Degree Of Discoloration Research Articles

Study on stability of rose anthocyanin extracts and physicochemical properties of complex with whey protein isolate after spray drying.

Pingyin rose is an edible flower rich in anthocyanins. In this study, antioxidant capacity and color were used as the main evaluation indexes to investigate the effects of common physical and chemical factors on the stability of rose anthocyanin extracts (RAEs). In addition, the physicochemical properties of the whey protein isolate (WPI)-RAEs complex after spray drying were studied. Vitamin C, temperature, and some metal ions can cause different degrees of discoloration of RAEs solution. More importantly, heat treatment, as well as most metal ions and sugars, had no significant effect on the antioxidant capacity of RAEs solution (p>0.05). Moreover, compared to spray-dried pure WPI, the WPI-RAEs powder was delicate and uniform, and had higher particle size, bulk density, moisture activity, and better gel properties. The release rate of all WPI-RAEs sol/gel to RAEs reached about 89% in the intestinal digestion stage, but the WPI-RAEs interaction reduced the digestibility of protein in the intestinal digestion stage. We hope that this study can provide a theoretical basis for the development and utilization of WPI-RAEs as food ingredients.

Study on the Methods for Reducing Discoloration of Orpiment Pigment used in Traditional Material Dancheong

The purpose of this study was to address the unstable Orpiment pigment by enhancing its stability through mixing and blending pigments to reduce discoloration. This experimental study focused on reproducing the natural color of orpiment by combining pure orpiment with two types of ochre and calcite powder to create complemented pigments. Experiments on artificial aging and coating adhesion were conducted to verify the stability of pure orpiment and the complemented pigments. Additionally, layering tests were carried out with lead(Pb) present in Red lead and copper(Cu) present in Malachite to observe the degree of discoloration. The experimental results of this study determined that mixing pure orpiment with calcite powder most closely resembles the hue and brightness of pure orpiment, despite noticeable fading under ultraviolet light. Conversely, orpiment mixed with ochre was lower in brightness and hue but demonstrated marked improvement in resisting discoloration. Therefore, combining orpiment and ochre in a ratio of 4:6 5:5 is expected to minimize color changes due to environmental factors when applied to external Dancheong. Additionally, when layering pure orpiment and complemented pigments on top of pigments containing lead and copper elements, the complemented pigments showed a reduction in discoloration compared to that of pure orpiment. Therefore, to prevent discoloration entirely, it is necessary to combine complemented pigments with further preventative painting techniques during the traditional Dancheong painting process.

Discoloration Evaluation of Stone Cultural Heritage Based on Hyperspectral Imaging

ABSTRACT Discoloration poses a serious threat to stone cultural heritage, making accurate assessment crucial for its protection and repair. Current detection methods are limited by coverage, slow speed and direct contact with cultural heritage. To address these issues, a spectral index based on the correlation between spectral reflectance and brightness was developed to identify discoloration boundaries in stone cultural heritage. Color difference ΔE* was then calculated to assess the deterioration of sandstone cultural heritage such as Leshan Giant Buddha over recent years. The results show that a strong correlation between the spectral index and the color changes on the Buddha’s face, with the three-band index using 530, 550, and 555 nm showing the best results in identifying discoloration areas. Among the evaluation models, the Competitive Adaptive Reweighted Sampling-Support Vector Machine Regression (CARS-SVR) model effectively quantifies the degree of discoloration. Brightness (L*) shows the strongest response to black pollution on the Buddha’s face. Discoloration is divided into five levels, with severe discoloration concentrated in the nose area, consistent with field survey findings. This study demonstrates the feasibility of using hyperspectral technology for quantitative discoloration assessment in stone cultural heritage.

Quantification of pitting corrosion resistance in stainless steel with hyperspectral imaging in the Vis/NIR range

The impact of 316L stainless steel discolouration on chloride induced pitting corrosion was quantified. Several degrees of discolouration were produces by chemical passivation, simulated rouging or anodic polarization. Discolouration was characterized by spectral analysis in the visible and NIR range (400-1000 nm). Pitting corrosion resistance was quantified by pitting potential measurements. The spectra were used to indicate whether pitting or transpassive behaviour would occur using chemometric classification techniques with 88% accuracy. In addition, pitting potentials were predicted combining chemometrics and survival analysis techniques with a 90 mV RMS error in cross-validation. XPS analysis linked pitting resistance with the Cr/Fe balance.

Bactericidal Effects and Quality Impact of Peroxyacetic Acid and Sodium Hypochlorite on Chicken Carcasses.

