Objective To investigate the electromyographic changes in the anterior temporal and masseter muscles of patients with long-term unilateral mandibular first molar loss. Methods Eighteen patients with one-year or more than one-year loss of unilateral mandibular first molar were selected as experimental group,and eighteen volunteers from similar places,had similar dietary habits in the same age and gender with normal occlusion were recruited as control group. Surface electromyography was used for the evaluation of the electrical activities of bilateral anterior temporal and masseter muscles in mandibular postural position ( MPP ) , maximal clenching in intercuspal position ( ICP) and masticating situations. The data were analyzed using SPSS 17. 0 software package to compare the differ-ences among groups. Results The average electrical activities of anterior temporal and masseter muscles in MPP of experimental group were significantly higher than the contral group,and the missing side was higher than the non-missing side ( P <0. 05 ) . The average electrical activities of anterior temporal and masseter muscles in maximal clenching and masticating were significantly lower than the control group,especially in the masticating situation( P<0. 05 ) . The asymmetry index of anterior temporal muscles and masseter muscles in MPP and maximal clenching were significantly different(P<0. 05). Conclusion Long-term loss of unilateral mandibular first molar can affect the electrical activities of the anterior temporal muscles and masseter muscles in the experimental group,especially for the missing side and in the masticating situation. These results also suggest that it might be one of the potential factors on mastication system disorders.

Objective: To investigate the role of nucleotidebinding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in hyperalgesia induced by temporomandibular joint osteoarthritis (TMJOA) in rats. Methods : Twenty 6-week-old male SD rats were randomly divided into NS group and MIA group．The rat model of TMJOA was established by injection monosodium iodoacetate ( MIA) into the upper cavity of temporomandibular joint (TMJ) ．The changes of pain threshold in the TMJ region of rats after MIA injection were detected by Von Frey．The changes of condyle structure were observed by Hematoxylin-eosin ( HE ) and Safranin O-fast green stains．Histopathological changes of trigeminal ganglion (TG) were observed by HE stains．The expression and distribution of TG NLRP3 protein were detected by immunohistochemistry．Western blot was used to detect the protein levels of NLRP3 and interleukin (IL) -1 β in TG．The mRNA levels of NLRP3，apoptosis-associated speck-like protein (ASC) ，cysteinyl aspartate specific proteinase ( Caspase-1) ，IL-1β and IL-18 in TG were detected by quantitative real-time polymerase chain reaction ( qRT-PCR) . Results : Compared to saline group，the pain threshold of experimental TMJ osteoarthritis rats decreased (P＜0. 05) ．TMJ and TG showed obvious pathological changes．The protein and mRNA levels of NLRP3 expressed in the tissues of rats in the TMJOA group increased (P ＜0. 05 ) . Conclusion NLRP3 inflammasome may be involved in the regulation of hyperalgesia in TMJOA rats.