To assess the internal reliability of CBCT image observations in the peresent study, one observer assessed 10% of the total teeth (323 teeth) twice at 1-month intervals and the kappa agreement coefficient between two observations was 91.1% with a standard error of approximately 0.083 (0.911 ± 0.083). Also, the agreement for all teeth (3233) was estimated at a high and very good level (0.919 ± 0.025).
Out of 3233 molars, 157 teeth (4.86%) had C-shaped canals. Prevalence of C-shaped canals in males equal to 4.49% (52 teeth, prevalence confidence interval is 3.3% -5.68%) and in females equal to 5.06% (105 teeth, prevalence confidence interval equal to 4.12% -6.0%) was reported (p = 0.52).(Table 1)
Prevalence of molar teeth with C-shaped canals on the right was 4.66% (76 teeth, prevalence confidence interval is 3.64% − 5.68%) and on the left was equal to 5.05% (81 teeth, prevalence confidence interval equal to 3.98% -6.12%) (p = 0.66).(Table 2)
Prevalence of first molars with C-shaped canals was equal to 2.81% (38 teeth, prevalence confidence interval equal to 1.93% -3.69% ) and the prevalence of second molars with C-shaped canals was estimated to be 6.3% (119 teeth, prevalence confidence interval equal to 4.44% -6.5%). The prevalence of C-shaped canals in the second molar teeth was significantly higher than the first molars (chi-square test: p < 0.0001).(Table 3)
In details and according to the fallowing tables, in the mandible out of a total of 1580 molars, 43 teeth out of 567 molars belong to males (7.58% with a prevalence interval of 5.4% -9.76%) and 66 out of 1013 teeth belonged to females (6.52% with a confidence interval of prevalence equal to 5.0% -8.04%) were reported with C-shaped canals. There were no significant differences in the prevalence of C-shaped canals in mandibular molars according to gender (chi-square test: p = 0.48).(Table 4)
Out of a total of 1580 mandibular molars, 49 of the 733 teeth are located on the right (6.68% with a prevalence interval of 4.87% -8.49%) and 60 of the 847 teeth on the left side (7.08% with a prevalence confidence interval of 5.35% -8.81%) of patients's mouth had C-shaped root canals (without significant differences: p = 0.83).(Table 5)
Among mandibular molars, 27 first molars out of a total of 602 mandibular first molars(4.49% with a prevalence confidence interval equal to 2.84% -6.14%) and 82 second molars out of 978 mandibular second molars(8.38% prevalence confidence interval equal to 6.64% -10.12%)had C-shaped root canals. The prevalence of C-shaped canals in mandibular first molar teeth was significantly lower than mandibular second molars (chi-square test: p < 0.004).(Table 6)
Among the mandibular first molars, out of 27 teeth with C-shaped root canals, 24 teeth (3.99%, prevalence confidence interval equal to 2.43% -5.55%) had C1 structure, 2 teeth (0.33%, prevalence confidence interval equal to 0.13% -0.79% -) with C2 structure and 1 tooth (0.17%, confidence interval equal to 0.5% − 0.16% -) also had C3 structure.(Table 7)
Likewise, among the mandibular second molars, out of 82 teeth with C-shaped root canals, 54 teeth (5.52%, prevalence confidence interval equal to 4.09% -6.95%) had C1 structure, 24 teeth (2.45%, prevalence confidence interval equal to 1.48% -3.32%) had C2 structure and 4 teeth (0.41%, prevalence confidence interval equal to 0.81% -0.01%) had C3 structure. .(Table 7)
In the maxilla and out of a total of 1653 molars, 9 teeth out of 591 molars belong to males (1.52%, with a prevalence interval of 0.53% -2.51%) and 39 out of 1062 teeth belonged to females (3.67% with a confidence interval of prevalence equal to 2.54% -4.8%) were estimated with C-shaped canals. The prevalence of C-shaped canals in maxillary molars was significantly higher in females than males (chi-square test: p < 0.02).(Table 8)
Out of a total of 1653 maxillary molars, 27 of the 897 teeth located on the right (3.01% with a prevalence interval of 1.89% -4.13%) and 21 of the 756 teeth on the left side of patients's mouth (2.78% with a prevalence confidence interval of 1.61% -3.95%) had C-shaped root canals (without significant differences: p = 0.89).(Table 9)
Among maxillary molars, 11 first molars out of a total of 749 maxillary first molars(1.47% with a prevalence confidence interval equal to 0.61% -2.33%) and 37 second molars out of 904 maxillary second molars(4.10% prevalence confidence interval equal to 1.34% -3.3%)had C-shaped root canals.There was no significant difference in the prevalence of C-shaped canals between the first and second maxillary molars (chi-square test: p = 0.28). (Table 10)
In the maxilla and out of 749 first molars, 11 teeth had C-shaped canals. Of these teeth, 1 tooth (0.13%, prevalence confidence interval equal to 0.13% -0.39% -) with structure A,2 teeth (0.27%, prevalence confidence interval equal to 0.1% -0.64% -) with B1 structure, 6 teeth (0.8%, prevalence confidence interval equal to 0.16% -1.44%) with Structure C,1 tooth (0.13%, prevalence confidence interval equal to 0.13% − 0.39% -) with D structure and 1 tooth (0.13%, prevalence confidence interval equal to 0.13% − 0.39% -) with E2 structure was observed (Table 11).
Also,In the maxilla out of 904 second molars, 37 teeth had C-shaped canals. Of these teeth, 8 teeth (0.88%, prevalence confidence interval equal to 0.27% -1.49%) have structure A, 4 teeth (0.44%, prevalence confidence interval equal to 0.01% -0.87 0%) has structure B1, 7 teeth (0.77%, prevalence confidence interval equal to 1.34% 0.2%) with B2 structure, 5 teeth (0.55%, prevalence confidence interval equal to 0.03% -0.07%) with structure C and 13 teeth (1.44%, prevalence confidence interval equal to 2.22% -0.66%) also had E2 structure (Table 11).