Surface Color Change Research Articles

An in vitro evaluation of surface roughness, color stability and bacterial accumulation of lithium disilicate ceramic after prophylactic periodontal treatment

Objective: to evaluate the effect of scaling procedures using different ultrasonic tips on the surface roughness, color stability and bacterial accumulation of lithium disilicate ceramic. Material and Methods: Scaling procedure was carried out using ultrasonic scaler (Satalec, Acteon, North America) with stainless-steel tip (US), titanium tip (UT) and plastic tip (UP), on disc shaped lithium disilicate samples cemented into a cavity prepared onto the labial surface of freshly extracted bovine teeth (10 samples per group). The samples were stored in coffee solution in an incubator at 37°C for 12 days, which is equivalent to 1 year of coffee consumption. The surface roughness was measured before and after the scaling procedure using a profilometer and atomic force microscopy. The color parameters were measured before and after scaling and staining procedures using VITA Easyshade Advance 4.0 according to the CIE L*a*b* color order system. The samples were then incubated with Streptococcus mutans (S. mutans) suspension. After incubation, the plates with 30 to 300 typical colonies of S. mutans were counted in a colony counter and mean values of colony forming units were obtained (CFU/mL). Results: The titanium scaling tip showed a statistically significant higher mean values of change in surface roughness Ra and bacterial count than the plastic scaling tip. Color changes (E) were not a statistically significant among the groups. The results showed a statistically significant positive (direct) correlation between surface roughness and color change (p = 0.012) and also between surface roughness and bacterial count (p = 0.00). Conclusion: Within the limitations of this study, titanium scaling instruments cause irreversible surface alterations of lithium disilcate ceramics which was in direct correlation to the color changes and bacterial accumulation; therefore, dentists should proceed with caution when scaling lithium disilicate surfaces. The findings of the current study may indicate the need for instruments or equipment that can remove plaque and calculus without causing surface damage. Keywords Surface properties; Color; Bacterial adhesion; Ultrasonics; Dental scaling; Ceramics.

Conveyor belt catalytic infrared as a novel apparatus for blanching processing applied to sweet potatoes in the industrial scale

In this study, effects of conveyor belt catalytic infrared blanching (CBCIRB) on peroxidase (POD), moisture reduction, physical and chemical properties, and microstructure of sweet potato slices were investigated. The parameters of CBCIRB were infrared irradiation distance (6, 12, and 18 cm), sample thickness (3, 5, and 7 mm), and conveyor speed (0.7, 0.35, 0.1 m/min, etc.). Meanwhile, the effect of conventional hot water blanching (HB) on sweet potato slices were also investigated. The results showed that shortening the infrared irradiation distance and reducing the slice thickness could both accelerate the POD inactivation rate. When 90% POD inactivation was achieved, CBCIRB samples yielded better hardness and higher preservation of phytochemicals than HB samples. The appropriate CBCIRB parameters were the slice thickness of 3 mm, infrared radiation distance of 12 cm and conveyor belt speed of 0.16 m/min, the moisture reduction, surface colour change, hardness, vitamin C retention rate, β-carotene retention rate, and total phenol content were: 78.34%, 7.41, 1690.4 g, 75.16%, 133.49%, and 1.03 mg/g, respectively. The microstructure observation showed that the damage of sweet potato slice cells by HB was more severe than CBCIRB. Overall, CBCIRB achieved higher product quality in a relatively uniform air environment.

