Relationship between C-shaped root canal configuration in mandibular second molars and radix entomolaris in mandibular first molars: a CBCT-based study in a Western Chinese population.

Hebah H Al-Awdi, Eissa A Al-Shujaa, Ahmed A Madfa, Li Peng

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Article in Clinical oral investigations, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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Hebah H Al-AwdiState Key Laboratory of Oral Diseases and National Clinical Research Centre for Oral Diseases, Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.

Eissa A Al-ShujaaState Key Laboratory of Oral Diseases and National Clinical Research Centre for Oral Diseases, Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.

Ahmed A MadfaDepartment of Restorative Dental Science, College of Dentistry, University of Ha'il, Ha'il, Kingdom of Saudi Arabia.

Li PengState Key Laboratory of Oral Diseases and National Clinical Research Centre for Oral Diseases, Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China. 43339426@qq.com.

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6 · The paper itself

Abstract

objectivesMandibular molars exhibit considerable morphological variability in root and root canal anatomy among individuals and across populations. The aim of this study was to investigate whether an association exists between C-shaped root canal configuration (CSRC) in mandibular second molars (MSMs) and the presence of radix entomolaris (RE) in mandibular first molars (MFMs). MATERIALS AND

methodsThis retrospective CBCT study included 1637 subjects (682 males and 955 females), involving 3274 MSMs and 3274 MFMs. CSRCs in MSMs were categorized using the Fan et al. categorization system (C1-C5). Whereas RE in MFMs were assessed according to American Association of Endodontists (AAE) in which RE identified as an extra distolingual root, both anatomical features were evaluated for frequency and bilateral symmetry. McNemar's tests were used to evaluate bilateral symmetry. The chi-square test and Cramer's V were used to examine the relationship between CSRCs and REs as well as the association between age and gender on the co-occurrence of these characteristics. Binary logistic regression analysis was used to assess if CSRCs might predict the existence of REs. The level of statistical significance was P < 0.05.

resultsA total of 1637 patients and 6548 teeth were evaluated in this study. The prevalence of CSRC in MSMs was 46%, while radix RE in MFMs was observed in 31.6% of cases. CSRCs prevalence were slightly higher on the left side, whereas RE was more frequent on the right side. Bilateral symmetry of CSRCs was (86.6%) while was high (90.7%) for REs, A significant association was found between CSRC and RE (χ² = 4.884, p = 0.027). Logistic regression analysis demonstrated that the presence of CSRCs significantly increased the odds of REs by 1.27 times (OR = 1.265, 95% CI: 1.027-1.559, p = 0.027). No significant association was observed between age group and the coexistence of both variations (χ² (2) = 2.654, p = 0.265). In contrast, gender showed a significant association with both variation (χ² (1) = 20.431, P < 0.001), with females demonstrating a higher prevalence compared to males.

conclusionsRE in MFMs was associated with CSRC in MSMs. Both variations were more common in females, unaffected by age, and showed high bilateral symmetry, highlighting the importance of careful clinical and radiographic assessment for endodontic treatment planning. CLINICAL RELEVANCE: The presence of C-shaped root canal configuration may indicate an increased likelihood of anatomical complexity in mandibular molars. Careful radiographic evaluation, preferably using CBCT, can improve the detection of root canal variations and support more accurate endodontic treatment planning.

Indexed as

Cone-Beam Computed TomographyDental Pulp CavityMolarTooth RootAdultChinaEast Asian PeopleFemaleHumansMaleMandibleMiddle AgedRetrospective StudiesC-shape root canal systemDistolingual rootMandibular first molarsMandibular second molarsRadix Entomolaris

Identifiers

PMID42377571

DOI10.1007/s00784-026-06991-9

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