Received: 23 December 2020
Accepted: 11 March 2021
First Online: 27 March 2021
: The study was approved by the Ethics Committee at the School of Stomatology, the Fourth Military Medical University. All participants gave informed consent. This retrospective study involved no more than minimal risk to subjects, did not adversely affect the rights and welfare of subjects, contributed to greater public good, and could not practically be carried out otherwise.
: Informed consent for publication was obtained from all participants.
: There are no actual or potential conflict of interest needs to be disclosed, including any financial, personal or other relationships with other people or organizations that could inappropriately influence, or be perceived to influence, their work.