Surface Color Change Research Articles

İlave Polisaj Uygulamasının Kompozit Rezinlerin Yüzey Pürüzlülüğü ve Renk Değişimine Etkisinin İncelenmesi

İlave Polisaj Uygulamasının Kompozit Rezinlerin Yüzey Pürüzlülüğü ve Renk Değişimine Etkisinin İncelenmesi

Effect of Wheat Germ Oil on Hair Texture Improvement

Purpose: The current study aimed to assess the effects of wheat-germ oil on improving hair texture. Hence, an agent with wheat-germ oil was developed, and it was applied to damaged hair. Methods: The hair texture improvement agent was produced with different amounts of wheat-germ oil (0, 1, 2, and 3 g). After applying the agent to bleached hair, it was heat-treated and left in natural condition. Each sample was assessed before and after application and was then compared. To understand the change in surface color, the L*, a*, and b* values and the degree of fading were evaluated using a color-difference meter. In addition, to understand the effects of this agent, hair tensile strength, absorbance with the use of methylene blue, and hair gloss were measured. Results: After the application of the agent, the L* value decreased. In level 7, there were no significant changes in the L* value in terms of the amount of wheat-germ oil. The a* value did not significantly decrease, and the b* value did not remarkably increase. Moreover, fading as much as 10.58 NTU was observed on day 1, but not on day 4. In levels 7 and 9, the hair tensile strength of each sample increased. Based on the analysis of absorbance with methylene blue, the value after application decreased. Moreover, there was no significant difference in terms of hair gloss. Conclusions: The current study presented the effects of wheat-germ oil on improving the texture of damaged hair. However, more studies on the effects of wheat-germ oil on improving hair texture according to varying amounts and research methods should be conducted in the future.

Varying the Polishing Protocol Influences the Color Stability and Surface Roughness of Bulk-Fill Resin-Based Composites.

Surface properties of composites such as roughness and color impact periodontal health and aesthetic outcomes. Novel bulk-fill composites with improved functionality are being introduced and, in light of the existing variety of finishing/polishing procedures, research of their surface properties is warranted. Sixty discs were prepared from bulk-fill composites (Filtek™ Bulk Fill Posterior Restorative and Fill-Up™) and incremental-fill Filtek™ Z250. They were further divided according to different polishing procedures (n = 5): three multi-step polishing procedures or finishing with a bur (control). Surface roughness (Ra) was measured using an atomic force microscope (The AFM Workshop TT-AFM). A spectrophotometer (Spectroshade Micro Optic) was used to determine color stability, after exposure to a coffee solution. Data were analyzed using two-way MANOVA (significance level of 5%). Resin composite type, polishing procedure, and their interaction had a statistically significant effect on surface roughness (p < 0.001) and color change (p < 0.001). Fill-Up™ exhibited the highest surface roughness and greatest color change. Differences in color change were statistically significant (p < 0.001). Filtek™ Bulk Fill registered the lowest surface roughness and color change, after the three-step polishing procedure. Both parameters were significantly correlated (ρ = 0.754, p < 0.001) and found to be material dependent and polishing-procedure dependent. Higher surface roughness relates to greater color changes.

Effects of Artificial Staining and Bleaching Protocols on the Surface Roughness, Color, and Whiteness Changes of an Aged Nanofilled Composite

