1Department of Periodontology, College of Dentistry, Chonnam National University, Korea.
2Dental Science Research Institute, Chonnam National University, Korea.
Corresponding author: Ok-Su Kim, Department of Periodontology, College of Dentistry, Chonnam National University, 5, Hakdong, Donggu, Gwangju, 501-757, Korea. periodrk@jnu.ac.kr