1. Department of Prosthodontics, Yonsei University College of Dentistry, Seoul, Korea.
2. Department of Dental Biomaterials and Bioengineering, Research Institute of Yonsei University College of Dentistry, Seoul, Korea.
3. Department of Dental Biomaterials, Wonkwang University School of Dentistry, Iksan, Korea.
4. Department of Periodontology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.