1. Department of Conservative Dentistry, Kyung Hee University Dental Hospital, Seoul, Korea;
2. Department of Dentistry, Naval Medical Center, ROK Navy, Jinhae, Korea;
3. Department of Conservative Dentistry, Graduate School, Kyung Hee University, Seoul, Korea;
4. Department of Conservative Dentistry, School of Dentistry, Kyung Hee University, Seoul, Korea