Exploring the hidden canal: A meta-analysis on middle distal canal configuration in mandibular first molar

Comprehensive knowledge of the internal root canal morphology is essential for achieving predictable outcomes in endodontic procedures, as missed canals or anatomical variations can compromise treatment success. The middle distal canal (MDC) in mandibular first molars (MFMs) is a rare anatomical variant that may lead to treatment failure if undetected. Despite reports across various populations using advanced imaging, the global prevalence, and anatomical patterns of MDC remain unclear due to methodological differences.

This meta-analysis aimed to estimate the worldwide occurrence of the MDC in MFMs and assess the anatomical variations based on population groups and imaging modalities.

Following Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines and registered in International Prospective Register of Systematic Reviews (CRD420250643655), a strategic search of five databases was conducted up to March 22, 2025. Eighteen observational studies using the cone-beam computed tomography (CBCT), micro-computed tomography (micro-CT), or clearing techniques were included. Data had been analyzed utilizing a random-effects model with subgroup analysis by region and modality.

The confluent canal type showed the highest pooled prevalence (7.90%). MDC prevalence was the highest in North Indian (5.70%) and Kashmiri (5.00%) populations. Clearing techniques detected more MDCs (2.35%) compared to CBCT (2.00%) and micro-CT (1.00%).

Although infrequent, MDC is clinically significant. Advanced imaging and meticulous canal exploration are recommended for its detection.