Hardness and fracture toughness of resin-composite materials with and without fibers

摘要

Objective. To investigate the surface micro-hardness (VHN) and fracture toughness (K-IC) of resin-composites, with and without incorporated short fibers, after solvent storage.Methods. Three resin-composites incorporating fibers, additional to particle reinforcement, were examined: everX (TM), NovoPro Fill (TM) and NovoPro Flow (TM). Four composites were used as controls, with only particle reinforcement: Filtek bulk Fill (TM), Filtek bulk one (TM), Filtek XTE (TM), and Filtek Flow XTE (TM). For hardness measurement, materials were cured in 2 mm thick molds for 20 s by a LED source of average irradiance 1.2 W/cm(2). Specimens (n = 6/group) were stored dry for 1 h and then in either water or 75% ethanol/water for 1 h, 1 day and 30 days at 37 +/- 1 degrees C. Vickers hardness was measured under a load of 300 g for 15 s. For fracture toughness (K-IC) measurements, single-edge-notched specimens (n = 6/group) were prepared: (32 x 6 x 3 mm) for 3-point bending and stored for 1 and 7 days in water at 37 degrees C. Fractured surfaces of fiber-reinforced composite were examined by scanning electron microscopy (SEM). VHN data were analyzed using three-way ANOVA, one-way ANOVA and the Tukey post hoc test (p = 0.05). K-IC data were analyzed by two-way ANOVA and one-way ANOVA and the Tukey post hoc test (p = 0.05). An independent t-test was used to detect differences (alpha = 0.05) in K-IC between stored groups for each material.Results. VHN decreased for all composites with storage time in both solvents, but more appreciably in 75% ethanol/water (an average of 20%). K-IC ranged from 2.14 (everX Posterior) to 0.96 NovoPro Flow) MPa. m(0.5). The longer storage period (7 days) had no significant effect on this property relative to 1 day storage.Significance. Reinforcement with short fibers, and possibly matrix compositional differences, significantly enhanced the fracture toughness of EVX. However, for nano-fiber containing composites, there were no evident beneficial effects upon either their fracture toughness or hardness compared to a range of control composites. Water storage for 7 days of all these resin-composites produced no significant change in their K-IC values, relative to 1 day storage. (C) 2019 Published by Elsevier Inc. on behalf of The Academy of Dental Materials.