Effects of in vitro erosion on surface texture, microhardness, and color stability of resin composite with S-PRG fillers

Are S-PRG composites able to resist against erosive and abrasive challenges and protect surrounding enamel in situ?

OBJECTIVES

This study evaluated the resistance of S-PRG (Surface Pre-Reacted Glass-ionomer) composites and other restorative materials against erosive and abrasive challenges and their protective effect on enamel adjacent to the restorations.

MATERIALS AND METHODS

Bovine enamel blocks were prepared and randomized into 12 groups, including 6 types of material, each of them subjected to erosion_e or erosion+abrasion_ea: Beautifil II (S-PRG); Beautifil Bulk Restorative (S-PRG); Filtek Z250 XT; Filtek Bulk Fill; EQUIA Forte; Riva Light Cure. Cavities were prepared in the middle of enamel blocks and restored with the materials. Initial profiling measurement was performed on the material and on adjacent enamel (100, 200, 300, 600 and 700 μm from the restoration margin). Palatal intraoral appliances with the restored enamel blocks were used by the volunteers (n = 10). During 5 days appliances were immersed in 2.5 % citric acid for 2 min; 6 × /day (erosion_e). For ea condition, blocks were brushed for 1 min after each acid immersion. Final profile assessment was performed. Data were analysed by two and three way ANOVA followed by Tukey's test (p < 0.05).

RESULTS

Material wear: Riva Light Cure showed the highest wear followed by EQUIA Forte and then all resin composites, including the ones with S-PRG (p = 0.000). Enamel wear: there was significant interaction among type of restorative material, wear condition and distance (p = 0.014), enamel around materials showed similar wear (p = 0.983) and the enamel subjected to ea exhibited highest wear (p = 0.000).

CONCLUSION

SPRG based composites showed resistance against erosive and abrasive challenges but were not able to protect enamel adjacent to the restorations.

CLINICAL SIGNIFICANCE

S-PRG composites exhibit resistance to material wear comparable to resin composites. However, they have shown an inability to effectively protect the adjacent enamel under in situ erosive-abrasive conditions, despite the presence of mineral-loss-preventing ions surrounding materials.

Analysis of Physical and Mechanical Properties of Universal Composites under Different Types of Polishing before and after Acid Challenge

This study aimed to evaluate in vitro the degree of surface smoothness provided by two different polishing techniques and the effect of acid challenge on the alteration of surface roughness (Ra), microhardness (Knoop), and color (ΔE00) of three nanoparticulate composites, simulating 1 year of exposure to hydrochloric acid (HCl). Eighty specimens for each composite were divided into four groups (n = 240), being control without polishing, control with wear, WPC (wear + polishing with Cosmedent Kit), and WPB (wear + BisCover LV liquid polish). Repeated measures ANOVA was applied for Ra and Knoop Microhardness. For the color (ΔE) three-way ANOVA was applied. In cases of statistically significant the Tukey posttest was applied (α = 0.05). Both types of polishing tested resulted in a surface smoothness below the critical value established by the studies (Ra ≥ 0.2 μm), even after immersion. The microhardness of all composite resins decreased after the challenges. The specimens immersed in HCl showed a lower microhardness (42.2 Kgf/mm2) when compared to the specimens immersed in artificial saliva (44.7 Kgf/mm2). Regarding the color change, the composites presented values compatible with clinical acceptability, with a statistically significant difference only between the control group and the other types of polishing for the Z350 XT resin (ΔE00 = 3.78). It was concluded that both mechanical and chemical polishing produced a satisfactory surface smoothness, even after immersions in artificial saliva and HCl. The microhardness of the composites was affected by the challenges and the composites tested were within clinical acceptability with regard to color change.