Effect of bismuth oxide radioopacifier content on the material properties of an endodontic Portland cement-based (MTA-like) system

The effect of bismuth oxide (Bi2O3) radiocipacifier addition on the material properties of an endodontic Portland cement-based system were investigated. Increasing Bi2O3 content from 0 to 10 wt % resulted in a deterioration of mechanical strength from 82 to 40 MPa, decreasing gradually on further addition to 29 MPa for 40 wt %. Bi2O3 content increase also gradually increased the relative porosity of the set material from 15 to 31%. Strong linear correlationships were found for increases in relative porosity, dry and strut densities, and Bi2O3 content increase. Material constants, such as critical flaw size, were found to alter drastically with Bi2O3 addition and remained constant with further increase, thus affecting the potential longevity of the endodontic model system. The cement system was also found to be comparable in composition and strength to commercial MTA but had lower porosity because of the better workability of the Portland cement component.