Can sterilization methods influence surface properties of resin composites? A purpose for previewing bias in laboratory bacterial adhesion tests

This study aimed to evaluate the influence of sterilization methods on conventional and bulk-fill resin composites' (BFRCs) surface properties in an attempt to preview bias in laboratory bacterial adhesion tests. Two regular viscosity conventional resin composites [Filtek Z350 XT™ (Z350) and IPS Empress Direct™ (ED)] and two regular viscosity BFRCs [Filtek Bulk Fill™ (FILT) and Tetric N-Ceram Bulk Fill IVA™ (TBF)] were used. The materials were characterized by Scanning Electron Microscopy (SEM), surface roughness (SR), and wettability (W) after sterilization with hydrogen peroxide gas plasma (HPGP) and steam sterilization (SS). Nonsterilized samples served as a control group (n = 5). Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (p < 0.05). For SR, there were no statistically significant differences among the groups (p > .05). SS method decreased the contact angle for FILT and Z350 (p < .01). The SS promoted more exposition of filler particles, while the HPGP method did not alter the tested materials' morphology. Therefore, sterilization methods affected the resin composites tested selectively. HPGP seems to be the most recommended method to sterilize the tested resin composites before laboratory bacterial adhesion tests.     

The effects of intrinsic and extrinsic acids on nanofilled and bulk fill resin composites: Roughness,surface hardness,and scanning electron microscopy analysis

The objective of this study was to examine the effects of extrinsic or intrinsic acids on nanofilled and bulk fill resin materials in vitro. A total of 90 disks were prepared using dental restorative material (Filtek Z350XT, GrandioSO, Filtek Bulk Fill, X‐tra fil). Thirty disks of each material were sub‐divided into three groups (n = 10) that were immersed for 7 days in deionized water (DW), 5% citric acid (CA—pH 2.1), or 0.1% hydrochloric acid (HCl—pH = 1.2). Surface hardness and roughness (stylus profilometer by R_a parameter) analysis were performed before and after immersion. Morphological changes were evaluated by scanning electron microscopy. The data were analyzed by two‐way ANOVA and Tukey's test (α = 0.05). All tested materials did not show significant differences in the effects of the DW, CA, or HCl solutions on surface roughness (p = .368). Likewise, the hardness loss was not affected by the solutions tested (p = .646), but there was a difference in the resin type (p = .002). Filtek Bulk Fill resin hardness was less affected, while Filtek Z350XT and GrandioSO presented the most hardness loss after 7 days of solution immersion. In terms of this experimental study, the results demonstrate the effectiveness of the mechanical properties (roughness and hardness surface) of nanofilled and bulk fill resin materials to resist erosion from extrinsic and intrinsic acids, therefore being potential candidates for dental applications.     

Surface roughness and filler particles characterization of resin‐based composites

The purpose of this study was to evaluate the surface roughness (Ra), and the morphology and composition of filler particles of different composites submitted to toothbrushing and water storage. Disc‐shaped specimens (15 mm × 2 mm) were made from five composites: two conventional (Z100?, and Filtek? Supreme Ultra Universal, 3M), one “quick‐cure” (Estelite ∑ Quick, Tokuyama), one fluoride‐releasing (Beautiful II, Shofu), and one self‐adhering (Vertise Flow, Kerr) composite. Samples were finished/polished using aluminum oxide discs (Sof‐Lex, 3M), and their surfaces were analyzed by profilometry (n = 5) and scanning electron microscopy (SEM; n = 3) at 1 week and after 30,000 toothbrushing cycles and 6‐month water storage. Ra data were analyzed by two‐way analysis of variance and Tukey's test (α = 0.05). Filler particles morphology and composition were analyzed by SEM and X‐ray dispersive energy spectroscopy, respectively. Finishing/polishing resulted in similar Ra for all the composites, while toothbrushing and water storage increased the Ra of all the tested materials, also changing their surface morphology. Beautifil II and Vertise Flow presented the highest Ra after toothbrushing and water storage. Filler particles were mainly composed of silicon, zirconium, aluminum, barium, and ytterbium. Size and morphology of fillers, and composition of the tested composites influenced their Ra when samples were submitted to toothbrushing and water storage.     

