Comparative study of free-volume changes in light-cured (dimeth)acrylate-type dental resin composites affected to artificial aging in dry-air and water-immersed mode

This research is intended to compare degradation processes in light-cured (dimeth)acrylate-type polymer/filler dental composites affected aging dry-air and water-immersed mode. The positron annihilation lifetime (PAL) spectroscopy has been employed study changes atomic-deficient structure these under aging. Under light-curing polymerization initiating crosslinking of monomer chains, fragmentation free-volume holes resin matrix dominates over enhanced fraction trapped positrons, since filler–particles assemblies get be more tightly covered by surrounding polymer causing disappearing interfacial voids at the filler–polymer surface. Therefore, PAL spectra-transforming trend obeys inverse positron-to-Ps trapping conversion. In contrast, restoratives direct Ps-to-positron After aging, observed density sites are ascribed a strong agglomeration Ps-decay sub-system accompanied weaker appearance traps sub-system. water Ps-decaying suppressed due absorbed molecules, this effect being slightly revealed lower polymerization. New interfaces all composites. agglomerated inside artificially aged cause their progressive microcracking.