Micro-CT Evaluation Of Apical Delta Morphologies

Object:To investigate the prevalence and the morphological characteristics of apical delta in Chinese permanent teeth with the high resolution micro-CT technology.Materials and methods:One thousand four hundred extracted permanent teeth(100 each tooth location except the wisdom teeth)with completely formed apices were selected from the tooth and canal morphology database constructed previously by our team for 15 ?m micro-CT scanning.Reconstructed each root canal system with VGStudio MAX 2.1 software(Volume Graphics,Heidelberg,Germany)three-dimensionally and selected the teeth with the apical delta structure.Recorded the number of apical delta branches(ADBs).In addition,each branch of the apical delta was segmented using Otsu image segmentation method and a 3D model was recieved.Calculated the diameter,length,ellipticity and tortuosity of each branch with the centerline method.Results:A total of 136 apical deltas were detected from the 1400 extracted permanent teeth.Apical deltas were commonly found in molars(15.8%)compared with the premolars and anterior teeth(8.75%,6.3%).In maxillary molars with separated roots,apical deltas were mostly located in the mesiobuccal root(11.2%),seldom in the distobuccal root(1.7%)and minimally in the palatal root(1.1%).In mandibular molars with separated roots,no significant difference was found in the prevalence of apical delta between the mesial and distal root(P>0.05).In maxillary premolars with separated roots or root bifurcated in the apical,4.8%of the buccal roots had an apical delta;no apical delta was detected in the palatal root.The median vertical distance from the start of apical delta to the apex was 1.87 mm(ranging from 0.62 to 5.08 mm),and 13%of the apical deltas had a vertical distance more than 3 mm.Great morphological variability was observed in the apical deltas,and the number of ADBs was varied greatly from 3 to 18.The median diameter and length of ADBs were 132.3 ?m and 934.5 ?m respectively.The ADBs were not straight with cross-sectional shapes being non-circular.Conclusions:apical delta was a common variation of root canal system in human teeth,and was mostly found in molars.The number and three-dimensional morphologies of ADBs varied greatly,which brought severe challenges to the infection control of the root canal system.