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The aim of this study was to evaluate the effect of different photoactivation methods and base materials on the stress generated by the polymerization shrinkage of composites. The evaluated groups for the base material were: (G1) 1 coat of adhesive; (G2) 3 coats of adhesive, and (G3) flowable composite as a liner. The groups were divided in agreement with the photoactivation method: Continuous light (CL); Stepped Light (SL); Intermittent Light (IL); LED and Xenon Plasma Arc (XP). The generated stress was measured in a universal testing machine 5 minutes after the end of the photoactivation. The results were submitted to ANOVA and the averages values compared by Tukey test (5%). Inside of G1 group the mean values varied between 1.62 MPa (XP) to 2.22 MPa (CL), in which the XP method presented statistically inferior values to the other appraised methods. The values inside of G2 and G3 varied from 1.64 MPa (LED) to 2.15 MPa (CL) and 1.24 MPa (IL) to 1.92 MPa (SL), respectively, and the methods LED and IL presented statistically inferior values comparatively to the method CL inside of G2 and CL and SL inside of G3. The use of base materials was shown efficient in the reduction of the stress level generated by the polymerization shrinkage of restorative composites when LED or Intermittent light photoactivation methods are used.References
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