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Cone-beam computed tomographic analysis of middle mesial canals and isthmus in mesial roots of mandibular first molars-prevalence and related factors

Context: The internal anatomy of mandibular first molars has been studied in depth in different populations. However, limited information is present in differentiating a true middle mesial (MM) canal from an isthmus. Aims: The primary aim of this study was to identify the prevalence of a true MM canal and isthmus by retrospectively analyzing cone-beam computed tomography (CBCT) images in vivo. The secondary aim was to determine any correlation between related factors such as sex and age. Materials and Methods: CBCT images of 130 patients with the age group of 13–70 years were selected. Findings of MM canals and isthmus were recorded along with variables such as age and sex. Prevalence was compared using the Chi-square test (P < 0.05). Results: Out of 143 mandibular first molars, the prevalence of the MM canal was 18.2%. There was no statistically significant difference between sex and prevalence of the MM canal and isthmus. The prevalence of isthmi in the mesial roots was 78.4%. Their presence was significantly higher in the apical third area (37.1%) (P < 0.05). Both MM canal and isthmus were seen significantly higher in the age group of 31–50 years (P < 0.05). Conclusions: This study showed a high prevalence of MM canals (18.2%) and isthmus (78.4%). The prevalence of the MM canal and isthmi was significantly higher in the middle age groups. This knowledge may direct the clinicians in locating them leading to good endodontic prognosis.