[Comparison of three root canal disinfection methods for removal of Enterococcus faecalis under minimally invasive root canal treatment].

PURPOSE: To obtain an efficient and simple root canal disinfection method based on minimally invasive root canal treatment by comparing different root canal disinfection methods between minimally invasive root canal treatment and conventional root canal treatment. METHODS: Sixty-six extracted maxillary first molars were randomly divided into experimental group (computer-guided precision minimally invasive root canal treatment) and control group (conventional root canal treatment). All teeth were prepared to ProTaper universal F2, and Enterococcus faecalis infection models were established.Each group was randomly divided into three subgroups, sodium hypochlorite+EDTA root canal irrigation, sodium hypochlorite+EDTA+ultrasonic and sodium hypochlorite +EDTA +Er: YAG laser. After root canal disinfection,the samples were collected by paper tip method and cultured, and colony forming units (CFU) values of each sample were calculated. Then dentin debris was prepared and collected with F3 file. After being diluted and cultured, the CFU value was calculated. Statistical analysis was performed by SPSS 26.0 software package. RESULTS: Comparison of the amount of bacterial inner wall of root canal between the experimental group and the control group showed that the germicidal efficacy of group C and group B were significantly better than that of group A (P＜0.05), but there was no significant difference between group B and group C(P＞0.05). In the experimental group, there was significant difference between group B1, C1 and A1 (P＜0.05). The results of group B1 and C1 were lower than that of group A1, but there was no significant difference between group B1 and group C1(P＞0.05). In the control group, there were significant differences between group B2, C2 and A2 (P＜0.05). The results of group B2 and C2 were lower than that of group A2, but there was no significant difference between group B2 and C2(P＞0.05). Comparison of the amount of bacteria in dentin debris between the experimental group and the control group showed that the effect of group C was the best, followed by group B, and group A, and there were significant differences between three groups(P＜0.05). CONCLUSIONS: The disinfection effect of Er:YAG laser or ultrasound assisted computer-guided precision minimally invasive root canal treatment is similar to conventional root canal treatment, and Er:YAG laser is better than ultrasound in removing bacteria from dentinal tubules, which is more suitable for minimally invasive root canal treatment.