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Effect of photoactivation mode on the hardness and bond strength of methacrylate- and Silorane monomer-based composites.

PURPOSE
To evaluate the Knoop hardness (KH) and the bond strength (BS) at the tooth/restoration interface of conventional methacrylate- (Filtek Supreme) and silorane-based (Filtek P90) composites photoactivated by different methods using an LED Freelight 2.


MATERIALS AND METHODS
Bond strength was tested in a universal testing machine by the "push-out" test in restored cavities measuring 2 × 1.5 × 2 mm with a C-factor of 2.2, prepared in 60 bovine teeth. To restore the cavities, the respective adhesive system of each composite was used (Single Bond 2 and P90 system adhesives). The composites were photoactivated by 3 different methods: continuous light: 40 s at 1000 mW/cm²; soft-start: 10 s at 150 mW/cm² + 38 s at 1000 mW/cm²; pulse delay: 5 s at 150 mW/cm², followed by a 3-min wait (without photoactivation) and 39 s at 1000 mW/cm². Before the push-out test was performed, the KH was analyzed at the top and bottom of the restorations. Data were statistically anaylzed using ANOVA and Tukey's test.


RESULTS
The photoactivation methods produced no differences in BS or KH in the same composite, while Filtek P90 (28.0 MPa) showed higher BS values than Filtek Supreme (22.3 MPa) and a lower KH.


CONCLUSION
The composite Filtek P90 was capable of increasing bond strength, but presented lower Knoop hardness.