Chewing Patterns Altered by Temporomandibular Joint Internal Derangements

Previous studies have suggested that some differences exist between the chewing movements of normal asymptomatic subjects and those with temporomandibular joint (TMJ) internal derangements. 

Objectives: The objectives were to find specific factors that are mathematically distinct between the chewing timings, movement pattern shapes, variability and movement velocities of normal asymptomatic subjects and a group of subjects with verified TMJ internal derangements.

Methods:

The chewing movement recordings of 29 subjects (34.2 + 16.8 yrs) were randomly selected from a large database of patients exhibiting unilateral or bilateral temporomandibular joint internal derangements.  The chewing movements of a control group of 29 asymptomatic subjects (32.9 +11.7 yrs, p > 0.78) with verified normal TM joint function were also recorded.  Means and standard deviations of the opening, closing, turning point, terminal chewing position and velocity patterns were calculated.  A two-tailed Student’s t test with unequal variances was used to compare several parameters of the two groups (alpha = 0.05).

Results:

With respect to the timing of opening and closing the control group functioned faster and with less variability (p < 0.0002).  With respect to the movement pattern the vertical dimension was consistently larger in the control group chewing an identical bolus (p < 0.0001).  The consistency of the terminal chewing position was also significantly less variable (Vertical - p < 0.0041, A/P p < 0.029, Lateral P < 0.028) in the control group.  The maximum lateral width was significantly greater (p < 0.0075) and both the peak and average velocities were significantly greater (p < 0.0001 for both) in the control group.

Conclusions:

This group of subjects with verified TMJ internal derangements exhibited significantly slower, smaller and more variable chewing patterns than the age-matched control group.