Influence of Demographic Factors on the Prevalence of a Second Root Canal in Mandibular Anterior Teeth – A Systematic Review and Meta-Analysis of Cross-Sectional Studies Using Cone Beam Computed Tomography

•Males showed higher odds of having a second root canal in mandibular incisors.•Geographic region seemed to influence lower incisors second root canal prevalence.•Asians seemed to present lower proportion of mandibular incisors second root canal.•Age and voxel size appear not to influence the second root canal prevalence.•Knowing these preoperative factors may help to anticipate complex morphologies. The purpose of this systematic review was to assess the influence of population demographic characteristics on the prevalence of a second canal in mandibular anterior teeth. Four electronic databases and five peer-reviewed journals were searched from May 2018 to September 2019 for prevalence studies using cone-beam computed tomographic imaging on second canal morphology in mandibular anterior teeth. The identified studies were subjected to a hand search of bibliographic references followed by contact with the authors. Full text analysis and critical appraisal (JBI) was undertaken on 40 papers by 2 evaluators. Sixteen studies were included into a meta-analysis. Forest plots with proportion and odds ratios with a 95% confidence interval were calculated. Meta-regression was performed in order to identify possible sources of heterogeneity. The 16 selected studies presented an average JBI score of 77.7% and revealed data from 40,784 mandibular anterior teeth (14,278 central incisors, 14,433 lateral incisors, and 12,073 canines). The overall prevalence of a second canal for central incisors, lateral incisors and canines was 20.4% (15.0%-25.7% CI 95%), 25.3% (20.0%-30.7% CI 95%) and 5.9% (4.1%-7.7% CI 95%), respectively. Males showed significantly higher odds of having a second canal for both incisors (p