ECOLOGICAL AND MICROBIOLOGICAL ASSESMENT OF LAKE KOMSOMOLSKOYE WATER QUALITY UNDER URBANIZATION

The ecological state of Lake Komsomolskoye (Kazan) in the fall-winter season was evaluated using bacterioplankton and bacteriobenthos indicators. In the summer of 2019, comprehensive actions were taken to clear the lake bottom of silt deposits. As a result, a significant improvement in hydrochemical parameters of the water was observed duringthe subglacial period of 2020 compared to the previous year. Indicators of microbial water quality conformed to Roshydromet regulatory requirements. Due to the high sulfate concentration in the bottom layer and especially in the benthos, mass development of sulfate-reducing bacteria took place. During the ice-covered period, purple phototrophic and colorless sulfur bacteria occurred in the surface water layer. Oxygen depletion in lake water can cause mass development of anaerobic purple bacteria, as well as a change in surface water transparency and color. Additional aeration of the Lake Komsomolskoye hydroecosystem with a sufficient amount of oxygen in winter can improve the hydrochemical composition and eco-trophic structure of the microbial community. These studies are part of the system of observations of urban water bodies designed to develop a program of actions for maintaining the ecological well-being of their ecosystems.

Superficial Effects of Different Finishing and Polishing Systems on the Surface Roughness and Color Change of Resin-Based CAD/CAM Blocks

Objective: CAD/CAM blocks are widely used in dental restorations around the world. This study aimed to investigate the effects of different polishing and finishing systems on surface roughness and color change of resin-based CAD/CAM blocks. Material and Methods: In this study, material samples of 2×7×12mm were prepared. In three different experimental groups, surface polishing was carried out with one-step, two-step and multi-step polishing systems. The samples in one subgroup of each experimental group were polished with the diamond paste. Once the initial roughness and color values of the samples were measured using a profilometer and a spectrophotometer, the samples were immersed in coffee. Surface roughness and color change (∆E00) results were statistically analyzed using two-way variance analysis (ANOVA). Results: Finishing and polishing systems created significantly different levels of surface roughness on the hybrid ceramic block (Vita Enamic) but not on the composites block (Brilliant Crios, Grandio Blocs). While the two-step and multi-step finishing and polishing systems produced the lowest color change on hybrid ceramic blocks, one-step and two-step systems achieved this on composite blocks (p<0.05). In all test groups, the supplementary polishing performed after regular polishing procedures helped us reduce the surface roughness and color change on CAD/CAM blocks. Conclusions: The findings obtained in this study suggest that one and two-step polishing systems are more suitable for resin-based composite CAD/CAM blocks; for hybrid ceramic CAD/CAM blocks, on the other hand, two and multi-step finishing and polishing systems seem to be more efficient concerning lower surface roughness and resistance to color changes.

Plant-Origin Stabilizer as an Alternative of Natural Additive to Polymers Used in Packaging Materials.

Over the past 25 years, cannabis plants have gained major popularity in the research community. This study aimed to evaluate the antioxidant capacity and stabilization efficiency of cannabidiol (CBD) extract in two different polymers: polylactide (PLA) and ethylene–norbornene copolymer (Topas) that are used in packaging materials more often. The research technology included weathering in a special chamber, surface free energy and color change measurements, surface morphology and Fourier-transform infrared spectroscopy (FTIR) analysis, thermogravimetry, and determination of the oxidation induction time or temperature (OIT) values, based on which the effectiveness of the cannabidiol extract could be estimated. Obtained results showed that the addition of CBD to polymer mixtures significantly increased their resistance to oxidation, and it can be used as a natural stabilizer for polymeric products. Moreover, samples with cannabidiol changed their coloration as a result of weathering. Therefore, this natural additive can also be considered as a colorimetric indicator of aging that informs about the changes in polymeric materials during their lifetime. On the other hand, surface properties of samples with cannabidiol content did not alter much compared to pure Topas and PLA.

Pre-Stabilization of Zr Getters for 5-Nine Purity Nitrogen Gas Purification

We confirm whether Zr powders can restrain a rapid nitrification reaction and offer a stable oxidation reaction according to temperatures in nitrogen gas purification. A pellet-type, porous Zr getter is prepared (diameter: 10 and thickness: 3 mm) using Zr powder with an average particle size of 45 μm. While maintaining the whole system, the Zr getter reaction is confirmed with an increase in temperature from 150 to 550 oC at increments of 100 oC under 99.999 % purity nitrogen atmosphere comprising of 10 ppm of impurity. Surface color, pore size, stabilized layer, and phase change are confirmed with optical microscopy, SEM-EDS, Micro-Raman, and X-ray diffraction (XRD) according to the Zr getter temperature. The surface color of the Zr getter changes from metallic silver to dark gray as temperature increases. In the EDS results, the nitrogen component is not observed, and oxygen content increases from each surface at elevated temperatures. The Raman and XRD results show the oxidation layer as a result of 350 oC annealing. Therefore, the Zr getter can be applied as a nitrogen getter under 5-nine purity nitrogen atmosphere after appropriate oxidized pre-stabilization process to prevent rapid nitrification reaction.

