Enhancing caries resistance in occlusal fissures with a short-pulsed CO_2 9.6 urn laser - an in vitro pH-cycling study - preliminary results

摘要

Treatment of occlusal surfaces with a short-pulsed CO_2 9.6 um wavelength laser has previously been proposed as a method for caries prevention. A sample of 20 extracted human molars were measured before and after demineralization-remineralization pH-cycling with ICDAS II visual inspection, DIAGNOdent, quantitative light-induced fluorescence (QLF), SoproLife in daylight and blue light-induced fluorescence mode, optical coherence tomography (OCT) and polarized Raman spectroscopy (PRS). Per tooth, one fissure was subjected to laser treatment using a short-pulsed CO2 laser at 9.6 um wavelength with a fluence of 3.5 J/cm2, 20 Hz pulse repetition rate, 20 us pulse duration, angulated handpiece, and focus diameter of 600 um, while the other fissure was left untreated as control. The teeth were subjected to a demineralization-remineralization pH-cycling for 9 days.rnCross-sectional micro-hardness testing was done as a gold standard to compare results with findings from the other detection methods used. Due to the small sample size reported, the trend observed was that laser treated fissures demonstrated a smaller relative mineral loss AZ than the controls. QLF findings followed a similar trend. Using a rotary catheter probe, OCT measurements were acquired from the various fissures to generate circularly mapped OCT depth images. PRS measurements of parallel- and cross-polarized spectra were acquired with a Raman microscope system. Preliminary OCT images showed differences in the initial air-tooth interface, with PRS results indicating a change in the surface property along with biochemical alterations after pH-cycling. Following pH-cycling, an increase in the OCT subsurface light backscattering intensity in the control fissures was observed compared to the laser test fissures. Porphyrin based fluorescence methods like DIAGNOdent and SoproLife, respectively demonstrated only additional light scattering due to the demineralization process.