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