Effects Of Functional Mandibular Lateral Shift On Mandibular Growth And Development In Growing Rats

Objective:The purpose of this study was to examine the effects of functional mandibular lateral shift on the growth and morphology of the condyle and mandibular bone in growing rats through vivo experiments.Materials and Methods:Fourty-eight 5-week-old male Sprague-Dawley(SD)rats were randomly divided into experimental group,which received oblique guide appliance that shifted mandible to the left during closure,and contral group.The rats were anesthetized after 1,2,4weeks,and scanned by computed tomography(CT).The image data were transferred to the computer workstation and saved as a DICOM format file,and the EZ3D2009 software was used to read the image data for reconstruction.The sagittal section of mandible,sagittal and coronal section of condyle were observed.coracoid height and length,height of condylar,mandibular body height,mandibular length,the angle between the long axis of the coronoid process and mandibular plane,the angle between the long axis of condyle and mandibular plane,condylar length and width,were measured and compared their changes in each rat.And at the 4th week,the rats were given 99mTc-MDP SPECT/CT scan.The volume of interest(VOI)of bilateral was delineated and the SUVmax values were measured and compared.Results:At 4 weeks,the condylar height and coracoid process height was shorter on the experimental group compared with the control group,and the angle between the long axis of condyle and coracoid process and mandibular plane of rats in the experimental group was also significantly lower than that in the control group.At the same time,the mandible length in the left side was shorter than that in the control group from 2 weeks.When the left and right mandibles of rats in the experimental group were compared,only at 4 weeks,the length of the left mandibles was significantly smaller than that of the right mandibles,which had no statistical significance with the data.According to the sagittal view of the condyle,the experimental rats developed an asymmetric condyle.the condyle on the left side was shorter and wider than that of the right at 4 weeks.Coronal view of the condyle showed that the condyle was rhicker inshorter in the experimental group compared with the control group,and there was no significant difference on both sides.SPECT/CT results showed although there was no statistical difference in the SUVmax value of the TMJ on both sides in the experimental group,it was significantly higher than that of the control group.Conclusions:Functional shift of mandibule produce a series of morphological asymmetry in the mandibular bone and condyle,all of these changes are greater over time.At the same time,functional deviation also will increase condylar bone metabolism on both sides,and this change may be related to bone remodeling and degenerative changes.