Caries-selective ablation: wavelength 377 nm versus 2.9 um

摘要

The aim of this study was to compare the conditions for selective removal of carious lesions by pulsed lasers emitting wavelengths in the near UV in contrast to lasers emitting in the IR spectral region at 2.9 $mu@m. Absorption measurements of carious lesions and healthy dentin revealed highest absorption differences at wavelengths between 320 and 520 nm. The effects of a frequency doubled, gain-switched Alexandrite-laser (wavelength 377 nm) and a q-switched Er:YAG-laser (wavelength 2.9 $mu@m) on carious and healthy dentin were studied in comparison. Both lasers emitted pulses of 200 ns duration. The ablation thresholds for the different tooth structures were determined. The ablation threshold of carious lesions is about the same for the Er:YAG as for the second harmonic Alexandrite-laser. For the Er:YAG-laser the ablation threshold of healthy dentin is about 2 times higher than the ablation threshold of carious lesions. In the case of the second harmonic Alexandrite-laser the difference between ablation is 4 times higher. Thus, regarding the window of fluences sufficient for truly caries selective ablation, the conditions for selective removal of carious dentin are better in the near UV than in the IR spectral region at 2.9 $mu@m.