IADR Abstract Archives
Are Inert Glasses Really Inert?
Objectives: Inert glasses are widely used as structural fillers in composite resins to reduce shrinkage and improve mechanical properties. These glasses are assumed to be chemically stable when in contact with oral fluids and are not expected to result in significant ion release and degradation. The aim of this study was to investigate the degradation and ion release of a typical “inert glass”.
Methods: An inert SiO2-Al2O3-BaO-B2O3-F glass (75mg) particle size @1micron typical of those used commercially was immersed into 50 mL of Tris Buffer (pH 7.3) for times up to 28 days. The glass was filtered off after each time point and dried overnight for characterisation. ATR-FTIR and XRD was used to investigate glass degradation. Solid state 19F, 27Al and 11B-NMR was used to investigate the glass structure before and after immersion. The supernatant solution after filtration was characterised using ISE and ICP-OES to quantify the ion release.
Results: ATR-FTIR and XRD confirmed the glass was amorphous and did not show any evidence for degradation after immersion. However, there was significant release of boron, silicon barium and fluoride upon immersion of up to 17, 85 and 17 ppm respectively. There was also evidence for silicon release, suggesting degradation of the glass. There were no significant changes in the 27Al and 11B-NMR spectra, before and after immersion. However, the 19F-NMR spectra showed evidence of significant changes after immersion.
Conclusions: The inert glass exhibited glass degradation and ion release, suggesting that not all inert glasses are completely inert. Glass suppliers should not claim inert properties if the glass presents significant ion release upon immersion. Clinically glass particles in the surface of composite resin restorations that are prone to glass degradation are likely to adversely influence the wear behaviour. Furthermore, increased glass degradation would be expected under acidic conditions compared to pH 7.3 investigated here.
Methods: An inert SiO2-Al2O3-BaO-B2O3-F glass (75mg) particle size @1micron typical of those used commercially was immersed into 50 mL of Tris Buffer (pH 7.3) for times up to 28 days. The glass was filtered off after each time point and dried overnight for characterisation. ATR-FTIR and XRD was used to investigate glass degradation. Solid state 19F, 27Al and 11B-NMR was used to investigate the glass structure before and after immersion. The supernatant solution after filtration was characterised using ISE and ICP-OES to quantify the ion release.
Results: ATR-FTIR and XRD confirmed the glass was amorphous and did not show any evidence for degradation after immersion. However, there was significant release of boron, silicon barium and fluoride upon immersion of up to 17, 85 and 17 ppm respectively. There was also evidence for silicon release, suggesting degradation of the glass. There were no significant changes in the 27Al and 11B-NMR spectra, before and after immersion. However, the 19F-NMR spectra showed evidence of significant changes after immersion.
Conclusions: The inert glass exhibited glass degradation and ion release, suggesting that not all inert glasses are completely inert. Glass suppliers should not claim inert properties if the glass presents significant ion release upon immersion. Clinically glass particles in the surface of composite resin restorations that are prone to glass degradation are likely to adversely influence the wear behaviour. Furthermore, increased glass degradation would be expected under acidic conditions compared to pH 7.3 investigated here.