An evaluation of the CO2 laser for endodontic disinfection.

The goal of this study was to evaluate the bactericidal action of the CO2 laser on animal teeth infected with an endodontic bacterial species. After instrumentation, 24 freshly extracted incisors were inoculated with a known concentration of Actinomyces odontolyticus and incubated anaerobically for 18 h. The incisors were separated into three groups: group 1--untreated control teeth; group 2--teeth treated with 3% NaOCl; and group 3--teeth lased with a CO2 laser at 5 W using three successive 9.9 s irradiation periods with 10 s between treatments. For each of the three groups, 60 microliters samples were removed using gel loading capillary pipette tips, and the diluted samples were plated in triplicate on Columbia agar plates. After a 5- to 6-day incubation, the colony-forming units were counted, and the quantitative results were subjected to an analysis of variance. The results of this analysis indicated an average 85% decrease in the colony-forming units in the laser-treated group, compared with the control group. According to Fisher and Scheffé tests, the differences in the averages between the control and laser groups were statistically significant (p < 0.05). The NaOCl treatment was statistically superior to the CO2 laser treatment.