1. Division of Oral Bioengineering; Institute of Medicine and Dentistry, Niigata University; Niigata 951-8514 Japan
2. Department of Materials Science and Technology; Niigata University; Niigata 950-2181 Japan
3. Division of Periodontology, Institute of Medicine and Dentistry; Niigata University; Niigata 951-8514 Japan
4. Institute of Research Collaboration and Promotion; Niigata University; Niigata 950-2181 Japan
5. Department of Mechanical and Control Engineering; Niigata Institute of Technology; Kashiwazaki 945-1195 Japan