1. Department of Dental Hygiene, Kangwon National University, Samcheok, Republic of Korea
2. Department of Preventive Dentistry and Public Oral Health, Research Center for Orofacial Hard Tissue Regeneration, College of Dentistry, Yonsei University, Seoul, Republic of Korea
3. Department of Dental Hygiene, Cheongju University, Cheongju, Republic of Korea
4. Pediatric Dentistry, College of Dentistry, Wonkwang University, Sanbon 435-040, Republic of Korea