Pain and limitation with chewing: Experimental validation of the JFLS

Objectives: Item selection for the JFLS via Rasch measurement model resulted in a psychometrically strong instrument which measures limitation of the masticatory system in a hierarchical manner, and construct validation indicates that reported limitations are not biased by characteristic pain intensity, jaw symptoms, biobehavioral symptoms, clinical findings, or overall disability. What reported limitations actually index in the JFLS, however, is not well understood. The present study addressed mastication using graded food stimuli coupled with multidimensional outcome measures in order to better understand “functional limitation”. Methods: Ten asymptomatic and 10 TMD individuals chewed, in sequence, 6 foods ranging in texture from applesauce to jerky and one laboratory non-food as the stimuli; the subjects rated pain, limitation, and effort associated with each chewing task, and each food was repeated twice in that session. Results: ICC for trial reliability indicated that pain and limitation ratings generally exceeded 0.9, while those for effort were more variable. Collapsing trial data associated with the 3 chewing stimuli that were most difficult to masticate, the composite variate of pain, limitation, and effort in MANOVA significantly discriminated TMD from controls (W=0.553, 0.419, 0.496, respectively; p<0.03). Correlation between stimulus-associated limitation and JFLS limitation were as predicted, with Pearson r values increasing up to 0.79 as the range of raw ratings associated with each food increased. Conclusion: These experimental results were consistent with previously reported Rasch results from the paper instrument, providing experimental support for the hierarchical character of the JFLS. Experimental chewing can produce reliable experiential data of pain and limitation; this model shows promise for ecologically valid studies of pain associated with function. This research was supported by NIDCR Grant U01-DE013331 and by School of Dental Medicine funds.