Anatomical complexity in mandibular second molars: prevalence of C-shaped canals, radicular grooves, taurodontism, and radices molarum in Saudi population.

This study aimed to conduct a comprehensive evaluation of anatomical variations in mandibular second molars - comprising C-shaped canals, radicular grooves, taurodontism and radices molarum - in a Saudi subpopulation, using cone-beam computed tomography (CBCT). A cross-sectional analysis was performed on 642 high-resolution CBCT scans of mandibular second molars collected from adult patients at a leading dental centre in the Ha'il region, Saudi Arabia. Morphological features were assessed by calibrated examiners using established classification systems for C-shaped canal configurations, radicular groove location and depth, taurodontism subtypes and radix molaris types. Statistical analyses explored associations between anatomical traits and demographic variables such as sex and age. C-shaped canals were identified in less than 9% of cases, with the most complex morphologies observed at the apical third. Lingual radicular grooves were more prevalent than buccal grooves, with deep grooves significantly more common than shallow ones. Taurodontism was detected in 3.3-3.6% of molars, predominantly in women, with hypertaurodontism being the most frequent subtype. Radix entomolaris and radix paramolaris were rare, found in 1.4-2.0% and < 1.1% of cases, respectively. Anatomical variations were more prevalent in women and individuals aged 18-40 years. Mandibular second molars in this Saudi cohort exhibited notable anatomical complexity, with clinically significant implications for endodontic diagnosis and treatment. CBCT proved essential for accurately identifying these variations, underscoring its role in preoperative planning. The findings emphasise the need for individualised, morphology-based endodontic strategies and highlight the importance of population-specific anatomical data to optimise treatment outcomes.