Objectives. Soft denture liners provide a favorable environment for adhesion and colonization of microorganisms. This in vitro study aimed to examine the efficacy of different concentrations of copper oxide nanoparticles (CuO NPs) incorporation into soft denture liner on the biofilm formation of the microbial species. Methods. Field Emission Scanning Electron Microscopy (FESEM) images from NPs were recorded. Antifungal susceptibility testing of CuO NPs against five standard strains of Candida albicans (CBS 10261, 1905, 1912, 1949, 2730), Streptococcus mutans (ATCC35668), Streptococcus sobrinus (ATCC27607), and Streptococcus salivarius (ATCC9222) was performed by the broth microdilution method with the Clinical and Laboratory Standards Institute reference method. The biofilm inhibition percentages of CuO NPs on the soft denture liners were determined by XTT assay. Results. The characterization of CuO NPs by scanning electron microscope (SEM) analyses confirmed the synthesis of NPs with appropriate structure and size with a mean diameter of 18.3 ± 9.1 nm. The CuO NPs successfully inhibited the growth of the tested standard strains of C. albicans and Streptococcus spp. at concentrations ranging from 64 to 128 µg mL−1. Indeed, incorporation of CuO NPs at a concentration of 500 µg mL−1 into the soft denture liners exhibited a significant activity (75%) in inhibition of C. albicans. biofilm formation in a dose-dependent manner. The biofilm formation of C. albicans in the presence of CuO NPs was lower than Streptococcus spp. in comparison with the control group ( p < 0.05 ). Conclusion. Incorporation of CuO NPs significantly decreased the colonization and plaque formation of the oral pathogens, especially C. albicans accumulation. These NPs may be useful as a promising agent for the antimicrobial management of soft denture liner materials.

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Background:A precise impression is mandatory to obtain passive fit in implant-supported prostheses. The aim of this study was to compare the accuracy of three impression materials in both parallel and nonparallel implant positions.Materials and Methods:In this experimental study, two partial dentate maxillary acrylic models with four implant analogues in canines and lateral incisors areas were used. One model was simulating the parallel condition and the other nonparallel one, in which implants were tilted 30° bucally and 20° in either mesial or distal directions. Thirty stone casts were made from each model using polyether (Impregum), additional silicone (Monopren) and vinyl siloxanether (Identium), with open tray technique. The distortion values in three-dimensions (X, Y and Z-axis) were measured by coordinate measuring machine. Two-way analysis of variance (ANOVA), one-way ANOVA and Tukey tests were used for data analysis (α = 0.05).Results:Under parallel condition, all the materials showed comparable, accurate casts (P = 0.74). In the presence of angulated implants, while Monopren showed more accurate results compared to Impregum (P = 0.01), Identium yielded almost similar results to those produced by Impregum (P = 0.27) and Monopren (P = 0.26).Conclusion:Within the limitations of this study, in parallel conditions, the type of impression material cannot affect the accuracy of the implant impressions; however, in nonparallel conditions, polyvinyl siloxane is shown to be a better choice, followed by vinyl siloxanether and polyether respectively.

Objectives: This study aimed to evaluate the effect of different concentrations of titanium dioxide (TiO 2 ) and copper oxide (CuO) nanoparticles on the water sorption and solubility of heat-cured polymethyl methacrylate (PMMA).Materials and Methods: Fifty disc-shaped specimens (10 × 2 mm) of heat-cured PMMA were prepared and divided into five groups (n = 10) to be modified with 2.5 wt.% or 7.5 wt.% of either TiO 2 or CuO nanoparticles. One group was left unmodified, serving as the control group. Water sorption and solubility were measured by weighing the specimens before and after immersion in distilled water and desiccation. The data were analyzed by using one-way ANOVA and Tukey's post hoc test (α = .05).Results: The 2.5 wt.% CuO nanoparticles significantly decreased the water sorption (p = .016), but did not change the water solubility (p = .222) compared with the control group. The 7.5 wt.% CuO and both concentration of TiO 2 nanoparticles did not change the water sorption, but significantly increased the solubility of heatcured PMMA (p ≤ .05).Conclusion: Adding 2.5 wt.% CuO nanoparticles to heat-cured PMMA decreases the water sorption; although, it has no significant effect on the solubility. Likewise, 2.5 and 7.5 wt.% TiO 2 and 7.5 wt.% CuO do not affect the water sorption, but increase the water solubility of heat-cured PMMA.Clinical Significance: Reinforcing the heat-cured PMMA denture base resin materials with the right concentration and type of nanoparticles can decrease the water sorption of resin base materials, and consequently can influence the durability of dentures.

