Journal of Prevention and Treatment for Stomatological Diseases ›› 2021, Vol. 29 ›› Issue (12): 836-842.doi: 10.12016/j.issn.2096-1456.2021.12.006

• Clinical Study • Previous Articles     Next Articles

CBCT study of the root and root canal morphology of mandibular second molars in a population in western Guangxi

XING Huiyan(),HU Yuping,JIANG Wenqiong,ZHANG Ran,WEI Fangyuan,TAN Yanning,DENG Min,LI Shufang()   

  1. Department of Stomatology, Affiliated Hospital of Youjiang Medical College for Nationalities, Baise 533000, China
  • Received:2021-03-18 Revised:2021-05-31 Online:2021-12-20 Published:2021-08-17
  • Contact: Shufang LI E-mail:1835878458@qq.com;303121175@qq.com
  • Supported by:
    Science and Technology Project of Baise City(20184425)

Abstract:

Objective To observe the root and root canal morphology of mandibular second molars in Western Guangxi by CBCT, to provide a reference for clinical diagnosis and treatment. Methods In total, 564 patients′ 1 128 mandibular second molars that satisfy the inclusion criteria were analyzed with a planmecaromexis CBCT machine and its own image analysis software. The patients′ gender, age and ethnic differences in the root and canal morphology and the symmetry of the bilateral root and canal were statistically analyzed. Results Among the 1 128 mandibular second molars, 662 were the Zhuang ethnic group and 384 were the Han ethnic group, and 82 were other ethnic groups; the double root type and C-shaped root type accounted for a relatively high proportion: 73.94% and 24.47%, respectively. The detection rates of the double root type were higher in males than in females (P < 0.05); the detection rates of the C-shaped root type were higher in females than in males (P <0.05); the root type of the teeth was mainly double-rooted in the Zhuang ethnic group (P<0.01). The incidence of type IV in the mesial root of the double root type mandibular second molar was the highest (P < 0.01), and the incidence of type I in the distal root was the highest (P < 0.01). The C-shaped root canal is more continuous at the mouth of the root canal, more downward corresponds to a worse continuity: in three different levels of root canal orifice, root middle and root apex, the root canal orifice is dominated by the C1 type, and both root middle and root apex are mainly C3-type (P < 0.01). The difference in symmetry of bilateral roots and root canals was statistically significant among different gender groups, age groups, and ethnic groups (P < 0.05): there were more males than females, the results in the 18-35-year-old group and the Zhuang ethnic group were higher. Conclusion The root and root canal morphology of mandibular second molars in western Guangxi people are complex and changeable. The roots are mainly double root type in the Han ethnic group and the Zhuang ethnic group. C-shaped roots are also common. The detection rate of C-shaped roots in the Zhuang ethnic group was higher, and the symmetry rate of bilateral roots and that of bilateral root canals was higher in the Zhuang ethnic group than in the Han ethnic group.

Key words: western Guangxi, the Zhuang ethnic group, the Han ethnic group, mandibular second molar, root, root canal, cone-beam CT, C-shaped canal system, symmetry

CLC Number: 

  • R78

Figure 1

Root anatomy of mandibular second molars a: double roots type; b: three roots type; c: tapered root type; d: C-shaped root type; all axial images were taken in the middle third of the root"

Table 1

Root morphology of 1 128 mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
Three roots 4 4(0.35) 0(0) 4.00 0.046 2(0.18) 2(0.18) 0(0) 2.00 0.368 2(0.18) 1(0.09) 1(0.09) 0.50 0.779
Double roots 834 486(43.09) 348(30.85) 22.83 1.77E-6 503(44.59) 288(25.53) 43(3.81) 381.12 1.75E-83 495(43.88) 280(24.82) 59(5.23) 341.92 5.66E-75
Tapered root 14 3(0.26) 11(0.98) 4.57 0.033 10(0.89) 4(0.35) 0(0) 10.86 0.004 10(0.89) 4(0.35) 0(0) 10.86 0.004
C-shaped root 276 117(10.37) 159(14.10) 6.39 0.011 183(16.22) 78(6.91) 15(1.33) 156.59 9.94E-35 155(13.74) 99(8.78) 22(1.95) 96.93 8.93E-22
Total 1 128 610 518 698 372 58 662 384 82

Table 2

Age, gender and ethnic differences in the mesial root canal morphology of 834 double-rooted mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
223 103(12.35) 120(14.39) 1.30 0.255 133(15.94) 82(9.83) 8(0.96) 106.29 8.32E-24 130(15.59) 80(9.59) 13(1.56) 92.73 7.32E-21
65 37(4.44) 28(3.36) 1.25 0.264 41(4.92) 21(2.52) 3(0.36) 33.35 5.72E-8 30(3.60) 31(3.72) 4(0.48) 21.63 2.01E-5
60 40(4.80) 20(2.39) 6.67 0.010 46(5.51) 13(1.56) 1(0.12) 54.30 1.62E-12 39(4.68) 15(1.80) 6(0.72) 29.10 4.80E-7
384 246(29.50) 138(16.55) 30.38 3.56E-8 214(25.66) 144(17.27) 26(3.12) 141.06 2.34E-31 227(27.22) 133(15.95) 24(2.87) 161.27 9.59E-36
102 60(7.19) 42(5.03) 3.18 0.075 69(8.27) 28(3.36) 5(0.60) 61.82 3.76E-14 69(8.27) 21(2.52) 12(1.43) 55.24 1.01E-12
Total 834 486 348 503 288 43 495 280 59

