Conversion of dual cure luting cements.

This investigation determined the efficiency and rate of cure of polymeric luting agents when cured under manufacturers' instructions with the appropriate visible light source, and under conditions where light was excluded and curing was reliant on the chemical reaction only. Indentation hardness was used as a reflection of conversion. There was a rapid increase in hardness immediately after light curing followed by a steady increase in hardness over the next 24 h. The non-irradiated chemically cured samples exhibited steadily increasing hardness over 24 h, but were too soft to test in the initial 30 min. Hardness values were extrapolated to obtain predicted values of flexural strength. Dual curing was more effective than chemical curing alone. The results suggest that the formulation of dual cure materials is a balance between high levels of conversion in all aspects of the restoration and colour instability due to amine degradation. Clinically there may be poorly cured areas in the deeper aspects of a deep cavity.