A laboratory investigation of the bactericidal effect of a NdYAG laser

Abstract

Laser irradiation produces bactericidal effects which may be of use in dentistry. The aims of this study were to investigate the effect of pulsed NdYAG laser irradiation on bacteria in a laboratory model, in the presence and absence of a black dye, Suomi ink. The experiments were carried out in small capillary tubes containing a measured volume of Enterococcus faecalis broth culture. This model simulated the number of organisms that could be expected to occur in an infected root canal. Laser irradiation was delivered from a NdYAG laser via a 320-microns fibre. Powers of 0.3 to 3.0 W were used for 20 to 60 s. Controls received no irradiation. The effect of the black dye was investigated by the addition of a fixed volume to the culture before lasering. The treatments were evaluated for bactericidal effect by comparing the number of viable bacteria remaining in the irradiated and the control specimens. At energy doses of 54 J and above, without black dye, a reduction of 10,000-fold or greater occurred. A similar reduction was achieved at energies above 25 J when black dye was added. These results indicate the energy levels which should be investigated to assess the potential role of the NdYAG laser in endodontics.

Irradiation of infected root canals with a diode laser in vivo: Results of microbiological examinations

“…In a laboratory experiment, Rooney et al [27] achieved a 1000-fold reduction in heatresistant bacteria (Enterococcus faecalis) through irradiation with a pulsed Nd:YAG laser, corresponding to a log kill of 4. They required an energy of 1.8 W for 30 seconds or 54 J, respectively.…”

Rationale for using a double-wavelength (940 nm + 2780 nm) laser in endodontics: literature overview and proof-of-concept

“…As endodontic pathogens present pigments such as melanin in their bacterial membranes, diode lasers have been demonstrated great bactericidal ability by directly interacting with bacterial pigmented membranes [28][29][30] or even with the bacterial microenvironment, most likely in the form of heat [31].…”

Surgical laser use in implantology and endodontics

“…[60][61][62] The fi ne (200-320 µm) diameters of quartz optic fi bres associated with diode and Nd:YAG lasers has enabled these wavelengths to be easily used in bacterial decontamination of the root canal (Figs 27-35). [63][64][65] Of the current lasers available, the CO 2 wavelength would appear least successful in effecting bacterial decontamination 66 and the effectiveness of laser use appears to depend on fl uence values and direct access. 67 In addition, some concern has been expressed that the plume produced during laser action might allow bacterial contamination to spread.…”