title: The effect of TiO2 concentration on properties of apatite-mullite glass-ceramics for dental use.
abstract: 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).
  
  
  METHODS
  Ten novel glass-ceramic materials were produced based on the general formula (4.5SiO2-3Al2O3-1.5P2O5-3CaO-CaF2-xTiO2) 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 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 μm/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.
authors.affiliation: Academic Unit of Restorative Dentistry, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield, S10 2TA, UK; Almerqup University, Faculty of Dental Surgery, Department of Restorative Dentistry, Zeleten, Libya. Electronic address: hfamdbayada@gmail.com.
authors.forename: Hawa M
authors.initials: HM
authors.lastname: Fathi
authors.affiliation: Academic Unit of Restorative Dentistry, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield, S10 2TA, UK. Electronic address: a.johnson@sheffield.ac.uk.
authors.forename: Anthony
authors.initials: A
authors.lastname: Johnson
mesh_terms: D001031:Apatites / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D004055:Differential Thermal Analysis; D005898:Glass / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012995:Solubility; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D003764:Dental Materials; C009495:titanium dioxide; D014025:Titanium
keywords: Apatite-mullite; BFS; Glass-ceramics; Solubility; TiO(2)