Method: Three materials were divided into 5 groups. Two resin composites, nanofilled (Z350 XT/3MESPE) and microhybrid (Opallis/FGM), pre–heated and room temperature, and a resin cement (AllCem/FGM) were tested. Following the guidelines from ISO 4049, each material (0,05mL) was pressed under 15kg between two glass plates covered with polyester film for 180 seconds. After pressed, the material was light polymerized with a LED for 40s and the film thickness measured using a digital micrometer. When testing the groups of pre-heated resin composites the material was heated (64°C) on a specific device (CalSet/AdDent) before all procedures. Data were analyzed using t-Student, ANOVA and Tukey post hoc test (α=.05).
Result: Resin cement group showed the lower film thickness mean (28,2 µm), followed by the microhybrid and the nanofilled, 45,3 µm and 59,7 µm, both pre-heated. Thus, the higher values were obtained with room temperature composites. Nanofilled room temperature group presented the highest thickness (96,1 µm). Statistical difference was found between all groups.
Conclusion: Pre-heating influenced the film thickness of both composites. Composition plays major role on material viscosity, and in this study microhybrid composite showed better results among test groups. Although not presenting the lower film thickness, as resin cement, some composites could be used for luting indirect restorations when heated.