Mechanical and Chemical Properties of Zr and P-Doped Lithium Disilicate Glass Ceramics in Dental Restorations

The Weibull modulus, flexural strength, fracture toughness, Vickers microhardness, and chemical durability of sintered Li2OSiO2 glass ceramic specimens doped with P2O5 or ZrO2 were evaluated in accordance with the norm of EN ISO 6872. Peak crystallization temperatures, crystalline phases, and microstructure were characterized by means of differential thermal analysis, X-ray diffraction, and scanning electron microscopy methods, respectively. Phase formation induced by the addition of P2O5 led to precipitation of Li3PO4, which in turn caused more intensive crystallization of Li2SiO3. The high-temperature crystalline phase Li2Si2O5 was precipitated more intensively in P2O5 containing specimens resulting in an interlocked microstructure of needle like disilicate crystals. Therefore, the P-doped glass ceramic exhibited the optimum mechanical and chemical properties (i.e., m=15, sf=181 +/- 15 MPa, KIC=1.94 +/- 0.19 MPa m1/2, Hv=3.7 +/- 1.1 GPa, chemical solubility=53 +/- 9 mu g/cm2)