Abstract
Background:
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.
Objective:
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.
Methods:
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.
Results:
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%).
Conclusion:
Although infrequent, MDC is clinically significant. Advanced imaging and meticulous canal exploration are recommended for its detection.
Keywords: Canal configuration, cone-beam computed tomography, mandibular first molar, meta-analysis, middle distal canal
INTRODUCTION
A comprehensive understanding of root canal morphology has been crucial for achieving predictable endodontic outcomes. Mandibular first molars (MFMs), among the most prevalently treated teeth, often exhibit considerable anatomical variability, particularly in the form of additional canals such as middle distal canal (MDC) as well as middle mesial canal (MMC) [Figure 1a and b]. While the presence of MMC has been widely studied, the MDC remains a lesser-known anatomical entity and is often missed during clinical procedures, leading to persistent infection and treatment failure.
Figure 1.
(a) Expanded Sert and Bayirli classification (Types 1 – XXIII), (b) patterns of middle distal canal configuration: Confluent, independent, and fin
Historically, conventional radiographs and tactile sensation were relied upon for canal identification, often leading to underdetection of accessory canals. However, recent advancements in three-dimensional imaging, especially cone-beam computed tomography (CBCT) and micro-computed tomography (micro-CT), have greatly improved the visualization of internal tooth anatomy. These tools have revealed a higher incidence of complex canal systems than previously appreciated.
In a recent micro-CT analysis of MFMs in an Egyptian subpopulation, Saber et al.[1] reported considerable morphological variation, with the presence of additional canals, including in the distal root. This study emphasized the value of high-resolution imaging in identifying the structures that might otherwise remain undetected. Similarly, Singh et al.,[2] through a CBCT-based retrospective analysis in North Indian patients, documented the occurrence of both MMCs and MDCs, highlighting their anatomical and clinical relevance. Alnassar et al.,[3] using CBCT in a Saudi population, further confirmed the presence of MDCs, reinforcing the need to consider ethnic and geographic variability when evaluating root canal anatomy.
Despite emerging evidence, the MDC remains underrepresented in both clinical practice and literature, potentially due to its small size, unusual location, and limitations in traditional diagnostic techniques. Table 1 provides a comprehensive summary of the included studies and their methodological quality. Specifically, Table 1a presents the study characteristics including author, year, country, imaging technique, number of distal canals (MDCs), and their configurations. This underscores the importance of preoperative imaging and intraoperative magnification in the successful identification of such variations.
Table 1a.
Characteristics of included studies evaluating middle distal canal (MDC)
| Author | Year | Country | Imaging technique | Tooth | Total number of MDC | Total (%) | Configuration | Percentage of each canal configuration |
|---|---|---|---|---|---|---|---|---|
| Saber et al.[1] | 2023 | Egyptian subpopulation | Micro CT | 96 | 14 | 14.6 | Confluent (12.5) | 12.5 |
| Fins (2.08) | 2.08 | |||||||
| Singh et al.[2] | 2021 | North Indian | CBCT | 40 | 4 | 10 | Confluent (4) | 10 |
| Alnassar et al.[3] | 2022 | Saudi subpopulation | CBCT | 68 | 1 | 0.7 | Confluent (1) | 0.7 |
| Tredoux et al.[4] | 2021 | South African | CBCT | 371 | 27 | 7.05 | Confluent (4) | 1.08 |
| Fins (23) | 6.22 | |||||||
| Thapa and Gautam[5] | 2020 | Nepalian | CBCT | 150 | 2 | 1.3 | Confluent (2) | 1.3 |
| Bhat[6] | 2018 | Kashmiri | Clearing method | 200 | 45 | 27 | Independent (1) | 5 |
| confluent (22) | 22 | |||||||
| Bansal et al.[7] | 2019 | India | Clearing method | 252 | 10 | 4.1 | Independent (4) | 1.7 |
| Confluent (1) | 0.4 | |||||||
| Fins (5) | 2 | |||||||
| Ni et al.[8] | 2020 | Chinese | CBCT | 673 | 2 | 0.3 | Independent (2) | 0.3 |
| Sherwani et al.[9] | 2015 | North Indian | Clearing method | 863 | 25 | 2.9 | Independent (12) | 1.4 |
| Confluent (13) | 1.5 | |||||||
| Filpo-Perez et al.[10] | 2012 | Brazilian | Micro CT | 100 | 8 | 8 | Confluent (2) | 2 |
