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The present investigation was undertaken to obtain information about the structural, thermal, morphological, surface charge and textural properties of the synthesized dodecyltrimethylammonium-smectite composites at various surfactant concentrations by means of powder X-ray diffraction, attenuated total reflection Fourier transform infrared, thermal analyses, scanning electron microscopy, electrophoretic mobility and surface area measurement techniques. The basal spacing values of organo-smectites varied between 13.55 and 17.00 angstrom that point out the successful intercalation of the surfactant cations into smectite layers with different molecular arrangements either lateral monolayer or lateral bilayer. Intercalation of surfactant cations led to appreciable decreases in the intensities of the bands at 3402 and 1635 cm(-1) which originate from OH stretching and bending vibration of sorbed water molecules, respectively. Thermal analysis data showed that all organo-smectites had lower adsorbed water losses than raw and sodium-smectite and the removal of surfactant species occurred in the temperature range of 130-720 degrees C. The specific surface areas, pore volumes and micropore surface areas of organo-smectites decreased while the average pore width of these species increased with respect to that of raw smectite. The surfactant cations located in the interlayer spaces caused significant alterations in electrophoretic mobility values and morphology of raw smectite. (C) 2015 Elsevier B.V. All rights reserved.

Organosmectites were prepared by the intercalation of hexadecyltrimethylammonium cations at various ratios into interlayer of Unye smectite. Structural, thermal, morphological and textural properties of the synthesized organosmectites were characterized. Afterwards, a novel potentiometric PVC-membrane thiocyanate selective electrode was prepared based on the obtained hexadecyltrimethylammonium modified smectites as electroactive material. The basal spacing values of organosmectites were observed in the range of 15.61 and 35.50 A. Powder X-ray diffraction data show that the surfactant cations penetrated into the smectite layers with different molecular arrangements. Modification of smectite with hexadecyltrimethylammonium led to appreciable decreases in the intensities of the FUR bands at 3402 and 1635 cm(-1) and the new characteristic vibrational bands at 2927, 2850, 1472 and 722 cm(-1) originating from the surfactant molecules appeared. The thermal analysis data showed that the decomposition of surfactant species occurred in the temperature range of 170-720 degrees C and the amount of dehydrated water gradually decreased with the increase in surfactant amount. The intercalation of surfactant species within the gallery spacing led gradually to smaller surface areas. In addition, the electrophoretic mobility values indicate that excess surfactant loadings also generate positive charges on the organosmectite surfaces. The most convenient membrane composition resulting in the best potentiometric performance was investigated. The optimum membrane composition was determined to have 20.0% (w/w) 2.5CEC.HDTMA-smectite, 26.0% (w/w) PVC, 54.0% (w/w) DBP The fabricated electrode exhibited a linear response over the thiocyanate concentration range of 1.0 x 10(-4)-1.0 x 10(-1) M (R-2 = 0.9996) with a slope of -48.6 mV/decade. The detection limit, response time and pH working range were determined as 4.3 x 10(-5) M, similar to 10 s and 4-8, respectively. The proposed electrode exhibited selective potentiometric response to thiocyanate comparable to most of the common anions. (C) 2015 Elsevier B.V. All rights reserved.

To evaluate the fracture strength of inlay-retained, surface-retained, and cantilevered fiber-reinforced adhesively fixed dental prostheses (FRA-FDPs) in the anterior region.Thirty-two sound human right central incisors and canines were divided into four groups. Test groups were as follows: group 1, both teeth had deep cavity preparation; group 2, both teeth had shallow cavity preparation; group 3, only the canine teeth had deep cavity preparation; group 4, no preparation was made on the abutment teeth. Lateral pontics were restored with FRA-FDPs. All restorations were subjected to fracture loading from the lateral pontic. The restorations were tested in a universal testing machine (LRX Material Testing Machine) with a crosshead speed of 1 mm/min. One-way ANOVA was used for statistical analyses. Fracture modes were examined visually.The highest (667.3 ± 90.4 N) and the lowest (409.3 ± 158.1 N) debonding values were found for groups 4 and 3, respectively.Different preparation designs (inlay-retained, surface-retained) had no significant effect on fracture strength of FRA-FDPs in the anterior region. However, a cantilever design exhibited significantly lower fracture strength. Delamination of the veneering composite was observed as the primary failure type after fracture tests.

The aim of this study was to investigate the effect of different resin cement film thicknesses on the shear bond strength of resin core materials to lithium disilicate ceramics. Forty IPS Empress 2 ceramic disks were bonded to the core materials (Bis-core and Smile) with resin cement film thicknesses of 50 or 100 μm. Shear bond strength was measured using a universal testing machine. Data were analyzed using two-way analysis of variance and independent t tests. The core material used and resin cement film thickness had a significant effect on shear bond strength values (P.001). Greater resin cement film thickness resulted in decreased bond strength of the core materials to lithium disilicate ceramics.