1. a Department of Oral Anatomy and Neurobiology , School of Dentistry, Kyungpook National University , 2-188-1 Jung-Gu Samduk-Dong, 700-412, Daegu, Republic of Korea
2. b Department of Dental Hygiene , Daegu Health College , San 7, Taejeon-1Dong, Buk-gu, 702-722, Daegu, Republic of Korea
3. c Department of Dental Hygiene , Dong-Eui University , 995 Eomgwangno, Busan Jin Gu, 614-714, Busan, Republic of Korea
4. d Department of Preventive Dentistry , School of Dentistry, Kyungpook National University , 2-188-1 Jung-Gu Samduk-Dong, 700-412, Daegu, Republic of Korea