氧化锌晶须填充尼龙1010复合材料的摩擦磨损性能

采用模具挤压成型的方法制备了氧化锌晶须填充尼龙1010复合材料,使用纳米力学测试系统测试了不同含量氧化锌晶须复合材料的硬度和弹性模量,在UMT试验机上考察了复合材料的摩擦磨损性能,然后对磨损表面进行了SEM观察。结果表明：复合材料的硬度和弹性模量随氧化锌晶须含量的增加而增大;ZnOw在保持尼龙1010摩擦性能的同时,可使其耐磨性能提高60％左右。纯尼龙的主要磨损机制为粘着磨损和熔融,填充ZnOw后复合材料的磨损机制转变为疲劳剥层。     

Y-PSZ/BGC生物陶瓷的纳米力学性能及摩擦学行为研究

合成了生物活性玻璃粉末,采用无压烧结工艺制备了Y-PSZ/BGC复合陶瓷材料。利用纳米硬度分析测试系统(Triboindenter)测定了复合陶瓷的纳米力学性能,用销盘式摩擦磨损试验机考察了血浆润滑条件下复合陶瓷的生物摩擦学性能。结果表明:BGC的加入量在10%~15%(质量分数)范围内,复合陶瓷的纳米力学性能最佳,同超高分子量聚乙烯配副时的摩擦因数和磨损率也最小。磨损表面的N元素波谱分析结果表明,摩擦副表面存在血浆蛋白质的沉积。     

Comparison of mechanical and optical properties of a newly marketed universal composite resin with contemporary universal composite resins: An in vitro study

The purpose of this study was to evaluate the surface roughness, microhardness, color change, and translucency of a newly marketed universal nanohybrid composite resin (CR) (G-aenial A'CHORD) comparing with four contemporary universal CRs including two nanofilled (Filtek and Estelite Asteria) and two nanohybrid CRs (Charisma Dimond and Neo Spectra ST HV in vitro). Sixty-five specimens (8.0 mm × 2.0 mm) were fabricated (n = 13, per group). After finishing and polishing, specimens were subjected to surface roughness and microhardness tests. Color and translucency of the specimens were evaluated at baseline and after darkening with coffee solution at day 1 and day 7. A representative specimen from each group was investigated under scanning electron microscopy (SEM). Data was analyzed statistically (p < .05). There were significant differences among the groups in terms of surface roughness, microhardness, color, and translucency. The surface roughness was recorded as: Charisma Diamond > Neo Spectra ST HV, Filtek > Estelite Asteria, G-aenial A'CHORD, whereas Vickers Hardness number was as: Filtek, Charisma Diamond > Neo Spectra ST HV > G-aenial A'CHORD, Estelite Asteria. Color change was as: Charisma Diamond > Neo Spectra ST HV, Filtek, G-aenial A'CHORD > Estelite Asteria and the translucency was as: Neo Spectra ST HV > G-aenial A'CHORD, Filtek > Estelite Asteria, Charisma Diamond. SEM examinations revealed smooth surfaces for G-aenial A'CHORD, Neo Spectra ST HV and Estelite Asteria. Mechanical and optical properties of universal composite resins with different compositions show variations.     

Investigation of surface roughness values of various restorative materials after brushing with blue covarine containing whitening toothpaste by two different methods: AFM and profilometer

The aim of this study is to evaluate the effect of whitening toothpaste on the surface roughness of resin-based restorative materials by different measurement methods. Twenty four specimens from each of human enamel, a microhybrid composite and two nanohybrid composites discs (8.0 diameter × 4.0 mm thick) were divided into two groups (n = 12) according to toothbrushing solutıon and subjected to simulation toothbrushing (30,000 cycles) with both distilled water and whitening toothpaste containing blue covarine. Surface roughness was examined using atomic force microscopy (AFM), profilometer, and scanning electron microscopy (SEM), and the data obtained were subjected to analysis. Ra values of Tescera (TES) were significantly higher than Sonicfill 2 (SF2) when brushing both toothbrushing solutions for initial or 30,000 cycles. Roughness increased for SF2 and TES when brushed for 30,000 cycles and was higher than enamel and Herculite XRV Ultra (HXU). Human enamel was obtained lower surface roughness values brushed with toothpaste compared with distilled water. Evaluation of the surface roughness of control groups using the AFM revealed no statistically significant difference between the groups, but significant differences were found using a profilometer. The use of abrasive whitening toothpaste containing blue covarine and the number of brushing cycles affect the surface properties of human enamel and the restorative material, and also, the clinical success of the restoration. Toothbrushing for 30,000 cycles increased the surface roughness of all materials. The type of toothbrushing solution partially has affected surface roughness.     

