Physical properties of a hybrid and a nanohybrid dental light-cured resin composite

This work was aimed at the study of some physical properties of two current light-cured dental resin composites, Rok (hybrid) and Ice (nanohydrid). As filler they both contain strontium aluminosilicate particles, however, with different size distribution, 40 nm-2.5 μm for Rok and 10 nm-1 μm for Ice. The resin matrix of Rok consists of UDMA, that of Ice of UDMA, Bis-EMA and TEGDMA. Degree of conversion was determined by FT-IR analysis. The flexural strength and modulus were measured using a three-point bending set-up according to the ISO-4049 specification. Sorption, solubility and volumetric change were measured after storage of composites in water or ethanol/water (75 vol%) for 1 day, 7 or 30 days. Thermogravimetric analysis was performed in air and nitrogen atmosphere from 30 to 700°C. Surface roughness and morphology of the composites was studied by atomic force microscopy (AFM). The degree of conversion was found to be 56.9% for Rok and 61.0% for Ice. The flexural strength of Rok does not significantly differ from that of Ice, while the flexural modulus of Rok is higher than that of Ice. The flexural strengths of Rok and Ice did not show any significant change after immersion in water or ethanol solution for 30 days. The flexural modulus of Rok and Ice did not show any significant change either after immersion in water for 30 days, while it decreased significantly, even after 1 day immersion, in ethanol solution. Ice sorbed a higher amount of water and ethanol solution than Rok and showed a higher volume increase. Thermogravimetric analysis showed that Rok contains about 80 wt% inorganic filler and Ice about 75 wt%. © 2009 Koninklijke Brill NV, Leiden

Effect of the silane concentration on the selected properties of an experimental microfilled composite resin

The aim of present study was evaluate the effect of different percentages of an organo-functionalized silane monomer as adhesion promoter between barium borosilicate glass fillers and (co)monomer blend in experimental dental composite resin. Gamma-methacryloxypropyltrimethoxysilane (γ-MPS) was assessed in an experimental luting cement, at the concentrations of 0, 1, 3, 5, 7 and 10 (wt%). The experimental resin without fillers was used as control group. The flexural strength (FS) and elastic modulus (E) were obtained by mini-flexural test and expressed in MPa and GPa, respectively. Water sorption (WS) and solubility (SL) were determined based on ISO standard 4049:2000. Kruskal–Wallis and Student–Newman–Keuls test were used for comparisons of FS, E and WS. The comparisons of SL means were performed using one-way ANOVA and Tukey's method (α = 5 %). The treatment with 3 % silane revealed statistically higher FS, while the group treated with 1 % silane showed statistically higher E than 3 % silane (p < 0.05) and E similar to control. The experimental composite without filler content showed the highest SL (p < 0.05) while the control composite showed the highest WS (p < 0.05). Based on present findings, flexural strength and elastic modulus can sometimes be improved with lower concentrations (1–3 %) rather than higher concentrations (5–7 %) of the silane (γ-MPS) used as coupling agent on barium borosilicate glass filler microparticles of the dental composite resin

Simulation of conversion profiles inside a thick dental material photopolymerized in the presence of nanofillers

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