**2. Materials and Methods**

#### *2.1. Ethics*

The guidelines in the Helsinki Declaration were followed in this investigation. This study was approved by the Institutional Review Board of the School of Dentistry, Kyung Hee University (KHDIRB1606-6). The participants were recruited from patients in the Department of Pediatric Dentistry, School of Dentistry, Kyung Hee University. Written consent for participation in the study was obtained from the parent and child.
