1. Department of Preventive Dentistry, Kyushu University Faculty of Dental Science, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;
2. Department of Environmental Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and
3. Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan