A white spot lesion is the first clinical sign of a caries lesion and represents mineral loss from the enamel subsurface. The purpose of this study was to evaluate the microhardness and surface roughness of white spot lesions after application of a resin infiltrant and subjection to different challenges. Caries-like lesions were induced in bovine enamel discs (n=50), and the specimens were randomly divided into five study groups (n=10): demineralized enamel (negative control, G1), infiltrated enamel (G2), infiltrated enamel submitted to brushing (G3), infiltrated enamel submitted to pH cycling (G4), and infiltrated enamel submitted to artificial aging (G5). Half of each enamel surface was used as its own positive control. Roughness data were analyzed using the Kruskal-Wallis test followed by the Dunn test. Results from microhardness were analyzed by two-way analysis of variance, followed by the Tukey test for multiple comparisons. The level of significance was set at 5%. Microhardness and roughness values obtained from the test side of the specimens were significantly lower compared with the sound enamel for all groups. Microhardness values obtained for G2, G3, and G5 were not significantly different. Values found for G1 were significantly lower compared with those for G2, G3, and G5. The lowest microhardness values were observed for G4, which was significantly different from the other groups. Surface roughness was not significantly different between G2 and G3. The resin infiltrant presented superiority over the unprotected white spot lesions, as they were more resistant to mechanical and aging challenges. However, resin infiltration was not able to reestablish the properties of sound enamel and was not resistant to a new cariogenic challenge.
The thermocycling was concluded as being able to change composite resins' surface roughness, whereas different finishing and polishing methods did not result in surface roughness changes after thermocycling.
The aim of the study was to evaluate the effect of erosive pH cycling with solutions that simulate dental erosion on Martens hardness (HMV) and elastic modulus (Eit) of dentin restored with fluoride-releasing adhesive systems. Twenty-seven bovine dentin slabs were restored with three adhesive systems: Adper Single Bond 2 total-etch adhesive system, One Up Bond F and Clearfil SE Protect fluoride-containing self-etching adhesive systems. The restorations were made with Filtek Z250. The HMV and Eit values at distances of 10, 30, 50 and 70 µm from the interface were evaluated using a dynamic ultra microhardness tester before and after immersion in deionized water, citric acid and hydrochloric acid (n=9). Data were submitted to repeated-measures ANOVA and Fisher's PLSD tests (=0.05). After erosive cycling, HMV values of dentin decreased in all groups. For dentin restored with Adper Single Bond 2, the lowest values were found closer to the hybrid layer, while for One Up Bond F and Clearfil SE Protect, the values remained unaltered at all distances. For dentin restored with fluoride-releasing adhesive systems, a decrease in Eit was found, but after 30 µm this difference was not significant. The acid substances were able to alter HMV and Eit of the underlying dentin. For fluoride-releasing adhesives, the greater the distance from bonded interface, the lower the Eit values. The fluoride in One Up Bond F and Clearfil SE Protect was able to protect the underlying dentin closer to the materials. In this way, the fluoride from adhesive systems could have some positive effect in the early stages of erosive lesions.
The purpose of this study was to evaluate the bonding interface between a self-adhesive resin cement to in vitro eroded dentin. Seventy-two third molars were used and divided into two groups: sound dentin and in vitro eroded dentin. The in vitro erosion was performed following a demineralization protocol, in which the specimens were immersed in a demineralizing solution for 2 minutes per cycle and remineralizing solution for 10 minutes per cycle for 9 days. Both groups were submitted to four dentin surface treatments: control group (without any treatment), 2% chlorhexidine, 20% polyacrylic acid, and 0.1 M EDTA (n = 9). Blocks of resin-based composite were bonded with RelyX U200 self-adhesive resin cement applied on the pretreated dentin surfaces. The teeth were sectioned into beams (1mm2) and submitted to microtensile bond strength testing to evaluate the bond strength of self-adhesive resin cement to dentin after 24 hours and 8 months of immersion in artificial saliva. Three specimens of each group were longitudinally cut and evaluated using confocal laser scanning microscopy to analyze the dentin/cement interface. Eroded dentin showed higher bond strength values when compared to sound dentin for the 2% chlorhexidine group (p = 0.03), 24 hours after adhesion. When considering eroded dentin, the 0.1M EDTA group showed higher bond strength values with a statistically significant difference only for the control group (p = 0.002). After 8 months of storage, the present results showed that there was no statistically significant difference between the two substrates for all experimental groups (p>0.05). Analysis of the microscopy confocal showed different types of treatments performed on dentin generally increased tags formation when compared to the control group. The eroded dentin showed a significant increase in density and depth of resinous tags when compared to sound dentin. The storage of samples for 8 months seems to have not caused significant degradation of the adhesive interface.
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