1. Division of Orthodontics, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan
2. Division of Preventive Dentistry, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan
3. Medical Support Center, Dental Hygienist Section, Medical and Dental Hospital, Niigata University, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan