根尖双分叉和delta是尖部根管系统的两种变异形态。感染根管的根尖双分叉和delta内含有大量的微生物，能逃避根管的机械清理并抵抗药物的杀菌作用，是根尖周持续感染的重要原因。准确了解根尖双分叉和delta的形态特征，研究可进入该区域并能杀灭微生物的药物可有效控制该区域感染。申请人前期已成功构建恒牙根管形态数据库，发现钙硅纳米介孔材料(MCSNs)在超声驱动下能进入牙本质小管和3D打印树脂牙的根尖双分叉和delta内。同时，亲水硅烷季铵盐K21具有低毒且高效的抗菌作用，可通过混合-耦合法结合到MCSNs上。基于以上认识，申请人拟在所建数据库的基础上，研究根尖双分叉和delta的形态特征，合成含K21的MCSNs，筛选其进入根尖双分叉和delta的有效模式，并在体内外评价其对该区域内粪肠球菌感染控制的效果。有望形成一种渗透性和生物相容性好，抗菌性强的根尖双分叉和Delta内感染控制新材料。

Apical bi-furcation and delta are two anatomic variations of apical root canal system. The infected bi-furcation and delta area always contain a large amount of infectious bacteria which can escape the canal mechanical debridement and resist the bactericidal effects of intra-canal medication, constituting an important reason for the persistent apical inflammation. Precise information of the 3-dimensional (3D) anatomic features of apical bi-furcation and delta area and looking for medications capable of eliminating bacteria in this area would help the infection control in the area. The early-stage studies of this project have successfully established a database of root canals in permanent teeth and also revealed that the calcium-silicate mesoporous nano-particles (MCSNs) could infiltrate into dentinal tubules and bi-furcation and delta area of 3D printed resin teeth by ultrasound activation. Meanwhile, the hydrophilic quaternary ammonium silane K21 is found to be low-toxic and effective in its anti-bacterial ability, and could be incorporated into MCSNs particles by a mixing-coupling method. Based on these information, the main purposes of this project are to systemically investigate the 3D anatomy and related variation features of apical bi-furcation and delta area based on the established database, synthesize K21-loaded MCSNs particles (Q-MCSNs), determine the effective method for the Q-MCSNs to infiltrate into the bi-furcation and delta by ultrasound and evaluate its ability in the E. facaelis infection control of apical bi-furcation and delta area both in vitro and in vivo. This project could possibly lead to a new effective anti-bacterial material with high infiltration ability and biocompatibility for the infection control in the bi-furcation and delta area.