Presence of a distolingual root in mandibular first molars as an indicator of association with other tooth canal anatomies: A systematic review.

Understanding anatomical variations in root canal morphology is crucial for achieving successful endodontic outcomes. The presence of a distolingual root (DLR) in mandibular first molars (MFMs) has been proposed as an indicator of complex root canal anatomy in other teeth. This systematic review aimed to evaluate the association between DLRs in MFMs and root canal configurations in other teeth across different ethnic populations. Following PRISMA guidelines, a comprehensive search of PubMed, MEDLINE Complete, Scopus, ClinicalKey, and relevant registries was performed up to October 10, 2025, using the keywords "distolingual root" and "radix entomolaris." Inclusion criteria comprised in vivo CBCT-based clinical studies that reported both DLR prevalence and its association with root canal morphology of other teeth. Study quality was assessed using the Newcastle-Ottawa Scale. Twelve studies involving 8,024 participants and 51,762 teeth were included. Reported DLR prevalence ranged from 3.6 % to 41.2 %. Studies from East Asia (Taiwan, South Korea, China) consistently demonstrated positive correlations between DLRs in MFMs and complex canal anatomies in mandibular lateral and central incisors and first premolars. In contrast, data from India and Turkey showed variable or negative associations. The presence of a DLR in MFMs may serve as a reliable anatomical marker for anticipating complex canal configurations in adjacent or contralateral teeth. Ethnic differences were evident, highlighting the need for standardized CBCT-based multicenter studies to confirm these findings and improve predictive endodontic diagnosis.