[1] Hiroshima Univ, Grad Sch Biomed & Hlth Sci, Dept Oral Epidemiol, 1-2-3 Kasumi,Minami Ku, Hiroshima, Hiroshima 7348553, Japan
[2] Hiroshima Univ, Grad Sch Biomed & Hlth Sci, Dept Publ Oral Hlth, 1-2-3 Kasumi,Minami Ku, Hiroshima, Hiroshima 7348553, Japan
[3] Tokuyama Cent Hosp, Div Dent & Oral Surg, Community Hlth Care Org, 1-1 Kodacho, Yamaguchi 7450822, Japan
[4] Nagoya Univ, Grad Sch Med, Dept Prevent Med, 65 Tsurumaicho,Showa Ku, Nagoya, Aichi 4668550, Japan