Accuracy Of Mesiodistal Angulation Of Maxillary Teeth Measured By Cone-beam Computed Tomography Reconstructed Panoramic Image

Objective:The purpose of this study is to explore a method to measure the mesiodistal angulation of maxillary tooth accurately by comparing 3 different central planes close to tooth cervical zone to reconstruct cone-beam computed tomography(CBCT).CBCT images were reconstructed by 3 central planes on the sagittal section of upper right incisor,which were the horizontal lines of labial cervical margin,palatine cervical margin and the most curve point of cingulum when Frankfort horizontal plane(FH plane)paralleled to the ground plane.This study can give some guidance of how to reconstruct CBCT images accurately by comparing measurement between CBCT images and their panoramic-like images.Method:CBCT images of 30 patients with individual normal occlusion were collected.The Dolphin Imaging 11.9 software was used to open the CBCT images and reconstruct them to the 3D image.The mesiodistal angulation of 14 maxillary teeth were measured using the USC root vector analysis program(the University of Southern California root vector analysis program)and treated as the standard value.Then,these CBCT images were reconstructed into panoramic-like images using Invivo Dental system,when head positions were adjusted to Frankfort horizontal plane(FH plane)paralleled to the ground plane.The maximum sagittal overlap section of the right upper central incisor of each CBCT image was taken as the reference sagittal section,and the reconstruction central plane on the sagittal section were the horizontal line of labial cervical margin,palatine cervical margin and the most curve point of cingulum.These panoramic-like images were saved and imported into the Geogebra Geometry software(International Geogebra Institute,Austria)to measure the mesiodistal angulation of 14 maxillary teeth,which were treated as the measured value.By comparing the measured value with the standard value,we can find reconstruction planes which can accurately reconstruct with CBCT images.Result:Among the 14 maxillary teeth measured by the reconstruction plane of the labial cervical margin,palatine cervical margin and the most curve point of cingulum,there are 7 teeth(13、16、17、21、22、26、27),5 teeth(16、17、21、26、27)and 5 teeth(16、17、21、26、27)were different from the standard value(P<0.0036),respectively.For all reconstruction planes,the measurement difference of 4 molars between the measured values and the standard values were greater than 2.5 degrees(P=0.000).For the reconstruction planes of the palatine cervical margin and the most curve point of cingulum,the difference of other teeth was less than 2.5°(P≥0.05).For the reconstruction planes of the labial cervical margin,the measured values of the left upper central incisor(3.625°,95% CI[1.897°,5.353°])and the left upper lateral incisor(2.915°,95% CI [1.353°,4.477°])showed different from the standard values(P<0.05)above the limit of 2.5 degrees.Conclusion:When the head position was adjusted to FH plane paralleled to the ground plane,for the maximum sagittal overlap section of the right upper central incisor,the reconstruction planes of the palatine cervical margin and the most curve point of cingulum were accurate to measure maxillary teeth except molars on panoramic-like images.