| ObjectiveInvestigate the effect of occlusal trauma on the expression of type Ⅰ、Ⅲ collagen and MMP-3 in periodontal ligament by establishing occlusal trauma model with rats, to further explore the mechanism for the occurrence and development of occlusal trauma in periodontal tissue, as well as toprovide a theoretical basis for clinical interventive methods and future research.Method:Part Ⅰ:25 male Wistar rats were divided into 5 groups randomly, each group had 5 rats. Grouping:blank control group, occlusal trauma groupsincluding 1 w group,3 w group,4 w group,2 w after trauma and removal of trauma in 2 w group. The wax type and cobalt chromium alloy casting 3/4 crown were made with isolated mandible ofWistar rat and then fixed to the first molar in right mandibular of experimental rats to establish occlusal trauma model.PartⅡ:Removing casting crownimmediately after the rats were executed, and collect the mandibular first molar and its surrounding tissues as specimens to maketissue slice, To observe thechanges of morphology and type I and typeⅢcollagen in the experimental molar afterHE staining and picrosirius red stainingpartⅢ:Observe changes of the expression of MMP-3 and type I collagen by immunohistochemistry methodStatisticalanalysis:Data analysiswas done by GraphPadPrism 6 statistical software, Using one-way AVOVA analysis and unpaired t test,P<0.05was significant.Result:1.Establishing animal model:All the crowns were well fixed in 28 days. X-ray films showed that the periodontal ligament was widened and the alveolar bone was absorbed around the mandibular molars of experimental rats.2.Observation of mandible tissue slices:2.1 HE staining:control group:no obvious histological abnormality was found. Cementum and alveolar bone are smooth; periodontal tissue fibers arranged neatly, the fibroblasts are evenly distributed in the main fiber, consistent with the main axis. In the experimental group, the periodontal fiber arrangement was disordered, the periodontal ligament was widened, and the alveolar bone surface was not smooth in the 1w group.hyalinization、periodontal ligament cavity、lacuna-shaped alveolar bone absorption and osteoclasts were found in 3w group and 4w group.Lighter periodontal injury,less hyalinization and osteoclasts were found in removal group, new bone deposition was visible in alveolar bone lacuna2.2Picrosirius red staining:The tissue ofcontrol group was mainly composed of type Ⅰ collagen, type Ⅰ and type Ⅲ collagen ratio were 81.60% and 11.89%respectively.l W group of type Ⅰ collagen content began to decrease,3W group reached the lowest (P<0.05). The content of type Ⅰ collagen in the 2W group and removal group was higher th, but it was still lower than that in control group (P< 0.01); compared with the control group,the ratio of type Ⅲ collagen in1w group,3w groups was increased,,4 weeks group reached the highest, the ratio of typeⅢcollagen in removal group was lower compared with 1w group,3w group, and 4 w group, but still higher than control group, differences have statistical significance since 3w (P< 0.01). At the same time, the contents of type Ⅰ and type Ⅲ collagen were statistically significant in each group (P<0.05).3 Immunohistochemical test3.1MMP-3 test:MMP-3 was weakly positive in normal periodontal tissue, which was mainly located in the cytoplasm of periodontal ligament fibroblast. The positive reaction of MMP-3 was gradually increased in 1w and peaks at 3w,which located in periodontal ligament extracellular matrix, osteoclasts and bone resorption lacunae (P < 0.01). MMP-3 expression gradually decreased in the in4w group(P< 0.05), The expression of MMP-3 in the removal group was close to the normal group (P>0.05).3.2Type Ⅰ collagen test:Type Ⅰ collagen fiber bundles were neatly arranged in normal periodontal tissue, mainly stained in periodontal ligament cells interstitial.In the experimental group, type Ⅰ collagen fibers were disordered in 1w group, the positive intensity was decreased and down to the lowest in3w group,and the collagen fibers were broken and incoherent (P< 0.01). The expression of 4w group began to rise, and the expression level of the removal group was higher than that of 4w group. The morphology of collagen fibers in the group began to recover, but it was still lower than the normal level (P<0.05).Conclusion:1.The occlusal trauma model in rat molar through the adhesive casting crowns to induce the formation of early contact is effective and feasible, and can be applied to b research in occlusal trauma.2.Under the state of occlusal trauma, the proportion of type Ⅰ and Ⅲcollagen in periodontal ligament changes.The changes of content and morphologyas well as expression of type Ⅰ collagen immunohistochemistry were consistent, which further showed that the metabolism of type Ⅰ collagen was an important foundation for the remodeling of periodontal ligaments.typeⅢcollagenmay play an important role in periodontal tissue remodeling.3.MMP-3 was involved in the remodeling of periodontal ligamentwith occlusion trauma, which may affect the ECM remodeling of periodontal ligament through the regulation of collagen type Ⅰ collagen.The metabolism of periodontal ligament is in a dynamic balance state with the change of the internal and external environment.4.The repair of periodontal tissue requires a certain period of time, to remove the trauma factors as soon as possible is the key to the treatment of occlusal trauma... |
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