Received: 11 May 2021
Accepted: 16 November 2021
First Online: 15 December 2021
: For both surveys, ethical approval was obtained from the Ethics Committee of the Chinese Stomatological Association. Written informed consent was obtained from the children’s parents or guardians prior to the implementation of data collection. All methods were carried out in accordance with relevant guidelines and regulations.
: Not applicable.
: The authors declare that they have no competing interests.