The purpose of this study was to compare the product profile of a Silorane based composite which polymerizes by a cationic ring opening process with the product profile of different methacrylate based restoratives. Four methacrylate based materials Filtek Z250, Filtek P60,Tetric ceram, Spectrum TPH and a Silorane based material were investigated with regard to their compressive strength, flexural strength, E-Modulus and ambient light stability. The data were analyzed by 1-way ANOVA and 2 sample t test (p<0.05). Shrinkage data were determined by the Archimedes method and the bonded disk method. The reactivity of the Silorane and Tetric ceram were derived from the time resolved shrinkage behaviour and the development of the E-Modulus over time. The Silorane Composite revealed with 0.94 vol% (bonded disk method) and 0.99 vol% (Archimedes method) the lowest polymerization shrinkage among all tested composites. Its reactivity was comparable to the reactivity of Tetric Ceram. However, the ambient light stability of >10 min for Silorane was higher than the ambient light reactivity of the other tested methacrylates (55-90 s). The ring opening chemistry of the Siloranes enables at the first time shrinkage values lower than 1 vol% and mechanical parameters as E-Modulus and flexural strength comparable to those of clinically well accepted methacrylate based composites.