Table 1 Frequency of root canal configuration according to tooth type and 2 classification systems

Vertucci classification

 I

787 (70.6%)

780 (70%)

972 (87.3%)

2539 (76%)

< 0.001¹

 II

8 (0.7%)

7 (0.6%)

22 (2%)

37 (1.1%)

0.003¹

 III

300 (26.9%)

310 (27.8%)

77 (6.9%)

687 (20.6%)

< 0.001¹

 IV

0 (0%)

3 (0.3%)

34 (3.1%)

37 (1.1%)

< 0.001¹

 V

3 (0.3%)

3 (0.3%)

5 (0.4%)

11 (0.3%)

0.695¹

 NC

16 (1.4%)

11 (1%)

4 (0.4%)

31 (0.9%)

0.030¹

p-value

< 0.001¹

< 0.001¹

< 0.001¹

Ahmed classification

 ¹MI¹⁻¹

787 (70.6%)

779 (69.9%)

972 (87.3%)

2538 (75.9%)

< 0.001¹

 ¹MI^1–2

3 (0.3%)

3 (0.3%)

4 (0.4%)

10 (0.3%)

0.905¹

 ¹MI^1–2−1

300 (26.9%)

311 (27.9%)

77 (6.9%)

688 (20.6%)

< 0.001¹

 ¹MI²⁻¹

8 (0.7%)

7 (0.6%)

22 (2%)

37 (1.1%)

0.003¹

 ¹MI^{2−1−2−1}

16 (1.4%)

11 (1%)

4 (0.4%)

31 (0.9%)

0.030¹

 ²MI

0 (0%)

3 (0.3%)

35 (3.1%)

38 (1.1%)

< 0.001¹

p-value

< 0.001¹

< 0.001¹

< 0.001¹