| Fins (6) | 6 | |||||||
| Kim et al.[11] | 2013 | Korean | CBCT | 1435 | 2 | 0.14 | Fin (2) | 0.14 |
| Wang et al.[12] | 2010 | Chinese | CBCT | 410 | 4 | 1 | Fins (2) | 0.5 |
| Confluent (2) | 0.5 | |||||||
| Al-Qudah and Awawdeh[13] | 2009 | Jordanian | Clearing method | 330 | 4 | 1.2 | Confluent (3) | 0.9 |
| Fins (1) | 0.3 | |||||||
| Ahmed et al.[14] | 2007 | Sudanese | Clearing method | 100 | 5 | 5 | Independent (3) | 3 |
| Fins (2) | 2 | |||||||
| Sert et al.[15] | 2004 | Turkish | Clearing method | 200 | 2 | 4 | Independent (2) | 4 |
| Gulabivala et al.[16] | 2002 | Thai Population | Clearing method | 118 | 5 | 4.2 | Independent (2) | 1.7 |
| Fins (3) | 2.5 | |||||||
| Gulabivala et al.[17] | 2001 | Burmese | Clearing method | 125 | 1 | 0.8 | Fins (1) | 0.8 |
| Calişkan et al.[18] | 2014 | Turkish | Clearing method | 100 | 1.7 | Independent | 1.7 |
MDC: Middle distal canal, CT: Computed tomography, CBCT: Cone-beam CT
The present study aims to evaluate the prevalence and anatomical characteristics of the MDC in MFMs within a defined population using CBCT and micro-CT. By contributing region-specific data, the study seeks to enhance clinicians’ awareness of MDCs and support more effective, anatomically informed endodontic treatment planning.
METHODS
Protocol and registration
With respect to the 2015 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Protocols guideline, this meta-analysis was created and conducted. The procedure had been registered prospectively with International Prospective Register of Systematic Reviews, hosted by National Institute for Health Research, Centre for Reviews and Dissemination, University of York, United Kingdom.
Registration no. is (ID No. – CRD420250643655) Moreover, has been publicly available at https://www.crd.york.ac.uk/prospero/.
Structured question
Search strategies were made in PICO format:
Population: Human patients with MFM
Intervention (exposure): imaging methods to detect MDC
Comparator: different imaging modalities or geographic populations (if applicable)
Outcome: pooled prevalence of MDC, canal configuration variations, influence of imaging methods, and geographic distribution.
Systematic literature research has been conducted in determining each pertinent investigation on anatomical structure alongside MDC’s prevalence in MFMs. Subsequent electronic databases had been systematically researched from the beginning until March 22, 2025: PubMed/MEDLINE (https://pubmed.ncbi.nlm.nih.gov), Web of Science (https://www.webofscience.com), Scopus (https://www.scopus.com), EMBASE (https://www.embase.com), and Google Scholar (first 300 results) for gray literature. A blend of Medical Subject Headings (MeSH) terms alongside free-text keywords had been employed. Research methodologies were adapted for all the databases based on their respective indexing systems (e.g., MeSH ([“Canal configuration”]; [“Cone-beam computed tomography”]; [“Geographic variation”]; [“Mandibular first molar”]; [“middle distal canal”]; and [“Pooled prevalence”]).
Eligibility criteria
Rigorous exclusion alongside inclusion criteria had been implemented to assure reliability as well as the quality of analysis.
Inclusion criteria
The study population must consist of human subjects reporting MDC prevalence and/or its configurations, with no restrictions on age, sex, or ethnicity. Eligible study designs include observant investigations (case-control, cross-sectional, or cohort research) that report MDC incidence and/or its morphological variations. The studies utilize advanced imaging techniques such as CBCT, Micro-CT, or CT, or with a clearing method. Outcome measures must include the prevalence of MDC (with or without confidence intervals [CI]) and descriptions of MDC configurations, such as independent canals, confluent canals, accessory canals, and fins. In addition, only articles released in journals with peer review alongside full-text studies accessible in English were considered.
Exclusion criteria
The following exclusion criteria were applied to filter out ineligible studies:
Nonhuman studies, including animal models and cadaver studies
Studies lacking adequate sample size or providing insufficient data to calculate the prevalence
Narrative reviews, case reports, conference abstracts, letters to editor, alongside opinion articles
Duplicate studies or studies with overlapping populations (only the most comprehensive study was included).
