1 Department of Physiology, Tokyo Dental College, Tokyo, Japan.
2 Department of Clinical Sciences and Stomatology, Polytechnic University of Marche, Ancona, Italy.
3 Brodie Tooth Development Genetics and Regenerative Medicine Research Laboratory, College of Dentistry, University of Illinois at Chicago, Chicago, IL, United States.
4 Department of Periodontal Medicine, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.