Abstract
Resin-based composite materials that include diacrylates such as urethane-dimethacrylate(UDMA)and triethyleneglycol-dimethacylate(Tri-EDMA)have been used as restorative materials for crowns and bridges.In this study, to improve the viscoelastic properties of such restorations, six experimental composite materials produced using ultrafine SiO2 particles(0.007 and 0.14 μm)were made.Stress relaxation modulus(Er(20)), water absorption, thermal expansion and residual monomers for these materials were determined and discussed.The results obtained were as follows: (1)the temperature dependence of Er(20)decreased by adding the SiO2 filler, (2)the increase of filler particle size reduced the amount of thermal expansion, (3)the increase of UDMA raised Er(20)in the temperature range below 50℃. Although the addition of filler produced an increase of water absorption or residual monomer, the marked improvemet of relaxation modulus was observed.This finding may be favorable as restorative materials for crowns and bridges.