This study evaluated the surface roughness and color alteration of an aged nanofilled composite exposed to different staining solutions and bleaching agents. Ninety nanofilled composite (Filtek Z350XT, 3M/Oral Care) specimens were submitted to 5,000 thermal cycles and immersed in (n = 30): red wine, coffee, and artificial saliva at 37°C for 48 h. Groups were subdivided according to the bleaching protocol (n = 10) with 20% carbamide peroxide, 38% hydrogen peroxide, or without bleaching - control. Mean surface roughness values (Ra - μm) and color parameters (L*, a*, b*) were measured at baseline (T0), after thermal cycling aging and staining (TS), and after bleaching (TB). Color (ΔE00) and whiteness index (ΔWID) changes were determined after aging and staining (Ts-T0) and after bleaching (TB-TS). The adopted perceptibility and acceptability thresholds of the nanofilled composite were 0.81 and 1.71 ΔE00 units and 0.61 and 2.90 ΔWID units, respectively. Ra was analyzed using mixed models for repeated measurements and L* by the Tukey-Kramer test. The a* and b* values were evaluated by generalized linear models for repeated measures. ΔE00 was tested using two-way ANOVA and Tukey tests, and ΔWID by Kruskal-Wallis and Dunn tests (α = 5%). Ra of all groups decreased after aging and staining (TS, p &amp;lt; 0.05), but increased after bleaching only for groups stained with red wine (TB). Aging and staining decreased the luminosity of the composites, but L* increased after bleaching (p &amp;lt; 0.05). Aging and staining increased a* and b* values, but after bleaching, b* values decreased (p &amp;lt; 0.05). After bleaching, ΔE00 and ΔWID were greater in stained groups at both time intervals, regardless of the bleaching protocol. Stained resin composites exhibited perceptible but unacceptable color (ΔE00 &amp;gt; 1.71) and whiteness (ΔWID &amp;gt; 2.90) changes, regardless of the bleaching treatment performed. Therefore, red wine affected the surface roughness of the aged nanofilled resin submitted to bleaching. Bleaching was unable to reverse the color changes promoted by red wine and coffee on the aged nanofilled composite.

Dyed fabric illumination estimation with regularized random vector function link network

AbstractThe unstable light source in the printing and dyeing environment would cause the change of fabric surface color and lead to serious color difference evaluation error. To solve this problem, a dyed fabric illumination estimation with regularized random vector functional link network (RRVFL) was proposed in this study. First, the Gray‐Edge framework is used to extract the color features of the sample images collected from the actual scene, and the extracted color features and the illumination information of the sample images constitute a data set. Then, considering the ill‐conditioned solution of the output weight of the traditional random vector functional link network (RVFL), regularization is proposed to solve this problem. Thus, we constitute a highly robust RRVFL dyed fabric illumination model. By analyzing the parameters that affect the precision of RRVFL model, the optimal parameters of RRVFL can be selected. Finally, the traditional RVFL, extreme learning machine (ELM), back‐propagation (BP), regularized extreme learning machine (RELM), support vector regression (SVR), and RRVFL estimation algorithm proposed in this study were compared and analyzed using the measurement standards of angle error, colorimetric error, and T‐test, respectively. The experimental results show that RRVFL has the best predictive results and the most stable performance compared with the traditional algorithm. RRVFL is 0.00036, 2.8050, 3.3518, 4.1669, and 2.9289 less than RVFL, ELM, BP, RELM, and SVR, respectively, in terms of average angle error. RRVFL is 0.0131, 0.0763, 0.0232, 0.0241, and 0.0221 lower than RVFL, ELM, BP, RELM, and SVR, respectively, in the average colorimetric error.

Surface Change of Liquid Ga Electrode By Na Electrodeposition in NaTf2N-TEATf2N Ionic Liquid

