Decontamination of Hard Tissue Using a Scanning Pulsed 9.3-μm CO 2 Laser

Purpose: The aim of the study was to evaluate the use of a scanning 9.3-μm CO 2 laser beam to reduce or eliminate bacteria on hard tissue as a new method of non-specific decontamination to prevent cross-contamination during dental or medical procedures. Methods: A low energy level of a 9.3-μm CO2 laser beam was designed to deliver overall uniform photothermal energy in a 2-mm-diameter beam to eliminate bacteria on the surface of dental enamel without damaging the surface of the tooth. The study was conducted in two parts. The first part consisted of 10 human molars polished to a 1-μm finish and inoculated with S. mutans. The bacteria were stained with methylene blue and imaged through cross-polarization microscopy, and the area of the imaged surface containing bacteria was analyzed using ImageJ. The second part of the study consisted of 20 uncleaned extracted human molars used for evaluating cross-contamination of bacteria by measuring bacteria Colony Forming Units (CFU) ejected during an aerosol-generating procedure in vitro. Tryptic soy agar (TSA) plates were used to collect bacteria while cutting enamel. The TSA plates were incubated at 35o C for 24 hours, after which bacteria colonies were counted. Results: Examination using cross-polarization microscopy and imaging showed that the CO 2 laser eliminated >98% of bacteria on the surface without altering the surface of teeth and similarly >98% in the aerosol/splatter from cutting of the enamel. Conclusion: The 9.3-μm CO2 laser resulted in nearly a complete elimination of viable bacteria.