1. Department of Periodontology, Wonkwang University Daejeon Dental Hospital, Wonkwang University College of Dentistry, Daejeon, Korea.
2. Department of Periodontology, Research Institute for Periodontal Regeneration, Yonsei University College of Dentistry, Seoul, Korea.
3. Department of Health Insurance Research, Ilsan Hospital, National Health Insurance Service, Goyang, Korea.