目的: 用梯度离心法构建粪肠球菌牙本质小管感染模型, 评价新型低温等离子体设备对牙本质小管内粪肠球菌的抗菌效果。方法: 选用无龋坏单根管离体牙制备4 mm×4 mm×2 mm标准牙本质块, 置于粪肠球菌菌液中, 梯度离心后培养24 h, 用于构建牙本质小管粪肠球菌感染模型, 将20个粪肠球菌牙本质小管感染样本随机平均分为5组: 低温等离子体射流处理0、5、10 min组, 氢氧化钙糊剂封药7 d组, 2%(质量分数)氯己定凝胶封药7 d组。用扫描电镜和激光共聚焦显微镜评估牙本质小管内感染情况, 并评价低温等离子体的抗菌效果。结果: 扫描电镜和激光共聚焦显微镜结果表明, 利用梯度离心法, 培养24 h后, 粪肠球菌可以充分进入牙本质小管, 深度超过600μm, 能够成功构建粪肠球菌感染牙本质小管模型; 低温等离子体能够进入牙本质小管中发挥作用, 经过10 min的低温等离子体处理, 牙本质小管内绝大多数粪肠球菌被杀灭, 效果超过氢氧化钙糊剂封药7 d以及2%氯己定凝胶封药7 d。结论: 梯度离心法能够有效建立粪肠球菌牙本质小管感染模型, 低温等离子体能够在10 min内有效杀灭牙本质小管中的粪肠球菌, 优于氢氧化钙糊剂封药7 d和2%氯己定凝胶封药7 d。

Objective: To construct a model of Enterococcus faecalis (E. faecalis) infection in dentinal tubules by gradient centrifugation and to evaluate the antibacterial effect of low-temperature plasma on E. faecalis in dentinal tubules. Methods: Standard dentin blocks of 4 mm×4 mm×2 mm size were prepared from single root canal isolated teeth without caries, placed in the E. faecalis bacterial solution, centrifuged in gradient and incubated for 24 h to establish the model of dentinal tubule infection with E. faecalis. The twenty dentin blocks of were divided into five groups, low-temperature plasma jet treatment for 0, 5 and 10 min, calcium hydroxide paste sealing for 7 d and 2% chlorhexidine gel sealing for 7 d. Scanning electron microscopy and confocal laser scanning microscope were used to assess the infection in the dentinal tubules and the antibacterial effect of low-temperature plasma. Results: The results of scanning electron microscopy and confocal laser scanning microscopy showed that after 24 h of incubation by gradient centrifugation, E. faecalis could fully enter the dentinal tubules to a depth of more than 600μm indicating that this method was time-saving and efficient and could successfully construct a model of E. faecalis infection in dentinal tubules. Low-temperature plasma could enter the dentinal tubules and play a role, the structure of E. faecalis was still intact after 5 min of low-temperature plasma treatment, with no obvious damage, and after 10 min of low-temperature plasma treatment, the surface morphology of E. faecalis was crumpled and deformed, the cell wall was seriously collapsed, and the normal physiological morphology was damaged indicating that the majority of E. faecalis was killed in the dentinal tubules. The antibacterial effect of low-temperature plasma treatment for 10 min exceeded that of the calcium hydroxide paste sealing for 7 d and the 2% chlorhexidine gel sealing for 7 d. These two chemicals had difficulty entering deep into the dentinal tubules, and therefore only had a few of antibacterial effect on the bacterial biofilm on the root canal wall, and there was also no significant damage to the E. faecalis bacterial structure. Conclusion: Gradient centrifugation could establish the model of E. faecalis dentin infection successfully. Low-temperature plasma treatment for 10 min could kill E. faecalis in dentinal tubules effectively, which is superior to the calcium hydroxide paste sealing for 7 d and the 2% chlorhexidine gel sealing for 7 d.