| Objective: This study aims to ascertain the improvement of patients’ masticatory function, based on the analyses of surface electromyography(s EMG) and masticatory efficiency of unilateral mastication patients whose inducing factors were regularly removed 6 month ago. According to the results of the analysis, intervention therapy was made to randomly sampled part of the unilateral mastication patients. Then the effect of the intervention therapy were examined by comparing the electromyography activity of masticatory muscle and masticatory efficiency before and after the intervention. This study can provide some experimental basis for judging whether further intervention therapy is needed in clinical patients with unilateral mastication. Methods : 1) By combining clinical stomatological examination with inquiry, 30 unilateral chewing patients(15 males and 15 females, aged 19.3±0.5) were randomly selected as the experimental group, in which 17 cases of left side chewing and 13 right side chewing were included. The conventional inducing factors for the unilateral chewing of this group had been removed 6 months before the experiment. At the same time, free-sided chewing people were randomly selected as control group(n=30, 15 males and 15 females, aged 19.6±0.3). The s EMG of masseter muscle and anterovent of digastric muscle was separately recorded for both the groups in the mandibular postural position, maximum opening and closing movement and chewing. The s EMG parameters were analyzed statistically. Then the absorbance value were tested and analysed in order to compare the masticatory efficiencies during random, left side, and right side chewing, 5 respectively. 2) The 30 unilateral chewing patients were halved into two groups, i.e. intervention group and non-intervention group. After 6 months of intervention, the s EMG of masseter muscle and anterovent of digastric muscle was again recorded from these two groups in the mandibular postural position, maximum opening and closing movement and chewing, and the masticatory efficiencies at random of the two groups before and after 6 months of the intervention were statistically analyzed. Results:1) The average EMG value during maximum opening and closing movement of right anterovent of digastric muscle(RDA) in unilateral chewing group were lower than those in free-sided chewing group, and the average EMG value of right masseter muscle(RMM) during chewing in unilateral chewing group were lower than those in free-sided chewing group either(P<0.05).2) The peak EMG values of left anterovent of digastric muscle(LDA) and RDA at maximum opening in unilateral chewing group were lower than those in free-sided chewing group, and the peak EMG values of left masseter muscle(LMM) and RMM during chewing were lower than those in free-sided chewing group as well(P<0.05).3) The asymmetry index of masseter muscles(As MM) during MPP, maximum opening and closing movement, and chewing in unilateral chewing group were higher than that of free-sided chewing group, and asymmetry index of anterovent of digastric muscle(As DA) during maximum opening and closing movement and chewing in unilateral chewing group were higher than those in free-sided chewing group either(P<0.05).4) The average EMG value of RDA during maximum opening and closing movement in the intervention group of unilateral chewing showed a significant improvement after the intervention(P<0.05), and the average EMG value of RMM during chewing had an obvious increase after the intervention(P<0.05), while the average EMG value of LDA during chewing in the intervention group were higher than those in the non-intervention group(P<0.05).5) The peak EMG values of LDA and RDA during maximum opening and closing movement in the intervention group of unilateral chewing showed a significant improvement after the intervention(P<0.05), and the peak EMG values of LMM and RMM during chewing had an obvious increase after the intervention(P<0.05), while the peak EMG value of LDA during maximum opening and closing movement in the intervention group were higher than those in the non-intervention group(P<0.05).6) After the intervention, the As MM at MPP, maximum opening and closing movement and chewing in intervention group of unilateral chewing showed an obvious decrease(P<0.05), and the As DA at maximum opening and closing movement and chewing showed an obvious decrease either(P<0.05), while the As MM and As DA in the intervention group were lower than those in the non-intervention group(P<0.05).7) There was significant difference of absorbance value between the unilateral chewing group and bilateral chewing group(P<0.01). In the left side chewing group, random chewing and left side chewing were both higher than right side chewing(P<0.05). Moreover, in the right side chewing group, random chewing and right side chewing were both higher than left side chewing(P<0.05)..8) The masticatory efficiency at random chewing in the intervention group of unilateral chewing showed an obvious increase after the intervention(P<0.05), and the masticatory efficiency at random chewing in the intervention group were higher than in the non-intervention group(P<0.01). Conclusions:1) After the removal of the inducing factors for unilateral mastication, the average EMG of RMM and RDA and average EMG peak of LMM, RMM, LDA, RDA are lower than free-sided chewing group. Moreover, the bilateral asymmetry of masseter muscles existed during MPP, maximum opening and closing movement and chewing, that of anterovent of digastric muscles existed during maximum opening and closing movement, and the masticatory efficiency of unilateral mastication cases is lower than that of free-sided chewing group. These results suggest that the conventional removal of inducing factors for unilateral mastication cannot achieve the purpose of restore bilateral masticatory function. 2) After therapeutic intervention,the average EMG and average EMG peak of masseter muscles and anterovent of digastric muscles have the obvious increase, and the bilateral symmetry of masseter muscles and anterovent of digastric muscles has a significant improvement, while the masticatory efficiency at random chewing has an obvious changes, which suggests that the masticatory function of unilateral chewing was improved to a certain extent after intervention. |
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