Funding for this research was provided by:
Fundamental Research Funds for the Central Universities (#SWU1809103)
Chongqing Social Science Planning Project (#2019PY57)
Text and Data Mining valid from 2020-03-30
Received: 15 October 2019
Accepted: 19 March 2020
First Online: 30 March 2020
Ethics approval and consent to participate
: This study was approved by the ethical review board of the Stomatological Hospital of Chongqing Medical University, China. Before each assessment, an assent form was obtained from the subject and additional signed consent form was obtained from one of the subject’s parents.
: Not applicable.
: The authors declare that they have no competing interests.