| Aims:In order to investigate the roles of parathyroid hormone (PTH1-34) on alveolar bone formation of female rats by the method of bone measurement, the models of osteoporosis animals were built by removing bilateral ovarian tissue of female Wistar rats. This research could provide basic experimental data to explain how to increase the implant osseointegration and how to improve planting success rate in dental implants, thus further to provide a theoretical basis for the clinical application of PTH1-34to treat postmenopausal women who suffer from osteoporosis.Methods:48Female Wistar rats which were healthy and3～4months old were choosed and randomly divided into three groups. Group A included18rats, group B included15rats and group C included15rats. Bilateral ovarian tissue were removed completely from the rats in group B and group C (group OVX), and equivalent adipose tissue around the ovary were removed from the rats in group A (group SHAM). Eight weeks later, weights as well as the contents of alkaline phosphatase (ALP), estrogen (E2), and parathyroid hormone (PTH) in serum of all rats were measured. Then,6rats from group A,3rats from group B and3rats from group C were randomly choosed to be killed. The killed rats were taken bilateral maxilla and tibia near metaphysic, followed by the measurement of the mineral density of bone tissues using dual energy X-ray absorptiometry. And then slices of bone tissues were maken to identify whether the osteoporotic models are successfully built through histopathologic study. After the models were successfully built, we implanted titanium threaded cylindrical implant in the right tibia near metaphysis in the remaining rats. After implanting,0.9%physiological saline was injected to the enterocoelia of the rats in group A and group B with the dose of1ml/kg, and parathyroid hormone was injected to enterocoelia of the rats in group C with the dose of20μ g/kg (freeze-dried powder was maked into suspension with20μ g/ml by physiological saline and the suspension was shaken up before using) every other day. The dose was proofreaded according to the weight of rats once a week. At4weeks and8weeks after implanta-tion surgery, the contents of alkaline phosphatase (ALP), estrogen (E2) and parathyroid hormone (PTH) in serum of rats in each group were measured. At the same time, half the rats in every group were killed. The mineral density of the maxilla and the left tibia near metaphysic were measured by using dual energy X-ray absorptiometry. Then, undecalcified sections were prepared with toluidine blue dyeing to examine histologically and histomorphometricallyResults:1、Castration operation of the rats was sucessful.8weeks after castration, the weight of the rats in group OVX(group B and group C) significantly increased.compared to the rats in group SHAM(group A). it was statistical significance (P<0.05) for the discrepancy between group OVX and SHAM; Compared with the rats in group SHAM, the mineral density of tibia and maxillary of rats in group OVX were significantly lower through the dual energy X-ray absorptiometry, and it was also statistical significance (P<0.05) for the discrepancy between group OVX and SHAM. The histological observation showed that compared with SHAM group, the number of bone trabecula reduced and they got thin, sparse and not continuous in the the maxilla and the tibia near metaphysis of OVX group, which further confirmed the osteoporosis. What mentioned above proved that the experimental animal model of osteoporosis was built successfully.2、4weeks、8weeks after implantation, the weight of rats in each group increased:it was not statistical significance (P>0.05) for the discrepancy of weight between group C and B,but it wa it was statistical significance (P<0.05) for the discrepancy of weight added between group C and B; it was statistical significance (P<0.05) for the discrepancy of weight between group C and A,but it was not statistical significance (P>0.05) for the discrepancy of weight added between group C and A.3、4week、8weeks after implantation, compared with group B, the activity of ALP in serum increased obviously in group C (P<0.05), In the serum, it was not statistical significance (P<0.05) for the discrepancy of E2, PTH between the two groups (P>0.05). Comparing with the rats in group A, activity of ALP increased and E2level was still lower in group C. It was statistical significance (P<0.05) for the discrepancy between the two groups. In the serum, PTH decreased slightly in group C, while it increased in group A. However, it was not statistical significance (P>0.05) for the discrepancy between the two groups.4、4weeks、8weeks after implantation, the bone density of the freshly isolated left tibia and the maxillaby was measured by using dual energy X-ray absorptiometry. It was found that the density of tibia and mandible bone in group C was higher than that in group B：it was not statistical significance (P>0.05) for the discrepancy between the two groups after4weeks;But it was statistical significance(P<0.05) after8weeks.Compared with A group, the bone densityis in group C was lower than that in group A in, However, it was not statistical significance (P>0.05) for the discrepancy between the two groups after8weeks.5、4weeks、8weeks after implantation, they were examed histologically and histomorphometrically.4weeks later, it was found that implant bone contact rate，，trabercular width and combinded bone lamella width of rats were much higher in groop C than that in group B (P<0.05);However, in terms of thickness of cortical, trabercular area, there was no difference between group C and group B.It was found that trabercular area,trabercular width and combinded bone lamella width of rats were much lower in groop C than that in group A (P<0.05);However, in terms of implant bone contact rate,thickness of cortical bone, there was no difference between group C and group A.8weeks later,it was found that implant bone contact rate, trabercular area,trabercular width and combinded bone lamella width of rats were much higher in groop C than that in group B (P<0.05);However, in terms of thickness of cortical bone, there was no difference between group C and group B. There was no difference between group C and group A in all of the terms, although every term grew higher except the term of thickness of cortical bone. What mentioned above proved that PTH could improve the quality of osseointegration of the rats.Conclusion:1、The osteoporosis model of the rats which is built by removing bilateral ovarian tissues is similar to the osteoporosis of post-menopausal women. Both of them belong to the high turnover osteoporosis, and have certain etiological and pathological similarity. The model is built scientifically and it can be used to investigate the influence of PTH1-34on osseointegration in the condition of osteoporosis.2、Intermittent application of parathyroid hormone (PTH1-34) with small doses can increase the density of alveolar bone mineral, improve their bone structure, increase implant bone contact rate, trabercular area, trabercular width and combinded bone lamella width, further to improve the osseointegration quality of the rats. |
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