Table 3

Age, gender and ethnic differences in the distal root canal morphologyof 834 double-rooted mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
795 458(54.91) 337(40.41) 18.42 1.78E-5 480(57.55) 273(32.73) 42(5.04) 362.33 2.09E-79 472(56.60) 266(31.89) 57(6.83) 324.96 2.73E-71
8 6(0.72) 2(0.24) 2.00 0.157 6(0.72) 2(0.24) 0(0) 7.00 0.030 5(0.60) 3(0.36) 0(0) 4.75 0.093
2 2(0.24) 0(0) 2.00 0.157 1(0.12) 0(0) 1(0.12) 1.00 0.607 1(0.12) 1(0.12) 0(0) 1.00 0.607
21 14(1.68) 7(0.84) 2.33 0.127 9(1.08) 12(1.44) 0(0) 11.14 0.004 12(1.44) 7(0.84) 2(0.24) 7.14 0.028
8 6(0.72) 2(0.24) 2.00 0.157 7(0.84) 1(0.12) 0(0) 10.75 0.005 5(0.60) 3(0.36) 0(0) 4.75 0.093
Total 834 486 348 503 288 43 495 280 59

Figure 2

Classification of C-shaped root canals in mandibular second molars a: C1 type; b: C2 type; c: C3 type; d: C4 type; all axial images were taken in the middle third of the root"

Table 4

Age, gender and ethnic differences in the root canal orifice morphology of 276 C-shaped mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
C1 186 83(30.07) 103(37.32) 2.1 0.143 135(48.91) 45(16.30) 6(2.17) 141.19 2.19E-31 110(39.86) 63(22.83) 13(4.71) 75.90 3.29E-17
C2 50 24(8.70) 26(9.42) 0.08 0.777 28(10.14) 16(5.80) 6(2.17) 14.50 0.001 23(8.33) 22(7.97) 5(1.81) 12.28 0.002
C3 40 10(3.62) 30(10.87) 10.00 0.002 20(7.25) 17(6.16) 3(1.09) 12.35 0.002 22(7.97) 14(5.07) 4(1.45) 12.20 0.002
Total 276 117 159 183 78 15 155 99 22

Table 5

Age, gender and ethnic differences in the middle of root canal morphology of 276 C-shaped mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
C1 37 16(5.80) 21(7.61) 0.68 0.411 29(10.51) 6(2.17) 2(0.72) 34.43 3.33E-8 21(7.61) 12(4.35) 4(1.45) 11.73 0.003
C2 115 52(18.84) 63(22.83) 1.05 0.305 84(30.43) 29(10.51) 2(0.72) 91.11 1.64E-20 43(15.58) 28(10.14) 44(15.94) 4.19 0.123
C3 124 49(17.75) 75(27.17) 5.45 0.020 70(25.36) 43(15.58) 11(3.99) 42.21 6.83E-10 74(26.81) 41(14.86) 9(3.26) 51.11 7.96E-12
Total 276 117 159 183 78 15 138 81 57

Table 6

Age, gender and ethnic differences at the apex of root canal morphology of 276 C-shaped mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
C1 47 17(6.16) 30(10.87) 3.60 0.058 35(12.68) 9(3.26) 3(1.09) 36.94 9.54E-9 24(8.70) 19(6.88) 4(1.45) 13.83 0.001
C2 38 16(5.80) 22(7.97) 0.95 0.330 28(10.14) 9(3.26) 1(0.36) 30.37 2.54E-7 19(6.88) 14(5.07) 5(1.81) 7.95 0.019
C3 119 47(17.03) 72(26.09) 5.25 0.022 78(28.26) 36(13.04) 5(1.81) 67.68 2.01E-15 67(24.28) 42(15.22) 10(3.62) 41.16 1.15E-9
C4 72 37(13.40) 35(12.68) 0.06 0.814 42(15.22) 24(8.70) 6(2.17) 27.00 1.37E-6 45(16.30) 24(8.70) 3(1.09) 36.75 1.05E-8
Total 276 117 159 183 78 15 155 99 22

Figure 3

Root canal classification of mandibular second molars with tapered roots a: multiple root canals; b: C-shaped root canal; c: single root canal"

Table 7

Age, gender and ethnic differences in root canal morphology of tapered mandibular second molars n(%)"

Type Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
C-shaped root canals 6 1(7.14) 5(35.71) 2.67 0.102 5(35.71) 1(7.14) 0(0) 7.00 0.030 4(28.57) 2(14.29) 0(0) 4.00 0.135
Multiple root canals 5 1(7.14) 4(28.57) 1.80 0.180 3(21.43) 2(14.29) 0(0) 2.80 0.247 3(21.43) 1(7.14) 1(7.14) 1.60 0.449
Single root canal 3 1(7.14) 2(14.29) 0.33 0.564 2(14.29) 1(7.14) 0(0) 2.00 0.368 2(14.29) 1(7.14) 0(0) 2.00 0.368
Total 14 3 11 10 4 0 9 4 1

Table 8

Bilateral symmetry rate of root and root canal morphology of mandibular second molars n(%)"

Symmetry category Total Gender χ2 P Age (year) χ2 P Ethnic groups χ2 P
Male Female 18-35 36-55 56-78 Zhuang Han Others
The root morphology is symmetrical 505 276 229 4.37 0.036 308 169 28 232.88 2.70E-51 300 171 34 210.23 2.23E-46
The shape of root canal is symmetrical 410 236 174 9.38 0.002 249 138 23 186.88 2.62E-41 241 140 29 164.55 1.85E-36
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