Influence of preheating on elastic modulus, flexural and cohesive strength of bulk-fill composites

ABSTRACT The purpose of this study was to evaluate the influence of pre-heating of bulk-fill composites on flexural strength, modulus of elasticity and cohesive strength. Five composites were tested: Tetric N-Ceram Bulk-fill (TBF). X-tra Fill (XTF), Filtek Bulk-fill (FBF), Aura Bulk-fill (ABF) and Filtek Z250 (FZ, control). The samples were conditioned at 37ºC for 24 hours before being tested. Results were statistically analyzed by ANOVA and Tukey test. FBF, XTF and FZ composites had the highest cohesive strengths, and preheating positively influenced this property. XTF and FBF materials without preheating showed the highest values of flexural strength and modulus of elasticity. For these properties, preheating caused a reduction in XBF, FBF and ABF resins, had no effect on TBF resin and caused an increase in FZ resin. The preheating positively influenced the cohesive strength of the studied materials, improving the performance of all bulk-fill resins. Tetric N-Ceram Bulk Fill/ Ivoclar did not show changes on modulus of elasticity and flexural strength when preheated, while the other bulk-fill composites presented lower results for these two properties after heating.