1. Department of Operative Dentistry and Endodontics, Iwate Medical University, School of Dentistry, 1-3-27, Chuo-douri, Morioka 020-8505, Iwate, Japan;
2. Department of Dental Materials Science, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu 061-0293, Hokkaido, Japan
3. Division of Pediatric Dentistry, Hokkaido University, Graduate School of Dental Medicine, Kita 13, Nishi 7, Kita-ku, Sapporo 060-8586, Hokkaido, Japan
4. Division of Cariology and Endodontology, Hokkaido University, Graduate School of Dental Medicine;