| abstract |
A curable composition that includes a urethane multifunctional (meth)acrylate, an inorganic filler having a primary particle dimension of at least 200 nm, a photoinitiator system that can be activated by electromagnetic radiation in the range of 340-550 nm, a reactive diluent, and a reinforcing silica having a primary particle dimension of 100 nm of less. The sum of the absolute value of the difference in the refractive index of the filler and the refractive index of the composition cured without filler plus the birefringence of the filler is 0.054 or less, i.e. 0.054≥|n filler −n matrix |+δ filler , where n filler is the refractive index of the filler, n matrix is the refractive index of the composition cured without filler, and δ filler is the birefringence of the filler. |