Effects of mouthwashes on color stability and surface roughness of three different resin-based composites.

The aim of this study is to evaluate the effects of different types of mouthwashes (Klorhexidin, Curasept ADS 205, Meridol, Listerine Cool Citrus) on the surface roughness and color changes of a microhybrid (Point 4), a bulk fill (SonicFill), and a nanohybrid (Nova Compo-N) resin-based composite (RBC). Disk-shaped specimens were prepared from tested RBCs and divided into four subgroups which immersed in four different types of mouthwashes. The specimens were subjected to immersion cycles in the mouthwashes and artificial saliva (n = 8). Each cycle consisted of complete immersion in a mouthwash for 21 min and afterwards in saliva for 12 h at 37°C, and this cycle was repeated 8 times. The surface roughness was evaluated using a profilometer and coloration was evaluated using a spectrophotometer before and after immersion time. One-way analysis of variance (ANOVA) for the evaluation of surface roughness data was performed, and interrelation between groups was identified with the Sheffe's multiple comparison test. There were no significant differences between the Ra values of the RBCs before and after immersion in mouthwashes (P > 0.05). There were significant differences between ΔE value of the SF and NCN groups before and after immersion time (P < 0.05). Mouthwashes contribute to oral health, especially in patients at high risk of caries. However, in such patients, patient-specific recommendations should be made when using mouthwashes due to the large number of composite fillings.

Effect of additive manufacturing process and storage condition on the dimensional accuracy and stability of 3D-printed dental casts

Statement of problemAdditively manufactured dental casts are gaining popularity as the digital workflow is adopted in dentistry. However, studies on their dimensional accuracy and stability under different storage conditions in the dental laboratory are lacking. PurposeThe purpose of this in vitro study was to compare the effects of different additive manufacturing processes and storage conditions on the dimensional accuracy and stability of 3D-printed dental casts. Material and methodsA completely dentate maxillary typodont model was digitized 10 times with a dental laboratory laser scanner, and the standard tessellation language (STL) files were used to manufacture 3D-printed diagnostic casts with the digital light projection (DLP) 3D printer (Asiga MAX) and material jetting (MJ) 3D printer (ProJet 3510 DPPro). Twenty DLP-printed and 20 MJ-printed diagnostic casts were digitized within 24 hours of production. Subsequently, all 3D-printed diagnostic casts were stored for 3 months, either in closed laboratory boxes or in dental laboratory open-face plastic containers with direct exposure to full-spectrum balanced light. After 3-month storage, all 40 3D-printed casts were digitized again. All scanned files were compared with the corresponding STL files in a surface-matching software program. The dimensional accuracy was measured and compared by the root mean square (RMS, in μm). Repeated measures analysis of variance (ANOVA) was used to compare RMS values among the variables, and the Tukey honestly significant difference (HSD) test was used for post hoc multiple comparisons (α=.05). ResultsThe casts produced from the DLP 3D printer had a significantly higher mean ±standard deviation RMS of 153.7 ±25.4 μm than those produced with the MJ 3D printer with RMS of 134.1 ±16.0 μm (P<.001). The storage condition (box storage versus light exposure) did not affect the accuracy of the DLP-printed casts (P=.615) or the MJ-printed casts (P=.999). When comparing all 3D-printed casts after 3-month storage, group DLP-3M-Lit had the highest mean ±standard deviation RMS of 163.0 ±26.5 μm, and group MJ-3M-Box had the lowest RMS of 132.8 ±16.9 μm. The DLP-printed casts stored under light exposure were significantly less accurate than the MJ-printed casts stored in the box (P=.048). DLP-printed casts stored under light exposure showed significant surface color change under visual inspection. ConclusionsThe MJ 3D printer produced more accurate 3D-printed dental casts than the DLP 3D printer. After 3-month storage, the DLP-printed casts stored under light exposure were the least accurate, and the MJ-printed casts stored without light exposure were the most accurate. The surface color change of DLP-printed casts stored under light exposure after 3-month storage was evident.

