1Clinical efficacy of characteristic periodontal therapy on advanced periodontitis: a 6-year follow-up case reZHANG Hao-yun, WANG Cui, HU Wen-jieCOLUMN OF CHARACTERISTIC PERIODONTAL THERAPY TO PRESERVE MORE NATURAL TEETH513-5222Restoration of the periodontal health, function and esthetics of a patient with aggressive periodontitis by characteristic periodontal therapy: a 3-year follow-up case reportLIU Qian, FENG Xiang-hui, YU Xiao-qian, HU Wen-jieCOLUMN OF CHARACTERISTIC PERIODONTAL THERAPY TO PRESERVE MORE NATURAL TEETH523-5283Clinical observation of combined periodontal, orthodontic and implant therapy for severe periodontitis: a case report of 5-year follow-upWANG Cui, ZHANG Hao-yun, HU Wen-jie, SHI JieCOLUMN OF CHARACTERISTIC PERIODONTAL THERAPY TO PRESERVE MORE NATURAL TEETH529-538,5454Multidisciplinary treatment of consecutive missing maxillary anterior teeth with severe periodontitis : a case report of 4-year follow-upZHANG Bo, ZHEN Min, YANG Gang, HU Wen-jie, LIU Yun-song, XUN Chun-leiCOLUMN OF CHARACTERISTIC PERIODONTAL THERAPY TO PRESERVE MORE NATURAL TEETH539-5455Research on prediction methods of growth potential of mandibular retromolar region in adolescents based on genetic algorithms optimizationYAN Jing, ZHAO Xue-jiao, YU Miao, WANG Li-yao, LI Zhen-zhen, XU Yi-shan, YANG Lu-yiORIGINAL CONTRIBUTIONS546-550,5546Detection and analysis of the number of bacterial colonies in the air of dental clinic during ultrasonic cleaningXU Xiong-jun, CHEN Xiao-chuan, CHEN Qiong-yu, YUAN JiaORIGINAL CONTRIBUTIONS551-5547Clinical significance of new classification of supernumerary teeth by CBCTSU Sha, ZHAN Li-ping, HE Cai, GAO Run-taoORIGINAL CONTRIBUTIONS555-5588Research progress in traumatic tooth ankylosis of immature permanent teethLYU Li-hua, SU Ji-meiREVIEW559-5639Research progress of 3D printing technology in the field of dental materialsREN Zi-long, ZHOU Chen, WANG Zhong-shanREVIEW564-56910Management of dental caries in childrenLIU Ling, MA Yuan, WANG An-qi, LEI Shuang, CHEN XuNATIONAL HEALTH ASSISTING ALL-ROUND WELL-OFF COLUMN570-573 