Abstract
The aim was to evaluate the surface roughness and bacterial adhesion on enamel irradiated with high intensity lasers, associated or not to a fluoride varnish. Eighty fragments of bovine enamel were equally divided in 8 groups (n=10). Group 1 was not treated and Group 2 received only a 5% fluoride varnish application. The other groups were irradiated with an Er:Cr:YSGG (8.92 J/cm2), an Nd:YAG (84.9 J/cm2) and a diode laser (199.04 J/cm2), associated or not to a 5% fluoride varnish. The surface roughness was measured before and after treatments. Afterward, all samples were incubated in a suspension of S. mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted by a stereoscope and the results were expressed in CFU/mm2. One-way ANOVA and the Tukey´s test compared the roughness data and the Student´s test compared the results obtained in the bacterial adhesion test (a=5%). The results showed that the irradiated samples without varnish presented the same roughness and the same bacterial adhesion that the non-irradiated samples. However, samples irradiated in the presence of fluoride varnish showed higher surface roughness and higher bacterial adhesion than the non-irradiated samples and those irradiated without varnish. Presence of pigments in the varnish increased the lasers' action on the enamel surface, which produced ablation in this hard tissue and significantly increased its surface roughness. For this reason, the enamel's susceptibility to bacterial adhesion was higher when the irradiation of the samples was made in presence of fluoride varnish.
Highlights
Irradiation of dental enamel with high power lasers has shown to be effective in preventing dental caries, because they can provide significant reduction in mineral loss by the acid challenges in the oral cavity [1,2]
The results revealed that the samples irradiated in the presence of fluoride varnish (G4, Group 6 (G6) and Group 8 (G8)) showed higher surface roughness than the non-irradiated samples (G1 and Group 2 (G2)) and those irradiated without varnish (G3, Group 5 (G5) and Group 7 (G7)) (p
The null hypothesis that the enamel roughness would not change after laser irradiation with or without fluoride over the enamel surface, was rejected, since the irradiation without 5% NaF presence did not change the surface roughness of bovine enamel
Summary
Irradiation of dental enamel with high power lasers has shown to be effective in preventing dental caries, because they can provide significant reduction in mineral loss by the acid challenges in the oral cavity [1,2]. Different hypotheses have been proposed to explain the changes promoted by irradiation in dental enamel resulting in a preventive effect. All theories are related to the temperature increase in the irradiated tissue, which leads to structural and chemical changes in enamel and dentin [3]. The main chemical changes in enamel due to photothermal effects are that the prevailing CO3 component in the phosphate position decreases and the acid phosphate ions condense to form pyrophosphate ions. The hypothesis is that these effects make enamel less soluble to acids [4]
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