Root Morphology And Canal Configuration Of Maxillary Permanent Molars With Guizhou Population:A Cone-beam Computed Evaluation

Objective: In order to provide references for clinical practice and help for clinical diagnosis and treatment,the morphology and variation of root and canals in maxillary first and second permanent molars of Guizhou population was evaluated by cone-beam computed tomography.Methods: A total of 32 months data was collected from July 2018 to February 2021.Based on certain inclusion criteria,CBCT images of 3035 maxillary permanent molars were included(1488 maxillary first permanent molars and 1547 maxillary second permanent molars).All images were obtained using 3D Accuitomo Type F17(Tokyo,Morita,Japan)CBCT equipment.The CBCT images were used to analyze the type of roots,type and number of fused root,type and number of canals,curvature of canals,the incidence of C-shaped canal in maxillary permanent molars,and then explore the correlation between the above indicators and gender and age.Results: In the maxillary first permanent molars,the main type of root was 3-rooted(95.77%),and four canals(58.74%).In the maxillary second permanent molars,3-rooted(62.31%)and three canals(72.40%)were the main type.The differences of the 2-rooted,3-rooted types in maxillary permanent molars among different genders were statistically significant(P < 0.05),and differences of the 1-rooted,3-rooted types in the second permanent molars among different genders were also statistically significant(P<0.05).In maxillary first permanent molars,the probability of root fusion was 4.17%(62/1488),and the most common fusion type was DB fused with P.In maxillary second permanent molars,the incidence of fused roots was 36.59%(566/1547),and the most common fusion type was all roots fused into Y shape or cone shape.In maxillary permanent molars,the incidence of fused roots was higher in females than in males(P<0.05).The rate of MB2 in maxillary first permanent molars was 59.95%,and the incidence of MB2 in maxillary second permanent molars was 21.01%.In maxillary first permanent molars,the main type of canal in mesiobuccal was I(39.14%),followed by type IV(36.61%)and Type II(17.42%).In maxillary second permanent molars,the most common root canal type in mesiobuccal was type I(73.58%),followed by type II(10.45%)and type IV(9.26%).The incidence of moderately curved canal was 49.90%(734/1471)and the severe curved canal was48.33%(711/1471)in the first permanent molars.In the second permanent molars,the proportion of severe curved canal was 71.37%(972/1362).There was no statistical significance in the difference of canal curvature between different genders(P>0.05).In maxillary first permanent molars,the probability of C-shaped canals was 0.05%(8/1488),and the main type was MB fused with DB into to C-shaped canal.In maxillary second permanent molars,the probability of C-shaped canals was 5.23%(81/1547),MB fused with DB into to C-shaped canal was dominant(3.75%).The bilateral symmetry of roots and canals in maxillary first and second permanent molars was 76.70% and 72.09%,respectively.The bilateral symmetry of mesiobuccal canal of maxillary first permanent molars is 62.67%,and that of in maxillary second molars is 80.16%.Conclusion: The root canal system of maxillary first and second permanent molars in Guizhou has certain characteristics: The most common types of maxillary first permanent molars were 3-rooted and 4-canals.The most common types of maxillary second permanent molars were 3-rooted 3-canal.The most common fusion root types of maxillary first permanent molars was DB fused with P.The most common fusion root types of maxillary second permanent molars were all root fused into Y shape or cone shape.The incidence of female fused roots was higher than that of male,and there are differences between age groups.The most common types of mesiobuccal canal in maxillary permanent molars were type I,II and IV.The first maxillary permanent molars were mainly moderately curved canal,while the second maxillary permanent molars were mainly severely curved canal.The probability of C-shaped root canals was 0.05% in the first maxillary permanent molars and 5.23% in the second maxillary permanent molars.CBCT can be more effective in the study of dental morphology,providing a certain reference for clinical treatment of dental diseases.