Abstract: A polymeric composition which is capable of being shaped and which preferably is in the form of a sheet, the composition being formed by partially reacting a mixture of(a) the precursors of a polyurethane comprising at least one polyfunctional compound capable of reacting with isocyanate groups and at least one polyisocyanate, and,(b) the precursors of a cured polyester resin comprising at least one ethylenically unsaturated polyester and at least one ethylenically unsaturated monomer copolymerizable therewith,and the composition containing at least one alpha, alpha diketone as a photosensitive catalyst.

Abstract: A dental filling composition comprising(a) from 60 to 80% by weight of the composition of an inorganic particulate filler selected from glass, quartz or silica of which at least 50% of the particles have a maximum dimension of not greater than 300 microns, and(b) a polymerizable material comprising:A polymerizable prepolymer being the reaction product of a urethane prepolymer and 2-hydroxy-ethyl methacrylate;The said urethane prepolymer being the reaction product of a di-isocyanate selected from the group consisting of 4,4'-di-isocyanatodiphenylmethane, hexamethylene di-isocyanate, 4,4'-dicyclohexylmethane di-isocyanate and 2,4-tolylene di-isocyanate, and a diol being the condensate obtained by reacting 2,2-bis-(p-hydroxyphenyl)propane and propylene oxide in a molar ratio of 1:2;Up to 100% by weight of the polymerizable prepolymer of methacrylic acid or an ester of methacrylic acid selected from the group consisting of methyl methacrylate, ethylene glycol dimethacrylate, hydroxyethyl methacrylate, triethylene