Abstract: Objective: To explore electromyographic activity of masticatory muscle after the RW-splint treatment of Angle class II malocclusion patients with TMD, and to offer the theoretic basis for these patients before the orthodontic treatment. Methods: After RW-splint successfully worn into patiens, surface electromyography II belongs to BioPAK system was used to measure electromyographic activity of the masticatory muscle among patients before RW-splint treatment and 1 week,2 months after RW-splint treatment, respectively. Results: EMG records of masseter muscle during ICP deceased in Angle class II malocclusion patients with TMD. Conculsion: RW-splint treatment can decrease the EMG records of masticatory muscle, however, it can’t play a obvious role in improving symmetry of bilateral masticatory muscle. Probably, RW-splint changes the position of tooth and jaw, concequently originally some premature contact and occlusal interference occurring, but this is a gradual process.

Key words: Temporomandibular disorders , RW-splint, Angle class II, masticatory muscle , EMG