Risk Factors Of Dehiscence And Fenestration In Mandibular Anterior Teeth Before Orthodontic Treatment

Objective: The purposes of this study were to determine risk factors by 3D model tooth arrangement and X-Ray images to detect patients have high-suspected dehiscence and fenestration at mandibular anterior region.Method: We selected patients who were perform orthodontic treatment in China Medical University from 2014-2017.All the patients were divided into two groups.We selected 48 patients in group with dehiscence and fenestration randomly as experimental group.We matched patients in group without dehiscence and fenestration by sagittal facial type(ANB)and vertical facial type(FH-MP)as control group.48 pairs including 96 patients were selected.Every patient was taken 3D tooth arrangement and measured tooth crowding at the low anterior teeth,ratio of width and length about anterior arch,the average tooth crowding in the mandibular anterior tooth region and the torque of teeth.The torque of teeth was corrected by standard torque and we recorded the labio-lingual inclination of each tooth.We also preformed cephalometric analysis and measured alveolar bone thickness,mandibular alveolar and basal height,the absolute angle of incisor and basal bone,and thickness of mandibular cortex at the lateral cephalogram and panoramic radiograph.The chi-square test and Conditional Logistics Regression were used to compare the control and experimental group.Then the curve of ROC and classical tree were built by the positive index which were obtained by 3D tooth arrangement.Significance was set at P <0.05.Result: In the two groups,tooth crowding of low anterior region,the average crowding amount of each mandibular anterior crowding tooth,the angle of L1-NB,thickness of mandibular cortex at lateral cephalogram and labio-lingual inclination of each tooth have relationship to the accidence of dehiscence and fenestration(P <0.05).The area under ROC curve of the average crowding amount of each mandibular anterior crowding tooth and the labio-lingual inclination of each tooth were 0.724 and 0.574.From classification tree,we could find the prevalence of dehiscence and fenestration was 29.69% when the average tooth crowding less than 0.52mm;The prevalence of dehiscence and fenestration was 90.16% when the average tooth crowding exceed 1.11mm;The prevalence of dehiscence and fenestration was 32.80% when the average tooth crowding exceed 0.52 mm and the labio-lingual inclination less than 5°.Conclusion: We could detect some factors to screen dehiscence and fenestration.It is necessary to take CBCT for diagnosing dehiscence and fenestration when the average tooth crowding of low anterior tooth region exceeds 1.11 mm.