Properties of model E-glass fiber composites with varying matrix monomer ratios

ObjectiveTo evaluate properties of fiber-reinforced-composites (FRC) containing Bis-EMA/UDMA monomers but identical dispersed phase (60% wt BaSi glass power +10% wt E-glass fibre).MethodsA control (Group A), monomer mixture comprising 60% Bis-GMA, 30% TEGDMA, and 10% PMMA (typical FRC monomers) was used. The following monomer mass fractions were mixed: 50% bis-GMA plus 50% of different ratios of Bis-EMA+UDMA to produce consistent formulations (Groups B-E) of workable viscosities was also studied. Flexural strength (FS), fracture toughness (KIC), water sorption (SP), solubility (SL) and hygroscopic expansion (HE) were measured. FS and KIC specimens were stored for 1, 7 d, and 30 d in water at 37 °C. SP/SL specimens were water-immersed for 168d, weighed at intervals, then dried for 84 d at 37 °C. To analyze differences in FS, and KIC, a two-way ANOVA and Tukey post-hoc tests (α = 0.05) were conducted. For SP/SL, and HE, one-way ANOVA with subsequent Tukey post-hoc tests (α = 0.05) were utilized.ResultsFS and KIC for groups A, D, E decreased progressively after 1 d. Groups B and C (highest amounts of Bis-EMA) did not decrease significantly. The modified matrix composites performed significantly better than the control group for SP and HE. The control group outperformed the experimental composites only for SL with up to 250% higher SL for group E (6.9 μg/mm) but still below the maximum permissible threshold of 7.5 μg/mm. Significance:Experimentalcomposites with highest amounts of Bis-EMA showed improved hydrolytic stability and overall enhancement in several clinically-relevant properties. This makes them potential candidates for alternative matrices to a semi-interpenetrating network in fiber-reinforced composites

The effect of desiccation on water sorption,solubility and hygroscopic volumetric expansion of dentine replacement materials

ObjectiveTo evaluate water sorption, solubility and hygroscopic expansion and the effect of desiccation for a calcium silicate-based material, a conventional glass ionomer, and a resin-modified glass ionomer.MethodsWater sorption, solubility and hygroscopic expansion of Biodentine™ (BD), GC Fuji IX GP® FAST (FJ), and Ionolux (IO) were tested under two pre-storage conditions: with desiccation and without desiccation. Disc-shaped samples (n = 5) were immersed in water and weighed at different time intervals (1 h, 24 h, 3 d, 7 d and 30 d) and hygroscopic expansion was recorded at 7 d and 30 d. Data were analysed using Factorial repeated measures ANOVA, one-way/two-way ANOVA, Independent samples t-test and Tukey’s post hoc test (α = 0.05).ResultsWith desiccation, sorption of IO and FJ was 124.33 μg/mm3 and 79.97 μg/mm3 respectively. Solubility was −12.36 μg/mm3 for IO and −20.19 μg/mm3 for FJ. Hygroscopic expansion was 3.01% for IO and −2.35% for FJ.Without desiccation, sorption was in the order: IO ˃ BD ˃ FJ (130.35 μg/mm3, 122.07 μg/mm3, and 107.21 μg/mm3 respectively), while solubility order was: BD ˃ FJ ˃ IO (154.83 μg/mm3, 88.82 μg/mm3, and 25.67 μg/mm3 respectively). IO and FJ showed significant difference in sorption and solubility between the two pre-storage treatment groups (p ˂ 0.005). Hygroscopic expansion was in the order: IO ˃ BD ˃ FJ.SignificanceBD had the highest solubility while IO had the least. The relatively stable polymeric resin in IO may contribute to its low solubility but high hygroscopic expansion. Desiccation had significant effect on sorption, solubility and volumetric expansion of water-based materials.KeywordsSorptionSolubilityHygroscopic expansionDesiccationDentine replacemen