Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm. The present study investigated the irradiation effect of the light on carious human dentin classified into “remove,” “not remove,” and “unclear” categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm2 and irradiation time of 2 s, the ablation depth of “remove” and “not remove,” and also the ablation depth of “unclear” and “not remove,” were significantly different (p<0.01). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85 μm proved an effective less-invasive caries treatment.
Less invasive treatment and preservation of teeth, referred to as minimal intervention, are strong requirements in dentistry.
In our previous study, the fundamental ablation properties of human dentin at wavelengths around 5.8 μm were investigated,
and the results indicated that the wavelength of 5.85 μm was optimal for selective removal of carious dentin with less
damage to normal dentin. The purpose of this study was to investigate the relationship between the ablation depth and
hardness of human dentin including carious lesion. A nanosecond pulsed laser produced by difference-frequency
generation was used for irradiations to human carious dentin. It was observed that correlation between ablation depth and
Vickers hardness after 2 s laser irradiation at the wavelength of 5.85 μm and the average power density of 30 W/cm2. On the other hand, ablations did not depend on Vickers hardness at the wavelength of 6.00 μm. A nanosecond pulsed laser
with the wavelength at 5.85 μm is useful for selective ablation of human carious dentin in accordance with the hardness.
Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, the wavelength of 5.85 μm could realize the selective excavation of human carious dentin, but it was necessary to evaluate the stage of caries progression in order to control the ablation property.
Less-invasive treatment of caries has been needed in laser dentistry. Based on the absorption property of dentin substrates, 6 μm wavelength range shows specific absorptions and promising characteristics for the excavation. In our previous study, 5.8 μm wavelength range was found to be effective for selective excavation of carious dentin and restoration treatment using composite resin from the irradiation experiment with bovine sound and demineralized dentin. In this study, the availability of 5.8 μm wavelength range for selective excavation of human carious dentin was investigated for clinical application. A mid-infrared tunable nanosecond pulsed laser by difference-frequency generation was used for revealing the ablation property of human carious dentin. Irradiation experiments indicated that the wavelength of 5.85 μm and the average power density of 30 W/cm2 realized the selective excavation of human carious dentin, but ablation property was different with respect to each sample because of the different caries progression. In conclusion, 5.8 μm wavelength range was found to be effective for selective excavation of human carious dentin.
Conventional dental lasers have not realized a selective excavation of carious dentin. Objective of this study is to
determine the optimal irradiation condition for the selective excavation by using a wavelength around 5.8 μm. A
nanosecond pulsed laser with a wavelength of 5.8 μm was obtained by difference-frequency generation technique. The
laser delivers 5 ns pulse width at a repetition rate of 10 Hz. 5.8 μm wavelength range, a short wavelength required high
excavation energy and a long wavelength required low excavation energy to induce the selective excavation with a low
thermal side effect. 5.8 μm wavelength provides a selective excavation technique for minimal intervention.
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