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Mechanics- and Behavior-Related Temporomandibular Joint Differences.
J C Nickel1,2, Y M Gonzalez2, Y Liu3
1Oregon Health & Science University, School of Dentistry, Department of Oral and Craniofacial Sciences, Portland OR, USA.
Journal of Dental Research
|September 14, 2024
Summary
Temporomandibular joint (TMJ) disc displacement increases tissue loading, measured by energy density (ED) and duty factor (DF). Mechanobehavior scores (MBS) are significantly higher in displaced TMJs, indicating potential for degenerative changes.
Area of Science:
- Biomechanics
- Orthodontics
- Biomaterials
Background:
- Temporomandibular joint (TMJ) fatigue is linked to loading magnitude (energy density, ED) and frequency (jaw muscle duty factor, DF).
- Understanding these factors is crucial for assessing TMJ health and predicting disease progression.
Purpose of the Study:
- To measure ED and DF in subjects with and without TMJ disc displacement (±D).
- To compare mechanobehavior scores (MBS = ED² × DF) between groups.
- To evaluate MBS as a potential biomarker for TMJ structural changes.
Main Methods:
- Observational study using magnetic resonance imaging (MRI) to classify TMJ disc displacement.
- Jaw muscle activity recorded in-field to determine duty factors (DF).
- Modeled TMJ loads and in vivo dynamic stereometry used to estimate energy densities (ED).
- Multivariate analysis of variance, t-tests, and K-means cluster analysis performed.
Main Results:
- Average EDs were significantly higher (2-fold) in +D TMJs compared to -D TMJs.
- Duty factors (DF) were higher during daytime and for masseter vs. temporalis muscles.
- Daytime masseter MBSs were highest in females with +D TMJs, exceeding those in -D TMJs by 2- to 43-fold.
- Cluster analysis identified groups with significantly higher MBS in +D TMJs.
Conclusions:
- Mechanobehavior scores (MBS) are significantly elevated in TMJs with disc displacement.
- MBS may serve as a valuable biomarker for predicting the progression or reversal of degenerative TMJ conditions.
- The findings highlight the impact of loading parameters on TMJ tissue health.
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