Mapping of tank silt application using Sentinel-2 images over the Berambadi catchment (India)

Mapping soil properties is becoming more and more challenging due to the increase in anthropogenic modification of the landscape, calling for new methods to identify these changes. A striking example of anthropogenic modifications of soil properties is the widespread practice in South India of applying large quantities of silt from dry river dams (or “tanks”) to agricultural fields. Whereas several studies have demonstrated the interest of tank silt for soil fertility, no assessment of the actual extent of this age-old traditional practice exists. Over South-Indian pedological context, this practice is characterized by an application of black-colored tank silt to red-colored soils such as Ferralsols. The objective of this work was to evaluate the usefulness of Sentinel-2 images for mapping tank silt applications, hypothesizing that observed changes in soil surface color can be a proxy for tank silt application. We used data collected in a cultivated watershed in South India including 217 soil surface samples characterized in terms of Munsell color. We used two Sentinel-2 images acquired on February and April 2017. The surface soil color over each Sentinel-2 image was classified into two soil types (“Black” and “Red” soils). A change of soil color from “Red” in February 2017 to “Black” in April 2017 was attributed to tank silt application. Soil color changes were analyzed accounting for possible surface soil moisture changes. The proposed methodology was based on a well-balanced Calibration data created from the initial imbalanced Calibration dataset thanks to the Synthetic Minority Over-sampling Technique (SMOTE) methodology, coupled to the Cost-Sensitive Classification And Regression Trees (Cost-Sensitive CART) algorithm. To estimate the uncertainties of i) the two-class classification at each date and ii) the change of soil color from “Red” to “Black”, a bootstrap procedure was used providing fifty two-class classifications for each Sentinel-2 image. The results showed that 1) the CART method allowed to classify the “Red” and “Black” soil with correct overall accuracy from both Sentinel-2 images, 2) the tank silt application was identified over 202 fields and 3) the soil color changes were not related to a surface soil moisture change between both dates. With the actual availability of the Sentinel-2 and the past availability of the LANDSAT satellite imageries, this study may open a way toward a simple and accurate method for delivering tank silt application mapping and so to study and possibly quantify retroactively this farmer practice.

Surface Integrity of Dimethacrylate Composite Resins with Low Shrinkage Comonomers.

The goal of current research was to investigate the influence of adding low shrinkage “Phene” like comonomers hexaethylene glycol bis(carbamate-isoproply-α-methylstyrene) (HE-Phene) and triethylene glycol bis(carbamate-isoproply-α-methylstyrene) (TE-Phene) on the surface and color characteristics of composite resin. A range of weight fractions (0, 10, 20, 30, 40 wt.%) of HE/TE-Phene monomers were mixed with bisphenol A glycidyl methacrylate (GMA)/triethylene glycol dimethacrylate (TEGDMA) monomer. Experimental composite resins were made by mixing 71 wt.% of silica fillers to 29 wt.% of the resin matrix. A Vickers indenter and glossmeter were used for testing surface hardness (SH) and gloss (SG) at 60°. A chewing-simulator was used to evaluate the surface wear after 15,000 cycles. Color change (∆E) and translucency parameter (TP) were measured using a spectrophotometer. Data showed that HE/TE-Phene monomer had no negative impact (p > 0.05) on surface gloss, wear, color change and translucency of experimental composite resins. Surface hardness was in a reducing direction with the increas in HE/TE-Phene weight fraction (p < 0.05). The study results suggested that incorporating HE/TE-Phene monomers up to 30 wt.% with Bis-GMA/TEGDMA resin did not negatively influence the surface integrity of composite resins except for SH.

