A Comparative Analysis of Temporomandibular Disorders Using a Jaw Motion Analyzer and Surface Electromyography

Quantification of mandibular movement allows both dynamic and static evaluation of temporomandibular joint (TMJ) status, which would provide important information in temporomandibular disorders (TMD) diagnosis and treatment. The ultrasonic Jaw Motion Analyzer (JMA; zebris) system could analyse the 3-dimensional motion of the mandible without any radiation. Using the JMA, this study aimed to investigate the differences in mandibular movements and masticatory muscle activities among patients with different diagnoses of anterior disc displacement based on TMJ magnetic resonance imaging (MRI).

Seventy-four adult subjects with 148 TMJ were divided into 3 groups based on MRI: the No Disc Displacement (NDD), the Anterior Disc Displacement with Reduction (ADDWR), and the Anterior Disc Displacement without Reduction (ADDWoR). The JMA and surface electromyography (sEMG) were used to measure several mandibular movements and sEMG. Comparison and correlation analysis were performed among groups.

Significant differences were found between NDD, ADDWR, and ADDWoR in the following items: the incisal range of motion during right and left laterotrusion, maximum mouth opening, the surface area of Posselt envelope movement in the frontal plane, condylar range of motion in opening movement, and sEMG of masseter during maximum voluntary clenching.

Significant differences were found in mandibular movements and muscle activity between patients with NDD, ADDWR, and ADDWoR.

The JMA and sEMG provide important information on mandibular movement and muscle activities, which may provide additional insights into TMD diagnosis and treatment.