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Abstract Zr-based bulk metallic glass (Zr-based BMG) biomedical parts are polished to produce the clinically desired surfaces. In view of this, the present work proposes an environmentally friendly flexible plasma electrolytic polishing (PeP) technique for processing the Zr52.5Cu17.9Ni14.6Al10Ti5 BMG. The stable polishing process and the postelectrochemical composition changes of the Zr-based BMG were investigated, and the surface smoothing mechanism was thus revealed. The roughness and gloss of the polished surface were evaluated to optimize the electrolyte composition ratios and other important process parameters. The crystallization degree and corrosion resistance of the polished surfaces were examined to ensure the applicability of PeP for biomedical Zr-based BMGs. The results showed that a high voltage of 300–380 V led to the development of a steady vapor gaseous envelope and plasma channels for Zr-based BMG polishing. It was noted that the preferential plasma discharge of the high parts (Zr elements) during PeP reacted with the fluoride salt electrolyte and formed a water-soluble zirconium fluoride (ZrF4). Moreover, by using an optimal electrolyte with 3% ammonium salt and 0.1% fluoride salt, the workpiece could be polished efficiently without crystallization. Overall, the surface roughness of the workpiece after the PEP was reduced by 8 times, while the gloss was increased by 10 times and the surface corrosion resistance was enhanced remarkably.

The leading quality indicators of cold-rolled strip products include surface roughness and surface finish. The present study investigates the effects of the reduction ratio and lubrication condition (dry or lubricated) on the surface roughness and surface gloss of S304 stainless steel strips and titanium grade 1 strips processed at room temperature with a rolling speed of 0.33 m/s. The results show that for both materials, the contact ratio between the workpiece and the roller increases with an increasing reduction ratio and gives rise to a higher surface gloss. Moreover, the surface gloss obtained under dry conditions is higher than that obtained under lubricated conditions. The peak cross-sectional and pit cross-sectional areas for both materials decrease as the reduction ratio increases. The corresponding improvement in the surface gloss is particularly apparent under dry conditions due to the absence of oil in the oil pits on the rolled surface. The titanium workpiece has a low yield strength of 170 MPa, and hence a high surface gloss can be obtained under a relatively low reduction ratio of 7%. By contrast, the S304 workpiece has a high yield strength of 215 MPa. As a result, a reduction ratio of at least 17.7% is required to flatten the oil pits and obtain a better surface finish. This study identifies the critical operating parameters of cold rolling affecting surface roughness and glossiness and provides insights into enhancing surface finish. Furthermore, it pinpoints that the valley cross-section area is a critical factor in determining the gloss of a surface with noticeable defects.

The gloss transition defect of injection-molded surfaces should be mitigated because it creates a poor impression of product quality. Conventional approaches for the suppression of the gloss transition defect employ a trial-and-error approach and additional equipment. The causes of the generation of a low-gloss polymer surface and the surface change during the molding process have not been systematically analyzed. This article proposes the causes of the generation of a low-gloss polymer surface and the occurrence of gloss transition according to the molding condition. The changes in the polymer surface and gloss were analyzed using gloss and topography measurements. The shrinkage of the polymer surface generates a rough topography and low glossiness. Replication to the smooth mold surface compensates for the effect of surface shrinkage and increases the surface gloss. The surface stiffness and melt pressure influence the degree of mold surface replication. The flow front speed and mold temperature are the main factors influencing the surface gloss because they affect the development rate of the melt pressure and the recovery rate of the surface stiffness. Therefore, the mold design and process condition should be optimized to enhance the uniformity of the flow front speed and mold temperature.

The study aims to assess the effect of printing orientation on surface roughness and gloss of resins for 3D printing of aligners. Squared specimens (14 × 14 × 4 mm) were printed using Dental LT Clear (Formlabs, Somerville, MA, USA; LT) or Tera Harz TC-85 DAC (Graphy, Seoul, Republic of Korea; TC) with different orientations: 0° (horizontal), 90° (vertical), and as per the manufacturer’s recommendation (40° for LT, 60° for TC). A profilometer was used to measure roughness (Ra) in µm, while gloss was recorded in gloss units (GU) with a glossmeter. The collected data were statistically analyzed. Material type did not significantly influence roughness, while print orientation was an influential factor, with the orientation recommended by the manufacturer yielding the roughest specimens. Vertical printing resulted in significantly higher roughness than horizontal. Material type was a significant factor for gloss, with TC exhibiting significantly higher gloss than LT. Print direction significantly influenced gloss, with vertical printing resulting in the highest gloss. The finding of higher roughness for vertical prints can be explained by the presence of a greater number of layers. The superior gloss exhibited by TC regardless of print angulation could be related to the effective cleaning of uncured resin by centrifugation and to the high degree of monomer conversion in nitrogen atmosphere.

