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The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal–Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved.

To determine the surface microhardness of white portland cement associated with niobium nanoparticles, white portland cement associated with zirconium nanoparticles, and mineral trioxide aggregate. The present study is an experimental in-vitro study. The sample consisted of 03 study groups. These were divided into 09 subgroups of 04 hours, 14 days and 28 days. The instrument used to record the surface mechanical microhardness was the Vickers microdurometer. The Shapiro-Wilk statistical analysis was then performed to identify the normality of the data. The Anova test was applied to compare between the three groups and then the Tukey test for multiple comparisons with a 95% confidence level. White Portland cement associated with zirconium nanoparticles had the highest hardness value (p<0.05), followed by white Portland cement associated with niobium nanoparticles and aggregate control cement of mineral trioxide. The lowest value of surface microhardness was obtained by the addition of mineral trioxide (p<0.05). Surface microhardness values were significantly higher at 28 days than at 04 hours for all groups evaluated. White Portland cement with/without nanoparticulate additives generated higher surface microhardness than the control group added mineral trioxide in the evaluation periods.

The influence of regular relief formation modes on the microhardness of the formed groove surface near the apex at the bottom of the groove has been studied. It has been established that the rate of plastic deformation, expressed as the feed rate of the deforming element, has a significant impact on the plastic deformation mechanism, and the microstructure of the formed subsurface layer, as well as on the microhardness of the groove surface. The influence of the type of partially regular reliefs on the degree of plastic deformation was also investigated. It was found that the third type of partially regular relief, which has the highest groove density, provides higher microhardness values than the first and second types. This is explained by the significantly greater density of these type of partially regular relief grooves, which exert a mutual strengthening effect on the surface during formation. The experimental study conducted enabled the derivation of regression equations describing the influence of the feed rate of the deforming element and the type of partially regular relief created on the surface microhardness beneath the lateral ridges and the bottoms of the plastically deformed traces.

The success of an implant depends upon surface characteristics like roughness, topography, chemistry and hardness. The fabrication of a hard surface in combination with micron-, submicron- and nano-scale surface roughness is a great challenge for biomanufacturing industries. The surface microhardness (MH) needs to be maximized while controlling the Surface roughness (SR). The present research is the first study in which the application of Non-dominated sorting genetic algorithm (NSGA)-II coupled with Taguchi based Response surface methodology (RSM) is used to predict the optimal conditions of Powder mixed electric discharge machining (PMEDM) parameters to fabricate the biocompatible surface on β -phase Ti alloy. Batch vial tests were first carried out in accordance with the L 25 orthogonal array. ANOVA analysis gave the significant influencing factors and then mathematical models were developed between input parameters and output responses like SR and MH using Taguchi based RSM technique. These models were then optimized using NSGA-II to obtain a set of Pareto-optimal solutions. From the series of multiple solutions, the best optimal condition to achieve required low SR and high MH was determined, which are 13 A peak current, 5 μs pulse duration, 8% duty cycle (longer pulse-interval) and 8 g/l silicon powder concentration for achieving a required low SR and high MH. The MH considerably increased about 184% compared to the base material, and about 1.02 μm SR can be achieved in combination with micron-, submicron- and nano-scale surface features.

ObjectiveTo evaluate the remineralization of artificial interproximal enamel caries (AIEC) adjacent to alkasite, high viscous glass ionomer cement (HVGIC), and resin composite in class II restorations.Materials and methodsHuman enamel specimens were randomly assigned to 3 groups (n = 22): Filtek™ Z350, EQUIA Forte®, and Cention N®. The baseline hardness was determined using a Knoop microhardness assay. AIEC was formed in the specimens, and they were placed in contact with the proximal restorative materials then subjected to a 7-day pH cycling. Microhardness was determined post-artificial caries formation and post-pH cycling. The differences in the percentage of surface hardness recovery (%SHR) between the groups were compared using the Kruskal–Wallis test. The Dunn’s test was used for between-group comparisons (p < 0.05). Specimen surface morphology was evaluated using scanning electron microscopy (SEM), and the calcium, phosphorus, and fluoride contents were analyzed by energy-dispersive spectroscopy (EDS). ANOVA with the post hoc Tukey multiple comparison test was used to evaluate the differences between groups (p < 0.05).ResultsThe Cention N® %SHR was the highest, followed by EQUIA Forte®, and Filtek™ Z350. There was a significant difference in the %SHR between Cention N® and Filtek™ Z350 (p < 0.05). In contrast, there were no significant difference between Cention N® and EQUIA Forte®. Significantly increased enamel surface fluoride content was observed in the Cention N® compared with Filtek™ Z350 specimens (p < 0.05). The SEM image of the Cention N® specimens demonstrated the greatest mineral deposition.ConclusionsCention N® markedly increased the surface hardness and fluoride content of adjacent AIEC compared with Filtek™ Z350 restorations.Clinical relevanceCention N® is a promising alternative restorative material to remineralize initial enamel lesions in approximal adjacent surfaces, especially in high-risk caries patients.