A liquid metal electrode has interesting property such as phase change from a liquid to a solid depend on alloys composition. There are many reports of solid metal deposition on a liquid electrode, there are few papers of liquid metal deposition on a liquid electrode. In this study, Ga was used as the liquid electrode and Na electrodeposition was carried out in ionic liquid electrolyte at 160 oC. Since the melting point of Ga and Na are 29.8 and the 97.8 oC, at the moment when Na is electrodeposited, the liquid Na presents on the liquid Ga. In this experiment, we focused on the surface change of the Ga electrode before and after the electrodeposition of liquid Na.The experiment was conducted in a glove box under Ar atmosphere. NaTf2N (Sodium bis (trifluoromethanesulfonyl) imide) -TEATf2N (Tetraethylammonium bis (trifluoromethanesulfonyl) imide) mixed ionic liquid with molar ratio of 1 : 4 was used as an electrolyte at 160 oC. Liquid Ga or solid Ag plate was used as a working electrode and liquid Na was used as counter electrode and reference electrode. The voltammogram measurement was performed in the range from 2.5 V to -0.5 V (vs. Na/Na+) with sweep rate of 10 mV s-1. Constant current electrolysis was carried out at 5 mAcm-2 for 3 minutes. The liquid Ga electrode surface was taken by a digital camera. The time change of the open circuit potential of the Ga electrode after constant current electrolysis was measured by potentiostat.In voltammogram measurement, cathodic current on Ag working electrode flowed at lower than 0.0 V (vs. Na / Na +). In the liquid Ga electrode, cathodic current started at 0.6 V, then the cathodic current increased again at lower than about 0 V. The color of the liquid Ga surface changed slightly from bright metallic to black and gray. When the potential was reversed to anodic direction, the color of the Ga surface changed to gray, black and bright metallic. In liquid Ga electrode, start of cathodic current was more positive potential compared with solid Ag electrode. It is considered the cathodic current at range from 0.0 to 0.6 V may relate to formation of Na-Ga intermetallic compound. In constant current electrolysis, the potential change showed in two steps with similar the voltammogram measurement, color of the Ga surface changed to black in the first step and gray in the second step.In the open-circuit potential measurement, 3 potential plateaus of 1.9, 0.58, and 0.38 V (vs. Na / Na +) were observed. The potential plateau at 1.9 V corresponds to pure Ga, the potential plateaus 0.58 and 0.38 V may correspond to Na-Ga intermetallic compounds with different composition. It is known from the Na-Ga binary phase diagram that there are two intermetallic compounds, Ga4Na and Ga39Na22. In the surface color change of Ga electrode to black, it is considered that formation of Ga4Na on the surface because small amount of Na liquid was electrodeposited on the Ga electrode. Further, by depositing Na on the surface, Ga39Na22 may be formed on the surface, and even if more Na is deposited on Ga39Na22, the intermetallic compound does not change any more, and metal Na is deposited on the Ga39Na22. Therefore, the color of the electrode surface may have changed from black to gray.

Effects of mechanical abrasion challenge on sound and demineralized dentin surfaces treated with SDF

This study evaluated the effect of mechanical abrasion on the surface integrity, color change (ΔE) and antibacterial properties of demineralized and sound dentin surfaces treated with silver-diammine-fluoride (SDF). The dentin specimens were divided into two groups: sound and demineralized dentin, then divided into three sub-groups, control (no-treatment), SDF, and SDF + potassium-iodide (KI). Each sub-group was further divided into two groups, one exposed to mechanical brushing and the other without brushing. Specimens were analyzed for the ΔE, surface roughness/surface loss and antibacterial properties (CFU, optical density and fluorescent microscope). Repeated Measures ANOVA was used for statistical analysis of color change while one-way ANOVA was used for CFU analysis. SDF and SDI + KI groups showed significant reduction in ΔE with brushing in the sound dentin group unlike the demineralized group. The surface roughness values were higher for both SDF and SDF + KI groups but roughness values significantly decreased after brushing. Both SDF and SDF + KI groups revealed significantly less surface loss than control. The SDF group showed high anti-bacterial effect after brushing, unlike SDF + KI group. So, we concluded that mechanical brushing improved the esthetic outcome. While, SDF and SDF + KI could protect the dentin surface integrity. SDF-treated dentin possesses an antibacterial property even after mechanical brushing.

Moving toward Smart Cities: Evaluation of the Self-Cleaning Properties of Si-Based Consolidants Containing Nanocrystalline TiO2 Activated by either UV-A or UV-B Radiation.

This study evaluated the self-cleaning ability and durability of Si-based consolidants (an ethyl silicate consolidant and a consolidant based on nanosized silica) spiked with nanocrystalline TiO2 activated by either UV-A radiation (spectral region between 340 and 400 nm, and main peak at 365 nm) or UV-B radiation (spectral region between 270 and 420 nm, and main peak at 310 nm). Granite samples were coated with consolidant, to which nanocrystalline TiO2 was added at different concentrations (0.5, 1, and 3%, by wt.). Diesel soot was then applied to the coated surfaces, and the samples were exposed to UV-A or UV-B radiation for 1650 h. The surface color changes, relative to the color of untreated granite, were determined every 330 h by color spectrophotometry. Slight color changes indicated a recovery of the reference color due to the degradation of the soot. The final surfaces of both the untreated and treated surfaces were compared by stereomicroscopy and scanning electron microscopy. The main findings were that: (1) In general, the consolidant containing nanosized silica induced the most intense photocatalytic activity. In the more compact xerogel coating formed by the nanosized silica, more TiO2 nanoparticles were available to interact with the radiation. (2) For all consolidant mixtures, soot degradation remained constant or decreased over time, except with ethyl silicate with 0.5 wt % TiO2 (no self-cleaning capacity). (3) Soot degradation increased with the concentration of TiO2. (4) The UV-B radiation was the most effective in terms of soot degradation, except for the surface coated with the ethyl silicate and 3% wt. TiO2.

