1 Graduate Institute of Oral Biology, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
2 Graduate Institute of Oral Biology, School of Dentistry, National Taiwan University, Taipei, Taiwan; Department of Dentistry, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: hsinmingchen@hotmail.com.