fluorapatite and magnesium-fluoride

MgO, SiO(2), Al(2)O(3), MgF(2), CaF(2), CaCO(3), SrCO(3), and P(2)O(5) were used to prepare glass-ceramics for restorative dental materials. Thermal properties, phases, microstructures and hardness were characterized by DTA, XRD, SEM and Vickers microhardness. Three-point bending strength and fracture toughness were applied by UTM according to ISO 6872: 1997(E). XRD showed that the glass crystallized at 892°C (second crystallization temperature+20°C) for 3 hrs consisted mainly of calcium-mica and fluorapatite crystalline phases. Average hardness (3.70 GPa) closely matched human enamel (3.20 GPa). The higher fracture toughness (2.04 MPa√m) combined with the hardness to give a lower brittleness index (1.81 µm(-1/2)) which indicates that they have exceptional machinability. Bending strength results (176.61 MPa) were analyzed by Weibull analysis to determine modulus value (m=17.80). Machinability of the calcium mica-fluorapatite glass-ceramic was demonstrated by fabricating with CAD/CAM.

Topics: Aluminum Oxide; Aluminum Silicates; Apatites; Calcium Carbonate; Calcium Fluoride; Carbonates; Ceramics; Computer-Aided Design; Crystallization; Dental Enamel; Dental Marginal Adaptation; Dental Materials; Differential Thermal Analysis; Elastic Modulus; Fluorides; Hardness; Hot Temperature; Humans; Inlays; Magnesium Compounds; Magnesium Oxide; Materials Testing; Microscopy, Electron, Scanning; Phase Transition; Phosphorus Compounds; Pliability; Silicon Dioxide; Stress, Mechanical; Strontium; Temperature; Time Factors; X-Ray Diffraction