The effect of CO2 9.3 μm short-pulsed laser irradiation in enamel erosion reduction with and without fluoride applications

C. V. Silva & T. F. Mantilla & Y. Engel & J. P. Tavares & P. M. Freitas & P. Rechmann

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ABSTRACT

The aim of this in vitro study was to evaluate the protective effect of short-pulsed CO₂ 9.3 μm laser irradiation against erosion in human enamel without and combined with TiF4 and AmF/NaF/SnCl2 applications, respectively, as well as compared to the protective effect of these fluoride treatments alone. After polishing, ninety enamel samples (3 × 3mm) were used for 9 different treatment groups: 4% TiF4 gel (pH 1.5, 24,533 ppm F−); AmF/NaF/SnCl2 rinse (pH 4.5; 500 ppm F−, 800 ppm Sn2); CO₂ laser (average power 0.58 W); CO₂ laser (0.58 W) + TiF4; CO₂ laser (0.58 W) + AmF/NaF/SnCl2; CO₂ laser (0.69 W); CO₂ laser (0.69W) + TiF4; CO₂ laser (0.69 W) + AmF/NaF/SnCl2; negative control (deionized water). TiF4 gel was brushed on only once before the first erosive cycling, while samples treated with AmF/NaF/SnCl2 were daily immersed in 5 ml of the solution before cycling. Laser treatment occurred with a CO₂ laser (wavelength 9.3 μm, pulse repetition rate 100 Hz, pulse duration 14.6 μs/ 18 μs, average power 0.58 W/0.69 W, fluence 1.9 J/cm2/2.2 J/cm2, beam diameter 0.63 mm, irradiation time 10 s, air cooling). TiF4 was applied only once, whileAmF/NaF/SnCl2 was applied once daily before the erosive challenge. Surface loss (in μm) was measured with optical profilometry immediately after treatment, and after 5 and 10 days of erosive cycling (0.5% citric acid, pH 2.3, 6 × 2 min/day). Additionally, scanning electron microscopy investigations were performed. All application measures resulted in loss of surface height immediately after treatment. After 5 days, significantly reduced surface loss was observed after applying laser irradiation (both power settings) followed by applications of TiF4 or AmF/NaF/SnCl2 solution (p < 0.05; 2-way ANOVA and Tukey test) compared to fluoride application alone. After 10 days, compared to after 5 days, a reduced tissue loss was observed in all groups treated with AmF/NaF/SnCl2 solution. This tissue gain occurredwith the AmF/NaF/SnCl2 application alone and was significantly higher when the application was combined with the laser use (p < 0.05). Short-pulsed CO₂ 9.3 μm laser irradiation followed by additional application of AmF/NaF/SnCl2 solution significantly reduces the progression of dental enamel erosion in vitro.