Low-intensity pulsed ultrasound (LIPUS) is a non-invasive physical stimulation application for the therapy of articular cartilage injury. This study aimed to explore the therapeutic effects of low-intensity pulsed ultrasound in treating masticatory myositis and synovitis in temporomandibular joint disorders and to establish an evaluation system to evaluate the clinical efficacy.

TMD patients who met the inclusion criteria in the temporomandibular joint clinic of the affiliated Stomatological Hospital of Chongqing Medical University from April 3, 2021, to December 2021 were selected. Before the start and after 7 days of LIPUS treatment, the Fricton temporomandibular joint disorder index, Visual Analog Scale (VAS), and Pressure Difference of Precision Manometer (PD) were measured. A paired t-test was used to compare the values of the Fricton index, VAS, and PD before and after treatment in each group. One-way ANOVA analysis of variance was used to compare the differences between groups.

After one week of LIPUS treatment, the PI, DI and CMI of the Fricton index in the masticatory myositis (PI: P < 0.001; CMI: P < 0.001; DI: P = 0.2641, ns) and the synovitis group (DI: P < 0.001; CMI: P < 0.001, PI: P = 0.9729, ns) significantly decreased. The VAS of the masticatory myositis group and the synovitis group were significantly reduced (P < 0.001). The PD between the affected and healthy sides of the masticatory myositis group and the synovitis group was significantly reduced (P < 0.001), and the reduction was more evident in the M group.

LIPUS is effective in pain relief in patients with masticatory myositis and joint synovitis, meanwhile, masticatory myositis was more sensitive to LIPUS. A new comprehensive clinical efficacy evaluation system which includes PV, FI, and VAS was created to better 2 diagnose masticatory myositis and joint synovitis.