A critical analysis of the degree of conversion of resin-based luting cements

Objective

This study analyzed the degree of conversion (DC%) of four resin-based cements(All Ceram, Enforce, Rely X ARC and Variolink II) activated by two modes (chemicaland dual), and evaluated the decrease of DC% in the dual mode promoted by theinterposition of a 2.0-mm-thick IPS Empress 2 disc.

Material and Methods

In the chemical activation, the resin-based cements were prepared by mixing equalamounts of base and catalyst pastes. In the dual activation, after mixing, thecements were light-activated at 650 mW/cm² for 40 s. In a third group,the cements were lightactivated through a 2.0-mm-thick IPS Empress 2 disc. The DC%was evaluated in a FT-IR spectrometer equipped with an attenuated totalreflectance crystal (ATR). The data were analyzed by two-way ANOVA and Tukey''s HSDtest.

Results

For all resin-based cements, the DC% was significantly higher with dualactivation, followed by dual activation through IPS Empress 2, and chemicalactivation (p<0.05). Irrespective of the activation mode, Rely X presented thehighest DC% (p<0.05). Chemically activated Variolink and All Ceram showed theworst results (p<0.05). The DC% decreased significantly when activation wasperformed through a 2.0-mm-thick IPS Empress 2 disc (p<0.05).

Conclusions

The results of the present study suggest that resin-based cements could presentlow DC% when the materials are dually activated through 2.0 mm of reinforcedceramic materials with translucency equal to or less than that of IPS-Empress2.