Search Results (5)

This study aims to evaluate the shrinkage, degree of conversion, water sorption and solubility, and mechanical properties of a newly developed one-shade universal composite and compare it with five other commercially available universal composites with one or multiple shades. Our proprietary resin and filler technologies developed the experimental one-shade universal composite (Experimental). Volumetric shrinkage was determined using the AcuVol video imaging method (n = 5). Degree of conversion was measured using FTIR (n = 5). Water sorption and solubility (15 × 1 mm, n = 5) and flexural strength and modulus (2 × 2 × 25 mm, n = 5) were measured according to ISO-4049. Diametral tensile strength (6 × 3 mm, n = 8) was tested according to ANSI/ADA-Specification #27. The data were analyzed using one-way ANOVA and post hoc Tukey tests (p ≤ 0.05). Like Clearfil Majesty ES-2, Experimental showed lower or significantly lower volumetric shrinkage than other composites. Experimental exhibited a considerably higher degree of conversion and high flexural modulus compared to the others. However, there are no significant differences in flexural strength among these universal composites except for Omnichroma. Experimental also displayed significantly higher diametral tensile strength than the others, except similar to Filtek Supreme Ultra. Experimental has the lowest values of water sorption and solubility among the composites tested. The experimental universal composite demonstrated improved or comparable physical and mechanical properties compared to commercially available one-shade universal composites or multi-shade conventional universal composites, which is of significance for the clinical performance of dental restorations. Full article

The aim was to assess the blending effect of universal-shade resin-based composites (RBCs) (Omnichroma—OC; Clearfil Majesty Universal–CM; Venus Pearl—V; Transcend—T) used for repair for lithium disilicate blocks. Fifteen parallelepiped-shaped (10.5 × 10.5 × 3 mm) specimens with four cavities (3 mm in diameter and 2 mm in depth) were designed from lithium disilicate CAD/CAM blocks (CEREC Tessera HT A3) and milled. Specimens were then randomly divided into five groups based on the five resin composite materials for cavity restoration (n = 12): Group 1, control group (F); Group 2 (T); Group 3 (OC); Group 4 (V); and Group 5 (CM). After surface conditioning, composite resins were applied to the ceramic surface. Color measurements were taken with a colorimeter in the center of the resin restoration and on the CAD/CAM block. Tristimulus values were converted to CIELab color coordinates and color differences were expressed in ΔE₀₀ units using the CIEDE-2000 formula. F showed significantly better color matching (ΔE₀₀ = 2.51 ± 0.64) in comparison to single-shade RBCs except T (ΔE₀₀ = 2.55 ± 0.64). All groups exceeded perceptibility and acceptability thresholds. The control group presented higher color matching than the single shade universal composites except for Transcend. Full article

This study compared the repair bond strength values of two single-shade composite resins bonded to different computer-aided design and computer-aided manufacturing (CAD-CAM) substrates with different surface treatments. A total of 80 slice-shaped specimens were fabricated using two CAD-CAM materials: Lava Ultimate and VitaEnamic. The substrates were thermocycled and then, based on the surface treatment, each substrate material was subdivided into four groups: the air abrasion group (APA), the hydrofluoric-acid-etched group (HF) and two silicon carbide ground groups (SiCr). All of the groups received silane followed by Single Bond Universal Adhesive application prior to being repaired with a resin composite of a smaller disc shape. All the specimens were thermocycled prior to shear bond strength testing and subsequent failure analyses. Statistical analyses were conducted, and the level of statistical significance was set at 0.05. A comparison of the mean values showed a highly statistically significant difference among the eight groups. The highest value of mean shear bond strength was associated with Lava Ultimate substrates repaired using the Charisma Diamond ONE composite after APA surface treatment (36.7 ± 1.99). Meanwhile, the lowest value was recorded for the Vita Enamic group repaired using the OMNICHROMA composite after SiCr surface treatment (17.8 ± 1.6). The failure analysis revealed that cohesive failure in the substrate was the most predominant. Within the limitations of this study, Charisma Diamond ONE showed better bond strength values compared to Omnichroma. Meanwhile, APA is recommended for improved bond strength in repairs of Lava Ultimate restorations. Full article