In-process surface roughness measurement of bulk metallic glass using an adaptive optics system for aberration correction

Bulk metallic glasses (BMGs) have received extensive attention recently due to amorphous-related extraordinary properties such as high strength, elasticity, and excellent corrosion resistance. In particular, Zr-based BMGs are recognized as a biocompatible material and surface roughness may affect many aspects of cell attachment, proliferation and differentiation. Therefore, this study presents an in-process measurement of surface roughness by combining an optical probe of laser-scattering phenomena and adaptive optics (AO) for aberration correction. Measurement results of six Zr-based BMGs samples with a roughness ranging from 0.06 to 0.98 μm demonstrate excellent correlation between the peak power and average roughness with a determination coefficient (R²) of 0.9974. The proposed adaptive-optics-assisted (AO-assisted) system is in good agreement with the stylus method, and less than 8.42% error values are obtained for average sample roughness in the range of 0.05–0.58 μm. The proposed system can be used as a rapid in-process roughness monitor/estimator to further increase the precision and stability of manufacturing processes for all classes of BMGs materials in situ.     

Effect of rubber component on the performance of brake friction materials

Various composite friction materials containing 40 vol.% organic binder (phenolic resin plus styrene–butadiene–rubber (SBR)) with varying phenolic-resin/SBR ratio were prepared. The content of phenolic resin in each composite was indicated by the resin value (RV) index ranging between 0 and 100%. The composites with RVs greater than 50% form resin-based friction materials in which the primary binder is the phenolic resin. For RVs less than 50%, the composites become the rubber-based materials where the primary binder is the SBR. The analysis of mechanical properties exhibited that the conformability of the composites increases upon incorporation of SBR. The frictional analysis revealed that type of polymeric binder, i.e. resin or rubber, dominates greatly the frictional behavior of the composites. The increment of friction force and higher improvement in the frictional fade and recovery with sliding velocities are the general features of rubber-based friction materials. It was attributed to the inherent properties of rubber on the viscoelastic response at higher sliding velocities and entropic contribution on the mechanical properties at higher temperatures. The wear rate of resin-based materials and its drum temperature is lower than those of rubber-based materials. It was attributed to the strongly adhered multilayer secondary plateaus formed on the surface of resin-based materials.     

Stability analysis of rough journal bearings under TEHL with non-Newtonian lubricants

The combined effects of surface roughness and lubricants rheology on stability of a rigid rotor supported on finite journal bearing under thermal elastohydrodynamic lubrication have been investigated using the transient method. The newly derived time dependent modified Reynolds and the adiabatic energy equations were formulated using a non-Newtonian Carreau viscosity model. The simultaneous systems of modified Reynolds equation, elasticity equation, energy equation, and the rotor motion equation with initial conditions were solved numerically using multigrid multi-level method with full approximation technique. From the characteristic equation, the instability threshold is then obtained with various surface roughness parameters and the elastic modulus of the bearing liner materials. The results show that stability of the bearing system deteriorates with decreasing both the power law exponent and the elastic modulus of bearing liner material. The rough surface journal bearing with transverse pattern under TEHL regime exhibits better stability when compared with the rough surface journal bearing with longitudinal pattern.     

单晶硅在氮离子注入前后的力学性能研究

以微机电系统常用的单晶硅材料和经氮离子注入单晶硅后形成的表面改性层为研究对象,在原位纳米力学测试系统上进行微压痕实验,对样品的表面纳米硬度进行了测试。同时,还通过该仪器的原子力成像功能对实验区域扫描成像,在纳米尺度下观察和分析形貌。结果表明:单晶硅在氮离子注入前后的纳米硬度值与载荷有很大关系。通过对微压痕和原子力图像的分析,表明单晶硅在氮离子注入后的纳米硬度值有所降低,其主要原因是氮离子注入后导致晶格抵抗变形的能力降低。     

