Comparative Research Of Tooth Root Resorption In The Process Of Orthodontic Teeth Movement In Ovariectomized Rats

Objective: During orthodontic tooth movement, the mechanism of root resorption and alveolar bone resorption are essentially similar. The odontoclast which result in root resorption has similar biological properties with the osteoclast (OC) which cause alveolar bone resorption. Studies have shown that estrogen can inhibit osteoclast, estrogen deficiency accelerated alveolar bone loss. This study aims to establish an animal model in rats of osteoporosis: The internal environment of estrogen level decreasing,we observe whether the root resorption degree would be influenced under the same orthodontic force and the expression situation of factors related to root resorption. Preliminary discuss the relationship of estrogen level and root resorption. Offer help to explain the mechanism of tooth root resorption during orthodontic tooth movement. Method: Forty five 2 month-old female SD rats were divided randomly into three groups, 15 rats per group (osteoporosis, estrogen and control). When osterporosis is established,(Micro CT measured the parameter for shin bone to verify the model) each group was placed a coil spring between the upper first molar and upper incisors with forces of 80 gram. Every five rats were killed on the fifth day, the tenth day and the fourteenth day in each group respectively and the specimens were taken at the root area of upper first molar. In addition, blood (4ml) were collected through abdominalaorta before execution and placed on 4℃for 1 hour. After centrifugation, the plasma was analyzed for estrogen by RIA. Hematoxylin and eosin staining was performed to observe the histological changes of the roots. Result:Three months after surgery, three groups of rat vary from each other apparently in weight, bone density and the estrogen level in blood. The weight of the OVX and OVX+E group is higher than that of the SHAM group. The shin bone density of the SHAM group is higher than that of the OVX and OVX+E group. The estrogen in blood in the SHAM group is higher than that in the OVX and OVX+E group. Root resorption was commonly observed in every group. The prevalence of EARR rose significantly in the osteoporosis group as well as inctrement of root resorption. Conclusion:It was of more risk of orthodontic teeth root resorption in osteoporosis patients. The estrogen level in blood was one of the important factors which could influence root resorption during orthodontic treatment.