Funding for this research was provided by:
National Natural Science Foundation of China (No.81771126)
Fujian provincial healthy and family planning commission program (No.2015-CX-30)
Science Foundation of Fujian Province (2019J01319)
Text and Data Mining valid from 2019-12-01
Received: 27 September 2019
Accepted: 22 November 2019
First Online: 2 December 2019
Ethics approval and consent to participate
: The study protocol was evaluated and approved by the Institutional Ethics Committee of the School of Stomatology, Fujian Medical University (Ref.  NO.103). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All patients provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.