1. Department of Dental Hygiene, Tokyo Dental Junior College, 2-9-18 Misakicho Tokyo, Chiyoda-Ku 101-0061, Japan
2. Kobayashi Dental Clinic, Tokyo, Japan
3. Department of Oral Health and Clinical Science, Division of Dysphagia Rehabilitation, Tokyo Dental College, 2-9-18 Misakicho Tokyo, Chiyoda-Ku 101-0061, Japan
4. Division of General Dentistry, Division of Dysphagia Rehabilitation, Chiba Dental Center, Tokyo Dental College, 1-2-2 Masago Mihama-Ku, Chiba 261-8502, Japan