Funding for this research was provided by:
Training Project for Young Backbone Talents in Fujian Health System (2015-ZQN-ZD-27)
Text and Data Mining valid from 2019-11-14
Received: 24 July 2019
Accepted: 4 November 2019
First Online: 14 November 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.10). 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 to participate in the study.
: Not applicable.
: The authors declare that they have no competing interests.