1. Department of Periodontics Chang Gung Memorial Hospital Taipei Taiwan
2. Chang Gung University Taoyuan City Taiwan
3. Department of Periodontics and Oral Medicine, School of Dentistry University of Michigan Ann Arbor Michigan USA
4. State Key Laboratory of Oral Diseases National Clinical Research Center for Oral DiseaseDepartment of Prosthodontics, West China Hospital of Stomatology Sichuan University Chengdu China