Some effects of varying denture base resin polymer/monomer ratios

Variations in the polymer/monomer mixing ratios from 1.5:1 to 4.5:1 vol/vol have been evaluated to determine the effect on dimensional accuracy and impact resistance of a PMMA homopolymer. Two polymerisation cycles were used. It was shown that a wide variation in mixing ratios (1.5:1 to 4:1) had no effect on dimensional accuracy or impact resistance and that a polymerisation cycle that includes a final boiling period is preferred. It was further found that notched impact resistance was almost an order of magnitude below unnotched impact resistance, emphasising the weakening effect of sharp contours on the impact resistance of denture resins.