A Cone-beam CT Study Of Root Form Observation In Human Maxillary Anterior Teeth

Objective:To observe the root form and diameter in human maxillary anterior teeth by cone-beam computed tomography (CBCT) and to analyze the proper length and angle of dowel preparation in maxillary anterior teeth, provide some anatomical parameters related to the selection and research of dowel preparation instruments and post-core material, propose the design rationalism for individualized post-core restoration.Methods:A total of129human maxillary anterior teeth were selected and analyzed.The three-dimensional images of these teeth were obtained by multiplanar reconstructions (MPR) technique of CBCT,3times each parameter to get the value, and the root curvature and diameter were observed and measured by dedicated software:①Schneider method was used to separate the teeth into three groups, based on degree of curvature, as follows:straight (5degrees or less), moderate (10to20degrees), and severe (20 degrees or more).②We measured the radius of curvature and the length of the curved part using Schafer method.③We calculated the diameter of the roots every2mm from apical foramen.④We set one third of the smallest diameter between the mesio-distal diameter and the labio-lingual diameter as the dowel diameter according to classic prosthodontics. We performed the test of normality for all measured data by statistics software SPSS16.0.Results:The mean root curvature degree (labio-lingual) of maxillary central incisors was significantly smaller than that of maxillary lateral incisors and canines (P<0.05), while the root curvature (labio-lingual) radius of that was significantly larger than that of remaining groups (P<0.05). The mean length of the curved part (mesio-distal) of canines was significantly longer than that of maxillary central incisors and maxillary lateral incisors, and that of maxillary central incisors are the shortest (P<0.05). There were significant differences in the root length distribution of the curved part (mesio-distal) among the three different maxillary anterior teeth groups (P<0.05), while there were no significant differences in that of maxillary anterior teeth (P>0.05). The mean diameter measured labiolingually was significantly bigger than that of measured mesiodistally (P<0.05). The dowel diameter of distance from apical foramen (4mm) in.maxillary central incisors, lateral incisors and canines are (1.18±0.20)mm,(1.00±0.13)mm,(1.09±0.16)mm, and the dowel diameter of distance from apical foramen (6mm) in maxillary central incisors, lateral incisors and canines are (1.45±0.22)mm,(1.18±0.12)mm,(1.27±0.18)mm, respectively. Conclusion:It’s safer that the dowel length is shorter than6mm from apical foramen in maxillary anterior teeth. At the same time, we should select the proper dowel preparation instruments and use side-rolling skills considering the root diameter mesiodistally. Dowel should be prepared cone-shaped, and the dowel taper of maxillary lateral incisors are about0.05(0.05±0.02).while that of maxillary central incisors and canines are about0.07(0.07±0.02). There were differences in root form of human maxillary anterior teeth, and the root curvature and diameter of human maxillary anterior tooth varies greatly in CBCT. The3D-analysis of root form could provide some references for design of dowel preparation and finally easier fabrication of the individual post-core restoration.