Estabilidade de cor e comportamento mecânico de restaurações de resina composta do tipo Bulk-Fill

Abstract

Resin composites possess greater and greater applicability in restorative dentistry especially due to their ability in mimicking the optical characteristics of dental substrates, and not less important, due to their satisfactory mechanical performance. However, novel resin composites have launched, needing characterization and clinical evaluation. Hence, the purpose of this study was to investigate the color stability and mechanical behavior of new generation, bulk-fill resin composites. Twenty-eight samples were obtained from bovine incisors, which were prepared to cavities with 4 mm-width and 5 mm-thickness. Each sample was randomly separated into four groups (n=7) according to the restorative technique: Controle negativo – none material was applied; Controle positivo – conventional resin composite (Opallis; FGM) was applied using increments of up to 2 mm-thick; Bulk Fill – bulk-fill resin composite with regular viscosity (Opus Bulk Fill; FGM) was applied using only one increment of 5 mm-thick; and Combinada – bulk-fill resin composite with low viscosity (Opus Bulk Fill Flow; FGM) and Opallis were applied in sequence. Color of the restorations was measured using a digital spectrophotometer (Vita Easyshade; Vita Zahnfabrik) and CIEL * a * b * system. The samples were immersed in distilled water, at 37oC, for 30 days; next, they were once again color-measured. All samples were submitted to a mechanical testing machine (DL500; EMIC) for compressive strength evaluation. Young’s modulus and work of fracture were obtained from the stress-strain curves obtained through the mechanical test. All data were analyzed using Analysis of Variance and Tukey (α=5%). The Controle positivo resulted in greater color alteration than the other restorative techniques (p<0,001). All restored groups were stronger than the Controle negativo (p≤0,006). The different restorative techniques resulted in similar Young’s modulus and work of fracture (p≥0,242), except for the Bulk Fill technique, which demonstrated greater compressive strength as compared to the Controle positivo (p=0,05). Overall, the failure mode of the restorations was similar regardless of the group tested. In conclusion, bulk-fill resin composites and their respective restorative technique evaluated in this study are adequate, showing similar mechanical performance to the control technique (incremental technique), as well as greater color stability after a short period of water storage.