1. Department of Biomaterials, Okayama University Dental School, 2-5-1 Shikata, Okayama, 700-8525, Japan
2. Department of Dental Materials, School of Dentistry at Matsudo, Nihon University, 870-1 Sakaecho, 2-Nishi, Matsudo, Chiba, 271-8587, Japan
3. Department of Operative Dentistry, Okayama University Dental School, 2-5-1 Shikata, Okayama, 700-8525, Japan