IADR Abstract Archives
Mechanobehavior Scores in Individuals With Versus Without TMJ Disc Displacement
Objectives: Temporomandibular joint (TMJ) cartilages are susceptible to mechanical fatigue. This observational study tested for differences in mechanobehavior scores (MBS) in subjects with and without TMJ disc displacement (±D).
Methods: In accordance with Institutional Review Board oversight, Diagnostic Criteria for Temporomandibular Disorders examination and imaging protocols identified eligible consenting adult subjects. Specifically, magnetic resonance imaging was used to assign subjects’ TMJs to ±D groups. Subjects were trained to record in-field jaw muscle activities for calculation of duty factors (DFs, % muscle activity time/recording time). Modeled TMJ loads and in vivo dynamic stereometry were used to determine energy density (ED, mJ/mm3), a measure of the concentration of mechanical work done to TMJ tissues. MBS was defined by ED2xDF. Analysis of Variance (ANOVA) and regression and cluster analyses tested for group differences, where significance was defined by p<0.05.
Results: Of 242 individuals screened, 56 females (TMJs: 67 +D, 45 -D) and 52 males (TMJs: 43 +D, 61 -D) participated. Subjects produced 346 day- and 357 night-time jaw-muscle recordings of average duration 6.9±2.3 and 7.6±1.9 hours, respectively, and 199 (104 right, 95 left) intact dynamic stereometry recordings. Average EDs were 2-times and significantly higher in +D than –D TMJs (adjusted p<0.05). Day-time DF were approximately twice night-time DF. Significant differences in MBS occurred in females. Peak day-time masseter MBS for jaw-loading magnitudes of >1 to ≤5 N were up to 17-times and significantly higher in +D than –D TMJs (all adjusted p<0.05). Three MBS clusters were identified (R2=0.51, p=0.012). All –D TMJs were in the cluster with the lowest MBS.
Conclusions: Higher mechanobehavior scores due to higher TMJ energy densities and day-time masseter muscle duty factors at low jaw-loading magnitudes occurred in TMJs with disc displacement compared to those without disc displacement.
Methods: In accordance with Institutional Review Board oversight, Diagnostic Criteria for Temporomandibular Disorders examination and imaging protocols identified eligible consenting adult subjects. Specifically, magnetic resonance imaging was used to assign subjects’ TMJs to ±D groups. Subjects were trained to record in-field jaw muscle activities for calculation of duty factors (DFs, % muscle activity time/recording time). Modeled TMJ loads and in vivo dynamic stereometry were used to determine energy density (ED, mJ/mm3), a measure of the concentration of mechanical work done to TMJ tissues. MBS was defined by ED2xDF. Analysis of Variance (ANOVA) and regression and cluster analyses tested for group differences, where significance was defined by p<0.05.
Results: Of 242 individuals screened, 56 females (TMJs: 67 +D, 45 -D) and 52 males (TMJs: 43 +D, 61 -D) participated. Subjects produced 346 day- and 357 night-time jaw-muscle recordings of average duration 6.9±2.3 and 7.6±1.9 hours, respectively, and 199 (104 right, 95 left) intact dynamic stereometry recordings. Average EDs were 2-times and significantly higher in +D than –D TMJs (adjusted p<0.05). Day-time DF were approximately twice night-time DF. Significant differences in MBS occurred in females. Peak day-time masseter MBS for jaw-loading magnitudes of >1 to ≤5 N were up to 17-times and significantly higher in +D than –D TMJs (all adjusted p<0.05). Three MBS clusters were identified (R2=0.51, p=0.012). All –D TMJs were in the cluster with the lowest MBS.
Conclusions: Higher mechanobehavior scores due to higher TMJ energy densities and day-time masseter muscle duty factors at low jaw-loading magnitudes occurred in TMJs with disc displacement compared to those without disc displacement.