A Study On Complicated Root And Root Canal System In Maxillary Second Molar With Cone-beam Computed Tomography

Objective: This research aimed to investigate the root and root canal system of the maxillary second molar in the approach of CBCT,and to provided imaging basis for the morphology study and clinical treatment of the maxillary second molar.Methods: The CBCT images(18-69 years old)of 1001 patients(a total of 2002 maxillary first molars and 2002 second maxillary second molars)had been randomly selected for digital three-dimensional reconstruction.The data were used to research on: the variations of root and root canal;simultaneous occurrence of MB2 and its morphological characteristics in the ipsilateral maxillary first and second molars;the symmetry of root and root canal configuration in the bilateral maxillary second molars;the distance between the root tip of each tooth and the maxillary sinus.SPSS 19.0 software was is used for statistical processing.Results: The percentage of root number variation in maxillary second molars was relatively high,with one to four roots being detectedof variations,among which the three-roots-variation being most frequently detected.The main variant form of the root was the fusion of roots.The configurations of the mesiobuccal canals and MB2 were complex and varied:type I,type II,type III,type IV,and type V root canals had all been detected.The bending rate and curvature of the mesiobuccal canals and MB2 were the highest,followed by the conditions of distobuccal canals were less severe,and the palatal canals were relatively straight.In the mesiodistal directions,the root canal curvature rate and curvature of mesiobuccal canals and MB2 were 82.8%,89.7%;22.9±9.7°,17.5±10.4°;in the buccolingua ldirections: 83.4%,83.2%;14.7±8.2°,14.2±9.7°.The curvature of mesiobuccal canals,MB2,distobuccal canals,and palatal canals in the mesiodistal directions and buccolingual directions were statistically different(F=3.742,p<0.05).The mesiobuccal canals were bent to the distal and lingual sides.The MB2 were bent to the distal and buccal sides.The distobuccal canals were bent to the mesial and lingual sides.The curvatures of these three roots occurred in the middle 1/3 root region mostly.The incidence of MB2 in the maxillary second molar was 25.9%.The incidence of MB2 in bilateral maxillary second molars was 72.1%.The root canal orifice of MB2 was located on the mesial side of the mesiobuccal canal orifice and the palatal canal orifice,within 3 mm of the MB canal orifice.The incidence of MB2 in simultaneous maxillary first and second molars was 23.4%.There wassymmetrical distribution in the bilateral root and root canals of the maxillary second molars.The mesiobuccal root was most closely related to the maxillary sinus floor(F=11.001,p<0.05).Conclusion: The anatomical structure of root and root canal were complicated,and the curvature of root canal was complex.The incidence of MB2 in the maxillary second molars was high,and the configurations of canals was varied.The incidence of simultaneous MB2 in maxillary first and second molars was high.The maxillary second molars manifested high bilateral symmetry,The mesiobuccal root most closely related to the maxillary sinus floor.