The effect of TiO2 concentration on properties of apatite-mullite glass-ceramics for dental use

Objective. The aim of this study was to evaluate the effect of TiO2 concentration on the properties of apatite-mullite glass-ceramics namely strength and the chemical solubility to comply with the ISO standard recommendations for dental ceramics (BS EN ISO 6872-2008) [1]. Methods. Ten novel glass-ceramic materials were produced based on the general formula (4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-3CaO-CaF2-xTiO(2)) where x varied from 0.5 to 5 wt%. Glass with no TiO2 added (HG1T0.0) was used as a reference. Discs of 12 mm diameter and 1.6 mm (+/-0.2 mm) thickness were prepared for both biaxial flexural strength (BFS) and chemical solubility testing, in accordance with the BS EN ISO 6872-2008 [1] for dental ceramics. All produced materials were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Energy dispersive X-ray analysis (EDS) was also carried out on some samples to identify the element composition of samples. Results. Increasing the concentration of TiO2 from 0.5 wt% to 2 wt% significantly (P < 0.05) increased the chemical solubility of the material. With the material containing 2.5 wt% of TiO2, the solubility significantly reduced (P < 0.05) and resulted in a solubility value of 228.3 mu m/cm(2) and BFS value of 197.9 MPa. Increasing the TiO2 concentration more than 2.5 wt%, led to a significant (P < 0.05) increase in solubility and a reduction in BFS. Conclusions. TiO2 is an effective agent for improving the durability and the mechanical properties of an apatite-mullite glass-ceramic only up to 2.5 wt% concentration. (C) 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.