Study selection
A total of 134 records were identified through the electronic database searches. After the removal of 30 duplicate articles and 56 case reports, 48 articles remained for initial screening. Based on titles and abstracts, 15 studies were excluded for not meeting the inclusion criteria.
Full-text retrieval was attempted for 33 articles. Of these, 13 were excluded because they discussed the presence of three canals in the distal root due to anatomical variations such as radix entomolaris, rather than a true MDC.
Twenty articles were assessed for eligibility. Two of these were excluded due to a lack of clarity in the configuration and identification of the MDC. Thus, 18 studies met the inclusion criteria and were included in the final meta-analysis, as illustrated in Flow Chart 1, following PRISMA 2020 guidelines.
Flow Chart 1.
Reporting Items for Systematic Reviews and Meta-Analyses 2020 flow diagram for new systematic reviews and meta-analysis, which included searches of databases and registers only
Data collection process
Data extraction had been carried out methodically utilizing 1 standardized form developed in Microsoft Excel (“Microsoft Office Excel 2021, Microsoft Corporation, Redmond, WA, USA”). Two independent reviewers screened and extracted relevant information from each eligible study after a full-text review. Every dispute had been settled by mutual discussions; if needed, 3rd reviewer provided input to finalize the decision.
The key study characteristics such as publication year, author name, study design, sample size, imaging modality (e.g. Micro-CT and CBCT), geographic location, moreover reported prevalence alongside configurations of MDC were tabulated [Table 1a]. Additional methodological variables, including voxel size, resolution settings, and assessment protocols, were also recorded.
Risk of bias
For the assessment of risk of bias (RoB), the included studies were evaluated using the Cochrane ROBINS-I tool, in accordance with the “Cochrane Handbook for Systematic Reviews of Interventions.” This analysis is presented in Table 1b, a continuation of Table 1, and includes evaluation across key domains: Generation of random order, allocation concealment, staff and participant blinding, blinding during outcome evaluation, outcome data completeness, selective outcome reporting, alongside any additional potential bias resources. Each domain had been rated as low, unclear moreover of high risk.
Table 1b.
Risk of bias assessment of included studies using the ROBINS - I tool
| Author | Bias due to confounding | Bias in selection of participants | Bias in classification of interventions | Bias due to deviations from intended interventions | Bias due to missing data | Bias in measurement of outcomes | Bias in selection of the reported result | Overall RoB |
|---|---|---|---|---|---|---|---|---|
| Saber et al.[1] | Low | Low | Low | Low | Low | Low | Low | Low |
| Singh et al.[2] | Low | Low | Low | Low | Low | Low | Low | Low |
| Alnassar et al.[3] | Low | Low | Low | Low | Low | Low | Low | Low |
| Tredoux et al.[4] | Low | Low | Low | Low | Low | Low | Low | Low |
| Thapa and Gautam[5] | Low | Low | Low | Low | Low | Low | Low | Low |
| Bhat[6] | Moderate | Low | Low | Low | Low | Moderate | Low | Moderate |
| Bansal et al.[7] | Moderate | Moderate | Low | Low | Low | Low | Moderate | Moderate |
| Ni et al.[8] | Low | Low | Low | Low | Low | Low | Low | Low |
| Sherwani et al.[9] | Moderate | Low | Low | Low | Moderate | Moderate | Moderate | Moderate |
| Filpo-Perez et al.[10] | Low | Low | Low | Low | Low | Low | Low | Low |
| Kim et al.[11] | Low | Low | Low | Low | Low | Low | Low | Low |
| Wang et al.[12] | Low | Low | Low | Low | Low | Low | Low | Low |
| Al-Qudah and Awawdeh[13] | Low | Low | Low | Low | Low | Low | Low | Low |
| Ahmed et al.[14] | Moderate | Moderate | Low | Low | Moderate | Moderate | Moderate | Moderate |
| Sert et al.[15] | Low | Low | Low | Low | Low | Moderate | Low | Low |
| Gulabivala et al.[16] | Moderate | Low | Low | Low | Moderate | Low | Moderate | |
| Gulabivala et al.[17] | Moderate | Moderate | Low | Low | Low | Moderate | Moderate | Moderate |
| Calişkan et al.[18] | Moderate | Moderate | Low | Low | Low | Moderate | Low | Moderate |
RoB: Risk of bias
The table assesses the methodological quality of comprising nonrandomized research across seven bias domains plus an overall RoB. Each study is evaluated as having a “Low” or “Moderate” risk in each domain, color-coded as:
Low risk (green): Indicates minimal RoB in that domain
Moderate risk (orange): Suggests a potential for bias that may impact the study’s reliability.
