Effect of a calcium hydroxide-based intracanal medicament containing N-2-methyl pyrrolidone as a vehicle against Enterococcus faecalis biofilm

Abstract This study investigated the effect of a calcium hydroxide (CH) paste (CleaniCal®) containing N-2-methyl pyrrolidone (NMP) as a vehicle on Enterococcus faecalis (E. faecalis) biofilms compared with other products containing saline (Calasept Plus™) or propylene glycol (PG) (Calcipex II®). Methodology Standardized bovine root canal specimens were used. The antibacterial effects were measured by colony-forming unit counting. The thickness of bacterial microcolonies and exopolysaccharides was assessed using confocal laser scanning microscopy. Morphological features of the biofilms were observed using field-emission scanning electron microscopy (FE-SEM). Bovine tooth blocks covered with nail polish were immersed into the vehicles and dispelling was observed. The data were analyzed using one-way analysis of variance and Tukey tests (p<0.05). Results CleaniCal® showed the highest antibacterial activity, followed by Calcipex II® (p<0.05). Moreover, NMP showed a higher antibacterial effect compared with PG (p<0.05). The thickness of bacteria and EPS in the CleaniCal® group was significantly lower than that of other materials tested (p<0.05). FE-SEM images showed the specimens treated with Calasept Plus™ were covered with biofilms, whereas the specimens treated with other medicaments were not. Notably, the specimen treated with CleaniCal® was cleaner than the one treated with Calcipex II®. Furthermore, the nail polish on the bovine tooth block immersed in NMP was completely dispelled. Conclusions CleaniCal® performed better than Calasept Plus™ and Calcipex II® in the removal efficacy of E. faecalis biofilms. The results suggest the effect might be due to the potent dissolving effect of NMP on organic substances.

摘要 本研究探究了以N-2-甲基吡咯烷酮（N-2-methyl pyrrolidone, NMP）为载体的氢氧化钙（calcium hydroxide, CH）糊剂CleaniCal®对粪肠球菌（Enterococcus faecalis, E. faecalis）生物膜的抗菌效果，并与含生理盐水的Calasept Plus™以及以丙二醇（propylene glycol, PG）为载体的Calcipex II®进行了对比。方法 本研究采用标准化牛牙根尖管标本。采用菌落形成单位计数法检测抗菌效果；通过共聚焦激光扫描显微镜评估细菌微菌落与胞外多糖（exopolysaccharides, EPS）的厚度；利用场发射扫描电子显微镜（field-emission scanning electron microscopy, FE-SEM）观察生物膜的形态特征。将涂抹指甲油的牛牙块浸没于各载体中，观察其溶解情况。采用单因素方差分析与Tukey检验对数据进行统计学分析，检验水准为p<0.05。结果 CleaniCal®的抗菌活性最高，其次为Calcipex II®（p<0.05）；且NMP的抗菌效果优于PG（p<0.05）。CleaniCal®组的细菌与胞外多糖厚度均显著低于其余受试材料组（p<0.05）。场发射扫描电子显微镜图像显示，经Calasept Plus™处理的标本表面被生物膜覆盖，而其余受试药剂处理组标本则无此现象；值得注意的是，CleaniCal®处理组的标本清洁度优于Calcipex II®组。此外，浸没于NMP中的牛牙块表面指甲油完全溶解。结论 CleaniCal®在清除粪肠球菌生物膜方面的效果优于Calasept Plus™与Calcipex II®。本研究结果提示，该抗菌效果可能源于NMP对有机物的强效溶解作用。