In vitro wear, hardness, and conversion of diacetyl-containing and propanal-containing resin materials

Objectives. This study was conducted to determine the effect of diacetyl or propanal additives: 1) on the in vitro wear of 22 experimental resin composites; and 2) on the Wallace indentation hardness of the unfilled resins. The objective was to examine the correlation between wear, hardness, and quantity of remaining double bonds (determined previously). Methods. Diacetyl or propanal agents were added in varying concentrations to monomer mixtures. The resins were made light-curing and those used for measurement of wear were loaded with filler. The results were analyzed by ANOVA and Newman-Keulsʹ multiple range tests. Results. In the composite systems, adding diacetyl or propanal resulted in decreased in vitro wear. The quantity of remaining double bonds in the dental polymers with these additives was also reduced. Their effect on Wallace indentation depth was less clear-cut. Low concentrations of additives decreased indentation depth of the unfilled materials, whereas high concentrations increased indentation depth. If it is assumed that differences in the polymer have a major influence on the wear when the filler content and particle matrix interface are kept constant, then the hardness data on the unfilled resin can be used to correlate property changes of the polymer in the composite. A three-dimensional regression analysis found that in vitro wear decreased with decreasing Wallace indentation depth and decreasing quantity of remaining double bonds. Significance. Addition of diketone or monoaldehyde to resin monomers may provide a means of increasing wear resistance of composites and allow their use in stress-bearing areas.