A Cone Beam Computed Tomography Study On The Whole Tooth Mesiodistal Angulation And Faciolingual Inclination Of Near Normal Occlusion

Objective:The study was to determine the ideal standard and normal range for the mesio-distal angulation(tip) and bucco-lingual inclination(torque) for each tooth(crown and root) in three-dimensional space utilizing CBCT and Dolphin Imaging Software, so that to provide basic data for the diagnosis, design, and the assessment of the root position after orthodontic treatment.Methods: Under the standard of Andrews six keys, 58 near Andrews six keys to normal occlusion cases(19-27 years) were chosen to collect CBCT data, save as DICOM files,than using Dolphin Imaging version 11.5 software for three-dimensional reconstruction.One observer measured mesio-distal angulation and bucco-lingual inclination of each whole tooth two times separately at an interval of two weeks.The measurements were analyzed by SPSS 19.0 software.Shapiro-Wilk method was used to examine the normality of each tooth angulation and inclination. Using the paired t test to detect the symmetry of the left and right side, the gender differences were tested by independent t test.Result:1. The result produced by the examiner in different time is proved to be reliable in this experiment. The interclass correlation coefficient is quite efficient. The maxillary teeth angulation increase from incisors, and comes to the maximum at the canine(12.175±1.74°), then it begins to decrease gradually with the changes of tooth position,the first molars were nearly upright, and the second molars were a little mesial inclined. The mandibular teeth angulation increase from central incisor to the molars. As for the interdental tip, its ranges from 156 to 174°. As for the maxillary teeth inclination, the central incisor is the biggest on the buccolingual inclination(24.89±5.75°). With the backward of tooth position, decresed to about2.36°at the first molars,and then incresead for the second molars.The mandibular teerh inclination also were highest for the inciors,decrsead with the backward if tooth position, the second molars were the smallset(-14.21±5.24°).2. Compared to the Andrews' data, the mesiodistal angulation makes no differences except the maxillary premolars. However, as for the inclination, the dentition are quite different. Except for the mandibular postrior teerh were negative,the rest were postive. The obvious differences exist in maxillary anterior teeth and mandibular posterior theeth.Conclusion:1. With the CBCT and Dolphin Imagin to test the mesiodistal angulation and the buccolingual inclination, its result is quite reliable.2. Acquiring the relevant date from this experiment, it is conducive to locate of the tooth root in alveolar before and after orthodontic treatment.It was also helpful to diagnose, design and bracket selection.