Influence of surface sealant and erosive challenge on the color change of composite resin subjected to artificial staining.

The aim of this study was to evaluate the influence of surface sealant and erosive challenge on the color change of composite resin after artificial staining with coffee. Forty-eight composite specimens (8 × 1 mm) were prepared and divided into 4 groups (n = 12) based on the timing of sealant application (immediate vs delayed) and exposure to acid (erosive challenge vs no challenge). The groups were subjected to the procedures in the following order: 1, sealant application, erosive challenge, color measurement, coffee immersion, and color measurement; 2, sealant application, color measurement, coffee immersion, and color measurement; 3, erosive challenge, color measurement, sealant application, coffee immersion, and color measurement; and 4, color measurement, sealant application, coffee immersion, and color measurement. In groups 1 and 2, surface sealant was applied immediately after preparation of the specimens. In groups 3 and 4, sealant was applied after the first color measurement. Color was measured with a spectrophotometer using the CIE L*a*b* system. The erosive challenge (groups 1 and 3) was carried out in 0.01M hydrochloric acid, 150 mL/cycle, at room temperature (2-minute immersions 4 times a day for 5 days). After all specimens were immersed in coffee for 14 days, new color measurements were performed. For total color change (∆E*), groups 1 (21.01) and 2 (23.10) presented lower values than groups 3 (27.76) and 4 (26.57). For luminosity (∆L*), the opposite occurred (groups: 1, -16.84; 2, -17.72; 3, -22.62; and 4, -21.22). For ∆a* and ∆b*, the only statistically significant difference was the group 1 ∆b* value, which was the lowest among all groups. The opacity remained stable in all groups. The results suggest that resin luminosity decreases and color variation increases when surface sealant is applied after erosive cycling and storage.

Effect of Ceramic Barriers of Different Thicknesses on Microhardness of Light-Cured Resin Cements.

This study evaluated the microhardness of two resin cements and a low-viscosity resin composite when light-cured under different ceramic thicknesses. A total of 20 samples (10.0 × 1.0 mm) of each material were polymerized by means of a LED light source with an intensity of 1,100 mW/cm2 for 20 seconds. For each experimental group, different ceramic thicknesses (0.5 mm, 1.0 mm, and 1.5 mm) were applied to each sample. For the control group, the samples were polymerized without the presence of ceramics. Each material was then stored in dry vials that inhibited the passage of light for a period of 24 hours. After that time, each sample underwent Vickers hardness test (HMV, Shimadzu: 25 g/10 seconds). The data were collected and analyzed using analysis of variance and Tukey test (P < .05). For the control group, RelyX Veneer (3M ESPE), Filtek Flow Z350XT (3M ESPE), and Allcem Veneer (FGM) showed mean microhardness values and standard deviations of 44.42 ± 4.9, 44.25 ± 2.4, and 31.71 ± 2.4, respectively. The lowest microhardness value (24.13) was found when the greatest ceramic thickness (1.5 mm) was used on the Allcem Veneer cement (P < .01). The microhardness of resin-based materials was affected when the 1.5-mm-thick ceramic material was interposed during photoactivation.