Objective: This study aimed to investigate the effects of bleaching on the color, translucency, surface roughness, and surface hardness of monolithic zirconia with external stainin .Methods: In this experimental study, 32 specimens of monolithic zirconia (1 Â 1 mm; shade A2) were divided into two groups based on random permuted blocks. Overglaze and staining procedures were performed with a yellow stain or a value stain (GC Stain).Baseline color, translucency, roughness, and surface hardness were measured. The specimens were then randomly bleached with hydrogen peroxide (HP) 40% (20 min, twice with a 1-week interval in between) as office bleaching or carbamide peroxide (CP) 20% (4 h per day for 14 days) as home bleaching. Finally, the color, translucency, surface roughness, and surface hardness were measured again.Results: Bleaching with CP and HP caused a perceptible change in the color of the specimens (ΔE > 2), although this change was within the clinically acceptable range (ΔE < 3.3). HP significantly reduced the surface hardness of the specimens (p = 0.043). Changes in surface roughness of the specimens were neither statistically nor clinically significant (p = 0.19 and p = 0.25 for office and home bleaching, respectively). Conclusion:The effects of home and office bleaching on the surface characteristics of monolithic zirconia were almost the same. It is not necessary to exchange or even to polish the surfaces of zirconia restorations after exposure to bleaching agents. Further studies are recommended to confirm the color stability of externally stained monolithic zirconia.

A BSTRACT Aim: Use of monolithic zirconia for fabrication of all-ceramic crowns eliminates several shortcomings of layered zirconia crowns. Long-term success of restorations highly depends on the marginal fit. The crown thickness is among the factors that affect the marginal integrity. Meanwhile, reduced thickness of crowns has several advantages such as preservation of tooth structure. The aim of this study was to evaluate the marginal fit of monolithic zirconia crowns in reduced thickness and to compare the marginal fit of full-contour monolithic zirconia in different thicknesses with layered zirconia crowns. Materials and Methods: In this in vitro study, two standard brass dies (7 mm × 5 mm length diameter) were prepared with a heavy chamfer finish line with 0.5 and 1 mm depth. By using a CAD-CAM system, 30 crowns were made in three groups ( n = 10) of 1-mm thick layered zirconia, 1-mm thick monolithic zirconia, and 0.5-mm thick monolithic zirconia. Crowns were placed on master dies and randomly numbered. The marginal gap was measured on 18 points by using a digital microscope (×230). The mean ± standard deviation (SD) values were calculated and analyzed by Statistical Package for the Social Sciences (SPSS) software program through Kruskal–Wallis and Mann–Whitney tests (α = 0.05). Results: The marginal gap of 1-mm layered zirconia was significantly different from that of 1-mm monolithic zirconia ( P = 0.001) and 0.5-mm monolithic zirconia ( P = 0.004). Analysis of variance (ANOVA) revealed no significant difference between 0.5 and 1 mm thicknesses of monolithic zirconia ( P = 0.141). Conclusion: Marginal gap in all the three groups was clinically acceptable. The two different thicknesses of monolithic zirconia crowns had no significant effect on the restoration marginal fit; however, layered zirconia crowns showed a significantly higher marginal gap than monolithic zirconia crowns.

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