1. Department of Operative Dentistry, Faculty of Dentistry, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan
2. Department of Operative Dentistry, Hokkaido University, School of Dentistry, Kita 13, Nishi 7, Kita-ku, Sapporo 060-0813, Japan
3. School of Dental Science, University of Melbourne, 711 Elizabeth Street, Melbourne, Victoria 3000, Australia
4. Department of Oral Biology and Physiology, School of Dentistry, Medical College of Georgia, Augusta, Georgia 30912-1129, USA