1. Department of Periodontology; School of Dentistry; Dental Science Institute; Chonnam National University; Gwangju South Korea
2. Department of Preventive Medicine; Medical School; Chonnam National University; Gwangju South Korea
3. Jeonnam Regional Cancer Center; Chonnam National University Hwasun; Hwasun South Korea
4. Department of Preventive Medicine; Chungnam National University College of Medicine; Daejeon South Korea
5. Department of Epidemiology; Graduate School of Public Health; University of Pittsburgh; Pittsburgh USA
6. Department of Oral Pathology; School of Dentistry; Dental Science Institute; Chonnam National University; Gwangju South Korea