Effects Of Orthodontic Loading Time And Duration On The Periodontal Repair In Autologous Thooth Transplantation

Objective:The experimental study established the animal model of autologous tooth transplantation in Beagle dogs, following exerting the orthodontic force and changing its loading time after the autologous tooth transplantation. It aims to provide the clinical reference for orthodontic loading time and duration of autologous tooth transplantation through lots of comparative study. Materials and Methods:Twelve Beagle dogs were selected and grouped randomly in this research. Four first premolar teeth in every dog were carried on autologous transplant operation. These teeth were exerted the orthodontic force after the operation in two weeks, four weeks, eight weeks and twelve weeks respectively. The loading duration were one week, two weeks and four weeks respectively. The loadings sides are marked as the experimental group (TF Group), whereas the transplanted first premolars of the lateral sides without loading are marked as the control group (To Group)。We tested periodontal tissue samples in first premolar teeth with histological study to estimate the healing condition of the periodontal tissue of different stages; measured root absorption rate; analysed the effect of orthodontic loading time on reconstruction condition of periodontal tissue with statistical method. Bone morphogenetic protein-7(BMP-7) and vascular endothelial growth factor(VEGF) both play an important role in the periodontal repair. Through immunohistochemical coloration, we detected the expressions of BMP-7 and VEGF in periodontal tissue of animal model after autologous tooth transplantation, which helps to further analyse the repair condition of periodontal tissue. Results:Root absorption rates in the experimental group (Group TF) which was exerted the orthodontic force were lower than them in the control group(Group To). There are statistical significance between the two groups after the paired T Test) (P<0.05). The results of the histological observations revealed that the healing conditions of the periodontal tissue were better if the orthodontic force was loaded four or eight weeks and the duration of the loading time is two weeks after the autologous tooth transplantation. The results of immunohistochemical coloration revealed that the average expressions of bone morphogenetic protein-7(BMP-7) and vascular endothelial growth factor (VEGF) in experimental group is higher than those in control group. There are variable expressions of both factors during different stages after the autologous tooth transplantation. After four or eight weeks of autologous tooth transplantation, through exerting the orthodontic force, the expressions of BMP-7 and VEGF are relatively higher, which corresponds to the results of histological sections. Conclusion:Orthodontic force contributes to the improvement of root absorbtion and reconstruction of periodontal tissue in transplant teeth. The orthodontic loading time(X)and the duration(Y)have no obvious effect on root absorption rate of transplant teeth. When X is four weeks and Y is two weeks, the reconstruction effect of periodontal tissues in transplant teeth is the best.