[1] Department of Dentistry for Children and Disabled Persons, Graduate School of Dental Medicine, Hokkaido University, Kita 13 Nishi 7, Kita-ku, Sapporo 060-8586, Japan
[2] Department of Life and Environmental Sciences Design, Chiba Institute of Technology, Narashino, Japan
[3] Department of Dental Materials and Engineering, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan