Relationship of Limitation and Disability in TMD and Other Oral Conditions

Objective: In contrast to prior disablement models from the World Health Organization, the WHO now recognizes that disability need not be dependent upon functional limitation or impairment. Because limitation and disability are often both affected in TMD, it is not clear whether these are sufficiently independent measures to warrant routine assessment of both in this condition. This study evaluated the relationship of functional limitation to disability in five orofacial conditions primarily characterized by pain, by mechanical difficulties in using the jaw, or by both. Methods: Two measures of functional limitation (mastication, mobility via Jaw Functional Limitation Scale) and 4 measures of disability taken broadly (SF-36, Graded Chronic Pain, somatization, and depression) were administered to 145 consecutive patients comprised of five diagnostic groups: TMD (n=30), Primary Sjögren’s Syndrome (n=28), burning sensation and pain in the mucosa (n=28), skeletal malocclusion (n=27), and healthy dental recall patients as controls (n=30). Limitation measures were partitioned into none vs any, and median splits were used for assigning level of disability for each of those measures. Chi-square, as a model of independence, was used for model testing. Results: For all diagnostic groups combined, greater limitation was accompanied by greater disability (multiple p<0.05); the two limitation measures differentiated subjects while the disability measures performed similarly. Both off-diagonal cells in the 2x2 chi-square analyses, however, were large in each analysis, exhibiting clear evidence of disability also without limitation. The relationships of mastication and mobility with disability differed for each diagnostic group, per known pathophysiology. Conclusion: These data demonstrate good construct validity and utility for these functional limitation measures, provide further evidence for importance of considering both limitation and disability in all oral conditions, and support the importance of these two constructs as measuring independent processes. Funding provided by Folktandvarden, Linköping, Sweden.