1. Department of Periodontics and Oral Medicine; University of Michigan School of Dentistry; Ann Arbor Michigan
2. State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Disease, Department of Prosthodontics, West China Hospital of Stomatology; Sichuan University; Chengdu People's Republic of China
3. Department of Stomatology; The First Affiliated Hospital of Zhengzhou University; Zhengzhou Henan People's Republic of China