The paper presents the results of experimental studies on the impact of impulse shot peening parameters on surface roughness (Sa, Sz, Sp, Sv), surface layer microhardness, and the mean positron lifetime (τmean). In the study, samples made of the Inconel 718 nickel alloy were subjected to impulse shot peening on an originally designed stand. The variable factors of the experiment included the impact energy, the diameter of the peening element, and the number of impacts per unit area. The impulse shot peening resulted in changes in the surface structure and an increase in surface layer microhardness. After the application of impulse shot peening, the analyzed roughness parameters increased in relation to post-milling values. An increase in microhardness was obtained, i.e., from 27 HV 0.05 to 108 HV 0.05 at the surface, while the maximum increase the microhardness occur at the depth from 0.04 mm to 0.08 mm. The changes in the physical properties of the surface layer were accompanied by an increase in the mean positron lifetime τmean. This is probably related to the increased positron annihilation in point defects. In the case of small surface deformations, the increase in microhardness was accompanied by a much lower increase in τmean, which may indicate a different course of changes in the defect structure consisting mainly in modification of the dislocation system. The dependent variables were subjected to ANOVA analysis of variance (it was one-factor analysis), and the effect of independent variables was evaluated using post-hoc tests (Tukey test).

CoCrFeNiMn high-entropy alloy (HEA), as a difficult-to-cut material, produces a large amount of heat of plastic deformation in the cutting area during cutting, and this local overheating phenomenon will lead to thermal damage to the surface of the workpiece, forming burn defects. This study proposes the application of an icing clamp in the milling process of CoCrFeNiMn to achieve low-temperature machining in order to address issues such as poor machined surface quality. Finite element simulations of low-temperature milling of HEA were carried out. Orthogonal and single-factor experiments for low-temperature milling of HEA were designed. The action mechanisms of milling process parameters (spindle speed, feed speed, and cutting depth) on the cutting force and cutting temperature were analyzed, and simulation results related to chip shape and workpiece surface topography were obtained. The range of process parameters for the low-temperature milling experiments of HEA were determined. Finally, based on the error analysis between experimental and simulation data of cutting force, the reliability of the finite element simulation model was verified. The influence mechanisms of process parameters on surface roughness, 3D surface topography, surface micro-topography, and surface microhardness were analyzed under low-temperature and room-temperature. The formation characteristics of the machined surface and the material removal behavior were revealed.

Addressing the need for enhanced antibacterial properties in dental materials, this study investigated the impact of integrating zinc oxide nanoparticles (ZnO NPs) and mesoporous ZnO NPs into resin-modified glass ionomer cement (RMGIC) on microhardness and surface roughness. Seventy disk-shaped RMGIC specimens were allocated to seven experimental groups: RMGIC (control), RMGIC with 3 wt.% ZnO NPs, 5 wt.% ZnO NPs, 7 wt.% ZnO NPs, 3 wt.% mesoporous ZnO NPs, 5 wt.% mesoporous ZnO NPs, and 7 wt.% mesoporous ZnO NPs. Surface roughness and Vickers microhardness were quantified using a surface profilometer and Vickers microhardness tester, respectively. Statistical analysis was carried out with a significance level set at < 0.05. Incorporating 5 wt.% of ZnO NPs or mesoporous ZnO NPs into the RMGIC yielded the highest microhardness values, while the control group exhibited the lowest microhardness values. Notably, the microhardness values of RMGIC with 3 and 5 wt.% ZnO NPs or mesoporous ZnO NPs were significantly higher than those of the 7 wt.% concentration. Regarding surface roughness, the control group displayed the highest roughness value, while RMGIC with 5 wt.% mesoporous ZnO NPs exhibited the lowest roughness values. Therefore, incorporating up to 5 wt.% ZnO NPs or mesoporous ZnO NPs led to decreased roughness values, with a notable increase observed at the 7 wt.% concentration, albeit still lower than the control group's roughness values. Incorporating 5 wt.% ZnO NPs or mesoporous ZnO NPs resulted in significantly enhanced microhardness values compared to the control group and the 7 wt.% concentration. The introduction of up to 5 wt.% NPs led to reduced surface roughness, with the 7 wt.% concentration showing a slight increase in roughness. These findings highlight the importance of optimizing NP concentrations, particularly mesoporous NPs, in RMGIC to enhance mechanical properties, offering valuable insights for the development of dental materials with improved performance characteristics.

Background To evaluate surface microhardness, roughness, and gloss changes of tooth-colored restorative materials [a direct composite (G-aenial A’Chord), an indirect composite (Gradia Plus), an ormocer (Admira Fusion), a giomer (Beautifil II), and an alkasite (Cention N)] after exposure to simulated gastric acid. Methods A total of 110 disc-shaped specimens (22 discs of each material) were prepared using silicone molds (8 mm×2 mm) and exposed to either gastric acid or artificial saliva (control). Surface roughness (Ra), gloss (GU), and microhardness (VHN) were measured at baseline and after 96-hour of immersion in the solutions and the respective changes (∆Ra, ∆GU, ∆VHN) were calculated. Intergroup comparisons were performed using ANOVA (Tukey post hoc) or Kruskal-Wallis tests (Bonferroni correction). Independent samples t-test or Mann-Whitney U test was used for comparisons of each material across immersion media, while paired t-test was applied for time-dependent analyses. Results In the gastric acid medium, changes in all parameters led to significant differences among restorative materials, while in the artificial saliva medium, significant differences were observed in ∆VHN and ∆GU. The statistically significant difference between immersion media was observed in both ∆VHN and ∆Ra values for the giomer group, and in only ∆VHN values for the alkasite and indirect composite groups. In the gastric acid medium, the decrease in VHN and GU values was significant across all subgroups, while the increase in Ra was statistically significant only in the giomer and alkasite groups. Conclusions While the giomer group exhibited the most significant changes in roughness and microhardness following exposure to gastric acid, all tested materials executed clinically admissible results regarding surface gloss. Clinical trial number Not applicable.