[Effect of bite force lost on the expression of iNOS in the rat periodontium].

PURPOSE: To investigate the molecular mechanism of the effect of bite force loss on periodontium remodeling. METHODS: For establishing a rat model of different bite forces for the study, the left maxillary molars of Wistar rats were extracted and the left mandibular molar area was used as the model of the bite force lost. The animals were sacrificed after 6 hours,1,2,3 days and 1,2,3,4weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of iNOS protein in PDLC and osteoblasts with HE staining, immunohistochemistry and RT-PCR techniques, and the results were analyzed by one-way ANOVA,Dunnet t test and paired samples test. RESULTS: In the group of lost biting force, the derangement of periodontal ligament and resorption of alveolar bone were observed in histologic study: the structure of periodontal ligament deranged ,fibers and cells arrayed abnormally, there were many holes in the alveolar bone, even osteoclasts were present; the expression of iNOS was observed dramatically changed: the expression of iNOS in periodontal ligament fibroblasts and osteoblasts was higher than normal, especially at 2 days and 3 weeks,so as the results of RT-PCR.There was a significant correlation between bite force lost and the increased expression of iNOSmRNA. CONCLUSIONS: Bite force lost significantly increased the expression of iNOSmRNA in PDLC and osteoblasts, which suggests that iNOS may play an important role in the process of periodontium remodeling.