1. Department of Preventive and Social Dentistry; School of Dentistry, Kyung Hee University; Hoegi-dong, Dongdaemoon-gu Seoul 130-701 Republic of Korea
2. Department of Dental Hygiene; Hanseo University; 360 Daegok-Ri, Haemi-Myun, Seosan-Si Chungnam 356-706 Republic of Korea
3. Tooth and Periodontal Tissue Regeneration (MRC), Department of Maxillofacial Tissue Regeneration, School of Dentistry; Kyung Hee University; Hoegi-dong, Dongdamun-gu Seoul 130-701 Republic of Korea
4. Department of Conservative Dentistry, Hallym Hospital; Hallym University; 896 phyngchondong donganguanyangsi kyunggido South Korea