The Influence Of Orthodontic Load To The Periodontal Tissues Of Autotransplanted Tooth By Micro-CT

Autogenous tooth transplantation,or autotransplantation,is that the surgical transplant of a tooth from one location in the mouth to another in the same individual. Some auto-transplanted teeth might be placed lower than the occlusal plane or rotated when it couldn't be placed on the normal position.So the autotransplanted teeth must be adjusted by orthodontic treatment at the later stage.And when other teeth need to be corrected,it also would be included into the system.Recently,there are some research indicating that chewing stimulus in the early time will diminish the incidence of ankylosis.They presume that early load or control to the transplanted tooth by the orthodontic equipments will ensure the success of autotransplantation.Micro-computed tomography(Micro CT) is a update technique which can achieve three dimensional X-ray photographs with high resolution that be carried out quantitative analysis to the structure,density and mechanics.It can finish to analysis bone,tooth and many kinds of biomaterial samples in nondestructive condition.The experiment described which influence the load would produce to the prognosis of the autotransplanted teeth by Micro-CT.This may provide information for increasing the achievement ratio of the autotransplanted teeth.ObjectiveThe study aimed to establish the animal model of autotransplantation teeth in dogs, and load the transplanted teeth of one side at different time,laying the teeth of the opposite side unloaded as the control group.Morphological observation,analysis structure of the density and mechanics quantitatively.We hope to find the influence of orthodontic load to transplanted teeth,and look for a clue to treat the autotransplanted teeth in clinic.Methods8 male dogs were selected to prepare the animal autotransplanted teeth model, whose ages were 12 months,and their weights were 10-12kg.Autogenous tooth transplantation was done after general anesthesia by intramuscular injection of 2% ketamine hydrochloride and Su mian xin.Maxillary central incisors were chosen for experiment.Teeth were extracted carefully,and then transplanted the tooth of one side to the opposite tooth socket which had been managed to fit the donor teeth.Ligated them with the adjacent teeth。Dismantled the fixed equipments and undertook conventional root canal therapy after one week.Loaded(3oz) the left transplanted teeth at the 1^st,4^th and 8^th week respectively,and the right unloaded were as control. Killed the animal and the sample were scaned by Micro-CT after loading one month. Analyzed the correlated parameters and completed three-dimensional reconstruction. Compared the differences of periodontal healing,and concluded the influences of time of orthodontic load to the transplanted teeth.Results1 Periodontal examinationThe autotransplanted teeth loaded and unloaded didn't appear cinch or disappear. But through the examination by probing,we found that the periodontal pocket of autotransplanted teeth loaded and unloaded all were deeper than pre-operation and loss of attachment also appeared in some level.But the periodontal condition of the normal teeth loaded or unloded were similar.That indicated autotransplantation had more influences than orthodontics tooth movement.2 Micro CT detection2.1 morphosis observationThe autotransplanted teeth were reconstructed in three dimension by Micro CT.We could find that there is no ankylosis,some parts had slight root resorption,the alveolar bone density decreased in the apical zone obviously,and trabecular pattern was disordered in the transplanted teeth loaded at the first week.The transplanted teeth loaded at the 4^th week had no significant differences morphologically with 8^th week.There were slight ankylosis and root resorption,and the periodontal membrane space didn't widen obviously.The alveolar bone density in the apical zone didn't decrease obviously,and the trabecular pattern was uniform.There were narrower periodontal membrane space and some ankylosis loaded at the 12^th week after transplantation.There were almost no root resorption and narrower periodontal membrane space in unloaded transplanted teeth.We could see the conjunction of the bone trabecula and cement.2.2 bone architecture quantization comparisonThe parameter Tb.N was lowest and The Tb.Sp was highest in transplanted teeth loaded at the 1^st week.That indicated the bone reconstruction was least;The parameters BVF and BS / BV were bigger from the 4^th to the 8^th week after auto-transplantation,and there were little difference with normal teeth and transplanted teeth unloaded,which demonstrated the bone trabecular reconstruction had completed on the whole,and the healing of periodontal tissue were best;The parameters both Tb.N and Tb.Sp decreased in transplanted teeth loaded at 12^th week obviously,which showed there were some ankylosis.Conclusions1.It is safe and reliable that the animal model of the autotransplanted tooth using dogs.The animal model can provide a good clinical reference value.2.We can conclude that the autotransplanted teeth loaded can prevent ankylosis and don't increase significant probability of root resorption from the 4^th to 8^th week.