Effects of Intensity and Frequency on Tooth-ablation Efficiency with Er,Cr:YSGG-laser- irradiation

Objectives: The aim of this study was to examine the effect of an intensity and a frequency of laser irradiation on the cutting efficiency of Er,Cr:YSGG laser for enamel and dentin.
Methods: The percentage of air/water in spray during laser irradiation was fixed 85/75% for both enamel and dentin surface. Flattened surfaces of enamel and dentin were irradiated at nine points for approximately 1 s under the combination of various intensities (3.0, 4.0 and 5.0 W for enamel, 2.0, 2.5 and 3.0 for dentin) and frequencies (20, 30 and 40 Hz) using Er,Cr:YSGG laser (n=10). A high-speed video microscope was used to record each laser irradiation on the tooth surface. A slow video image was used to count the number of water micro-explosions yielded on the tooth surface during laser irradiation. A surface roughness tester was used to measure the depth of dimple prepared with laser irradiation on each specimen. Each individual depth of dimple was divided by the number of water micro-explosions (pulse). This allowed for the calculation of the cutting depth per pulse. Following laser irradiation, several representative specimens were observed using an SEM. Two-way ANOVA was used as the statistical analysis.
Results: There were significant effects of both the intensity and frequency of laser irradiation on the cutting depth for enamel and dentin surface (p < 0.05). The cutting depth per pulse with high intensity was significantly deeper than that with low intensity for both enamel and dentin (p < 0.05). The cutting depth per pulse with high frequency was significantly shallower than that with low frequency for both enamel and dentin (p < 0.05).
Conclusions: Both intensity and frequency were significantly effective in laser cutting for enamel and dentin.