2.2. Ethical considerations
The study passed ethical review by the Ethics Committee of Stomatological Hospital, Southern Medical University (Approval No: [2021] 43). The study was available on the website of the Chinese Clinical Trials Register (medical research record No: MR-44-22-012947). This study was conducted in accordance with the Declaration of Helsinki. Official permission was obtained from the concerned school authorities before starting the study. Written informed consent was obtained from all parents of the study participants and verbal assent from each child.