1. Department of Oral and Maxillofacial Pathology, Institute of Oral Biology, Kyung Hee University School of Dentistry, Seoul, Korea.
2. Department of Dental Materials, Kyung Hee University School of Dentistry, Seoul, Korea.
3. Department of Biomaterials and Prosthodontics, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Dentistry, Seoul, Korea.