1. Department of Community Oral Health, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan
2. Department of Oral Diagnostics, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan
3. Nihon University Dental Hygiene School, School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan
4. Kitahara Gakuin College of Dental Hygiene, Matsudo, Chiba 270–0034, Japan
5. Division of Oral Function and Rehabilitation, Department of Oral Health Science, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan
6. Department of Histology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271–8587, Japan