The aim of this study was to compare the surface roughness and gloss of polymer-infiltrated ceramics after simulated in vitro toothbrushing in different storage mediums. Four polymer- infiltrated ceramics were evaluated, Lava ultimate (LU), Vita enamic (EN), Shofu (SH), and Crystal ultra (CU). The control group was a feldspathic ceramic, Vita Mark II (VM). One hundred and twenty specimens (12 × 14 × 2.5 mm) were prepared using a precision saw. For each material (n = 24), the specimens were allocated into two groups, polished and stained. The specimens of each group were stored (for 7 days) in either citric acid (0.2N) or distilled water. Data for surface gloss (ΔE*SCE-SCI) and roughness (Ra) were evaluated before (baseline) and after simulated toothbrushing. For toothbrushing simulation, a toothpaste slurry containing a toothpaste of 100 relative dentin abrasion (RDA) and 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Data were analyzed using t-test and ANOVA. A p-value of ≤ to 0.05 was considered significant. The highest mean value of surface gloss was identified in CU (stained—water) (4.3 (0.47)) (ΔE*) and EN (stained—acid) (4.3 (1.00)) (ΔE*) specimens, whereas the lowest mean value was shown by SH (stained—acid) (2.04 (0.42)) (ΔE*) samples. The highest mean value of surface roughness was observed in SH (0.40 (0.99)) Ra (stained—acid) whereas the lowest in VM (0.13 (0.039)) Ra (polished— water). A significant difference (p < 0.05) was observed in surface roughness and gloss between the materials with simulated toothbrushing, except in VM and LU, respectively. Therefore, it can be concluded that simulated toothbrushing impacts on surface roughness and gloss, irrespective of the storage medium.

Background Recently, universal single-shade resin composites have become increasingly available in the dental market. The modification of their composition can have an inadvertent effect on their physical and surface properties, and subsequently determinantal effect on their clinical function and longevity. Therefore, this study aimed to evaluate the effect of different finishing and polishing (F/P) systems on surface roughness (Ra), surface gloss (GU), and Vickers microhardness (VMH) of universal single-shade RBCs. Materials and methods Four commercial RBCs were used; the universal single-shade RBCs were Omnichroma, Charisma® Diamond ONE, and Vittra APS Unique, and a conventional nanocomposite Filtek™ Z250 XT was used as a control. The 3 F/P systems were Sof-Lex™ XT, Enhance®/PoGo®, and Diacomp® Plus Twist. A total of 160 discs were used for the 3 F/P system groups for all RBCs ( n  = 10). After F/P, the Ra, GU, and VMH were assessed. The data were analyzed using 2-way ANOVA at p -value < 0.05. Results Significant differences were found among the four RBCs and the 3 F/P systems ( p  < .000). Omnichroma showed the lowest Ra and acceptable GU, but the lowest VMH. Charisma showed the highest Ra, acceptable GU, and VMH. Vittra showed acceptable Ra, GU, and VMH and Filtek showed the highest GU, VMH, and acceptable Ra. Conclusion Although conventional nanohybrid RBC (Filtek Z250 XT) showed better GU and VMH values, the universal single-shade RBCs demonstrated comparable surface properties. The highest GU & VMH and lowest Ra were achieved by Diacomp followed by Enhance and Soflex.

Mold surface temperature is one of the most critical process parameters in injection molding. This study aimed to determine the effect of mold surface temperature on plastic parts in injection molding of high-density polyethylene materials. Other process parameters were kept constant, and samples were prepared by changing mold surface temperatures by the injection molding method. The samples’ mechanical tests, thermal tests, and gloss measurements by a gloss meter were performed, and the amount of warpage and collapses was measured by a video measuring system. Microstructures were examined under a scanning electron microscope. It was observed that the mold surface temperature increased the crystallization rate, tensile and bending strength of the materials, decreased the thicknesses of the crystal lamella and impact strength, and had an effect on the melting temperature of the crystal. The microstructure investigations demonstrated that as the mold surface temperature increased, the cavity formation in the structure increased, and fibrillation decreased due to expansion and cooling time. It was determined that the amount of collapse and warpage was affected by the mold surface temperature and that the increase in the mold surface temperature decreased the amount of collapse and increased the amount of warpage and surface gloss. Graphic abstract

