1. Department of Operative Dentistry, Asahi University, School of Dentistry, 1851, Hozumi, Hozumicho, Motosugun, Gifu 501-02, Japan
2. Department of Endodontics, Asahi University, School of Dentistry, 1851, Hozumi, Hozumicho, Motosugun, Gifu 501-02, Japan