1. Department of Dental Biomaterials and Institute of Biodegradable Materials, Institute of Oral Bioscience and School of Dentistry (Plus BK21 Program), Chonbuk National University, Jeon Ju 561-756, South Korea
2. Department of Orthopedic Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Chonbuk National University Medical School, Jeon Ju 561-756, South Korea