Study of gala apples (Malus pumila) thin-layer microwave drying: drying kinetics, diffusivity, structure and color

Abstract The effect of microwave power, sample thickness, and diameter on drying kinetics, effective moisture diffusivity, and activation energy of apple cylinders for microwave drying were investigated. Also, the effect of the microwave power on the quality of the dried apples was studied by measuring the surface color change and scanning the surface structure. The same mass of fresh apples was dried at different power levels. Two diameters and three thicknesses were studied. Aghbashlo model showed the best fitting for the drying kinetics of apple. The drying time was reduced by increasing the power and the diameter, but the thickness had no clear effect. The effective diffusivity values ranged between 1.47 × 10-7 and 24.4 × 10-7 m2/s. The effective diffusivity increased by increasing the three studied parameters. The parameters' effects on the drying time and the diffusivity were studied using a full factorial experimental design. The power and the diameter had the highest effect on the drying time. However, the thickness had the highest effect on the effective diffusivity.

Effect of a continuous mechanical polishing protocol on the color stainability, microhardness, mass, and surface roughness of denture base acrylic resin

Statement of problemThe acrylic resin used in dental prostheses, which is subject to changes in its properties caused by hygiene chemicals, brushing, and colored beverages, can benefit from mechanical polishing methods. However, studies evaluating whether such procedures can be performed continuously without damaging the prosthetic materials are lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of a continuous mechanical polishing protocol on the color stainability, surface roughness, microhardness, and mass of a denture base acrylic resin. Material and methodsThe polishing protocol was tested in specimens submitted to one of the following conditions: immersion in coffee (CF) (n=20); toothbrushing (Br, 35 600 cycles in a brushing simulation machine) (n=20); and immersion in 1% sodium hypochlorite (HYP) (n=20). For each condition, half of the specimens were polished (aluminum oxide paste and felt wheel attached to an electric motor, 3000 rpm) at simulated biweekly intervals. Two groups (n=10) of specimens were immersed in distilled water and used as the control for the immersion groups. Thus, the present study consisted of a total of 8 groups (n=80). Before and after simulated periods of 12 and 24 months, surface roughness was evaluated by using a contact profilometer; a spectrophotometer was used to calculate color changes (ΔE00); and a Knoop microdurometer and a precision balance were used to assess microhardness and mass changes. Data were compared by using 2-way mixed ANOVA. The Tukey HSD and Student t tests were used for post hoc analysis (α=.05). ResultsThe polishing influenced surface roughness (Br, CF, HYP: P<.001) and color stainability (Br: P=.008; CF: P<.001). Significant increase in roughness was observed for the Br and HYP groups, and the polishing significantly reduced roughness under all experimental conditions. In general, the polishing did not affect the microhardness and caused minimum wear of the acrylic resin. ΔE00 values were above the clinical perceptibility threshold (ΔE00>1.30) for the Br group, exceeding the clinical acceptability threshold for the CF group (ΔE00= 2.51). Polishing reduced ΔE00 in these groups, making values similar to those found in the groups immersed in distilled water. The color in the HYP group was not influenced by polishing. ConclusionsIn general, the tested polishing protocol reduced the deleterious effects of brushing and contact with 1% sodium hypochlorite and coffee, reducing surface roughness and color change without affecting microhardness and mass in any clinically relevant way.

