[Visible light cured resin. Chronological change in mechanical properties of matrix resin immersed in MeOH].

Monomer composition was examined to improve durability of matrix resin of visible light cured composite resin. As a monomer, five kinds of cyclophosphazene monomers, two kinds of commercial monomers and a mixture of commercial monomers were prepared to the visible light cured resins. The mechanical properties of these set products were examined with time after immersion in MeOH, an aging accelerating solvent. Compressive strength of the resins using cyclophosphazene monomers tended to decrease with time, but it increased in accordance with the increase of the number of polymerization group. Compressive strength of the resins using commercial monomers tended to decrease, but that using the BMPEPP monomer tended to increase with time. Yield point of the resins with the cyclophosphazene monomer 4 PN-(EMA)8 tended to increase with the time but that of the resins with other cases monomers decreased. The yield point of all three resins made using commercial monomers tended to decrease with time, but the rate of decrease was small for BMPEPP monomer. Compressive elastic modulus of the resins using cyclophosphazene monomers tended to increase with time when the number of polymerization group was 6-8, while it decreased when the number was 4-5. When commercial monomers were used, it tended to decrease with time, but the rate of decrease was small for the BMPEPP monomer. Transverse strength of the resins using cyclophosphazene monomers showed a tendency to decrease with time. When a commercial monomer was used, cracks appeared in the Bis-GMA+Tri-EDMA monomer after 7 days, and with the other two monomers, the transverse strength tended to decrease with time, though the rate of decrease was small for the BMPEPP monomer. Transverse elastic modulus tended to decrease with time, but the rate of decrease was small for the BMPEPP monomer.