Revista Portuguesa de Estomatologia, Medicina Dentária e Cirurgia Maxilofacial Review Second root and second root canal prevalence in maxillary frst and second premolars assessed by cone beam computed tomography – a systematic review and meta-analysis Jorge N.R. Martins a,b, *, Duarte Marques a,b,c , Emmanuel João Nogueira Leal Silva d,e , João Caramês a,b,c , António Mata a,c , Marco A. Versiani f a Centro de Estudo de Medicina Dentária Baseada na Evidência, Faculdade de Medicina Dentária, Universidade de Lisboa, Portugal b Instituto de Implantologia, Lisboa c LIBPhys-FCT UID/FIS/04559/2013, Lisboa d Department of Endodontics, School of Dentistry, Grande Rio University, Rio de Janeiro, Brazil e Department of Endodontics, Rio de Janeiro State University, Rio de Janeiro, Brazil f Dental Specialty Center, Brazilian Military Police, Minas Gerais, Brazil a b s t r a c t a r t i c l e i n f o Article history: Received 22 July 2019 Accepted 4 September 2019 Available online 10 September 2019 The aim of this systematic review was to assess the influence of demographic factors (gen- der, 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 refer- ences were screened and the authors contacted. Scientific merit assessment was performed by two independent observers using the Joanna Briggs Institute Critical Appraisal tool. Over- all 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 pre- molars 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 re- vealed significant differences in the primary outcomes. (Rev Port Estomatol Med Dent Cir Maxilofac. 2019;60(x):xxx-xxx) © 2019 Sociedade Portuguesa de Estomatologia e Medicina Dentária. Published by SPEMD. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Keywords: Anatomy Cone-beam computed tomography Maxillary premolar Meta-analysis Systematic review * Corresponding author. E-mail address: jnr_martins@yahoo.com.br (Jorge N.R. Martins). http://doi.org/10.24873/j.rpemd.2019.09.451 1646-2890/© 2019 Sociedade Portuguesa de Estomatologia e Medicina Dentária. Published by SPEMD. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). rev port estomatol med dent cir maxilofac. 2019; 60(x) : xxx-xxx ARTICLE IN PRESS