Dentin thickness of C-shaped root canal walls in mandibular premolars based on cone-beam computed tomography: a retrospective cross-sectional study.

Objectives: This study aimed to measure the dentin thickness of C-shaped canals in mandibular first and second premolars at coronal, middle, and apical root levels using cone-beam computed tomography (CBCT). Methods: Dentin thicknesses of buccal, lingual, mesial, and distal root walls of 41 C-shaped premolars were measured at three different root levels on axial CBCT slices. The measurements were made at the midpoint of each third, along with 1 mm below and above the midpoint. C-shape configurations of the premolar root canals were also recorded. Analysis of variance, Kruskal-Wallis, and the independent samples t-tests were used for the comparisons (p = 0.05). Results: The thickest walls for both premolars were buccal and lingual walls at all three root levels (p < 0.05). The thinnest walls for the first premolar teeth were mesial and distal walls of the lingual canal, while it was the mesial end of the buccal and lingual canals for the second premolars (p < 0.05). Dentin wall thicknesses at the mesial end of buccal and lingual canals of C1-shaped first premolars were thinner than C2-shaped first premolars at the apical level (p < 0.05). Conclusions: Danger zones for C-shaped mandibular first and second premolars are predominantly mesial walls facing the radicular groove and distal wall of the lingual canal. CBCT imaging during endodontic treatment is recommended to avoid complications.