Development of Metal-Resin Composite Restorative Material Part 2 Effects of acid and heat treatments of silver-tin filler particles on flexural properties of metal-resin composite

The effects of acid and heat treatments of silver-tin filler particles on the flexural properties of metal-resin composite restorative materials were investigated. Five metal-resin composite restorative materials containing different silver-tin filler particles treated under different conditions were experimentally prepared. The conditions of the alloy particles were; 1) as atomized (NT), 2) 1.8% HCl acid-treated (AT), 3) heat-treated at 150°C for 5 min after AT (A15), 4) heat- treated at 200°C for 5 min after AT (A20) and 5) heat-treated at 250°C for 5 min after AT (A25). The flexural strength and the flexural modulus of elasticity were measured for the five metal- resin composites to evaluate the effects of the acid and heat treatments. The flexural strength of the prepared composites was significantly influenced by the surface condition of the filler particles (p<0.01), and increased significantly when the as atomized particles (NT) were acid-treated (AT) or acid- and heat-treated at 150°C (A15), but then significantly decreased as the heat treatment temperature increased (A20 and A25). The strength of the A15 composite was significantly higher than those of the other composites, and exceeded that (about 60 MPa) of the previous composite with no treatment. No significant difference was found in the flexural modulus of the composites.