Quantity of remaining double bonds of propanal-containing resins

Improved mechanical properties of resin composites have been reported to be a consequence of the addition of aldehyde to the resins. The objective of the present study was to examine whether this improvement could be attributed to an increased degree of conversion of double bonds. For this purpose, propanal was added to monomer mixtures, which were then made light-curing. The monomer mixtures were varied with respect to monomer composition and content of propanal. The quantity of remaining double bonds was determined by means of transmission infrared spectra of the resins recorded before and after wet or dry storage for one week. The addition of propanal resulted in a decrease in the quantity of remaining double bonds by as much as 89% as compared with the mixtures without propanal. Negative correlations of statistical significance were found between the content of propanal and quantity of remaining double bonds in BISGMA:TEGDMA-based as well as in UEDMA:HEMA-based resins for both modes of storage. Significant negative correlations were found between the quantity of remaining double bonds and the previously determined mechanical properties.