Funding for this research was provided by:
National Natural Science Foundation of China (81670988)
Science and Technology Planning Project of Shannxi Province, China (2020SF-013)
Received: 16 June 2020
Accepted: 4 November 2020
First Online: 10 November 2020
Ethics approval and consent to participate
: This study was approved by the institutional research ethics committee at the Stomatological Hospital of the Fourth Military Medical University, China (No. IRB-REV-2018044). The children’s parents/guardians were informed about the purpose of the study and inclusion of the extracted teeth in the research and provided informed consent in written format.
: Not applicable.
: The authors declare that they have no competing interests.