Single-shade universal resin composites (SsURC) are preferred in clinical practice to reduce time for shade selection and obtain good esthetic results. In this study, the static mechanical properties of seven new SsURCs were investigated, their spectral analyzes were performed and scanning electron microscopy (SEM) evaluations were presented. Charisma Diamond One/DO, Admira Fusion x-tra/AFX, Omnichroma/OC, OptiShade/OS, Essentia Universal/EU, Zenchroma/ZC, Vittra APS Unique/VU were used in a three-point bending test to determine flexural strength (F_S) and elastic modulus (E_M); Vickers micro-hardness (VHN) and hardness-ratio (HR) were performed with a micro-hardness tester from top/bottom after 24-h/15-days of storage in distilled water at 37 °C (±1 °C). The degree of conversion (DC) was assessed by using Fourier transform infrared spectroscopy (FTIR). The structure of the resin matrix and filler content were assessed by SEM. Data were analyzed using IBM SPSS V23 and the R program and the significance level was taken as p < 0.05. The main effect of the tested SsURCs was found to be statistically significant on F_S, E_M, VHN, and DC values (p < 0.001). Bis-GMA free SsURCs (AFX, DO, VU) showed better DC and HR except for OC. All seven tested SsURCs conform to the requirements of ISO standards for dental resin composites for all tested categories. Full article

Thalhammerite, Pd₉Ag₂Bi₂S₄, is a new sulphide discovered in galena-pyrite-chalcopyrite and millerite-bornite-chalcopyrite vein-disseminated ores from the Komsomolsky mine of the Talnakh and Oktyabrsk deposits, Noril’sk region, Russia. It forms tiny inclusions (from a few μm up to about 40–50 μm) intergrown in galena, chalcopyrite, and also in bornite. Thalhammerite is brittle and has a metallic lustre. In plane-polarized light, thalhammerite is light yellow with weak bireflectance, weak pleochroism, in shades of slightly yellowish brown and weak anisotropy; it exhibits no internal reflections. Reflectance values of thalhammerite in air (R₁, R₂ in %) are: 41.9/43.0 at 470 nm, 43.9/45.1 at 546 nm, 44.9/46.1 at 589 nm, and 46.3/47.5 at 650 nm. Three spot analyses of thalhammerite give an average composition: Pd 52.61, Bi 22.21, Pb 3.92, Ag 14.37, S 7.69, and Se 0.10, total 100.90 wt %, corresponding to the empirical formula Pd_8.46Ag_2.28(Bi_1.82Pb_0.32)_Σ2.14(S_4.10Se_0.02)_Σ4.12 based on 17 atoms; the average of five analyses on synthetic thalhammerite is: Pd 55.10, Bi 24.99, Ag 12.75, and S 7.46, total 100.30 wt %, corresponding to Pd_8.91Ag_2.03Bi_2.06S_4.00. The density, calculated on the basis of the empirical formula, is 9.72 g/cm³. The mineral is tetragonal, space group I4/mmm, with a 8.0266(2), c 9.1531(2) Å, V 589.70(2) ų and Z = 2. The crystal structure was solved and refined from the single-crystal X-ray-diffraction data of synthetic Pd₉Ag₂Bi₂S₄. Thalhammerite has no exact structural analogues known in the mineral system; chemically, it is close to coldwellite (Pd₃Ag₂S) and kravtsovite (PdAg₂S). The strongest lines in the X-ray powder diffraction pattern of synthetic thalhammerite [d in Å (I) (hkl)] are: 3.3428(24)(211), 2.8393(46)(220), 2.5685(21)(301), 2.4122(100)(222), 2.3245(61)(123), 2.2873(48)(004), 2.2201(29)(132), 2.0072(40)(400), 1.7481(23)(332), and 1.5085(30)(404). The mineral honours Associate Professor Oskar Thalhammer of the University of Leoben, Austria. Full article