| Objective:To observe the number and variation of root and canal of mandibular first molar in Yunnan province by using cone-beam computed tomography(CBCT),meanwhile,measure the curvature of the DL root and the length of the DL root from canal orifice to the bending point,and to provide anatomical experimental basis.Methods:The CBCT data of 500 patients(cases)were enrolled at the department of radiology of Yunnan stomatological hospital from February 2015 to April 2017,there were 298 males and 202 females.The patient's name,sex and age were recorded.We observed the images by NNT software at the cross,coronal and sagittal section.then the number of root and root canal,the type of root canal morphology and the prevalence of DL root were investigated.The root canal morphology was classified according to Vertucci.The curvature of the DL root in the buccolingual direction and in the mesial direction was measured by Schneider measurement.The length of the DL root from root canal orifice to the bending point was measured by NNT software.The differences of distolingual root between sexes and sides were tested by using Chi-square tests.The paired t test was used to compare the curvature of the DL root in the buccolingual and the mesiodistal direction.SPSS 17.0 software was used for statistical analysis and the test level was 0.05.Results:1.The number of root and root canal:The incidence of two roots was 72.3%(723/1000),and three roots was 27.7%(277/1000).The incidence of 2 root canals was 1.6%(16/1000),3 root canals was 57.2%(572/1000),4 root canals was 41.2%(412/1000).2.The prevalence of DL root was 32.4%(162/500)calculated by individuals and 27.7%(277/1000)calculated by teeth.The bilateral concurrence rate was 70.9%(115/162)and the left was 3%(5/162)and the right side was 26%(42/162).A significant right-side predilection was found between both sides(x2=6.836,P=0.009<0.05).There was no significant difference between males and females(?2=0.872,P =0.351>0.05).3.According to Vertucci's classification of root canal morphology,in mesial root,46(4.6%)type ?,285(28.5%)type ?,28(2.8%)type?,615(61.5%)type ?,21(2.5%)type ?,5(0.5%)type?.In distal root,565(56.5%)type ?,65(6.5%)type ?,8(0.8%)type ?,343(34.3%)type ?,19(1.9%)typeV,0(0%)type ?.There were 277(100%)type ? root canals in DL root.The most common configurations was 1 mesial root with 2 root canals and 1 distal root with 1 root canals(540/1000)or 1 mesial root with 2 root canals and 2 distal root with 2 root canals(274/1000).4.The angle of the DL root curvature in the bucco-lingual orientation(33.40±16.29)°was greater than that in mesio-distal orientation(16.99±11.44)(P<0.05).The curvature in the bucco-lingual orientation,51.6%(n = 252)of which were severely curved,42.9%(n = 252)were moderately curved,and 5.5%(n = 252)were straight.The curvature in the mesio-distal orientation,11.1%(n = 270)of which were severely curved,51.9%(n = 270)were moderately curved,and 37%(n = 270)were straight.5.The length of the DL root from canal orifice to the bending point was(6.476±0.8187)mm.Conclusions:1.The prevalence of DL root is higher in the mandibular first permanent molar in Yunnan,and the prevalence of right side is significantly higher than that of the left side.It is necessary to carefully explore the DL root canal in RCT.2.In Yunnan region,The most common configurations in the mesial root was Vertucci type ?,in the distal root,type ? canal configuration was the most common.The most common configurations was 1 mesial root with 2 root canals and 1 distal root with 1 root canals or 1 mesial root with 2 root canals and 2 distal root with 2 root canals.3.In Yunnan region,The angle of the DL root curvature in the bucco-lingual orientation was greater than that in mesio-distal orientation.The curvature in the bucco-lingual orientation,most of which were classified as severely curved.The curvature in the mesio-distal orientation.most of which were classified as Mild to moderate curved.The length of DL root from canal orifice to the bending point was 6.476±0.8187mm.4.CBCT is easy to study the root canal,which can assist the treatment of pulp and improve the success rate of root canal therapy. |
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