1. Department of Dental Hygiene, Kyung-Woon University, Gumi 39160, Korea
2. Department of Dental Hygiene, Dong-Eui University, Busan 47340, Korea
3. Department of Dental Hygiene, Ulsan College, Ulsan 44022, Korea
4. Department of Clinical Laboratory Science, Dong-Eui University, Busan 47340, Korea