[1] Hokkaido Univ, Grad Sch Dent Med, Dept Periodontol & Endodontol, Sapporo, Hokkaido 0608586, Japan
[2] Hokkaido Univ, Grad Sch Dent Med, Support Sect Educ & Res, Sapporo, Hokkaido 0608586, Japan
[3] Mitsubishi Gas Chem Co Inc, Tokyo 1258601, Japan
[4] Hokkaido Univ, Grad Sch Dent Med, Dept Biomed Dent Mat & Engn, Sapporo, Hokkaido 0608586, Japan
[5] Fukuoka Dent Coll, Sect Periodontol, Dept Odontol, Fukuoka 8140193, Japan