Direct-to-consumer, store-and-forward teledermatology with dermoscopy using the pharmacist as patient point-of-contact

Objective(s)To evaluate the frequency of nonmelanoma skin cancer (NMSC), NMSC precursors, and melanoma on a store-and-forward dermatology model featuring the pharmacist as the patient’s point-of-contact. The secondary objective was to define lesion changes and symptoms perceived by patients (clinical prediction rules by nonexpert observers) that can be predictive of malignity. MethodsA cross-sectional study of teledermatology consultation was performed. All patients who underwent a teledermatology consultation between September 2018 and March 2020 were included. A patient could have more than 1 lesion per consultation. The object of the study was a defined dermatologic lesion. The differences between the variables were analyzed using a univariate model based on the chi-square test for independent qualitative variables and Fisher exact test in cases when the expected values in any of the cells of a contingency table were less than 5. Statistical significance was set at P < 0.05 (2-tailed). ResultsA total of 225 lesions in 218 patients were considered for this study; 53.8% (n = 121) of the lesions were classified as benign, 16.4% (n = 37) as dubious, 23.1% (n = 52) as NMSC precursors, 5.8% (n = 13) as NMSC, and 0.9% (n = 2) as melanomas. Of the reported clinical lesion changes, spontaneous pain, pruritus, surface texture changes, color changes, or form changes had no statistically significant relationship with the diagnostic group, whereas the presence of spontaneous bleeding (P = 0.015) and size changes (P = 0.026) were more frequently observed in the “dubious lesion” and “of oncological relevance lesion” groups. ConclusionThis “direct-to-consumer,” store-and-forward teledermatology with dermoscopy model featuring the pharmacist as the patient’s point-of-contact is useful for the diagnosis of melanoma, NMSC, and NMSC precursors when backed by a robust dermatology service.

Deformation and surface color changes of beech and oak wood lamellas resulting from the drying process

The drying process was examined relative to parameters’ influence on the deformation and surface layer color changes of beech wood (Fagus sylvatica L.) and oak wood (Quercus robur L.). The goal was to analyze the impact of drying process conditions, wood and growth rings types, and load on the deformation and surface color changes of drying thin wooden elements. A further aim was to reduce the time of the lamella drying and minimize wood products defects. During each drying, 40 pieces of wood were dried, divided into two groups. For the first group, 30 pieces were dried under a uniformly distributed load of approximately 50 kg, while for the second group, 10 samples were dried without weight. The lamellas dried under load exhibited fewer cup, bow, and twist deformations than the lamellas dried without load. Cracks in the dried lamellas occurred comparably in those dried under and without load. Color changes in the specimens before and after drying were observed and measured. The differences in colorimetric parameters (a, b, and L) between wood without defects and with defects were less marked after drying than before drying. The color changes were only noticed in the surface layers of the specimens.

Surface colour and chemical changes of furfurylated poplar wood and bamboo due to artificial weathering

ABSTRACT Although furfurylation greatly improves dimensional stability, hardness, and biodegradation resistance of wood and bamboo, the effects of furfurylation on the resistance of wood and bamboo to weathering are still not clear. In this study, poplar wood and moso bamboo were furfurylated and underwent artificial weathering. The surface chemical changes of the control and furfurylated wood and bamboo samples were examined using the attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The colour changes were also investigated by measuring CIELab parameters. Results demonstrated that the wood/bamboo surfaces showed decreased lightness and became reddish and yellowish after artificial weathering. Furfurylation endowed poplar wood and bamboo with improved stability of photo-discolouration. Weathering caused remarkable degradation of lignin in the control and furfurylated sample surfaces with decreased aromatic carbons and increased oxygenated carbons. The poly(furfuryl alcohol) in sample surfaces could also be oxidized during weathering. Compared with the furfurylated bamboo, the furfurylated poplar wood had higher stability of photo-degradation.

Influence of lactose pre-crystallization on the storage stability of infant formula powder containing lactose and maltodextrin

The effect of different proportions of pre-crystallized lactose (PCL; 0–31%) on the physico-chemical properties of fresh and aged infant formula (IF) containing lactose and maltodextrin was investigated. Fresh powders with a higher proportion of PCL had a larger particle size and higher surface free fat and water activity (aw). Powders with 7–24% PCL showed a lower rate of increase in aw and lactose crystallinity during storage at RH 54% compared to the control. Aw correlated linearly with the glass transition temperature (Tg) and the relative effect of storage temperature on Tg was lower in samples with 7–24% PCL at RH 33%. Significantly (p < 0.05) lower surface free fat, particle size and color changes were observed in samples with 18–24% PCL under all ageing conditions (RH 11–54% and 25–45 °C). The presence of maltodextrin was found to work in conjunction with PCL to improve physicochemical properties and storage stability of IF powders.

