The Cone-beam Computed Tomography Study On Distolingual Root Canal Curvature On Permanent Mandibular First Molars

Objective:CBCT can show root anatomical morphology in coronal,sagittal and axial cross section and three-dimensional reconstructed images.This research study on DL root on mandibular first molar with this characteristic.The use of CBCT enables dentists to know accurately the morphology of teeth before they take root canal therapy and reduce the possibility of side perforation and needle broken.Operating efficiency and safety are largely enhance,so success rate of therapy is increased.Use the cone-beam computed tomography to measure the curvatures of the distolingual (DL) root canals of permanent mandibular first molars.Methods:The use of CBCT was observed in 757 cases of mandibular first molar root canal morphology of 513 patients. Select the three rooted mandibular first molar distalingual root (230 cases). The images were created using 3d reconstruction of the cone-beam computed tomography data. Using NNT image analysis software analyzed images. Each tooth were taken in clinical (CV) and proximalview (PV) image. The Curvature measurement bend position was measured using Schneider method.All the results do statistical analysis. Results:The two root is the most common form in the mandibular first molar,a proximal root and a distal root. Then the three root, a proximal root, a far buccal root, a distallingual root. Distal lingual incidence rate was 30.38%. The average curvature of the distallingual canal was 12.97 °±7.84±°in CV,and 30.45 °±11.52°in PV measured by Schneider method. Distallingual root in the buccolingual view is mostly mild bending or moderate bending. But in proximal view is severe bending. Measured on buccal-lingual radiographs were 66 case.There were 148 case (64.65%)classified as severly curved on mesial-distal radiographs.71 cases(30.87%)were moderately bent.The rest 11 cases were straight roots.Distal lingual root bending is most common in the crown third of the root, next in the apical third of the root, in the middle third of the root.No case bend in the crown third of root in buccal-lingual direction.Conclusion:Three-rooted mandibular first molars occurred frequently in this Chinese population. The DL root is bend in normal.It easy to lead to the failure of root canal therapy. The dentist need pay special attention to the DL root before root canal therapy.CBCT is an effective tool for the detection of additional distolingual roots and it is a valuable aid for dentists providing root canal treatment.