Antibacterial effect on Enterococcus faecalis of Er,Cr:YSGG laser irradiation compared to two irrigating solutions in root canals of extracted human teeth

Abstract

The objective of this study was to compare the antibacterial effect of Er,Cr:YSGG laser irradiation with two irrigating solutions in root canals of extracted human teeth. One hundred and twenty-five extracted single rooted teeth with straight roots were chosen. The canals were enlarged with K files to size 50 using crown-down technique and randomly assigned into four experimental groups of 30 teeth each and 5 teeth for sterility control group. After sterilization, all roots except the sterility control group were inoculated with 10 µl of 1x10⁸ CFU/ml of Enterococcus faecalis for 48 h at 37 ℃. The first group was used as a negative control group receiving no treatment. The second group and third group were irrigated with 5 ml of 2.5% NaOCl solution and 2% CHX solution for 10 min, respectively. The last group was irradiated with the Er,Cr:YSGG laser at 1.5 W output power with no air and water using four lasing cycles of 10 s each. After treatment, the canals were filled with sterile normal saline solution and were circumferentially filed with H-file size 50. The content in the canals was then transferred using a micropipette, plated on TSA agar immediately and incubated at 37 ℃ for 24 h. The colony forming units were counted, and the quantitative results were subjected to an One- Way ANOVA. The mean number of viable colonies in the negative control group was significantly higher than the other groups (p < 0.05). Comparing among the treated groups, the mean Log colony forming units (Log CFU) value obtained after Er,Cr:YSGG laser irradiation was statistically significantly higher than those of 2.5 % NaOCl and 2% CHX groups (p < 0.05). However, there was no significant difference between the 2.5 % NaOCl and 2% CHX groups (p> 0.05). It can be concluded that Er,Cr:YSGG laser irradiation can reduce the viable microbial population in root canals to a certain extent but is less effective than irrigating with 2.5 % NaOCl and 2% CHX solutions.