Bayesian Hierarchical Modelling of Root Canal Morphology in Mandibular First Premolars Across 21 Countries
Fatma P.H. Magat G. Karobari M.I. Buchanan G.D. Kopbayeva M. Taha N. Makahleh N. Fernández-Grisales R. Bekjanova O. Luu P. Bürklein S. Mufadhal A. Petridis X. Mora M.F. Sugumaran S. Allawi S. Ivica A. Lim W.Y. Fadag A. Jagtap R. Martín-Cruces J. Kulczyk T. Alfirjani S. Palma P.J. Hatipoğlu Ö.
2026John Wiley and Sons Inc
International Endodontic Journal
2026
Background: Understanding root canal morphology is crucial for successful endodontic treatment; however, the anatomy of mandibular first premolars (M1Ps) remains one of the most variable and challenging aspects. The Vertucci classification provides a standardised framework for describing canal configurations; however, population-level data integrating multiple countries are scarce. This study aimed to evaluate the global distribution and determinants of Vertucci canal morphology in M1Ps using a Bayesian hierarchical model. Methods: Cone-beam computed tomography (CBCT) data of M1Ps from 21 countries were analysed. The Vertucci classification was used as the categorical outcome variable. The predictors included tooth side (34/44), voxel size, field of view (FOV), sex and age, with the country modelled as a random intercept. A Bayesian hierarchical multinomial logistic regression was fitted using the brms package (rstan backend) with weakly informative priors. Posterior estimates were expressed as odds ratios (OR) and 95% credible intervals (CrI), and model-based predicted probabilities were computed for each Vertucci type. Results: Bayesian modelling estimated the posterior probability of Vertucci Type I configuration at 73.4% (95% CrI: 63.8%–81.5%). Non–Type I configurations showed lower but credible probabilities, including Type V (8.2%, 3.6%–15.9%), Type III (3.7%, 1.6%–7.7%), Type IV (2.9%, 1.2%–6.3%) and Type II (1.3%, 0.5%–3.1%). Unclassified canal patterns accounted for approximately one-tenth of the MnP1s (9.9%, 3.9%–19.2%). Substantial variability was observed between countries for non–Type I and unclassified configurations, whereas Type I remained consistently predominant. Sex and age exerted modest effects, whereas tooth side and field of view showed no meaningful associations. Increasing the voxel size was associated with a slight reduction in the probability of Type I and marginal increases in Type V and unclassified configurations. Conclusions: Although Vertucci Type I configuration predominates globally in MnP1s, clinically relevant non–Type I and unclassified canal patterns occur with non-negligible frequency and vary across populations. Bayesian hierarchical modelling enables the robust quantification of anatomical heterogeneity and uncertainty, supporting more reliable cross-country comparisons and cautious interpretation of less common canal configurations.
Bayesian hierarchical modelling , cone-beam computed tomography , mandibular first premolar , root canal morphology , Vertucci classification
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Department of Endodontics, Recep Tayyip Erdoğan University, Rize, Turkey
Department of Oral Radiology, Faculty of Dentistry, Necmettin Erbakan University, Konya, Turkey
Department of Conservative Dentistry and Endodontics, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Tamil Nadu, Chennai, India
Department of Odontology, School of Dentistry, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
Faculty of Medicine and Health, Sydney Dental School, The University of Sydney, Camperdown, NSW, Australia
School of Dentistry, Department of Therapeutics Dentistry, Kazakh National Medical University Named After S.D. Asfendiyarov, Almaty, Kazakhstan
Department of Conservative Dentistry, Jordan University of Science and Technology, Irbid, Jordan
Dental Teaching Clinics, Jordan University of Science and Technology, Irbid, Jordan
Department of Endodontics, School of Dentistry, CES University, Medellín, Colombia
Faculty of Dentistry, Tashkent State Medical University, Tashkent, Uzbekistan
Central Interdisciplinary Ambulance in the School of Dentistry, University of Münster, Münster, Germany
Department of Restorative and Aesthetic Dentistry, Faculty of Dentistry, Sanaa University, Sanaa, Yemen
Department of Endodontics, Section of Dental Pathology and Therapeutics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
Endodontic Department of Dentistry, Universidad Central del Ecuador, Quito, Ecuador
Department of Cardiology and Comprehensive Care Dentistry, NYU College of Dentistry, New York, NY, United States
Department of Endodontic and Operative Dentistry, Faculty of Dentistry, Damascus University, Damascus, Syrian Arab Republic
University of Zagreb School of Dental Medicine, Zagreb, Croatia
Department of Restorative Dentistry, National Dental Centre, Singapore, Singapore
Endodontics Department, Faculty of Dentistry, Ibb University, Ibb, Yemen
Division of Oral and Maxillofacial Radiology, University of Mississippi Medical Center School of Dentistry, Jackson, MS, United States
Endodontics and Restorative Dentistry Unit, School of Medicine and Dentistry, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
Department of Diagnostics, Poznan University of Medical Sciences, Poznan, Poland
Department of Conservative Dentistry and Endodontics, University of Benghazi, Benghazi, Libya
Center for Innovation and Research in Oral Sciences (CIROS) and Institute of Endodontics, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
Department of Restorative Dentistry, Recep Tayyip Erdogan University, Rize, Turkey
Department of Endodontics
Department of Oral Radiology
Department of Conservative Dentistry and Endodontics
Department of Odontology
Faculty of Medicine and Health
School of Dentistry
Department of Conservative Dentistry
Dental Teaching Clinics
Department of Endodontics
Faculty of Dentistry
Central Interdisciplinary Ambulance in the School of Dentistry
Department of Restorative and Aesthetic Dentistry
Department of Endodontics
Endodontic Department of Dentistry
Department of Cardiology and Comprehensive Care Dentistry
Department of Endodontic and Operative Dentistry
University of Zagreb School of Dental Medicine
Department of Restorative Dentistry
Endodontics Department
Division of Oral and Maxillofacial Radiology
Endodontics and Restorative Dentistry Unit
Department of Diagnostics
Department of Conservative Dentistry and Endodontics
Center for Innovation and Research in Oral Sciences (CIROS) and Institute of Endodontics
Department of Restorative Dentistry
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