1. Department of Operative Dentistry, Osaka University Faculty of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565, Japan, Department of Oral Biology, The Dental School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4BW, United Kingdom
2. Department of Operative Dentistry, Osaka University Faculty of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565, Japan
3. Dental Materials Science Unit, The Dental School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4BW, United Kingdom
4. Department of Oral Biology, The Dental School, University of Newcastle upon Tyne, Newcastle upon Tyne NE2 4BW, United Kingdom