1. Department of Periodontology, Daejeon Dental Hospital, Institute of Wonkwang Dental Research, Wonkwang University College of Dentistry, Daejeon, Korea.
2. Department of Periodontology, Ilsan Hospital, National Health Insurance Service, Goyang, Korea.
3. Department of Periodontology, Gangneung-Wonju National University College of Dentistry, Gangneung, Korea.