Microhardness and Chemical Composition of Glass Ionomer and Glass Hybrid Cements Modified with Experimental Bioactive...

The purpose of this in vitro study was to evaluate the effect of bioactive glasses containing a small proportion of fluoride and zinc in lower (BAG1) and higher ratios (BAG2) on the Vickers microhardness (VHN), surface morphology and chemical composition of high-viscosity glass ionomer cement and glass hybrid cement.

Fuji IX (Fuji) and Equia Forte HT (Equia) were modified with 5 wt% BAG1 and BAG2. Six groups were prepared and stored in distilled water: Fuji, Fuji+ BAG1, Fuji+BAG2, Equia, Equia+ BAG1, and Equia+BAG2. BAG1 and BAG2 were characterized using FTIR. VHN was measured after 24 hours and 7 days. Representative samples from all groups were stored in phosphate buffered solution and analyzed using SEM-EDS. Data were analyzed using ANOVA and paired t-tests (α = 0.05).

Fuji and Fuji+BAG1 showed the highest VHN at both time points, whereas BAG2 significantly reduced microhardness compared to original materials Fuji and Equia (p<0.05). All groups exhibited increased VHN over 7 days (p<0.05). FTIR confirmed the amorphous silicate and fluoride content. SEM-EDS confirmed the absence of crystalline precipitates on the material's surface when stored in phosphate containing solution.

BAG1 preserved or slightly enhanced microhardness, while BAG2 significantly reduced it. There were no crystalline precipitates on original or on materials modified with 5 wt% bioactive glass. Optimizing BAG composition is essential to balance mechanical stability and bioactivity of glass ionomers.