Influence of ZrO2 oxide on the properties and crystallization of calcium fluoro-alumino-silicate glasses

The impact of ZrO2 content of the glass on the formation, properties and crystallization of glass ionomer cements (GICs) was investigated. Glass series based on SiO2-Al2O3-ZrO2-P2O5-CaO-CaF2 system was synthesized and studied. The cements were characterized using a setting time, flexural strength, fracture toughness and in vitro biocompatibility test. The setting time of the ionomer cement increased with increasing the ZrO2 content of the glass. The cements showed a slight decrease of cell biocompatibility with increase the ZrO2 oxide content in the glasses. The results also showed that the flexural strength and the fracture toughness of the cements increased with immersion time and ZrO2 oxide content. The crystallization characteristics of the glasses were investigated by differential scanning calorimeter (DSC) and X-ray diffraction analysis (XRD). The addition of ZrO2 oxide in the glasses led to increase both the glass transition and crystallization temperatures. Fluorapatite [Ca5(PO4)3F], mullite [Al6Si2O13], cristobalite [SiO2] and zircon [ZrSiO4] phases were crystallized from the investigated glasses. The role played by the glass oxide constituents in determining the setting time, mechanical properties and crystallization characteristics of the prepared glass ionomer was discussed.