1. Department of Endodontics & Operative Dentistry and
2. Department of Biomaterials Science, Baylor College of Dentistry, Texas A & M University, Dallas, Texas, U.S.A. and
3. Present address: Department of Dental Materials Science, School of Dentistry, Meikai University, Saitama, Japan
4. Department of General Dentistry, Asahi University, School of Dentistry, Gifu, Japan,
5. Japan Institute of Advanced Dentistry, Osaka, Japan,