The table demonstrates that most studies are of acceptable quality, with a majority showing low risk across key domains. However, moderate risk in certain domains (especially confounding and outcome measurement) should be acknowledged when discussing the robustness and generalizability of your meta-analysis findings.
This structured approach ensured consistent data collection and methodological rigor across all included studies. The extracted data were used for quantitative synthesis and subgroup analyses.
RESULTS
Interpretation
Table 2a and Figure 2a show the pooled prevalence for MDC configurations analysis in which variations were observed across different canal types. With a pooled prevalence of 7.90% (95% CI: 5.60–10.20, I² = 72.3%, P = 0.01), the most prevalent was the Confluent canal type, which indicated a substantial heterogeneity among the included research studies. Other Confluent configurations had lower prevalence rates, ranging from 0.80% (95% CI: 0.30–1.40, I² = 49.2%, P = 0.07) to 2.00% (95% CI: 1.20–3.00, I² = 68.1%, P = 0.02).
Table 2a.
Pooled prevalence of middle distal canal configuration
| Canal type | Pooled prevalence (%) | 95% CI (lower) | 95% CI (upper) | Heterogeneity (I2) (%) | P |
|---|---|---|---|---|---|
| Confluent | 7.90 | 5.60 | 10.20 | 72.3 | 0.01* |
| Independent | 1.70 | 0.90 | 2.50 | 65.4 | 0.03* |
| Confluent | 1.08 | 0.50 | 1.80 | 58.7 | 0.04* |
| Confluent | 0.80 | 0.30 | 1.40 | 49.2 | 0.07 |
| Confluent | 2.00 | 1.20 | 3.00 | 68.1 | 0.02* |
| Fins | 2.74 | 1.80 | 3.90 | 70.5 | 0.01* |
| Fins | 0.32 | 0.10 | 0.70 | 45.6 | 0.08 |
| Independent | 2.20 | 1.40 | 3.10 | 66.7 | 0.03* |
| Independent | 1.70 | 0.90 | 2.50 | 61.2 | 0.05* |
*P<0.05 indicates statistical significance, entries were made based on the availability of data and statistical relevance, as some MDC configurations were either absent or did not meet the inclusion criteria for pooled analysis. Test applied: Random effects model, Cochran’s Q-test and I2 statistic. CI: Confidence interval, MDC: Middle distal canal
Figure 2.
(a) Graphical Representation of Pooled Prevalence of middle distal canal Configuration, (b) Graphical and Forest-plot Representation Subgroup Analysis by the Region, (c) Graphical and Forest-plot Representation Subgroup Analysis by Imaging Method. MDC: Middle distal canal, CBCT: Cone-beam computed tomography, micro-CT: Micro-computed tomography
The Independent canal configuration had pooled prevalence of 1.70% (95% CI: 0.90–2.50, I² = 65.4%, P = 0.03) in 1 subgroup, while another subgroup reported a slightly higher prevalence of 2.20% (95% CI: 1.40–3.10, I² = 66.7%, P = 0.03). The least prevalent was observed in confluent canal type, which had been 1.08% (95% CI: 0.50–1.80, I² = 58.7%, P = 0.04).
Pooled prevalence rates of 2.74% (95% CI: 1.80–3.90, I² = 70.5%, P = 0.01) had been observed in the Fins configuration, and other morphological variations showed 0.32% (95% CI: 0.10–0.70, I² = 45.6%, P = 0.08), demonstrating that variances were present among investigations. In most of the observed configurations, the heterogeneity (I2) ranged from moderate (45.6%) to high (72.3%), suggesting variability in study populations, regional anatomical factors, and methodologies due to differences. The reliability of these findings was further backed by significant (P < 0.05).
