| Objectives：To establish the osteoporosis experimental animal model ofovariectomized rats and orthodontics forces conducted to ovariectomized rats,observing the expression difference of MMP-9in the periodontium on thepressure side between osteoporosis rats and normal rats during orthodonticstooth movement, which investigate the relationship of MMP-9and alveolarbone resorption in tooth movement and osteoporosis effects on bonemetabolism.Methods: Fifty6-month Wistar rats were divided into10groups byweight randomly with5rats in each group. Control group (sham): groupA1(0-day activating), group A2(5-days activating), group A3(7-daysactivating), group A4(10-days activating), group A5(14-days activating);ovariectomized groups(OVX): group B1(0-day activating), group B2(5-daysactivating), group B3(7-days activating), group B4(10-days activating), groupB5(14-days activating). The rats in control group were only removed adiposetissue aroud the ovaries. Osteoporosis model was sucessfully established sixmonths after ovariectomy of rats. Based on this model, we devised anappliance by means of0.49N forces to make the first molar of rats movemesially.The rats were sacrificed at a scheduled time and excised left femur, tibiaand lumbar, then we use the dual-energy X-ray absorption metry to measurethe bone mineral densities. At the same time, All rats's bilateral upper jawspecimens(include upper molar and periodontium) were excised, fixed,decalcified, parafifn-embedded and sliced. The changes of periodontium onpressure side of moved tooth were observed with HE staining. The number ofosteoclasts in periodontium on pressure side of moved teeth was counted withTRAP staining. The content change of MMP-9in periodontium on pressure side were observed with immunohistochemical staining. We used the imageanalysis software6.0to analysis the half quantitative of MMP-9. Then weused statistical software18.0to analysis all of the experimental results. If thematerial was normal distribution, we used mean and standard deviation todescribe the results, and we used two independent T test sample to analysis. Ifnot, we used median and interquartile range to describe the results, and weused two independent sample of rank and wilcoxon comparison test toanalysis. Inspection standard α=0.05.Results:1result of bone mineral density (BMD): After we established theosteoporosis model for six months, The tibia,lumbar and femlur's BMD ofOVX group was0.14±0.01,0.17±0.01and0.18±0.01, the BMD of controlgroup was0.15±0.01,0.21±0.01and0.20±0.02. There was significantlystatistical difference of BMD between OVX group and control group.2result of HE staining: After conducted forces, compared with A1group,the periodontium on pressure side is narrowed significantly of A3,A4,A5group, periodontal fibers were arranged disordered, the number of fibroblastsdecreased, hyalinization and undermining resorption were discovered on A2and A3group, gradually hyalinization was removed. compared with controlgroups, the periodontium on pressure side became more narrowed in B3, B4,B5group, the number of fiberoblasts became more less, part of the fiberalmost parallelled to the longitudinax axis. The trabecular bone volume andtrabecular number of OVX rats were lower, the bone marrow cavity becamelarger and the number of osteoclasts inceased, hyalinization were occasionallydiscovered on B4and B5groups.3TRAP staining: TRAP+osteoclasts had increased in the periodontium onpressure side of OVX groups and control groups. There was significantlystatistical difference between OVX group and control group on0day,5day,7day,10day (p<0.05), There was no significantly statistical difference betweenOVX group and control group on14day (p>0.05).4result of immunohistochemical staining: MMP-9expressed mainly in cytoplasm of bone cells, vascular endothelial cells, fibroblasts and osteoclastslocated in resorption lacunae. ImagePro-plus software was used to measuremean optical-density (MOD) of MMP-9in periodontium. There wassignificantly statistical difference betweeen OVX groups and control groups(p<0.05).Conclusion：1The number TRAP+osteoclasts and the expression of MMP-9in theperiodontium on pressure side of OVX groups were more than that of thecontrol group. So the osteoporosis rats manifested more alveolar boneresorption.2Our experiment suggested that we should use light force and operatcarefully in the process of orthodontic to reduce the morbidity risk ofperiodontal disease. |
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