Effect of dielectric barrier discharge cold plasma treatments on flavor fingerprints of brown rice

A non-thermal processing method was developed to promote preservation of brown rice using dielectric barrier discharge cold plasma (DBD-CP). Physicochemical properties including free fatty acid (FFA) content, surface color change, volatile organic components (VOCs) and flavor fingerprints were evaluated in brown rice submitted to DBD-CP. FFA levels were 25.2% lower in treated samples compared to the control, and a more stable surface color was obtained at the end of the storage period. A total of 35 major VOCs could be detected in treated samples, and reduced levels of hexanal can be used as an indicator of DBD-CP treatment in brown rice during storage. Moreover, the flavor fingerprints in DBD-CP treated groups can be successfully distinguished through headspace gas chromatography ion mobility spectrometry. Collectively, application of DBD-CP treatment could be utilized as a feasible approach to promote stabilization of brown rice and preserve flavor during storage.

Effects of tri-frequency ultrasonic vacuum-assisted ethanol pretreatment on infrared drying efficiency, qualities and microbial safety of scallion stalk slices

This paper aims to evaluate the impact of simultaneous tri-frequency ultrasound (20 + 40 + 60 kHz) combined vacuum (0.6 bar) assisted ethanol (75%) pretreatment on the infrared drying process, qualities (rehydration, flavor, surface color), and microbial safety of scallion stalk slices. The slices were pretreated with different methods, using ethanol, vacuum (Water + VC), vacuum-assisted ethanol (Ethanol + VC), ultrasound (Water + US), ultrasound-assisted ethanol (Ethanol + US), ultrasonic vacuum (Water + USVC), and ultrasonic vacuum-assisted ethanol (Ethanol + USVC). It was found that Ethanol + USVC pretreatment significantly reduced the drying time and showed better flavor retention and antibacterial effect, and the slices produced showed moderate rehydration ratio (7.83) and surface color change (8.94).

A new method for dating the surface exposure age of granite rock walls in the Mont Blanc massif by reflectance spectroscopy

In the high mountain rock walls of the Mont Blanc massif, changes in the granite surface colour are related to its exposure age. The light grey colour of fresh rock surfaces turns orange when is long exposed to weathering. In order to study this colour/age relationship, reflectance spectroscopy was performed on 73 samples, and Terrestrial Cosmogenic Nuclide (TCN) dating was used to obtain their surface exposure age. The standard deviation of the reflectance values was calculated for each wavelength of the visible spectrum to study the behaviour of each spectral region. The aim was to find two colour regions that showed opposite behaviour, and once they are combined, they could provide a representative index of the rock colour changes that are linked to the degree of weathering. As an adaptation of the Green Red Vegetation Index used to measure colour changes in vegetation, the GReen-Infrared GRanite Index (GRIGRI), a normalized difference between the granite 770 nm and 530 nm reflectance values, was developed. The GRIGRI value of a weathered granite surface has a close relationship with its exposure age (R 2 = 0.85). The reflectance spectra of seven samples for which TCN dating failed and two samples for which the TCN age was considered to be an outlier were used to calculate their GRIGRI value to assess the colour-based ages, that were plausible according to rock wall morphology and the TCN exposure ages of the surrounding surfaces. We propose a new method of surface dating for the rock walls of the Mont Blanc massif using reflectance spectroscopy. • Mont Blanc granite surface colour is related to the time that it has been exposed to weathering. • Reflectance spectroscopy was used to quantify granite surface colour. • TCN dating was used to estimate granite surface exposure age. • We use different approaches to explore the relationship between the granite colour and its exposure age. • The ratio between the Green and Infrared reflectance values can be used to estimate granite exposure age.

