1. Department of Oral Medicine & Oral Diagnosis, School of Dentistry & Dental Research Institute, Seoul National University, Daehak-Ro 101, Jongno-Gu, Seoul, 110-744, Korea (ROK);
2. Clinic of Masticatory Disorders, Removable Prosthodontics, Geriatric and Special Care Dentistry, Center of Dental Medicine, University of Zürich, Plattenstrasse 11, CH-8032, Switzerland