1. Department of Dental Hygiene, College of Health Sciences, Seongnam Campus, Eulji University, Seongnam, Republic of Korea.
2. Department of Prosthodontics, College of Dentistry, Wonkwang University, Iksan, Republic of Korea.
3. Division of Restorative Science and Prosthodontics, College of Dentistry, The Ohio State University, Columbus, OH, USA.