Magnitude of Bite Force that is Interpreted as Clenching in Patients with Temporomandibular Disorders: A Pilot Study

Introduction: The magnitude of bite force that is interpreted as clenching (imagined clenching level: ICL) in patients with temporomandibular disorders (TMD) remains unknown. We aimed to investigate the relationship between ICL and symptoms of TMD to evaluate the suitability of the term clenching for interpreting bite force in these patients. Methods: A total 76 patients (16 men, 60 women; age, 41.1 ± 16.5 years) with temporomandibular disorders treated at the Temporomandibular Joint Clinic at Tokyo Medical and Dental University were selected. All patients completed a questionnaire that evaluated gender, age, pain intensity at rest and during maximum mouth opening and chewing, ICL, and TMD-related limitation of daily functions. Pain intensity and ICL were estimated using a visual analog scale for pain. TMD-related limitation of daily functions was evaluated using a 10-item questionnaire. Results: The mean (SD) visual analog scale score for ICL was 77.4 (± 18.7 mm) and was significantly correlated with the pain intensity during maximum mouth opening and chewing, and the TMD-related limitation of daily function score; however, only the latter was identified as significant in the multiple regression analysis (P<0.05). Conclusions: TMD patients imagined the clenching force at a magnitude of approximately 70% of the maximum bite force. Patients are considered unable to sustain clenching at this magnitude; therefore, clenching is not a preferred term when administering counseling and behavioral therapy to TMD patients.