1. State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Operative Dentistry & Endo-dontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, PR China, Department of Endodontics, Xiamen Stomatological Hospital, Xiamen Medical Colleage, Xiamen, Fujian
2. Institution of Stomatology, The PLA General Hospital, Beijing, P.R. China
3. State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Operative Dentistry & Endo-dontics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, PR China
4. State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Dis-eases & Shaanxi Key Laboratory of Stomatology, Department of Operative Dentistry & Endodon-tics, School of Stomatology, Fourth Military Medical University, Xi'an, Shaanxi, PR China