) were divided into groups with and without TMJ disc displacement.
• Anatomical data were used in a numerical model to predict eminence shapes, and jaw-tracking data were used to measure them.
• Third-order polynomials fitted coordinate data (x,y) for two sessions, sides, and methods (predicted, measured).

Main Results:

• Individuals with TMJ disc displacement exhibited a higher measured shape range (5:1) and left-right asymmetry prevalence (4:1) compared to those without.
• Model-predicted and measured TMJ eminence shapes showed significant differences (P < 0.01) near the eminence crest.
• Joint load minimization was consistent with eminence shape for anterior-posterior distances (x) less than 3.0 mm.

Conclusions:

• The hypothesis that TMJ eminence shapes perfectly minimize joint loads may not hold true, particularly in the presence of disc displacement.
• Significant differences between predicted and measured eminence shapes suggest that factors beyond simple load minimization influence their development.
• Further research is needed to elucidate the complex interplay of factors shaping TMJ eminence morphology.