1. Department of Prosthodontics Asan Medical Center, College of Medicine, University of Ulsan Seoul Korea
2. Department of Advanced Periodontics University of Southern California Los Angeles CA USA
3. Department of Preventive Medicine & Public Health College of Medicine, Yonsei University Seoul Korea
4. Department of Oral and Maxillofacial Surgery Asan Medical Center, College of Medicine, University of Ulsan Seoul Korea