Prevalence of radix molaris in mandibular molars of a Portuguese subpopulation

Abstract

Objectives: To evaluate the prevalence of radix molaris in mandibular first and second molars in a Portuguese subpopulation using cone-beam computed tomography and to characterize its anatomical features. Methods: This retrospective cross-sectional study included 505 cone-beam computed tomography scans comprising 1641 mandibular molars (776 first and 865 second molars). Based on tooth morphology assessment, the presence of radix molaris, its subtype (entomolaris or paramolaris), associated tooth, location, and patient sex were recorded. Main analyses used generalized estimating equations with an exchangeable correlation matrix to control for patient-level clustering. For the affected subsample (n = 18), data were aggregated per patient and evaluated using exact tests. Statistical significance was set at p < 0.05. Results: The overall tooth-level prevalence of radix molaris was 1.34% (95% confidence interval: 0.87–1.99). Radix entomolaris was the predominant subtype (1.16%), whereas radix paramolaris was rare (0.18%). Radix molaris was descriptively more frequent in mandibular first molars than in second molars. Type AC morphology and Type I curvature were the most frequent patterns among radix entomolaris cases. No significant associations were found between the presence of radix molaris and sex or molar type in the adjusted analysis (p > 0.05). Conclusions: Radix molaris was an uncommon anatomical variation in this Portuguese clinical subpopulation, with radix entomolaris as the predominant subtype. Although more frequently observed in mandibular first molars, no significant association with molar type was found. Recognition of this variation is clinically important to reduce the risk of missed canals and endodontic treatment failure.