1. Department of Periodontology, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
2. College of Medicine, Chang Gung University, Taipei, Taiwan.
3. California Northstate University, College of Medicine, Elk Grove, Calif.
4. Department of Prosthodontics, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan.
5. Department of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan.