ABSTRACT
Objective@#To observe the killing and clearance effect of an Er:YAG laser combined with sodium hypochlorite on Enterococcus faecalis at different depths of the root canal in vitro to provide a reference for clinical application.@*Methods @#A total of 75 models of Enterococcus faecalis infection were successfully established and randomly divided into three groups (25 per group). Ten random samples per group underwent no processing. The remaining models in group A were treated with an Er:YAG laser combined with sodium hypochlorite 52.5 g/L. Group B was treated with 52.5 g/L sodium hypochlorite (positive control), and group C was treated with normal saline (negative control). The bacterial reduction rate was calculated for each group. The bactericidal effect on the surface of the root canal wall was observed in 5 samples by scanning electron microscopy.@*Results@#There was no statistically significant difference (P > 0.05) between group A (100.00 ± 0.00) and group B (98.62 ± 2.01) but was a statistically significant difference between group A (100.00 ± 0.00) and group C (64.37 ± 2.45) (P < 0.05). The percentage reduction in bacteria was higher in group A (99.46 ± 2.31) than in groups B (92.89 ± 3.07) and C (56.72 ± 4.96) (P < 0.05). The decrease in bacteria was greater in group A (97.62 ± 3.73) than in groups B (72.49 ± 2.35) and C (44.42 ± 4.78) (P < 0.05). The bacterial reduction rate in group A (95.89 ± 2.46) was higher than that in groups B (63.88 ± 1.08) and C (33.31 ± 5.21) (P < 0.05). There were significant differences at different dentin depths in the bacterial reduction rates among groups A, B and C (P < 0.05). Electron microscopy analysis showed that the Er:YAG laser combined with 52.5 g/L sodium hypochlorite was better than either treatment alone at removing bacteria from the surface of the root canal wall.@*Conclusion@# An Er:YAG laser can effectively enhance the bactericidal effect of sodium hypochlorite on the inner wall of the root canal.