C-shaped Root Canal In Mandibular Posterior Teeth In A Chinese Population Of Shandong Province Evaluated By Cone-beam Computed Tomography

Objective:To evaluate the anatomical features of C-shaped canal system in mandibular posterior teeth using cone-beam computed tomography and to compare the incidence of C-shaped root canal of different posterior teeth,providing image basis for root canal therapy,which helps to improve the success rate of C-shaped roots canal treatment.Methods:To observe the root canal morphology of 2603 mandibular posterior of 350 people by CBCT,and to calculate the incidence of C-shaped root canal according to gender,age and dental location.At the same time,the recorded information was as follows:1.The position of mandibular posterior teeth 2.The distance from the cemento-enamel junction to the apical of the tooth,namely the length of the root canal 3.The types of C-shaped root canal between cervical 1/3,middle 1/3 and apical 1/3 were recorded,and the incidence of C-shaped root was calculated,and root canal morphology was observed.Statistical analysis was carried out in different groups using the corresponding statistical methods,among which the Fisher exact probability method was used in age group and the chi-square test was used in gender group and dental group.Results:1.The incidence of C-shaped root canal There were 691 mandibular first premolars of 350 patients,of which the C-shaped roots canal had 18,and the incidence was 2.6%(18/691);there were 659 mandibular second premolars,no C-shaped root canal was found,and the incidence was 0.00%(0/659);there were 621 mandibular first molars,and only one showed C-shaped root canal,and the incidence was 0.16%(1/621);there were 632 mandibular second molars,and 200 of them had C-shaped root canal,and the incidence was 31.65%respectively(200/632).2.The morphology of C-shaped root More than half of the 18 mandibular first premolars were accompanied by mesiolingual grooves(10,55.56%),and the rest had mesial grooves(5,27.77%)and lingual grooves(3,16.67%).The deep longitudinal groove of C-shaped root of mandibular first molar appeared in the tongue;the roots of 200 C-shaped root canals of mandibular second molars were all fused,and the deep longitudinal ditch of root surface often appeared in lingual side(194,97%),few in buccal side(6,3%).3.CBCT cross-section showed the types of C-shaped root canal There were 18 C-shaped root canals in mandibular first premolar,which the most common type of root canal configuration was C4 in the root canal orifice and in coronal region,followed by C3a in the middle region and C4 in the apical region.There was one C-shaped root canal in first molar,of which root canal configuration was C1 in root canal orifice and in coronal region,followed by C2 in the middle region and C3a in the apical region.There were 200 C-shaped root canals in second molar,which the most common type was C1 in the root canal orifice,and in the coronal region,the number of C1 type was slightly lower,but still the most commonly(108,54%),followed by C2 in the middle region and C3 in the apical region.4.The change of C-shaped root canal morphology There was no change in the classification of 18 C-shaped root canals from the root canal orifice to the root cervical of the mandibular first premolar,and different degrees of change had taken place from middle region to apical region.The C-shaped root canal morphology of mandibular second molar changed most in the whole length of root canal(177,88.5%),which in the cervical 1/3 of root there were 88 began to change(44%),and there were 41(20.5%)began to change in the root canal orifice,followed by 48 in the middle regent(24%),and 23 had not been changed along the root canal length(11.5%).5.Differences between groups Due to the small number of C-shaped root canals in mandibular second premolar and first molar,statistical analysis was not possible to perform,so the statistical analysis was performed only on the mandibular first premolar and the second molar.Mandibular first premolar and second molar showed no significant difference(P>0.05)in teeth position and gender group.In age group,no significant difference was showed in first premolar(P>0.05),while in second molar,20～30 and younger than 20s were more prone to have C-shaped root canal(P<0.001).Conclusion:The shape of C-shaped root canals in human mandibular posterior molars was complex,often occurring in second molars,followed by first premolars,rarely occurring in second premolars and first molars.