Repolishing in situ eroded CAD/CAM restorative materials and human enamel

This study aimed to evaluate the effects of repolishing on the surface microhardness (SMH), color change (ΔE), and translucency parameter (TP) of previously in situ eroded computer-aided design/computer-aided manufacturing (CAD/CAM) restorative materials and human enamel. Each of 8 volunteers wore an intraoral appliance containing 3 CAD/CAM restorative material specimens (IPS e.max CAD lithium disilicate ceramic, Lava Ultimate hybrid ceramic, and poly (methyl methacrylate) (PMMA) block) and 1 human enamel specimen. The specimens were subjected to in situ erosion cycles by rinsing with a cola drink (4 × 5 min/day) for 14 days. After erosion, the specimens were polished with a silicone polishing system (Ceramister, Shofu Inc, Kyoto, Japan). The SMH and color of the specimens were determined at baseline (T1), after erosion (T2), and after repolishing (T3). The ΔE and TP values of the specimens were further calculated. The data were statistically analyzed using repeated-measures analysis of variance (ANOVA) and Bonferroni's test (α = 0.05). After erosion, a decrease in the SMH of the restorative materials and enamel was observed (all P < 0.001), and a decrease in the TP of the enamel was observed (P = 0.016). The ΔE values of the enamel (ΔE = 7.32) and Lava Ultimate (ΔE = 3.19) exceeded the clinically unacceptable threshold after erosion. After repolishing, the SMH of the restorative materials and enamel at T3 was significantly higher than that at T2 (all P < 0.001). No significant difference was found in the TP and ΔE values of the restorative materials and enamel between T2 and T3. In conclusion, erosion negatively affected the surface properties and appearance of the CAD/CAM restorative materials and human enamel. Repolishing contributed to restoring the compromised SMH of the eroded restorative materials and enamel to a certain extent. However, repolishing did not restore the color of the eroded restorative materials and enamel.

Improving Weathering Performance of Wood by Borates Impregnation and Liquid Glass Coating

Weathering performance of impregnated and coated wood products is an important issue that influences their appearance as well as their service life after outdoor or indoor exposure. A novel procedure to improve the weathering performance of Scots pine wood (Pinus sylvestris L.) is proposed in this study. Wood samples were impregnated with ammonium tetrafluoroborate (ATFB), ammonium pentaborate (APB) and boric acid (BA), and afterward coated with a layer of liquid glass (LG). Surface hardness, color changes, and surface roughness of wood samples were investigated after 250 h and 500 h of exposure to artificial weathering. The results revealed that, except for untreated (control), all other treatment groups caused an increase in surface hardness of Scots pine after weathering. A decrease in the CIE L* value corresponds to the darkening of samples after weathering. Borates-impregnated and LG-coated Scots pine samples possessed the highest color stability. However, all treatment combinations resulted in reddish and yellowish tones after weathering. Exposure to weathering increased surface roughness of wood samples. The surface roughness of the untreated (control) group was higher than that of impregnated and coated samples.

Effects of bleaching gel containing TiO2 and chitosan on tooth surface roughness, microhardness and colour.

This study aimed to evaluate the effects of an experimental bleaching gel made with TiO2 and chitosan, along with the Opalescence Boost PF and Philips Zoom bleaching agents, on tooth surface roughness, microhardness and colour. The experimental gel, containing 6% hydrogen peroxide (HP), was evaluated against the two existing treatments, which incorporate 40% and 25% HP. For colour evaluation, 36 human premolar teeth were divided into three groups (n=12). For surface roughness and microhardness evaluation, 72 bovine incisor samples were divided into six groups (n=12). Data on colour alteration were analysed with the CIEDE2000 formula. Surface roughness was measured using a profilometer, and microhardness was measured with a Vickers hardness tester. ANOVA was used for statistical analysis. There were no statistically significant differences among the groups for surface roughness, microhardness values or colour change after bleaching (P>0.05). The lowest bleaching efficacy was observed for the 40% HP agent, and the highest efficacy was observed for the 25% HP agent (P<0.05). An experimental 6% HP gel containing TiO2 and chitosan provided effective bleaching without adverse effects on tooth surface roughness or microhardness. The use of TiO2 with chitosan can provide clinicians with positive results.

