Funding for this research was provided by:
National Research Foundation of Korea (MSIP no. 2017-0522)
Received: 29 October 2018
Accepted: 24 December 2019
First Online: 29 December 2019
Ethics approval and consent to participate
: Ethics approval was exempted because data were obtained from the plastic model. No of exemption: 2017–0292.
: Not applicable
: The author(s) declare(s) that they have no competing interests.