1. General Dentistry and Clinical Education Unit, Faculty of Dentistry & Medical and Dental Hospital, Niigata University , Niigata, Japan
2. Division of Periodontology, Department of Oral Biological Science, Niigata University Graduate School of Medical and Dental Sciences , Niigata, Japan
3. Department of Rheumatology, Niigata Rheumatic Center , Shibata, Japan