Effects of CO₂ laser irradiation combined with fluoride application on the demineralization, mechanical properties, structure, and composition of enamel

We investigated the effects of CO₂ laser irradiation combined with acidulated phosphate fluoride (APF). application on the demineralization of enamel. APF gel was applied to the buccal enamel of human premolars and CO₂ laser was applied. After the specimens were immersed in demineralization solution for 72 h, they were subjected to depth-dependent micro-CT and nanoindentation analyses. Micro-X-ray diffraction and X-ray photoelectron spectroscopy were performed to analyze the surfaces. Some surface regions of the enamel in specimens that were laser-irradiated with low output and APF-treated showed significantly higher values of MD and hardness than specimens treated with APF alone. A higher fluoride concentration in the enamel surface was observed in specimens treated with CO₂ laser irradiation plus APF gel application. In conclusion, CO₂ laser irradiation with low output is preferable to improve acid resistance.