Radiopacity and microhardness changes and effect of X-ray operating voltage in resin-based materials before and after the expiration date

this study observed alteration in the radiopacity and microhardness of expired resin-based materials compared to non-expired materials and the operating characteristics of the x-ray source used. five 2 mm-thick cured specimens were prepared for each material: composite resins (p60？, z100？), and a compomer (dyract ap？). radiopacity of the specimens was evaluated comparing the density of the resin-based material to an equivalent (mm) density of a 99.5% pure aluminum step wedge using a transmission densitometer. surface microhardness measurements were carried out using a calibrated vickers indenter on three different points of the same surface. anova and tukey tests (pre-set alpha = 0.05) revealed that expired materials showed no significant change in radiopacity. one material (filtek p60) demonstrated lower radiopacity with lower kvp. change in microhardness wa s statistically significant for z100: for this material, the microhardness after expiration was significantly lower than before the expiration date.