| Objective:To establish an experimental orthodontic movement of anterior teeth on rat and the retention using 0.25 ligature wire, and later to relapse the tooth movement on same animal model to study the phase of bone remodeling.Methods:36 female SD rats from the Experimental Animal Center of Zhengzhou University were provided for the experiment, a total of 6 groups of rat were made with 6 rats in each group. Maxillary central incisors were anchored to each other and continuous force of 20g was applied for 10 days, so that to rotate the root of both the maxillary incisors on animal models. After the rotation was complete orthodontic ligation wire of a diameter of 0.25mm was used to retain the tooth in rotated position. Each group of rats were maintained to continue retention for 1,4,7,14 and 21 days respectively and the retention wire removed, but in the control group no retention was done. The distance between the two maxillary central incisors was measured after 7 days of removal of appliances. The effectiveness of devices for retention was studied by the relationship between time period of maintaining retention appliance and the relapse of tooth movement distance and calculated as the distance difference of tooth and length of ligation wire used for retention.Results:The experimental group had significantly less relapse than the control group. The difference was statistically significant (P<0.05).Lesser the time of retention time longer the distance of recurrence was observed.Conclusions:Orthodontic ligature wire with a diameter of 0.25mm can be used as a fixed retainer to keep the anterior teeth to avoid relapse after orthodontic tooth movement in rats for the retention period on the animal model.Objective:To reverse the movement maxillary central incisors on experimental rats by removing retainer and different time period and study the animal model for bFGF and periodontal tissue changes during the retention period, to find out role of bFGF in bone remodeling. Provide a reference for clinical orthodontic maintained.Methods:The animal experiments by Zhengzhou University Center for the 36 female SD rats were randomly divided into five experimental groups, and a control group, with 6 rats in each group. After application of force for 10 days, keep teeth in position for 1,4,7,14 and 21 days, respectively. Animals were sacrificed. The control group received no treatment. Maxillary central incisor and surrounding alveolar bone were obtained and slices of the specimens were prepared on paraffin with routine HE staining and immunohistochemistry (SP method) experiment, which were Observed for bFGF expression at various stages of retention.Results:The rat maxillary incisors relapse the movement after removal of retention appliance, the periodontal tissue can be seen to maintain a clear bone hyperplasia, bFGF expression in the positive area with average integral optical density of positive cells in PU value maintaining the 1 day group,4-day group,7-day group,14-day group,21-day group rat maxillary incisor periodontal ligament and bFGF levels showed a downward trend. Groups with retention for 1 day,4-days,7 days and 14-days, had statistically significant (P<0.05), maxillary incisor periodontal ligament bFGF levels, compared to control group. However,21 days retention Group had no statistical difference (P> 0.05), but maxillary incisor periodontal ligament bFGF levels were still higher than the mean.Conclusions:After application of Orthodontic force, bFGF maintains phase of bone remodeling. The normal periodontal tissues contains bFGF, which increases during tooth movement and bFGF in maintaining the phase show decrease in concentration with time, but still higher than the normal level, while maintaining close to the normal level at 21 days. |
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