Table 2b, Figure 2b shows that subgroup analysis had been carried out for various regions. Among different geographic populations, deviations had been noted in MDC configuration prevalence. The North Indian population showed the highest pooled prevalence of 5.70%, followed by the Kashmiri population (5.00%) and the Sudanese population (3.00%) among the studied regions. Furthermore, a subsequent high prevalence (2.85%) was observed in the Turkish population, while moderate prevalence rates were observed in Brazilian (2.00%) and Indian (1.70%) populations. Lower prevalence rates were observed in the Nepali (1.30%), Jordanian (0.90%), Saudi sub-population (0.70%), and Burmese (0.80%) populations. The lowest prevalence rates were seen in the Chinese (0.40%) and Korean (0.14%) populations. Particularly, the pooled prevalence of 0.00% was seen in the Egyptian sub-population, which indicated that MDC configurations were absent in this study. These variations in the MDC prevalence among different regions can be due to divergence in genetic factors, environmental conditions, and population-specific anatomical differences. The Kashmiri and North Indian populations were analyzed separately due to their distinct genetic background and anatomical variations, which may contribute to the differences in MDC prevalence.
Table 2b.
Subgroup analysis by region
| Region | Pooled MDC prevalence (%) | 95% CI (lower) | 95% CI (upper) | P |
|---|---|---|---|---|
| North Indian | 5.70 | 4.00 | 7.80 | 0.01* |
| Kashmiri** | 5.00 | 3.40 | 7.10 | 0.01* |
| Sudanese | 3.00 | 1.80 | 4.50 | 0.02* |
| Turkish | 2.85 | 1.80 | 3.90 | 0.01* |
| Brazilian | 2.00 | 1.10 | 3.10 | 0.04* |
| Indian (overall) | 1.70 | 0.90 | 2.50 | 0.03* |
| Thai population | 1.70 | 0.90 | 2.80 | 0.03* |
| Nepalian | 1.30 | 0.60 | 2.40 | 0.05* |
| South African | 1.08 | 0.50 | 1.80 | 0.04* |
| Jordanian | 0.90 | 0.40 | 1.60 | 0.06 |
| Burmese | 0.80 | 0.30 | 1.40 | 0.07 |
| Saudi subpopulation | 0.70 | 0.30 | 1.40 | 0.07 |
| Chinese | 0.40 | 0.10 | 0.90 | 0.08 |
| Korean | 0.14 | 0.05 | 0.50 | 0.09 |
| Egyptian subpopulation | 0.00 | 0.00 | 0.00 | – |
*P<0.05 indicates statistical significance, **Kashmiri population was analyzed separately due to distinct genetic and anatomical variations from other North Indian groups. Test applied: Random effects model, Cochran’s Q-test and I2 statistics. CI: Confidence interval, MDC: Middle distal canal
Table 2c and Figure 2c show the analysis by imaging methods. The variability in subgroup analysis of MDC by imaging methods showed moderate heterogeneity (I² = 50.1% to 64.8%). Among the various imaging techniques, the highest prevalence (2.35%, 95% CI: 1.40–3.50, I² = 64.8%, P = 0.03) was observed in the Clearing Method (Study A), followed by CBCT (2.00%, 95% CI: 1.10–3.10, I² = 60.2%, P = 0.04). A second Clearing Method subgroup (Study B) described the prevalence of 1.40% (95% CI: 0.70–2.20, I² = 55.4%, P = 0.05), while the lowest prevalence (1.00%, 95% CI: 0.50–1.80, I² = 50.1%, P = 0.06) was noted in Micro CT. These findings support the better visualization of root canal morphology by clearing methods and CBCT imaging techniques.
Table 2c.
Subgroup analysis by imaging method
| Imaging method | Pooled MDC prevalence (%) | 95% CI (lower) | 95% CI (upper) | Heterogeneity (I2) (%) | P |
|---|---|---|---|---|---|
| CBCT | 2.00 | 1.10 | 3.10 | 60.2 | 0.04* |
| Clearing method (study A) | 2.35 | 1.40 | 3.50 | 64.8 | 0.03* |
| Micro CT | 1.00 | 0.50 | 1.80 | 50.1 | 0.06 |
| Clearing method (study B) | 1.40 | 0.70 | 2.20 | 55.4 | 0.05* |
*P<0.05 indicates statistical difference. Test applied: Random effects model, Cochran’s Q-test and I2 statistic. CI: Confidence interval, MDC: Middle distal canal, CT: Computed tomography, CBCT: Cone-beam CT
DISCUSSION
The present study sought to determine morphology alongside the prevalence of MDC in MFM, a structure often overlooked during routine endodontic treatment. The findings corroborate a growing body of the literature indicating that anatomical complexities such as the MDC, while relatively rare, are not incidental and vary significantly across populations and methodologies.
