Received: 14 May 2019
Accepted: 24 June 2019
First Online: 10 July 2019
Ethics approval and consent to participate
: The study was approved by the Institutional Review Board at the Faculty of Dentistry Mahidol University (MU-DT/PY-IRB 2016/059.0211).
: Not applicable.
: The authors declare that they have no competing interests.