Hansen, Tina http://orcid.org/0000-0002-9068-5968
Kjaersgaard, Annette
Article History
Received: 15 January 2020
Accepted: 28 April 2020
First Online: 13 May 2020
Ethics approval and consent to participate
: Since the current study involved a secondary analysis of freely available data, formal ethical approval was not needed. The primary data were collected upon approval by the ethics committee at Nippon Dental University School of Life Dentistry (Approval No. NDU-T2015–46) as described in Igarashi et al. [CitationRef removed].
: Not applicable.
: The authors declare that they have no competing interests.