| Objective Using animal models of deflective mastication to investigate the influence of deflective mastication to mastication muscles, then to study the effect of deflective mastication to temporomandibular disorders (TMD).Methods 80 white rats were used to establish animal models of deflective mastication by the way of extracting the right retromaxillary region teeth. The 80 young rats were divides into a 4 梬eek group and a 8 梬eek group according to the time; after extraction 4 weeks or 8 weeks. Each group was subdivided into two sets: 20 young rats were served as the experimental group and the other 20 young rats were served as the control. The electromyography (EMG) of the mastication muscles were studied and the mastication muscles of all the white rats were observed separately with light microscope, transmission electron microscope.Results Hyperactivity of bilateral anterior temporalis (TA) , posterior temporalis (TP) ,masseter muscle (MM) at the control group was significantly reduced with the splint in situ(P<0. 05). The EMG activity of TA, MM, and TP during maximal clenching was dramatically reduced in control group(P<0. 05) ,the asymmetry index of MM was obviously decreased and the activity index of MM was significantly increased (P< 0. 05). The silent period (SP) of the experimental group and the control group was different significantly(P<0. 05). The observation of light microscope, transmission electron microscope showed that inflammatory reaction, compensatory hyperplasia ,and degeneration. In light microscope, the mastication muscle fibers were suffered injury ,proliferation ,atrophy and degeneration from the deflective mastication group, but the extents of deterioration didn't become greater with the increase of the time.Conclusion The study demonstrate that deflective mastication is one of the causesof the TMD , and it has great significance for the clinical diagnosis, treatment and pre-vention for TMD.
|
PDF Full Text Request