Study Design, Population and Sample
This study conservatively estimated caries prevalence in IDC to be 50.0%. Standard error was set at 5.0%, and the response rate was assumed to be 90.0%. At least 427 children were needed for study validity.
Our study was reviewed and approved by the Ethical Review Committee of the Institute of Stomatological Research, Sun Yat-Sen University, before the study began. The approval number is ERC-2012-028.
The present cross-sectional study was conducted among individuals from special educational schools in Guangzhou in March and April of 2013. Stratified by the numbers of schools and of the IDC enrolled, a representative sample of 6 special educational schools with 551 children was randomly selected. Schoolchildren were selected if they met the inclusion and didn’t have any exclusion criteria. They were included if they were aged between 12 and 17 years old and had a clinical diagnosis of intellectual disability based on the criteria and classification established by Standardization Administration of the People’s Republic of China [14], as registered in their medical records. We excluded children from the study for the reason that their parents refused to allow them to undergo the dental examination. The parents of each child were contacted and informed in writing about the study design and dental examination proposed for their children. If they agreed to have their children participate in the survey, a document of informed consent was voluntarily signed by the parents. In total, 477 IDC were recruited in the final sample.