Objective To investigate the effects of occlusal rehabilitation on chewing patterns of patients with extensive tooth wear. Methods 29 patients with severe tooth wear were selected and divided into two groups: GroupⅠwith complete posterior tooth support（15 cases）and group Ⅱ with one- side or both side posterior support lost（14 cases）. 15 normal old persons were also selected as control group. The surface electromyography（EMG） of masseter（MM）, anterior temporalis（TA） and posterior temporalis（TP） during chewing movement were recorded in the stage of pre- treatment, 1 month after temporary restoration and 1 month after permanent restoration. The EMG activity, total cycle duration（TCD） and ratio of activation period to relaxation period（AP/RP） of chewing cycles were measured and compared. Results 1）Before treatment, the TCD of these two groups were longer than normal group, but the differences were not significant（P>0.05）. All of the AP/RPs of MM, TA and TP in group Ⅱ were significantly higher than that of normal group（P
