The effect of ZrO2 and TiO2 on solubility and strength of apatite–mullite glass–ceramics for dental applications

Abstract

The effect of ZrO2 and TiO2 on the chemical and mechanical properties of apatite-mullite glass-ceramics was investigated after sample preparation according to the ISO (2768:2008) recommendations for dental ceramics. All materials were characterized using differential thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. X-ray fluorescence spectroscopy was used to determine the concentrations of elements present in all materials produced. The chemical solubility test and the biaxial flexural strength (BFS) test were then carried out on all the samples. The best solubility value of 242±61μg/cm(2) was obtained when HG1T was heat-treated for 1h at the glass transition temperature plus 20°C (Tg+20°C) followed by 5h at 1200°C. The highest BFS value of 174±38MPa was achieved when HG1Z and HG1Z+T were heat-treated for 1h at the Tg+20°C followed by 7h at 1200°C. The present study has demonstrated that the addition of TiO2 to the reference composition showed promise in both the glass and heat-treated samples. However, ZrO2 is an effective agent for developing the solubility or the mechanical properties of an apatite-mullite glass-ceramic separately but does not improve the solubility and the BFS simultaneously.