Jaw and temple pain as distinct components within TMD pain

Research has suggested that pain is a multi-dimensional experience, but the interrelationship of these dimensions in people with TMD pain is not well understood.

Objective: Using confirmatory factor analysis, guided by previous exploratory factor analysis, assess whether the Symptom Severity Index (SSI) best fits a uni-dimensional or bi-dimensional model for TMD pain.

Methods: The 15-item SSI, which assesses pain frequency, duration, intensity, unpleasantness, difficulty to endure in the temple, jaw joint and jaw muscle regions, was completed by a convenience sample of 466 subjects at the University of Minnesota. The individual item responses, ranging from “never”/“zero” to “constant”/“worst imaginable” on a 29-point Likert scale, were shown to have a strong underlying factor (named “TMD pain”) and a plausible two-factor solution (named “jaw pain” and “temple pain”) in a previous exploratory factor analysis. In the current data using model fit statistics for the confirmatory factor analysis, the lowest Akaike's information criterion (AIC) and the Bayesian information criterion (BIC) were applied to select the best fitting model. Cronbach's alpha as a measure of the internal consistency of the identified scales was computed.

Results: A bi-factor model best explained the correlation in the data, suggesting one general underlying construct, TMD pain, with two additional dimensions, jaw pain and temple pain (AIC: 40348.6 and BIC: 40535.1 versus AIC: 42680.1/BIC: 42804.5 for the uni-dimensional model and AIC: 40937.4/BIC: 41065.8 for the two-dimensional model). Cronbach's alpha for the 15-item TMD scale was 0.97, for the 10-item jaw pain dimension scale it was 0.97, and for the 5-item temple pain dimension scale it was 0.95.

Conclusion: TMD pain frequency, duration, intensity, unpleasantness, difficulty to endure describe an underlying construct “TMD pain” with two dimensions named “jaw pain” and “temple pain”. Jaw and temple pain were confirmed to be two distinct components beyond the general TMD pain factor.