Matrix-filled liquid radiation curable resin compositions for additive fabrication are described and claimed. Such resins include a cationically polymerizable component that is an aliphatic epoxide, a multifunctional (meth)acrylate component, a cationic photoinitiator, a free-radical photoinitiator, and a matrix of inorganic fillers, wherein the matrix further constitutes prescribed ratios of at least one microparticle constituent and at least one nanoparticle constituent. Also described and claimed is a process for using the matrix-filled liquid radiation curable resins for additive fabrication to create three dimensional parts, and the three-dimensional parts made from the liquid radiation curable resins for additive fabrication.