Tongue strength, masticatory and swallowing dysfunction in patients with chronic temporomandibular disorder

Background: The possible factors related to functional impairment and limitations in patients with temporomandibular disorders (TMDs) still need to be clarified because recovery of orofacial functions is a goal of their treatment. Objective: To investigate whether chronic TMD patients had any changes in tongue strength, besides the difficulty in chewing and orofacial functional impairment, compared to a control group. Moreover, to examine whether tongue strength, chewing difficulties, and orofacial functions were associated. Methods: Twenty-three patients with chronic TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and volunteers without TMD (control group) were compared. Strength measures were obtained using the Iowa Oral Performance Instrument (IOPI) during tongue protrusion (TPS) and swallowing of saliva (SS) tasks. A scale was used to investigate self-reported chewing difficulties, and the orofacial muscles and functions were evaluated using the orofacial myofunctional evaluation with scores protocol (OMES). Results: Compared to the control group, TMD patients showed reduced TPS and SS, higher difficulty in chewing and worse myofunctional orofacial conditions. Tongue strength was correlated with mastication and swallowing behaviors, as well as with general myofunctional status. Chewing difficulty increased with decreasing tongue strength and with worsening of orofacial muscles and functions. Conclusion: Patients with chronic TMD showed reduced tongue strength and worse masticatory and swallowing functions, and these aspects were interrelated.