Objectives: To investigate the effects of a coffee beverage and two whitening systems on the surface roughness and gloss of glazed Lithium Disilicate Glass-Ceramics (LDGC) for computer-aided design/computer-aided manufacturing (CAD/CAM) systems. Methods: Sixty-eight LDGC disks (12 × 10 × 2 mm) were prepared from blocks of CAD/CAM systems (IPS e.max CAD ceramic). Baseline measurements for surface roughness (Ra) and gloss (GU) were taken using a 3-D optical profilometer and a glossmeter, respectively; then specimens were randomized into four groups (n = 17). All specimens were immersed in a coffee solution (24 h × 12 days) then subjected to two whitening systems. G1-negative control (kept moist × 7 days); G2-positive control (brushed with distilled water, 200 g/load, 2 min twice daily × 7 days); G3-whitening toothpaste (Colgate optic white; relative dentin abrasivity (RDA) = 100, 200 g/load, 2 min twice daily × 7 days); and G4-simulated at-home bleaching protocol (Opalescence,15% carbamide peroxide (CP), 6 h/day × 7 days). The study outcomes were measured at baseline and after the treatments. Data were analyzed using paired T-test and one-way ANOVA (α = 0.05). Results: The mean surface roughness significantly increased (p ⩽ 0.002) for all groups after the designated treatment protocols. Among groups, the mean surface roughness of G2 and G3 were significantly higher (p ⩽ 0.001) (Ra: 0.51 and 0.57 μm, respectively) compared to the control group (Ra: 0.23 μm), and were not significantly different from G4 (Ra: 0.46 μm). Surface gloss decreased with no significant change within or among groups after treatment. Conclusion: All glazed LDGC had a significant increase in surface roughness after being subjected to simulated 1 year of coffee drinking and whitening systems (15% CP and whitening toothpaste), and the greatest change was associated with brushing (simulating 8 months). However, coffee beverages and whitening systems had no significant effect on the surface gloss.

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.

ObjectivesTo investigate discoloration reduction and changes of surface properties of a CAD/CAM resin composite after 14 days´ storage in red wine and polishing with nine different prophylactic polishing pastes (PPPs).Materials and methodsRectangular discs (N = 172) were fabricated and polished (P4000) using GC Cerasmart (GC Europe) to investigate different polishing protocols with 1–4 related descending PPPs (22 in total): Cleanic/CLE-Kerr, CleanJoy/CLJ-Voco, Clean Polish/Super Polish/SPO-Kerr, Clinpro Prophy Paste/CPP-3M, Détartrine/DET-Septodont, Nupro/NUP-Dentsply Sirona, Prophy Paste CCS/CCS-Directa, Proxyt/PXT-Ivoclar Vivadent, and Zircate/ZIR Prophy Paste-Dentsply Sirona. Surface properties (roughness values (RV)/Ra, Rz, Rv, surface free energy (SFE), surface gloss (G), and discoloration (ΔE)) were analyzed before and after storage and additional polishing. Data were examined using Kolmogorov-Smirnov test, three-way ANOVA followed by Tukey-B post hoc, Mann-Whitney U, and Kruskal-Wallis H tests (α < 0.05).ResultsRegarding RV, CLE, followed by CCS, and CPP showed the highest values; the lowest presented SPO and DET (p < 0.001). No impact of PPP was observed on ΔE values (p = 0.160). The lowest SFE presented DET, followed by SPO; highest showed CCS followed by NUP and CPP (p < 0.001). Within G, lowest values were observed for CLE and NUP, followed by CCS, ZIP, and CLJ (p < 0.001); the highest presented SPO (p < 0.001). Polishing showed generally a positive impact on SFE values (p < 0.001–p = 0.007), except ZIP (p = 0.322) and CLE (p = 0.083). G increased and RV decreased after polishing (p < 0.001), except SPO, with no significant change for G (p = 0.786).ConclusionsPolishing with PPPs improves the surface properties and is generally recommended. The choice of PPP has a minor role in removing discolorations. Multi-step systems should be carried out conscientiously.Clinical relevanceThe proper selection of PPP is essential for the clinical outcome of surface properties of prosthetic restorations. Not every polishing paste leads to the same final surface quality.