Effectiveness of Different Diode Laser Wavelengths in Targeting Enterococcus faecalis Biofilm in Root Canal Treatment

Disinfection of the root canal system is crucial for the effectiveness of root canal treatment. Lasers and photoactivated disinfection (PAD) have emerged as preferred methods for eliminating pathogens from the root canal.

Sixty intact, freshly extracted adult human uniradicular mature teeth with a single root canal were collected. The crowns were removed, resulting in canals measuring 14 mm in length. The root canals were prepared, sterilized, and then inoculated with broth containing Enterococcus faecalis (E. faecalis), followed by incubation for 30 days in an aerobic environment at 37°C. Biofilm formation was verified using a scanning electron microscope. The samples were randomly divided into six experimental groups (n = 10). Group 1 consisted of teeth treated only with distilled water. Group 2 teeth received 3% NaOCl and 17% EDTA as part of Conventional Chemomechanical Debridement (CCMD) but no additional treatment. Groups 3-6 also received CCMD followed by additional laser disinfection as follows: Group 3 underwent photoactivated disinfection (PAD) using riboflavin with a 450 nm laser; Group 4 underwent PAD using toluidine blue O (TBO) with a 635 nm laser; Group 5 underwent conventional laser endodontics (CLE) with an 808 nm laser; and Group 6 underwent CLE using triple wavelengths of 450 nm, 635 nm, and 808 nm.

The Kruskal-Wallis test revealed significant differences in colony-forming units (CFUs) among the groups after treatment (p < 0.001). Subsequent analysis showed that the difference in mean CFUs between the PAD groups and the CLE groups was not statistically significant. The group treated with the triple laser wavelength exhibited the lowest average CFUs/mL, while the distilled water group had the highest mean value.

The study confirms that diode laser-assisted disinfection significantly enhances bacterial reduction compared with conventional irrigation alone. Although PAD methods reduced E. faecalis, their effect was not statistically superior to conventional laser endodontics (CLE). The triplewavelength diode laser group achieved the greatest bacterial reduction, likely due to the synergistic effects of thermal and photochemical interactions. These findings support the adjunctive use of laser disinfection to improve root canal decontamination, particularly when combined with chemomechanical preparation.

This study demonstrates that combining an irrigating solution with a diode laser enhances the effectiveness of reducing pathogenic numbers.