Objective: To determine the frequency and anatomical configuration of Radix entomolaris and Radix paramolaris in mandibular molars using cone-beam computed tomography (CBCT).

Methods: A quantitative, observational, descriptive, cross-sectional, retrospective study was conducted. A total of 750 anonymized tomographic records from adult patients treated at a radiology center in Quito, Ecuador, were analyzed. Multiplanar assessment included permanent mandibular molars and recorded sex, age group, laterality, number of roots and canals, internal configuration according to Vertucci, and three-dimensional root morphology. Frequencies, percentages, and 95% confidence intervals were calculated; associations with sex and age were explored using the chi-square test, with α = 0.05.

Results: Radix entomolaris was identified in 44 of 750 cases (5.9%; 95% CI: 4.4-7.8), whereas no cases of Radix paramolaris were observed. The frequency was 5.9% in both men and women and was not associated with sex (χ² = 0.00006; p = 0.994) or age group (χ² = 1.654; p = 0.647). Among positive cases, 29 were unilateral (65.9%) and 14 bilateral (31.8%); 44 had three roots and four canals, all coded records corresponded to Vertucci Type I, and 43 accessory roots were separate (97.7%).