Presence of a distolingual root in mandibular first molars as an indicator of association with other tooth canal anatomies: A systematic review
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.024 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.007 | 0.007 |
| Bibliometrics | 0.012 | 0.012 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".