1. Interdisciplinary Program of Bioengineering; College of Engineering; Seoul National University; Seoul 152-742 Korea
2. Department of Materials Science and Engineering; Hanyang University; Seoul 133-791 Korea
3. Department of Dental Biomaterials Science; Dental Research Institute and BK21 HLS; School of Dentistry; Seoul National University; Daehakro 101 Jongno Seoul 110-749 Korea