| The purpose of this study was to determine the ideal standard for the mesio-distal angulation (tip) and bucco-lingual inclination (torque) for each tooth (crown and root) in three-dimensional space utilizing CBCT. After determining a set of inclusion and exclusion criteria, 76 "near normal" cases were chosen and measured. To determine the reliability of our methodology we had 10 cases digitized by Dr. Tong and Dr. Kwon at two different time points and 10 cases digitized by Dr. Tong and Dr. Sakai at one time point and Dr. Kwon at another time point. The inter/intra-examiner correlation coefficients were 0.919 for the average of all the mean values for tip and 0.957 for the average of all the mean values for torque. We tested for symmetry of each case by comparing the left side to the right side using a paired T-Test. From our data the upper canine tip, the upper central torque and the lower 2nd premolar torque are the only values that fall below the p value (0.00357). After determining that there is near perfect symmetry we took an average of the left and right side to come up with one value for the ideal tip and torque for every tooth. In addition, we also were able to compare the differences in the tip and torque between male (n=22) and females (n=54) and between various ethnicities. While all genders and ethnicities follow the same trend there were a few teeth that had statistically significant differences in the tip or torque. Lastly, we also calculated the interdental tip (180° - (upper tip + lower tip)) and torque (180° - (upper torque + lower torque)). All the interdental tip angles fell within a 10 degree range of each other while the interdental torque angles increased from the central incisors all the way to the 2 nd molars, reaching close to 180 degrees. |
