Root and canal morphology of mandibular second molars in an Egyptian subpopulation: a cone-beam computed tomography study

Abstract

Background: This study was using Cone beam computed tomography (CBCT) to examine the anatomical variations in mandibular second molars in an Egyptian sub-population.

Methods: A total of 350 CBCT images (215 females and 135 males, aged 15-65 years) of mandibular second molars were evaluated. Samples were evaluated in terms of: number of roots, number of root canals, roots' cross section as well as prevalence and configurations of C-shaped canals. Statistical analysis was done to highlight differences between different categories and their prevalence among genders (significance level was set at p < 0.05). Data were presented as frequency and percentage values and were analyzed using chi square test followed by pairwise comparisons utilizing multiple Fisher's exact tests with Bonferroni correction. The significance level was set at p < 0.05 within all tests.

Results: Of the 350 mandibular second molars evaluated, 87.2% were non-C-shaped while 12.8% were C-shaped with no gender-based statistically significant differences (χ2 = 0.19, p = 0.656). Most samples had three root canals (80%) followed by two (16%), then one (3.2%), and finally four (0.8%) root canals. Among the non-C-shaped molars, presence of two roots was most common (83.4%) followed by presence of a single root (16.2%), and only one sample (0.2%) had three roots, and this had no correlation with gender (χ2 = 1.86, p = 0.431). In the mesial roots Type IV Vertucci was the most common configuration found (68.8%), while Type I was the most prevalent in the distal roots (91.8%). The long oval configuration was the most commonly found cross section in mesial roots while "oval" was the most prevalent in distal roots.

Conclusion: Egyptian sub-population shows highly variable morphological features in mandibular second molars, hence, CBCT is highly recommended on case-to-case conditions.

Keywords: C-shaped canal; Cone beam computed tomography; Endodontics; Mandibular second molar.

Fig. 1

Representative axial CBCT sections showing the classification by Fan et al. [18]. 1a: class C1, a continuous C shaped canal. 1b: class C2, a mesiobuccal-distal (MB-D) ribbon-like canal and a mesiolingual (ML) canal. 1c: class C3a, a mesial (M) canal and a distal (D) canal. 1d: class C3b, a mesiobuccal (MB), a ML and a D canal. 1e: class C4, a single round or oval canal

Fig. 2

Root canal configurations detected in the study according to Vertucci’s classification (Types I to VI)

Fig. 3

Pie chart showing number of roots and supernumerary roots

Fig. 4

The only sample of the study showing three roots (Radix entomolaris – 0.29%)

Fig. 5

Pie chart showing the percentage of C-shaped molars

Fig. 6

Samples of the C shaped molars included in the study

Fig. 7

Pie chart showing the percentage of molars showing a specific number of root canals