Prevalence of radix entomolaris and distolingual canals and their association with the incidence of middle mesial canals in mandibular first molars of a Saudi subpopulation

This study aimed to determine the prevalence of radix entomolaris (RE), distolingual canals (DLCs), and middle mesial canals (MMCs) in mandibular first molars within a Saudi subpopulation and to explore potential associations among these variations using cone-beam computed tomography (CBCT). A retrospective cross-sectional analysis was performed on 642 CBCT scans (1,284 mandibular first molars) from patients aged 18-65 years. Each molar was examined in axial, coronal, and sagittal views to identify distolingual canals (DLCs), radix entomolaris (RE), and Middle mesial canals (MMCs) bilaterally. Prevalence was analysed according to gender and age groups. Binary logistic regression assessed associations among variations and demographic predictors. DLCs were the most common variation, detected in 31.2% of left and 28.7% of right mandibular first molars. REs were found in 8.3% (left) and 9.7% (right), while MMCs were less frequent (2.6% left; 1.6% right). Age was significantly associated with the prevalence of DLCs, with higher rates observed in the 18-25, 31-40, and 41-50 year age groups (p < 0.05). Similarly, RE prevalence showed a significant age-related pattern, being more frequent in the 18-25 and 41-50 year groups (p < 0.05). MMCs were very rare on both sides, peaking at 1.1% on the left (31-40 years) and 0.6% on the right (26-30 and 31-40 years), with no statistically significant differences across age groups. A near-significant association was observed between left-sided DLCs and the presence of MMCs (OR = 3.33; p = 0.065). Gender was not significantly associated with any variation.DLCs and REs are relatively common in mandibular first molars in this Saudi subpopulation, while MMCs are rare but clinically relevant. Patients with 41-50 year age group are more likely to exhibit DLCs and REs, and the presence of a DLC may indicate a higher likelihood of an MMC. Incorporating CBCT evaluation in multiple planes is essential for accurate detection and successful endodontic management.