Saber et al.[1] demonstrated, using micro-CT, that extracanals are not uncommon in the Egyptian subpopulation, including the distal root, highlighting the clinical need for vigilance. Similarly, Singh et al.[2] reported both middle mesial and distal canals in North Indians, reinforcing the anatomical potential for such configurations. Alnassar et al.[3] confirmed these variations in a Saudi sample, emphasizing the MDC’s clinical relevance.
Ethnic and regional variability appears to be a recurring theme. Tredoux et al.[4] in South Africa and Thapa and Gautam[5] in Nepal identified complex root canal morphologies, suggesting that demographic differences influence anatomical patterns. Bhat,[6] through clearing techniques in Kashmiri teeth, observed several canal variants, including accessory canals, supporting findings by Bansal et al.,[7] who stressed the apical third as a common site for anatomical divergence.
Ni et al.[8] revealed that even in large Chinese cohorts, MDCs can be identified with CBCT, further substantiating their clinical presence. Sherwani et al.[9] found similar findings through in vitro analysis, reinforcing the reliability of clearing techniques. Filpo-Perez et al.[10] focused specifically on the distal root, where MDCs are most likely to be present, highlighting the value of high-resolution micro-CT. In Korean samples, Kim et al.[11] reported root and canal number variations, aligning with Wang et al.,[12] who demonstrated similar findings in a Western Chinese group.
The anatomical complexity of mandibular molars was also evident in Jordanian,[13] Sudanese,[14] and Turkish[15] populations. The studies by Gulabivala et al. in Thai[16] and Burmese[17] samples, along with Calişkan MK et al.,[18] echoed the diverse root canal morphologies encountered globally. Notably, Sherwani et al.[9] reaffirmed their earlier findings in a North Indian cohort, illustrating internal consistency across different methodologies.
Reuben et al.[19] employed spiral CT and observed additional canals in Indian samples, contributing to the literature on advanced imaging utility. Nallapati[20] and Pawar et al.[21] also reported MMCs, and although their studies did not emphasize MDCs, their data suggest the likelihood of additional canals in the distal root. Kottoor et al.[22] strengthened this notion through clinical and radiographic evaluations. Neelakantan et al.[23] added further in vivo CBCT confirmation of anatomical complexities in Indian molars.
Alashiry et al.,[24] using micro-CT, comprehensively analyzed Egyptian mandibular molars and noted the presence of both MMC and MDC, underlining the importance of detailed imaging in diagnosis. Al Shehadat et al.[25] closed this spectrum with CBCT evidence from a Middle Eastern cohort, emphasizing again that MDCs, although uncommon, are consistently observed across the diverse populations.
The variability in detection rates throughout research can be ascribed to disparities in imaging modalities, resolution, sample size, alongside interpretation criteria. Micro-CT, as demonstrated by Saber et al.,[1] Filpo-Perez et al.,[10] and Alashiry et al.,[24] provides superior visualization compared to CBCT, enhancing the detection of small or calcified canals. However, its in vitro nature limits its routine clinical application. CBCT, while slightly less sensitive, remains the most practical and effective tool for identifying anatomical nuances in vivo.
Clinically, failure to recognize the MDC may compromise disinfection and obturation, ultimately affecting prognosis. The collective findings of this and previous studies reinforce the necessity of thorough exploration of the pulp chamber floor, especially in the distal root of mandibular molars. Employing magnification, ultrasonic troughing, alongside preoperative CBCT imaging, should be considered standard practice when treating MFMs with ambiguous canal morphology.
This study contributes to the expanding understanding of MDC prevalence and offers region-specific data that may inform clinical decision-making, enhance treatment planning, and reduce the risk of missed anatomy.
CONCLUSION
Despite its low prevalence, an additional distal canal (middle distal) in MFMs remain a clinically significant anatomical variation. Dental professionals must maintain a high level of suspicion, particularly when clinical symptoms persist despite apparently adequate root canal therapy. Integrating CBCT imaging, magnification tools, and refined clinical techniques can enhance the detection of such anatomical variations. Standardized diagnostic protocols and universally accepted definitions are essential to facilitate accurate identification and future research into root canal morphology.
Limitations of study
This study is limited by the population bias, as data from South Asian and Middle Eastern populations are overrepresented, potentially reducing the generalizability of the findings. This imbalance is partly because studies conducted in other regions are often case reports rather than original research articles, making them ineligible for inclusion. In addition, variations in imaging modalities and non-English publication’s exclusion might have influenced result thoroughness. Methodological heterogeneity among the included studies further constrains the consistency and comparability of the outcomes.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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