Received: 24 March 2018
Accepted: 26 November 2018
First Online: 4 December 2018
Ethics approval and consent to participate
: This study was approved by the Hiroshima University Epidemiological Studies Ethics Committee. Written informed consent was obtained from all dental trainees enrolled in this study. Before collecting portfolio data, all participants were informed that their comments would be kept anonymous and used for research purposes only.
: Not applicable.
: The authors declare that they have no competing interests.
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