Preclinical study showed themain predictors of enamel erosion and demineralization and treatment analysis

The aim of this study evaluated the fluoride retention, morphologic changes on enamel surface and the resistance to demineralization after Er: YAG laser and fluoride gel pretreatments. Ninety-five bovine enamel specimens were obtained, half of the enamel surface were coated with nail varnish and wax (reference area), leaving other half to pre-treatments and to erosive challenge. The specimens were randomly divided into the following 5 groups: L laser irradiation; L+F laser and posterior application of fluoride (APF gel); F+L fluoride and posterior laser irradiation; L/F laser/fluoride application simultaneously; F APF gel (control group). The laser was irradiated for 10s (60mJ/2Hz), APF gel was applied for 4 min, and was exposed to Coca-Cola® for 1 min, four times/day/5 days. Fluoride retention was performed using EDS, morphological changes by SEM and enamel demineralization by micro hardness. SEM and EDS were performed for descriptive analysis of the data and micro hardness was performed for Dunn test/ANOVA one criteria. L/F showed higher retention of fluoride (174.0 %) followed by the F(27.0 %) and F+L (10.0 %). L(39.0 %) and L+F(7.5%) showed a decrease in the fluoride content , there was decrease Ca and P content about 0.2 to 8.0 % and 6 to 14.0 %, respectively, without cause alteration on Ca/P proportion. All the irradiated groups were ablated. Micro hardness was not significantly different between groups. L/F promoted higher retention of fluoride in the enamel and any pretreatment caused alteration on Ca/P proportion, Er: YAG laser promoted superficial enamel microablation under low fluency and the pretreatments was not able cause micro hardness alteration.