Nanofiller loading level: Influence on selected properties of an adhesive resin

ObjectivesTo evaluate the effect of the filler content in the cohesive strength (σ), Weibull modulus (m) and degree of conversion (DC) of an experimental adhesive system.MethodsA HEMA/Bis-GMA/TEGDMA-based adhesive was formulated and filled with silica nanofillers in the following weight percentages (wt%): R0 = 0%; R1 = 1%; R3 = 3%; R5 = 5% and R10 = 10%. The adhesive of Adper Scotchbond Multi-Purpose (SBMP) system was used as a commercial reference. Twenty dumbbell-shaped specimens with cross-sectional area of 0.5 mm2 were made per group and tensile tested with a crosshead speed of 0.5 mm/min until fracture. The cohesive strength was calculated in MPa. DC was obtained through FTIR after light curing for 25 s. Data were submitted to one-way ANOVA and Tukey's test (α = 0.05) and to Weibull analysis.ResultsMean σ results were: R0 = 65.4 ± 8.4; R1 = 73.2 ± 8.8; R3 = 72.0 ± 8.4; R5 = 73.1 ± 9.7; R10 = 85.5 ± 13.1 and SBMP = 79.0 ± 11.0 MPa. R10 presented the highest σ, while R0 showed the lowest. R5 and SBMP did not differ significantly (p < 0.05). Weibull analysis revealed no significant difference in structural reliability between groups. The experimental adhesives presented similar results of DC, which, in turn, were significantly higher than the SBMP.ConclusionsThe addition of 10% filler in weight improves the cohesive strength of the adhesive, not interfering in the structural reliability or the degree of conversion.