Evaluation Of Corticotomy-facilitated Orthodontic Tooth Movement By Micro-CT

[Objective]Assess the tooth movement of corticotomy-assisted tooth movement and unassisted tooth movement.Assess the structural of the alveolar bone during the tooth move.Analysis the structural of the alveolar bone and the tooth movement.[Subject]75 Adult male Sprague-Dawley rats weighing 140 to 160 g were divided into 3 groups.Orthodontic tooth movement was performed on the left side of the maxilla.One side of the maxilla was operated so that the opposite side could serve as a split-mouth unoperated control,and to allow the rat to chew on a normal diet on the unoperated side.[Method]Animals Surgery:corticotomy-assisted tooth movement(CO+TM),unassisted tooth movement(TM alone),and sham corticotomy without tooth movement(CO alone).The 75 rats were killed with an overdose of pentobarbital at4,7,14,21 and 28 days after activation,with 5 in each group.Each molar-bearing segment of the maxilla was excised and fixed.The periodontal tissue of the maxillary left and right first molar was scanned using a Microcomputed tomography system.For quantitation and analysis,CT scans were taken in the transverse plane at 3 different levels:the coronal(CL),the midroot(ML),and the apical levels(AL).At each level,the bone area found in between the maxillary first molar and the second one,and the mesial of the first molar were defined as region of interest.The BMD and BV were obtained from the Micro-CT scanning.Tooth movement was measured directly as the distance between the first and second left maxillary molars.Serial 4?m thick sections mesial and distal to the maxillary molars of the specimens were cut with a microtome and stained with hematoxylin and eosin.Collection and analysis all the data.[Results]In terms of the amount of tooth movement,our results illustrated that the TM group showed a steady increase beginning from baseline up to 28 days.The CO+TM group has a small amount at the beginning of the study,but obvious higher after 14 day point compared with the TM group.The bone density in CO+TM group both of mesial and distal always decreased.As for TM group,the density decreased in the early,but rebound after the 14th day.The bone volume in mesia of CO+TM group always decreased.As for TM group,the volume decreased in the early,but rebound after the 4th day.[conclusion]Alveolar bone corticotomy-assisted orthodontic treatment,greatly reducing treatment time compared with the traditional orthodontic treatment.Corticotomy-facilitated causes adjacent soft and hard tissue reconstruction activities aggressive,the phenomenon is called "regional accelerated phenomenon(RAP)" It is associated with increased perfusion and bone turnover and decreased bone density.