Surface color changes of oak (Quercus alba L.) treated with dopamine and iron ion compounds by acceleration of temperature–humidity condition

To change the surface color of oak (Quercus alba L.) to dark and grey, the water-soluble iron ion compounded dopamine solution was applied and accelerated in temperature–humidity condition. The colorimetric parameters before and after treatment were measured and X-ray photoelectron spectra were carried out for a further understanding. The results showed that iron ions and the compounds can significantly cause color changes to the oak, while the compounds treated groups seemed more uniform. With increasing concentration of the colorants, the color change was more obvious. During acceleration in temperature–humidity condition, the oxidation occurred, which further caused color change to oak. However, different oxidation reactions might occur between iron ions and compounds treated groups. The compounds system was more sensitive to temperature–humidity condition. Thus, the color difference was the highest. In a word, this treatment was effective considering the coloring effect and safety process.

Surface properties of coated MDF pre-treated with atmospheric plasma and the influence of artificial weathering

A non-thermal plasma treatment generated in air at atmospheric pressure was used for surface modification of medium density fiberboard (MDF) substrate. Untreated and plasma-treated substrates were coated with a waterborne acrylic coating and exposed to accelerated artificial weathering (AAW) in interior mode. Plasma treatment increased the surface free energy of MDF by about 50%, which positively influenced on the wettability of the MDF with the coating. Weathering of the coated MDF caused a decrease in surface gloss and color changes, which were less pronounced for plasma-treated samples. Attenuated total reflection Fourier transform infrared spectra and microscopic analysis revealed degradation of the acrylic resin on the coated MDF due to light irradiation during weathering. After 250 h of weathering, the surface roughness of the coated MDF increased by about 3 μm. The coated MDF surfaces started to lose their hydrophobic character after 50 h of weathering. Finally, the determination of mechanical properties showed that coated MDF became more resistant to scratching during AAW, while the adhesion of the coating film to the MDF substrate was not affected in a significant trend with time of AAW. In both cases, no influence of plasma treatment was detected.

Effect of finishing and polishing systems on the surface roughness and color change of composite resins.

BackgroundThis study is to examine the surface roughness and color changes occurring on composite resins following the application of different finishing and polishing systems. Material and MethodsIn our study, a total of 200 samples were prepared from composites resin (6×2 mm) containing supra-nano, submicron hybrid, nanohybrid, nano-ceramic and microhybrid filler. They were polished with diamond, aluminum oxide, silicon carbide finishing and polishing systems. The initial color values of composite samples were measured with a spectrophotometer and surface roughness values with a profilometer. After that, samples were immersed of coffee solution and color measurements were repeated on the 1st and 7th day. The differences between surface roughness (Ra) and color change values (∆Eab) were evaluated using two-way analysis of variance (ANOVA) test (p<0.05). ResultsFinishing and polishing systems produced a statistically significant difference between the surface roughness values of nano-ceramic, submicron hybrid and microhybrid composite resin samples (p<0.05). Supra nano composite, which showed the lowest surface roughness after all finishing and polishing systems, showed the least color change after 7 days compared to other composite groups (p<0.05). The microhybrid composite with the highest surface roughness was the most color changing composite group (p<0.5). ConclusionsThe spiral finishing and polishing system containing diamond particles was the system to provide the least color difference on all composite groups. However, color differences of all composite resin groups were found to exceed the perceptibility threshold (PT) and acceptability threshold (AT). Key words:Composite resin, color stability, surface roughness.

Complete denture hygiene solutions: antibiofilm activity and effects on physical and mechanical properties of acrylic resin.

