1. Department of Periodontology, School of Dentistry, Kyung Hee University, Seoul, South Korea.
2. Private practice, Seoul, Korea.
3. Department of Periodontology, Divisions of Dentistry, Hanyang University, College of Medicine, Seoul, Korea.
4. Division of Periodontics, Section of Oral and Diagnostic Sciences, Columbia University, College of Dental medicine, New York, NY.