1. Department of Preventive Dentistry and Public Oral Health; Yonsei University College of Dentistry; Seoul Korea
2. BK 21 PLUS Project; Yonsei University College of Dentistry; Seoul Korea
3. Department of Dental Hygiene; College of Health Science; Gachon University; Incheon Korea
4. Oral Science Research Center; Yonsei University College of Dentistry; Seoul Korea