Effect of bleaching protocols on surface roughness and color change of high- and low-viscosity bulk-fill composite resins.

The aim of this in vitro study was to evaluate the effect of bleaching protocols on the surface roughness (Ra), color change and surface micromorphology of a low-viscosity bulk-fill composite (Filtek Bulk Fill Flow, 3M ESPE), a highviscosity bulk-fill composite (Filtek Bulk Fill, 3M ESPE) and a conventional nanoparticulate composite resin (control) (Filtek Z350 XT, 3M ESPE). Forty samples of each composite (disks 5 mm in diameter and 2 mm thick) were randomly divided into four groups (n=10), according to bleaching protocol: a) 10% carbamide peroxide gel (Opalescence, Ultradent Products) (2 h/ day, for 14 days); b) 40% hydrogen peroxide gel (Opalescence Boost, Ultradent Products) (three bleaching sessions, once a week, 45 min/session); c) whitening rinse (Listerine Whitening Extreme, Johnson &amp; Johnson) (2 min/day, for 14 days); and d) distilled water (control). The samples were submitted to triplicate readings (Ra and color [CIELAB parameters]) before and after contact with bleaching protocols. Micromorphology was analyzed in a scanning electron microscope (SEM). Ra and color parameters (ΔL, Δa, Δb and ΔE) were analyzed by generalized linear models (α=0.05). The Ra of the high-viscosity bulk-fill was significantly higher than that of the other composites (p&lt;0.05). Ra increased significantly (p&lt;0.05) and surface became more irregular (SEM analysis) in all the composite resins, regardless of the bleaching protocol (p&lt;0.05). The high-viscosity bulk-fill composite resin group had significantly lower ΔE (p&lt;0.05) than the nanoparticulate composite resin group immersed in distilled water. It was concluded that the characteristics of each resin significantly influenced the Ra more than the bleaching protocol. The high-viscosity bulk-fill resin presented minor color change.

Color and dimensional stability of fast growing teakwood by mild pyrolysis and combination process

Fast-growing teakwood had been subjected to Mild Pyrolysis (MP) and combination (MP + steam) processes. Performa of treated wood was evaluated by surface color change, mass loss, and dimensional stability. The CIELab. system was used to evaluate the color change, while anti-swelling efficiency was used to determine dimensional stability. The two processes were conducted within pyrolysis reactor under atmospheric pressure in the presence of limited oxygen. MP process was applied by heating the wood for 2 hours at 170 and 190°C without steam, while combination process was employed by flowing steam for 0.5 and 1 hour during the 2 hours heating period. The result showed total color change and dimensional stability increased along with the increase in temperature. Even though MP process could reduced water absorption and swelling, but combination process permits a better results. Treated wood by MP and steam has lower total color change and mass loss, but greater dimensional stability.

Utilization of Three Bark Extractives as Natural Photostabilizers for the Photostabilization of Wood Flour/Polypropylene Composites

Three kinds of tree bark extractives from trembling aspen (Populus tremuloides) (AE), lodgepole pine (Pinus contorta) (LE), and western red cedar (Thuja plicata) (RE) were produced and used as antioxidants. The antioxidation activities of those extractives were evaluated and compared with commercial antioxidant butylated hydroxytoluene (BHT). The obtained extractives were applied as natural photostabilizers to produce wood flour/polypropylene (WF/PP) composites at an addition level of 2 wt%. The composites were subjected to QUV accelerated weathering tester for a total of 1200 h. The changes in surface color, surface morphology, and surface chemistry of composites were investigated during the exposure. The results showed that all bark extractives alleviated the photodegradation of composites successfully. Among them, RE was proved to be the most effective. It exhibited excellent UV absorption and similar free-radical inhibition ability compared with BHT. Consequently, composites containing RE exhibited less discoloration, less severe surface cracking, and less changes in surface chemistry during the whole weathering process. Overall, these results revealed that RE had great potential as a natural photostabilizer in polymer systems.