Atomic Force Microscope Investigation on Static Nanomechanical Properties Versus Dynamic Nanotribological Evaluation of Metal–ZrN and ZrN Thin Films

The present study offers for the first time a correlation between static nanomechanical properties (nanohardness (H), elastic modulus (E), H/E and H ³/E ² ratio) and dynamic properties (resulting from nanoscratch measurements) for Metal–ZrN thin films (Inconel–ZrN, Cr–ZrN and Nb–ZrN) as well as monolayer polycrystalline ZrN thin films. Metal–ZrN thin films have a great industrial potential, as they can combine high hardness with good elasticity and toughness making them effective for wear resistant application. Nanomechanical and nanotribological properties of Metal–ZrN and ZrN thin films deposited by DC unbalanced magnetron sputtering were investigated using an atomic force microscope interfaced with a Hysitron Triboscope. The elastic recovery of thin films under a normal load applied during nanoindentation was evaluated and correlated with elastic recovery of thin films under dynamic loading during nanoscratch measurements in order to asses which film compositions provide superior wear resistance. It is demonstrated that dynamic elastic recovery measurements correlated well with those derived from static nanoindentation tests. The nanoscratch test combines both normal and tangential loading, therefore, it is expected to be an even better predictor of wear-resistance. The AFM nanoindentation and nanoscratch measurements show superior nanomechanical and nanotribological properties for Metal–ZrN thin films when compared to polycrystalline ZrN thin films.     

Influence of the artificial saliva storage on 3‐D surface texture characteristics of contemporary dental nanocomposites

The aim of this study was to analyse the influence of the artificial saliva on a three‐dimensional (3‐D) surface texture of contemporary dental composites. The representatives of four composites types were tested: nanofilled (Filtek Ultimate Body, FUB), nanohybrid (Filtek Z550, FZ550), microfilled (Gradia Direct, GD) and microhybrid (Filtek Z250, FZ250). The specimens were polymerised and polished by the multistep protocol (SuperSnap, Shofu). Their surface was examined, before and after 3 weeks’ exposure to artificial saliva storage. The surface texture was analysed using the atomic force microscope (AFM). The obtained images were processed to calculate the areal autocorrelation function (AACF), anisotropy ratio S_tr (texture aspect ratio), and structure function (SF). The log–log plots of SF were used to calculate fractal properties, such as fractal dimension D, and pseudo‐topothesy K. The analysis showed changes in surface anisotropy ratio S_tr values, which became higher, whereas the S_q roughness (root‐mean‐square) reduced after the artificial saliva storage. All the samples exhibited bifractal structure before the saliva treatment, but only half of them remained bifractal afterwards (GD, FZ250), whereas the other half turned into a monofractal (FUB, FZ550). The cube‐count fractal dimension D_cc was found to be material‐ and treatment‐insensitive.     

Adhesive strength and physical, mechanical, and triboengineering properties of nano- and microstructural Al2O3 coatings

The methods of atom-force microscopy and measurement of the nanohardness, elasticity modulus, cohesion forces, and friction coefficient with scratch testing (the scratching method) are applied to study the Al₂O₃ oxide coatings produced by magnetron deposition on Al targets. The morphologies of the coatings are compared when they are produced by the reactive synthesis and magnetron target sputtering and application of oxygen ions in high-frequency plasma. The accomplished study of the tribological and mechanical characteristics demonstrates that the resulting coatings possess stronger hardness and elasticity modulus. Application of the oxide coatings reduces the friction coefficient considerably compared with the substrate; the scratch test reveals higher strength and better adhesion to the substrate. Comparative analysis shows that the Al₂O₃ coatings applied to the nanostructural TiN film are 1.5 times harder than the coatings deposited on steel.     

