MECHANICAL-PROPERTIES AND FAILURE ANALYSIS OF ALUMINA-GLASS DENTAL COMPOSITES

Strength measurements and fractography were used to investigate the fa ilure of alumina-glass dental composites containing 75 vol% alumina an d 25 vol% glass. Alumina compacts were prepared by slip casting and si ntering at 1100 degrees C for 2 h. Dense composites were made by infil trating partially sintered alumina with glass at 1150 degrees C for 8 h. Young's modulus and the hardness of the composites were 270 GPa and 12 GPa, respectively. The mean strength (460 MPa) and fracture toughn ess (4.0 MPa . m(1/2)) of the composites were insensitive to the glass thermal expansion coefficient (alpha(glass) = 5.9 x 10(-6) to 7.8 x 1 0(-6) degrees C-1). Typical flaws mere pores and cracklike voids forme d by poor particle packing and differential sintering near agglomerate s of alumina in the composite, Crack deflection and crack bridging wer e observed in indentation cracks, Fracture toughness was single-valued because the alumina particle size was small (approximate to 3 mu m), Alumina-glass composites are promising new ceramics for dental crown a nd bridge applications, because their strength and fracture toughness are approximate to 2 times greater than those of current dental cerami cs.