Dental compositions are described comprising an addition-fragmentation agent comprising at least one ethylenically unsaturated terminal group and a backbone unit comprising an \u03b1,\u03b2-unsaturated carbonyl; at least one monomer comprising at least two ethylenically unsaturated group; and inorganic oxide filler. The orifice installed within a reservoir controls the amount of the driving gas running between the cold reservoir and the pulse tube to constantly maintain a pressure of the cold reservoir. The solid polarization beam splitter component has at least four light entranceexit surfaces with at least one of the light entranceexit surfaces including a step.