Appropriated denture hygiene is a predictive factor for longevity of rehabilitation treatment and maintenance of the oral mucosal health. Although, disinfectant solutions are commonly used as denture cleansers, the impact of these solutions on acrylic resin-based dentures remain unclear. Objective To evaluate, in vitro, the antibiofilm activity of complete denture hygiene solutions and their effects on physical and mechanical properties of acrylic resin.Methodology For antibiofilm activity measurement acrylic resin specimens were contaminated with Candida albicans, Candida glabrata and Streptococcus mutans. After biofilm growth, the specimens were assigned to the hygiene solutions: Distilled water (Control); 0.2% Sodium hypochlorite (SH); Efferdent Power Clean Crystals (EPC) and 6.25% Ricinus communis (RC). The viability of microorganisms was evaluated by agar plate counts. In parallel, physical, and mechanical properties of the acrylic resin were evaluated after simulating a 5-year period of daily immersion in the previously mentioned solutions. The changes in surface roughness, color, microhardness, flexural strength, impact strength, sorption and solubility were evaluated. Data were compared by ANOVA followed by the Tukey test or Kruskal-Wallis followed by the Dunn test depending on the distribution (α=0.05).Results Regarding antibiofilm action, SH eliminated all microorganisms while EPC and RC exhibited moderate action against S. mutans (p=0.001) and C. glabrata (p<0.001), respectively. Relative to effects on the physical and mechanical properties of the acrylic resin, RC led to higher values of color change (p=0.030), hardness (p<0.001), surface roughness (p=0.006) and flexural strength (p<0.001). Moreover, RC induced the highest values of changes in solubility (p<0.001). EPC promoted greater changes in surface morphology, whereas immersion in SH retained the initial appearance of the acrylic resin surface. All hygiene solutions reduced the impact strength (p<0.05).Conclusion SH presented the most effective antibiofilm activity. In addition, changes on properties were observed after immersion in RC, which were considered within acceptable limits.

EFFECT OF AN IN-OFFICE BLEACHING AGENT CONTAINING TWO DIFFERENT CONCENTRATIONS OF TITANIUM DIOXIDE NANO PARTICLES ON THE COLOR AND SURFACE ROUGHNESS OF ENAMEL.

Background: The aim of this study was to evaluate the effect of two different concentrations of titanium dioxide nano particles TiO2NP on the color and surface roughness of enamel surface. Material and methods: 20 bovine anterior teeth were selected. Each tooth was divided into two equal halves and distributed to two groups A and B. Group A: one half is subjected to bleaching agent (AI) and the other half to bleaching agent mixed with 5% TiO2NP (AII). Group B: one half is subjected to bleaching agent (BI) and the other half to bleaching agent mixed with 10% TiO2NP (BII). Surface roughness (Ra) and color changes were evaluated using stereomicroscope and spectrophotometer. Results: There was no statistically significant difference in the roughness Ra between all bleaching groups at (p=5981>0.05). 10% concentration of TiO2NP group represented the lowest mean color value while there was no statistically significant difference in bleaching only groups and 5% concentration TiO2NP group using Pair-wise Tukey post-hoc (p>0.05). Conclusions: Titanium oxide nano particles had an influence on the efficiency of bleaching agent without jeopardizing enamel surface roughness.

Effect of different placement techniques on color stability and surface roughness of resin composites

Abstract Introduction Longevity and clinical success of dental restorations can be influenced by many factors during the restorative procedures. Objective This study aimed to evaluate the influence of different placement techniques on color stability and surface roughness of two resin composites. Material and method The groups of specimens (n=10) were divided according to resin composite (FiltekTM Z250 XT and FiltekTM Z350 XT) and placement technique: Mylar strip, spatula, dry brush, modeling liquid, and surface sealant. Color stability and surface roughness were accessed using a spectrophotometer (CIELab color space) and a rugosimeter (standard cutoff of 0.8 mm), respectively, after water storage. Subsequently, the specimens were immersed in coffee for 48 h and final color was measured. The data were analyzed using ANOVA and the Tukey’s post hoc test (α=5%) and the correlation between surface roughness (Ra) and color change (∆Eab) was assessed using the Pearson’s correlation coefficient. Result The different placement techniques influenced Ra and ∆Eab on both resin composites. The groups treated with surface sealant showed greater difference in ∆Eab for both resin composites. The FiltekTM Z250 XT resin showed greater color stability compared with the FiltekTM Z350 XT resin regardless of the placement technique used. Ra of each placement technique was similar among the resin composites except for the FiltekTM Z350 XT modeling liquid group, which presented lower Ra values compared with those of FiltekTM Z250 XT. A correlation between Ra and staining was identified (p=0.268). Conclusion Color stability and Ra are influenced by different placement techniques.

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

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