Effect of sapphire particle size on transmittance and strength of sapphire glass composites prepared by melt infiltration

Sapphire glass composites for dental applications were prepared by infiltrating glass melt into a presintered sapphire preform. Six different sapphire performs using powders with different particle sizes were prepared. After infiltrating glass into the porous sapphire preforms, their transmittance, strength and microstructure were examined. The infiltrated glass corroded the sapphire preform, and the dissolved aluminium ions reprecipitated on the sapphire grains during heat treatment for infiltration. A light transmittance of 10–40% at a wavelength of 550 nm was observed, which varied according to the particle size. Sample S 26·0, which was prepared using 26 μm sapphire powder, exhibited a light transmittance and biaxial strength of 35% and 230 MPa, making it suitable for use in dental crown materials. The maximum strength >450 MPa was obtained for the sample with sapphire particle size of 0·8 μm, when the glass was infiltrated at 1300°C for 720 min.