1New concept of tooth extractionLIU Chuan, LI Deng-ke, ZHANG Wu-yang, LIU Ping, WANG Xin, HU Kai-jin, XUE YangSYMPOSIUM645-6492New techniques for tooth extractionLI Yuan, ZHANG Wu-yang, DENG Tian-ge, HU Kai-jin, XUE YangSYMPOSIUM650-6543New tools for tooth extractionLI Guo-wei, MO Jing-zhen, ZHANG Shu-yin, XUE Yang, HU Kai-jinSYMPOSIUM655-6594New materials for tooth extractionMA Yang, ZHOU Hong-zhi, ZHANG Ze-wei, XUE Yang, HU Kai-jinSYMPOSIUM660-6635"Tao" and "Guide" in the teaching of periodontal preclinical trainingYANG Gang, ZHONG Jin-sheng, HU Wen-jie, LIU JianCOLUMN OF STOMATOLOGY EDUCATION AND RESEARCH664-6676Evaluation and analysis of the teaching effect of the periodontal preclinical practice course based on question-nairesWANG Cui, ZHANG Hao-yun, HU Wen-jie, ZHANG Yan-ling, YANG Ting, LIU JianCOLUMN OF STOMATOLOGY EDUCATION AND RESEARCH668-6717Application of 3D printed personalized model combined with digital surgical guide plates in clinical teaching of the completely impacted teeth extractionCHENG Gu, ZHOU Hai-hua, YANG Rong-tao, LYU Kun, LI Zu-bing, LI ZhiCOLUMN OF STOMATOLOGY EDUCATION AND RESEARCH672-6768Study on the effects of a following-up-cases teaching model in developing mind-set of undergraduate students of stomatologyLU Hong, HOU Meng-jie, LI Rui, TANG Xiao-lin, PAN Chun-ling, WANG Hong-yanCOLUMN OF STOMATOLOGY EDUCATION AND RESEARCH677-6809Effect of root canal preparation on dentinal crack formation using different Ni-Ti file systemsZHOU Yi-jia, MA Hong-tao, ZHU Ya-qinORIGINAL CONTRIBUTION681-685,69210Bactericidal effect of ultrasound,sonic device,and laser radiation on root canal irrigation in root infection mod-el in vitroMEI Xiao-han, LIU Jin, CHENG Xiao-gang, FAN Xiao-min, YOU Su-xia, TAN Min-juan, QIU Jun, ZHANG Ya-qingORIGINAL CONTRIBUTION686-69211Effect of permeable resin on microleakage of resin filling body after enamel edge bleachingZHANG Di, LI Min, LIU JinORIGINAL CONTRIBUTION693-69612Plaque removal effect of four sandblasting powders and their influence on the microstructure of tooth enamelLIU Ying, SUN Shang-min, LIU Zhao-gang, WANG Qiang, ZHAN De-songORIGINAL CONTRIBUTION697-70213Effect of five polishing medthods on surface roughness of glass ceramicsZHANG An-ling, QIU Sha, ZHANG Xiu-meiORIGINAL CONTRIBUTION703-70614Retrospective analysis of 66127 pediatric dental emergency casesSHEN Ye-qing, LIU Yi, ZHOU Zhuo-jun, LIAO QianORIGINAL CONTRIBUTION707-71015Comparative study on the effect of different expansion approaches on hard and soft tissues and the position of permanent incisor germs in children with deciduous anterior crossbiteLIU Ya-fei, ZUO Yan-ping, LIU Xin, ZHAO Li-xia, WEI Jing, ZHANG Chao, GUAN Xiu-juanORIGINAL CONTRIBUTION711-71816Study on the characteristics and relationship of morphology of mandibular symphysis and lower incisor angula-tion and position in different sagittal skeletal typesCHENG Jia-xiu, YANG Tong-tongORIGINAL CONTRIBUTION719-72217Efects of accelerated orthodontic tooth movement on external apical root resorption:a Meta-analysisYANG Xin-wei, AN Ran, LEI LangORIGINAL CONTRIBUTION723-72718Research progress in the strategy to promote periodontal healing after delayed replantation of avulsed teethDI Tian-kai, CHEN Yu-jiang, WANG Lu-lu, LIU Jia-jia, JIANG Yu-ran, WANG Xiao-jingREVIEW728-73319Research progress on the risk factors of root caries in the elderlyLI Guo, CHENG Xing-qun, WU Hong-kunREVIEW734-738,74420Research progress in 3D printing ceramic technology in stomatologyZHAO Zhen, DAI Kang, GAO BoREVIEW739-744 