| Objective: With the improvement of living standard, the morbidity rate of Diabetes mellitus (DM) is increasing. The age of people who suffer from Diabetes mellitus tends to be younger. Many orthodontic doctors have attached importance to DM sufferers'orthodontic therapy. Rapid palatal expansion (RPE) is used widely in clinic. That DM sufferers often have osteoporosis which can accelerate assimilator of bone will make disadvantage on RPE. So it is necessary to provides lots of evidence of science and statistics to DM sufferers'RPE therapy applying in clinic by animal experiment. The purpose of this study is to set up an animal model of helix expansion and explore effect and bone metabolism of RPE among normal rats, DM rats and Insulin treated rats. Fundamental experiment theory is provided and served to clinic.Method: Seventy-two male SD rats (5 weeks of age) whose weight range from 200 to 220 grams were chosen and randomly grouped into three groups of 24 rats, Group A, the normol group; Group B, diabetes group and Group C, Insulin treated group. Each group randomly grouped into two little groups, the expansion group of 8 rats and retention group of 16 rats. Streptozotocin (STZ) were celioinjected in rats of Group B and Group C with the amount of 60mg per kilogram. Rats in Group A were injected with the same amount of sodium citrate. Seventy-two hours later, blood was extracted from caudal vein and urine was sample before blood glucose and urinary glouse were respectively tested. Those rats whose blood glucose were above 16.7mmol/L and urinary glucose were three plus to four plus are diagnosed as diabetes. Four days after the model of diabetes mellitus was succeeded, rats in Group C began to receive subcutaneous injection at their necks. The amount of injection was adjusted according to the rats'blood glucose and urinary glucose till the blood glucose was 8-10 mmol/L. Group A and Group B were given the same amount of normal saline injection. Twenty-one days after the model of diabetes mellitus was established, all of the rats were equipped device of RPE. Helix springs were made by 0.45mm diameter stainless steel and produce 200g force by extend arch wire about 5mm. The arch wire is about 10mm long and the end of it was folded under the adjacency of two molars. Helix springs were powered every 3 days and the force was 200g all the time.The rats of expansion group of all groups were killed by abstracting blood from their carotids after 7 days'expansion. Each rat should be obtained 10ml blood which was centrifuged to get serum. Part of the serum was measured with automatic biochemistry analyzer to mensurate serum biochemical analysis, calcium, phosphorus, and alkaline phosphatase. Part of the serum was measured with automatic radioimmunoassay analyzer to mensurate serum calcitonin. Each rat should be peeled off palate right now after abstracting blood. Weighed them on electronic balance respectively and then smash the bones after plus the normal saline with the amount of 1ml/mg into plasma. Supernatant was obtained after centrifuge. The amount of histological calcitonin was then measured with automatic radioimmunoassay analyzer. After 7 days'expansion, the helix springs on rats of retention group should be paste in by self-curing resin to be retainers lasted 21 days. Tetracycline were injected into rats of retention group's stomach 30mg/kg the forth day and the third day before the end of expansion and retention. After 21 days'retention, all of the rats were killed by abstracting blood from their carotids. Each rat should be obtained 10ml blood which was centrifuged to get serum. Part of the serum was measured with automatic biochemistry analyzer to mensurate serum biochemical analysis, calcium, phosphorus, and alkaline phosphatase. Part of the serum was measured with automatic radioimmunoassay analyzer to mensurate serum calcitonin. 8 rats of retention group were obtained palate to measure the amount of histological calcitonin and the other 8 rats'palates were made undecalcificated tetracycline labeled bone sections which was about 20μm thick and toluidine blue stainsections.Results: 1 Biochemical indexes: The serum calcium of expansion group of Group B is higher than that of Group A and Group C, while there is no difference (P>0.05). The serum calcium of retention group of Group B is higher than that of Group A and Group C with a significant variance of P<0.05. The serum phosphorus of expansion group of Group B is lower than that of Group A and Group C, while there is no difference (P>0.05). The serum phosphorus of retention group of Group B is lower than that of Group A and Group C, while there is no difference (P>0.05). The serum alkaline phosphatase of expansion group of Group B is higher than that of Group A and Group C with a significant variance of P<0.01. The serum alkaline phosphatase of retention group of Group B is higher than that of Group A and Group C with a significant variance of P<0.01. The serum calcium, phosphorus and alkaline phosphatase of Group A, Group B and Group C have no significant variance between expansion group and retention group (P>0.05).2 The content of serum calcitonin: measured with automatic radioimmunoassay analyzer, the serum calcitonin of expansion group of Group B is lower than that of Group A and Group C, while there is no difference (P>0.05) and there is no difference between Group A and Group C (P>0.05). The serum calcitonin of retention group of Group C is lower than that of Group A, while there is no difference (P>0.05) and that of Group B is lower than that of Group A and Group C with a significant variance of P<0.01. The serum calcitonin of Group A, Group B and Group C have no significant variance between expansion group and retention group (P>0.05).3 The content of histological calcitonin: measured with automatic radioimmunoassay analyzer, the histological calcitonin of expansion group of Group C is lower than that of Group A, while there is no difference (P>0.05) and that of Group B is lower than that of Group A and Group C with a significant variance of P<0.01. The histological calcitonin of retention group of Group C is lower than that of Group A, while there is no difference (P>0.05) and that of Group B is lower than that of Group A and Group C with a significant variance of P<0.01. The histological calcitonin of Group A, Group B and Group C have no significant variance between expansion group and retention group (P>0.05).4 Undecalcificated tetracycline labeled bone sections: the tetracycline labeled bone sections were observed under fluorescence microscope .There's golden or Kelly tetracycline labeled line on the surface of trabeculae. There's two clear golden fluorescent lines near the palatal suture. The distance between those two lines is the amount of mineralization for 21 days. The mineralization apposition rate is not significantly different between Group A and Group C (P>0.05). The mineralization apposition rate of Group B is lower than that of Group A and Group C with a significant variance of P<0.05. There're a large amount of compact golden fluorescence at the fringe of trabeculae in Group A. At the fringe of trabeculae the golden fluorescence is not uniform in Group B. There're a large amount of compact golden fluorescence at the fringe of trabeculae in Group C.5 Undecalcificated toluidine blue bone stainsections: the colour of mineralizable bone is from cambridge blue to white. The colour of osteocyte is navy blue. The colour of osteoclast is cambridge blue which is coenocyte and large in size. In Group A, palatalbones stained are uniform and fibroblasts forms regular, near the palatal suture there's amount of osteocyte forming regularly with a little osteoclast. In Group B, palatalbones stained are not uniform with bone structure line derangement, fibroblast unregular and there's more osteoclast than Group A and Group C, with a little unregular shaped osteocyte. In Group C, bone structure line forms regular with regular fibroblasts, and near the palatal suture there's amount of osteocyte forming regularly with a little osteoclast.Conclusion: 1. That osteoporosis of DM rats induces the fall of MAR and the tardiness of bone formation is adverse to retention of RPE effect .2. Under the treatment with insulin, osteoporosis of DM rats tends to be improved and RPE could achieve comparatively good effect.
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