Acrylic copolymer systems consisting of methyl methacrylate and triethylene glycol dimethacrylate with different chemical compositions were synthesized through bulk polymerization using N,N-dimethyl-p-toluidine as an acelerator to obtain nonshrinkable polymers. The use of the tertiary amine on this formulation produces an increase on the volume of the material due to a phase separation in the copolymer, which compensates the volume reduction upon curing. The specific volumes of all materials were determined by volume dilatometry using a dilatometer specially constructed for this purpose.