Are glass ionomer cements bioactive? Analysis of ions release, pH, hydroxyapatite nanoprecursors formation, antibacterial activity, and cytotoxicity

Objective

This study assessed the release of F⁻, Ca⁺², PO₄⁻³, alkalinizing activity, cytotoxicity, antibacterial activity, and the hydroxyapatite nanoprecursor formation of six commercial glass ionomer cements (GICs).

Materials and methods

Bioglass (Biodinâmica), Gold label 9 (GC), Vitrofil (DFL), Maxxion (FGM), Vidrion (SS WHITE) and Ionglass (Maquira) were evaluated. pH analysis was performed at different times in initial pH (pH_i) 4 and 7 for 28 days. At day-28, the release of Ca⁺², PO₄⁻³ and F⁻ was analyzed. Fibroblastic cells were used for cytotoxicity tests. Samples were evaluated at 24, 48 and 72 h. The hydroxyapatite precipitate formation was analyzed using SEM/EDS, FTIR/ATR and XRD, after 28 days. S. mutans biofilms were cultured over GIC disks to antibacterial activity assessment.

Results

pH of all GIC were acidic over 28 days. Bioglass had greater F⁻ release when compared to Gold Label (p < 0.05), at pH_i 4. At pH_i 7, there was no difference on F⁻ release between GICs. Ionglass and Vitro fill had the highest Ca⁺² and PO₄⁻³ release. SEM indicated the presence of precipitates on the surface of all GICs and FTIR showed the presence of carbonate (1080/1413/1453 cm⁻¹). XRD did not indicate crystalline hydroxyapatite precursors peaks. All GICs presented cytotoxicity when compared to the control group in 72h (p < 0.05). The GICs did not have antibacterial activity against S. mutans (p < 0.05).

Significance

GICs released ions that are important for tooth remineralization. However, GICs showed low pH, cytotoxicity, lack of antibacterial activity and the absence of precursors of hydroxyapatite indicated that materials were not bioactive.