Text and Data Mining valid from 2019-09-11
Received: 31 March 2019
Accepted: 22 August 2019
First Online: 11 September 2019
Ethics approval and consent to participate
: This study has been approved by the Ethics Committee of Peking University School and Hospital of Stomatology and was conducted under the guidance of international ethical standards (IRB number: PKUSSIRB-201840168).
: Not applicable.
: The authors declare that they have no competing interests.