Irradiation Time and Ablation Rate of Enamel in Contact and Non-contact Irradiation with Er:YAG Laser

Abstract

The relationship between changes in ablation rate of enamel with irradiation time was investigated to find the most effective irradiation time for tooth ablation by Er:YAG laser. Previous studies have shown that the Er:YAG laser has the ability to ablate tooth material effectively, but that the efficiency and effectiveness of ablation are determined by various parameters such as energy, pulse frequency, the amount of water, and irradiation time. Contact and non-contact irradiation of the Er:YAG laser were carried out respectively for 1, 3, 5, and 7 s on the enamel surface of each specimen using a combination of a 400 mJ/pulse at 20 Hz and water flow rate of 6.75 mL/min, and quantitative measurements using a mass balance were performed to compare the resulting ablation rates. The ablation weight, by taking the mean of both contact and non-contact irradiation, generally increased with irradiation exposure time, but no significant increases in ablation were seen in specimens that had been exposed for > 3 s in either the contact or non-contact irradiation group. Results in the non-contact irradiation group indicated superior ablation of enamel compared to that in the contact irradiation group. Irradiation exposure of < or = 3 s per application of laser beam is recommended to ablate enamel effectively in both non-contact and contact irradiation.