Dental compositions and methods of formulating a dental composition are described. In one embodiment, the dental composition comprises a polymerizable resin comprising one or more ethylenically unsaturated monomers or oligomers and nano-particles. The nanoparticles have a refractive index of at least 1.600 and an average discrete or aggregate particle size of no greater than 100 nm. The dental composition further comprises inorganic metal oxide filler having a discrete or aggregate average particle size of at least 200 nm. The nanoparticles are present at a concentration to provide a refractive index differential between the cured polymerizable resin and inorganic metal oxide filler such that the contrast ratio of the dental composition is at least 40.