Objective: To assess the influence of cone-beam computed tomographic (CBCT) voxel size and population demographic aspects (age, gender and geographic region) on the prevalence of the second mesiobuccal root canal (MB2) in maxillary first and second molars.
Design: Prevalence studies using CBCT technology on MB2 canal were searched between May and September 2019. The protocol was registered in PROSPERO. Four electronic databases and 5 peer-reviewed endodontic journals were screened. Authors were contacted and bibliographic references hand-searched. Eighty three studies were submitted to full text analysis and scientific merit evaluation by 2 evaluators using Joanna Briggs Institute Critical Appraisal tool. Twenty six studies were finally pooled into a meta-analysis. Forest plots with a 95% confidence interval were undertaken. Meta-regression was used to identify possible sources of heterogeneity and funnel plot visual analysis to assess publication bias.
Results: The 26 studies reported anatomical data from the mesiobuccal root of 15,285 first molars and 8,641 second molars. Pooled prevalence of MB2 canal was higher in maxillary first molar (69.6%; 64.5%-74.8%) than in second molars (39.0%; 31.1%-46.9%) (p < 0.05). A significantly higher prevalence odds of having MB2 canal was detected in males (p < 0.05). Meta-regression excluded gender, age and voxel size as a source variance, but identified tooth group and geographic region as possible sources of heterogeneity.
Conclusion: MB2 canal prevalence was significantly higher in maxillary first molars. Males showed higher odds of having MB2 canal than females. Geographic region seemed to influence MB2 prevalence outcome. Knowing these preoperative factors would help to anticipate MB2 morphologies in clinics.
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