Second root and second root canal prevalence in maxillary first and second premolars assessed by cone beam computed tomography – a systematic review and meta-analysis

The aim of this systematic review was to assess the influence of demographic factors (gender, geographic region and age) on the prevalence of a second root and a second root canal in the maxillary first and second premolars by means of cone beam computed tomography. Four electronic databases and five peer-review journals were evaluated. Bibliographic references were screened and the authors contacted. Scientific merit assessment was performed by two independent observers using the Joanna Briggs Institute Critical Appraisal tool. Overall proportions and odds ratio forest plot were calculated and meta-regression performed to assess study heterogeneity. The review methodology protocol was registered before the study in PROSPERO. Nine studies were selected and data from 8,180 teeth (4,230 first premolars and 3,950 second premolars) were evaluated. The global proportion of a second root and second root canal were 43.2% and 77.2% for the first premolar, and 8.5% and 43.9% for the second. Tooth type, gender and geographic region in a comparison between groups revealed significant differences in the primary outcomes.