Jaw Opening, Chewing, and Bite Force in Patients with Temporomandibular Joint Pain and Matched, Healthy Control Subjects

Objective: The aim of this study was to evaluate the effect of temporomandibular arthralgia on mandibular mobility, chewing, and bite force. Methods: Twenty female patients, 19-45 yr, with unilateral temporomandibular joint (TMJ) pain as the single or overriding orofacial symptom. Inclusion criteria: TMJ tenderness at palpation, and TMJ pain during chewing and provocation. The chewing pain corresponded to 40±26mm (M±SD) on a 100mm visual analogue scale. The TMJ conditions were classified as 9 disc derangement disorders (6 displacements with and 3 chronic without reduction), 7 osteoarthritis cases (6 primary and 1 secondary) and 4 inflammatory disorders (3 synovitis/capsulitis and 1 polyarthritis). The patient group was compared with an age- and sex-matched control group of healthy volunteers without orofacial pain and TMJ tenderness. Exclusion criteria (both groups): <24 teeth and significant malocclusion. The following methods were used, (a) algometric assessment of pressure-pain thresholds (PPT) over the TMJ, (b) clinical and computerized, kinematic recordings of maximum unassisted jaw opening, (c) computerized, kinematic assessment of maximum velocity and cycle duration during chewing of soft gum, and (d) measurement of unilateral, molar bite force. The data were compared with t-tests with a significance level of P<0.05. Results: The PPT (kPa) in the patients’ pain side was significantly lower (68±19) than in the contralateral side (76±24), and also significantly lower than in asymptomatic controls (107±5). Jaw opening (mm) was significantly less in patients (42±8; controls: 52±3). Chewing and maximum closing velocity (mm/s) was significantly slower in patients (141±46 and 948±185) than in controls (175±43 and 772±101), and bite force (N) significantly lower in patients (237±99; controls: 389±80). Conclusion: These systematic findings supplement results from acute pain experiments, and confirm indications from unspecific patient groups; presence of chronic TMJ pain in patients is associated with marked functional impairment, probably due to a reflex avoidance mechanism.