Prevalence and morphological types of middle mesial canals in mandibular molars according to the Barros-Costa classification: a CBCT study in a Turkish subpopulation

OBJECTIVE: The purpose of this study was to assess the prevalence and configurations of middle mesial canals (MMCs) in a Turkish subpopulation using cone-beam computed tomography (CBCT) according to the Barros-Costa classification. MATERIALS AND METHODS: Two experienced endodontists assessed the prevalence of MMCs in mandibular molars of 213 Turkish patients aged 18-65 years (111 females, 102 males). MMCs were categorized using the Barros-Costa classification based on their association with the mesiobuccal and mesiolingual canals using CBCT scans in all three planes. Chi-square and Fisher's exact tests were used for unadjusted comparisons (p < 0.05). A multivariable generalized estimating equations (GEE) model with patient ID as the clustering variable was used to assess the associations between MMC presence and tooth type, age, and sex. RESULTS: Of 589 mandibular molars evaluated, 12.4% had an MMC. Distribution was: mesiolingual confluent (43.8%), mesiobuccal confluent (24.7%), independent (23.3%), and confluent (8.2%). MMCs were significantly more frequent in mandibular first molars (20.6%) than in second molars (6.6%) (p < 0.001). The most frequently observed MMC type was the mesiolingual confluent. In the multivariable GEE analysis, mandibular first molars had significantly higher odds of presenting an MMC than second molars (adjusted odds ratio = 3.54, 95% confidence interval: 2.16-5.80, p < 0.001), whereas age and sex were not significantly associated with MMC presence. CONCLUSIONS: Within the examined single-center Turkish subpopulation and under the specific CBCT acquisition protocol used, MMCs were detected more frequently in mandibular first molars than in second molars. The mesiolingual confluent configuration was the most frequently observed morphological type. These findings highlight the anatomical variability of MMCs and support careful assessment of the mesial root canal system during endodontic treatment.