From: Frequency of non-single canals in mandibular premolars and correlations with other anatomical variants: an in vivo cone beam computed tomography study
Cross-sections of C-shaped canals, N (%)
Coronal
Middle
Apical
C1
–
C2
27 (75)
15 (41.7)
C3
7 (19.4)
16 (44.4)
C4a
2 (5.6)
C4b
3 (8.3)
C4c
13 (36.1)
Total
36 (100)