Comparison of resistance of two types of heat-curing resins to impact force

ABSTRACT

Accidental fracture of acrylic dental appliances is common during denture service. Recent efforts had been made to improve this deficiency by developing different polymers bases upon polymethyl methacrylate with the addition of rubber. In this study, specimens were prepared according to the British St and ard Specification No. 771 to evaluate the impact of strength of high impact type and conventional heat-cure polymethyl methacrylate in relation to two different curing techniques. The fracture surfaces of two specimens of each group were examined using scanning electron microscope in order to study their microstructure. The results obtained from this study demonstrated a significant increase in the impact strength of high impact type [group 2] than conventional heat-cure polymethyl methacrylate [group 1]. A high significant increase in impact strength was observed in group 4 of high impact type when cured for long time at constant temperature and this technique may reduce the accidental fracture of acrylic dental appliances