Regional cutaneous and muscle sensitivity does not mediate changes in active mouth opening in temporomandibular disorders: a cross-sectional study.

BACKGROUND: One of the main goals of treatment in temporomandibular disorder (TMD) patients is to improve mouth opening range of motion. However, it is not clear which factors influence its alteration. The aim of this study was to compare differences in mechanosensitivity, mouth opening and psychosocial factors, between people with and without TMD, to evaluate if changes observed in active mouth opening are mediated by an increase in tissues' mechanosensitivity, and to evaluate factors related to mandibular-related disability. Subjects with and without TMD were recruited. METHODS: Cross-sectional study conducted in Spain. The measured variables were the Craniofacial Pain and Disability Inventory (CF-PDI), pain intensity, pressure pain thresholds (PPT) at local points; active and passive mouth opening; the Short-Form 12 questionnaire (SF-12); the State-Trait Anxiety Inventory (STAI); and the Neck Disability Index (NDI). Multivariable regression and mediation models were constructed. RESULTS: A total of 179 subjects (85 with TMD) were included. Subjects with TMD had less mouth opening range of motion, and lower PPT. Tissues' mechanosensitivity did not mediate the reduction in active mouth opening in subjects with TMD (overall indirect effect, 0.98; 95% confidence interval, -0.87 to 3.12). Finally, no variable showed an association with CF-PDI. CONCLUSIONS: Subjects with TMD seem to have decreased mouth opening, and greater mechanosensitivity of masticatory muscles, when compared with healthy controls. Tissues' mechanosensitivity does not seem to mediate the reduction of active mouth opening in subjects with TMD, and there seems to be no relationship between PPT measures, mental health outcomes, the NDI and mandibular-related disability.