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. 2018 Dec 27;4(1):e000468. doi: 10.1136/bmjsem-2018-000468

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© Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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Selection of the studies surveyed in the electronic databases and grey literature. Preferred Reporting Items for Systematic Reviews and Meta-Analyses algorithm. BBO, Biblioteca Brasileira de Odontologia (Brazilian Library of Dentistry); IBECS, Índice Bibliográfico Espanhol em Ciências da Saúde (Spanish Bibliographic Index in Health Sciences).