Development of low-shrinkage epoxy-methacrylate hybrid dental composite materials using a dual-curing system

The aim of this study was to develop and evaluate experimental dental composite materials that offer reduced polymerization shrinkage and improved monomer conversion compared to conventional methacrylate-based systems.

Experimental composites were prepared using a combination of free-radical and cationic initiators. The photopolymerization systems included 1 wt.% TPO, a 7:3 wt ratio of UDMA/TEGDMA monomers, 3 wt.% cationic initiator Sylanto 7MP, and epoxy monomer CADE. Inorganic fillers such as hydroxyapatite and dental glass-forming mixed oxides were incorporated. The composites were evaluated for monomer-to-polymer conversion, polymerization shrinkage, hardness, and sorption according to PN-EN ISO 4049 standards.

The experimental materials showed reduced polymerization shrinkage and higher conversion rates compared to traditional methacrylate-based composites. Mechanical testing confirmed satisfactory hardness and sorption values remained below 40 µg·mm⁻³ after seven days of incubation in various solutions, in accordance with PN-EN ISO 4049 requirements.

The incorporation of dual photoinitiator systems-combining both free-radical and cationic mechanisms-along with a carefully selected blend of monomers and bioactive inorganic fillers, resulted in composite materials with potentially improved performance characteristics. Notably, the materials demonstrated higher monomer-to-polymer conversion rates and reduced polymerization shrinkage, which may help to minimize marginal gap formation. The mechanical and sorption properties were within the limits defined by PN-EN ISO 4049. These findings may indicate that the developed composites could address some limitations of traditional methacrylate-based systems. Further in vitro and in vivo studies are warranted to evaluate long-term behavior, biocompatibility, and performance under functional loading conditions.

The newly developed composites reduce polymerization shrinkage and improve monomer conversion, which could potentially contribute to more durable dental restorations and may lower the risk of marginal leakage and postoperative sensitivity. Further studies are needed to assess their clinical performance.