A CBCT Analysis on Prevalence, Morphology, and Assessment of Lingual Wall Thickness of C-shaped Mandibular Second and Third Molars in an Eastern Indian Population: A Retrospective Observational Study

Introduction: Root canal anatomy can vary significantly across different ethnic groups, impacting treatment approaches. The presence of a thin lingual wall and a narrow isthmus in C-shaped canals poses a risk of strip perforation, making it challenging for clinicians to fully understand and manage their complex anatomy. A thorough understanding of the configuration of C-shaped canals, including morphologic variations and lingual wall thickness dimensions, is essential for preventing instrumentation errors and ensuring the success of root canal treatment. Aim: To evaluate the prevalence, morphology, and lingual wall thickness of C-shaped root canals in mandibular second and third molars among an Eastern Indian population using Cone Beam Computed Tomography (CBCT). Materials and Methods: This retrospective observational study was conducted in the Department of Conservative Dentistry and Endodontics, Dr. R. Ahmed Dental College and Hospital, Kolkata, West Bengal, India from February 2024 to July 2024. Out of the CBCT scans obtained from 426 patients, a total of 1,416 teeth were analysed, including mandibular second and third molars. The primary inclusion criteria were CBCT scans of fully erupted mandibular second and third molars. The methodology involved evaluating CBCT scans at three levels: coronal, middle, and apical. Additionally, the lingual wall thickness was measured at three zones (coronal, middle, and apical) for each C-shaped canal identified. Demographic parameters, including age and gender, were recorded for each patient to identify any potential associations with canal morphology and lingual wall thickness. For statistical analysis, the Chi-square test was used to analyse categorical variables, and the Kruskal-Wallis test was employed for continuous variables. The level of significance was set at p-value <0.05. Results: A total of 426 CBCT scans were screened, and 1,416 teeth (852 mandibular second molars and 564 mandibular third molars) in 237 males (55.63%) and 189 females (44.3%) were assessed for the presence of a C-shaped canals. The average age of participants was 29.3±8.78 years, with younger individuals having a higher incidence rate (p-value=0.0033). The incidence of C-shaped canals was 6.35% (n=90). Females had a higher proportion of C-shaped canals (71.1%) compared to males (26/90, 28.9%) (p-value <0.0001). Bilateral C-shaped canals were found in 36/54 cases (66.66%), with 29/44 (65.91%) and 7/10 (70%) significantly more prevalent than unilateral cases, which had 15/44 (34.09%) and 3/10 (30%) mandibular second and third molars, respectively (p-value=0.014). C-shaped canals were strongly linked to fused roots in 79 (87.8%) teeth (p-value <0.001). Type C1 was the most prevalent design, with 30 teeth (33.3%) at the coronal level and 36 teeth (40%) at the middle level, while Type C4 dominated the apical level with 43 teeth (47.8%) (p-value <0.001). Type C2 had thinner mesial lingual walls (p-value=0.02). Conclusion: The study identified a higher prevalence of C-shaped canals in mandibular second molars compared to third molars, with a significantly greater occurrence in females than in males. Type C1 configurations were predominant at the coronal and middle levels, while Type C4 was most frequent at the apical level. Lingual wall thickness was thinnest in Type C2 configurations at the mesial zone. These findings highlight the need for clinicians to account for the complex anatomy of C-shaped canals during root canal therapy.