Text and Data Mining valid from 2019-10-22
Received: 17 June 2019
Accepted: 9 October 2019
First Online: 22 October 2019
Ethics approval and consent to participate
: Approval of the present study was obtained from the institutional review board of Kyushu Dental University (No. 16–6).
: Not applicable.
: The authors declare that they have no competing interests.