Methods: Three kinds of BPO (benzoyl peroxide) containing monomers were prepared by dissolving various amounts (0, 0.5, or 1 mass%) of 4-META and 1% BPO in a UDMA (urethane dimethacrylate)-based monomer containing 41.6% methacrylic acid. In addition, a 0.7% DMPT (N,N-dimethyl-p-toluidine) containing UDMA monomer was prepared. Two kinds of the prepared monomers were then mixed with SUS447J1 stainless steel (Cr content: 30%) particles to produce BPO and DMPT containing pastes of which metal filler contents were 88.5, 90, or 91.5 mass%. Two kinds of the pastes were mixed at the ratio of 1.75:1. After mixing, the flexural properties of the nine kinds of metal-resin 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 flexural strength ranged from 42.2 MPa (at 0% 4-META and 91.5% filler) to 58.8 MPa (at 1% 4-META and 88.5% filler). The elastic modulus ranged from 14.0 GPa (at 0% 4-META and 88.5% filler) to 20.2 GPa (at 1% 4-META and 91.5% filler). Both the flexural strength and the elastic modulus significantly increased with the increase of 4-META content (p<0.01). However, the former significantly decreased and the latter significantly increased with the increase of metal filler content.
Conclusion: Effects of the important factors useful to develop a better composite resin for magnetic attachment have been clarified. The results were promising as a first step of development.