1. State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Operative Dentistry and Endodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, P.R. China.
2. Department of Stomatology, Lishilu Outpatient Department, Chinese PLA Second Artillery Corps, Beijing, P.R. China.