Employing severe plastic deformation to the processing of electrical discharge machining electrodes

The tool electrode has a significant role in electrical discharge machining (EDM) performance, as it affects machining efficiency, surface quality and the geometrical accuracy of the machined component. This study presents a new approach for developing a pure copper electrode using severe plastic deformation (SPD) to enhance the machining characteristics during EDM. Equal channel angular pressing (ECAP) is selected because it is the most successful SPD method of processing bulk materials. Finite element analysis, microstructural assessment as well as nanoindentation tests are carried out to determine the behavior of pure copper after one and two ECAP passes. The effectiveness of EDM when using ECAP-treated electrodes is evaluated by introducing new techniques of measuring the volumetric overcut (VOC) and corner sharpness. In addition, tool wear rate (TWR), material removal rate (MRR), electrode wear ratio, surface roughness, surface crack density and the critical crack zone are studied. The results emphasize that an electrode subjected to one pass of ECAP can enhance the workpiece accuracy by decreasing the VOC and increasing corner sharpness by 13 and 66%, respectively. It is also revealed that the nanohardness enhancement following ECAP leads to lower TWR and electrode wear ratio. An investigation of the surface characteristics indicates a thinner recast layer is achieved when using one ECAP pass-treated electrode, which leads to 26% lower surface crack density.     

Effect of in‐office bleaching agents on the surface roughness and morphology of different dental composites: An AFM study

The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modification will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek? Z350 composites were used. Atomic force microscopy was used for analyses of the same place of the sample before and after treatment. A total of 12 analyses were performed per group (n = 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were analyzed statistically using Kruskal–Wallis, Mann–Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the surface of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them. Microsc. Res. Tech. 76:481–485, 2013. © 2013 Wiley Periodicals, Inc.     

Mapping micro-mechanical properties of carbon-filled polymer composites by TPM

This paper presents a new approach to the characterisation of carbon-filled polymer composites by using a novel multi-function tribological probe microscope (TPM). The TPM is capable of measuring four functions in a single scan to provide area mappings of topography, friction, Young's modulus and nanohardness. The measurement is based on point-by-point scanning so values of the four measured functions are linked in space and in time. The specimens are PA6.6 and PA12 filled with carbon black or carbon fibre, specially prepared at the Institute for Materials Research III of Karlsruhe Research Centre. The four-in-one measurement of TPM enables us to identify the material difference on the surface in order to estimate the distribution of a particular material within the composite. For each specimen, mappings of topography, hardness and Young's modulus were obtained, and from the latter two, it is easy to see the existence of two different materials. Comparing the topography and hardness mappings, we are able to pick up the areas where carbons are located.     

Ultrastructural evaluation of enamel after dental bleaching associated with fluoride

This study evaluated the effects on human enamel after two bleaching procedures: with a fluoridated bleaching agent and with topical fluoride application postbleaching. It used 43 enamel blocks (3 mm(2) ) that were ground flat (600-2,000 grit) and polished with polishing paste (one and one-fourth). Specimens were randomly divided into three groups according to the bleaching procedure: (1) control group, (2) hydrogen peroxide 35% (HPF) and topical application of fluoride 1.23%, and (3) HP 38% (OP) with fluoride in its composition. Bleaching agents were used according to the manufacturer's instructions. Three methodologies were used: nanoindentation, to observe surface hardness and elastic modulus; atomic force microscopy, to observe surface roughness (R(a) - R(z)); and scanning electron microscopy, to observe the enamel surface effects. Group OP had a decrease in the elastic modulus after bleaching, which was recovered at 14 days. An increased roughness (R(a); 32%) was observed on group HPF and had an increased erosion on enamel surface (67%). It was concluded that topical application of fluoride, after using the nonfluoridated whitening agent, increased the roughness values and erosion of enamel.     

Influence of graphite and machining parameters on the surface roughness of Al-fly ash/graphite hybrid composite: a Taguchi approach

This paper presents an experimental investigation on the surface roughness of pure commercial Al, Al-15 wt% fly ash, and Al-15 wt% fly ash/1.5 wt% graphite (Gr) composites produced by modified two-step stir casting. The effect of reinforcements and machining parameters such as cutting speed, feed rate, and depth of cut on surface roughness, which greatly influence the performance of the machined product, were analyzed during turning operation. The optimum machining parameters were found in minimizing the surface roughness of the materials by using the Taguchi and ANOVA approach. Results show that the presence of the fly ash particles reduces the surface roughness of composites compared with pure Al. The inclusion of 1.5 wt% Gr in the Al-fly ash composite reduces the surface roughness considerably. A scanning electron microscopy investigation was carried out on the machined surfaces of the tested materials. Confirmation tests were performed to validate the regression models.