Effects of 4-META Content on Properties of Magnetic Composite Resin

Methods: Six kinds of base monomers were prepared by dissolving 2, 4, 6, 8, 10 or 12 mass% of 4-META in UDMA (urethane dimethacrylate)-based monomer containing 42% methacrylic acid. Then small amounts of benzoyl peroxide were added to the base monomers. To prepare catalyst monomers, small amounts of N,N-dimethyl-p-toluidine were added to UDMA monomer. Each of the base and catalyst monomers was then mixed with SUS447J1 stainless steel (30% Cr, 2% Mo) particles. The metal filler content in each paste was 90 mass%. The base and catalyst pastes were mixed at the ratio of 1.75:1. After mixing, the setting and flexural properties of six kinds of composites were measured at five replications according to the method described in ISO 4049:2000 for "Polymer-based filling, restorative and luting materials".

Results: The working time ranging from 125 sec to 161 sec satisfied the requirement of ISO 4049 (more than 90 sec) at all conditions. The setting time ranging from 254 sec to 285 sec also met the requirement (less than 5 min). The flexural strength was significantly affected (p<0.001) by the experimental conditions, and ranged from 53.2 MPa to 70.6 MPa. The elastic modulus, ranging from 17.5 GPa to 19.3 GPa, was also affected significantly (p<0.05). Both the flexural strength and the elastic modulus increased with the increase of 4-META content up to 10%, and then decreased at 12% 4-META.

Conclusion: The optimum 4-META content useful to develop a better composite resin for magnetic attachment has been clarified.