Influência da Fonte de Luz Fotoativadora na Fenda de Contração de Polimerização de Resinas Compostas Universais Influence of Photo-Activation Light Source on Polymerization Shrinkage Gap of Universal Composite Resins

The aim of this study was to investigate the influence of photoactivation light source on polymerization shrinkage gap formed by three different universal composite resins, Opallis (FGM), Filtek Z250 (3M Espe) and Filtek Z350 (3M Espe). So, four samples were achieved for each experimental group, being: G1A – Opallis + halogen lamp; G1B – Opallis + light emitting diodes (Led); G1C – Opallis + plasma arc; G2A Filtek Z250 + halogen lamp; G2B Filtek Z250 + Led; G2C Filtek Z250 + plasma arc; G3A Filtek Z350 + halogen lamp; G3B – Filtek Z350 + Led; G3C Filtek Z350 + plasma arc. Each composite was placed in a circular brass mold, and photocured according to manufacturer’s instructions. An exception occurred with plasma arc, when a three seconds photopolymerization time was adopted. Thereupon, the specimens were polished and, after twenty four hours, the polymerization shrinkage gaps of these samples were measured by scanning electronic microscopy. The measurements were obtained in four points located in positions corresponding to three, six, nine and twelve hours of a clock face. Results were submitted to analysis of variance and Tukey’s test with 5% confidence level. The highest mean of polymerization shrinkage gap was related to G3A (26,07μm), while the lowest one was associated to G1A (15,43μm). Therefore, is possible to conclude that different compositions of restorative resins are particularly affected by different photoactivation light sources in terms of polymerization shrinkage.