1. Department of Periodontology; School of Dentistry; Kyungpook National University; Daegu Korea
2. Department of Oral Microbiology; School of Dentistry; Kyungpook National University; Daegu Korea
3. Faculty of Health Science; Daegu Haany University; Gyeongsan Korea
4. Department of Metals, Institute of Biomaterials & Bioengineering; Tokyo Medical & Dental University; Tokyo Japan