Study on Selective-caries-removal with Er:YAG Laser using Caries-detecting-dye-solutions

Objectives: Concerning caries treatment, caries-detecting dye solution (CDS) has been improved, and instruments for selectively eliminating caries have been developed to reduce the extent of tooth elimination by MI concept. Focusing on the specific absorption of lasers, we previously reported that the rate of laser absorption improved using a blue or green CDS, and we revealed that the Er:YAG laser absorption improved by mixing compounds containing primary amino groups (Highly laser-absorptive substances) with CDS. In this study, we experimentally produced CDS with the highly laser-absorptive substances, and measured their Er:YAG laser efficiency of carious dentin removal, to evaluate the laser absorption properties of CDS with the highly laser-absorptive substances.

Methods: We experimentally produced CDS mixed with 1.0, 2.0, and 4.0% highly laser-absorptive substances. After producing 5x5 mm bovine tooth dentin specimens, they were immersed in 0.1 M lactic acid for 24 hours, and the artificial carious dentin was produced. After dropping CDS, we removed the artificial carious dentin using 10 pulses of Er:YAG laser irradiations were carried out at 1.0 W ,1 Hz with water. In this study, Erwin AdvErL was used as an Er:YAG laser apparatus (Morita, Japan). Formed cavities were measured using a 3D-morphological measurement apparatus, to investigate the removal volume. The data calculated were statistically evaluated using one-way variance analysis and Scheffe’s test (n=5).

 Results: The removal volume on Er:YAG laser irradiation rose with increases in the concentration of the highly laser-absorptive substances in CDS. The removal volume by Er:YAG laser was significantly higher with CDS at 4.0%(32±6.6mm³) than at another concentrations of the highly laser-absorptive substances (p<0.05).

Conclusions: Our results suggest the possibility that dental caries can be selectively removed by Er:YAG laser using caries-detecting dye solutions mixed with the highly laser-absorptive substances.