1. Department of Prosthodontics, State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Disease, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
2. Department of Stomatology, Chengdu Second People’s Hospital, Chengdu, China.
3. Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI.