Abstract: Objective: To investigate the effect of repositioning splint on temporomandibular disorders (TMD) by measuring the cross-sectional area of bilateral masseter muscles and the width of joint capsule by high-frequency ultrasound. Methods: Twenty-three patients with temporomandibular joint pain and joint play sound visited our department were randomly selected as the experimental group, and 20 healthy volunteers as control group. Experimental group was received positioning grind splint treatment. The thickness of bilateral masseter muscle and the width of joint capsule were measured by high-frequency ultrasound before treatment and 1, 2, and 3 months after treatment, and compared with the control group. The changes of symptoms before and after treatment in the experimental group were recorded. Results: In the experimental group, the average thickness of bilateral masseter muscle was 9.42 mm in the non-occlusal state and 13.04 mm in occlusal state before treatment. In the control group, the average thickness of bilateral masseter muscle was 8.48 mm in the non-occlusal state and 10.27 mm in occlusal state. There was statistical significance between two groups before treatment (P<0.001). Additional, the masseter muscle thickness had significant difference each month after treatment in the experimental group (P<0.001). The joint capsule width in the jaw plate had no statistically significant difference between two groups before treatment (P>0.05). After treatment, the symptoms of pain and ringing were significantly improved, and the cure rate was 52.2%. Conclusion: The effect occlusal plate is significant. High-frequency ultrasound can be used as an effective tool to evaluate the treatment effect of occlusal plate, providing a basis for clinical diagnosis and evaluation of the clinical effect of TMJ disorders.

Key words: temporomandibular joint disorder, high frequency ultrasound, masseter muscle thickness, joint capsule width