1Department of Periodontology, College of Dentistry, Seoul National University, Korea.
2Intellectual Biointerface Engineering Center, KOSEF, Korea.
Correspondence author: Chong-Pyoung Chung, Department of Periodontology, College of Dentistry, Seoul National University, 28 Yongon-Dong, Chongno-Ku, Seoul, 110-744, South Korea. Fax: 82-2-744-0051; ccpperio@snu.ac.kr