1. Department of Periodontology Veterans Health Service Medical Center Seoul Republic of Korea
2. Department of Prosthodontics Veterans Health Service Medical Center Seoul Republic of Korea
3. Research Institute of Veterans Health Service Medical Center Seoul Republic of Korea
4. Department of Periodontology, Daejeon Dental Hospital Wonkwang University Daejeon Republic of Korea
5. Department of Periodontology, School of Dentistry Wonkwang University Iksan Republic of Korea