There is an urgent need to develop efficient and environmentally friendly decontaminants for poultry products. In this study, we aimed to evaluate the practical application of peroxyacetic acid (PAA) as a replacement for sodium hypochlorite (SH) to sterilize fresh chicken carcasses, using microbial, color, and electronic-nose analyses. We evaluated the decontamination effects of different concentrations of PAA and SH on chicken carcasses. The bactericidal effects of PAA at pH 3, 7, and 9, and SH at pH 10, at concentrations ranging from 100 to 500 ppm on coliform bacteria, total bacteria, and Salmonella spp. were evaluated. PAA induced a similar bactericidal effect at lower concentrations than SH. Therefore, at the same concentration and treatment time, PAA showed better bactericidal effects than SH. Although treatment with PAA (pH 3) and SH (pH 10) resulted in considerable discoloration, the degree of discoloration decreased when the pH of PAA was increased to 7 and 9. Therefore, by increasing the pH of PAA, the discoloration effect on chicken carcasses can be reduced without altering the microbial-reduction effect. Electronic-nose analysis showed that the flavor of the chicken was almost unaffected by volatile components at a treatment time < 30 min. Therefore, this study experimentally identified the optimal PAA concentration for the decontamination of chicken carcasses. The study findings provide a theoretical basis for the replacement of traditional bactericides, such as SH, with PAA for the production of poultry products.

Preventive Effects of Laser Irradiation and Dentin Bonding Agent Application on Tooth Discoloration Induced by Mineral Trioxide Aggregate

The aim of the present study was to evaluate the effect of the pre-application of dentin bonding agent and laser application on the prevention of tooth discoloration caused by (MTA) in the presence of blood. Fifty extracted human anterior teeth were prepared by standardizing root lengths to 10 mm and shaping root canals. Specimens were divided into five groups (n = 10) based on the treatment applied to the pulp chamber dentin wall: Group 1/no surface treatment; Group 2/Optibond FL; Group 3/Clearfil SE; Group 4/Optibond Universal adhesive application; Group 5/Nd:YAG laser application. Root canals were filled with fresh human blood below the cemento-enamel junction (CEJ), followed by ProRoot MTA, and collagen barrier placement. Color changes were monitored using a spectrophotometer at 0, 7, 30, 90, and 180 days post MTA placement. Color differences (∆E) were calculated and analyzed using two-factor mixed-design ANOVA with Sidak adjustment at p = 0.05. The degree of coloration increased with time within each group (p &lt; 0.05). No significant differences were observed between Optibond FL and Optibond Universal within each time interval, or between Clearfill SE Bond and the control group (p &gt; 0.05). When compared to the control group, the Nd YAG group exhibited the least degree of discoloration in all time intervals (p &lt; 0.05). Although the Nd:YAG laser had promising results, none of the methods can guarantee a 100% prevention of discoloration resulting from tooth discoloration caused by MTA-blood contact.

Comparison of discoloration of ceramic containing 3D printable material and CAD/CAM blocks.

This study aimed to clarify aspects of the color and translucency of 3D printed dental material with CAD/CAM blocks. Three different ceramic-containing, resin-based CAD/CAM blocks and a 3D printable resin were evaluated after thermocycled and assessed for their degree of discoloration based on colorant types and storage times. Data were analyzed using repeated-measures analysis of variance followed by Tukey's post-hoc test. All materials in red wine had ∆E00 values higher than the clinically accepted threshold value. At 1 week and 1 month, the 3D material was statistically significantly more discolored than the other 3 materials (p<0.05). None of the materials exceeded the acceptable threshold value at any time point. The color changes increased over time in resin-based CAD/CAM blocks and 3D printable dental materials. After 1 week and 1 month, there was a statistically significant difference in the color change between the 3D printed material and the CAD/CAM blocks.

Enhanced performance of eco‐friendly PVC by utilizing halo‐benzothiazole derivatives and glucose/fatty acids esters

AbstractTwo halo‐benzothiazoles, namely, 2‐amino‐6‐bromo‐benzo[d]thiazole and 2‐amino‐6‐fluoro‐benzo[d]thiazole were utilized to modify poly(vinyl chloride) (PVC) and gave two modified PVC samples for biomedical applications. Prepared glucose‐fatty acid esters of palmitic, oleic, and octanoic acids were exploited as plasticizers to produce phthalate‐free eco‐friendly antimicrobial PVC. The chemical structures of all prepared compounds were confirmed via Fourier‐transform infrared spectroscopy. The thermal properties of modified PVC was determined using thermo gravimetric analysis and differential scanning calorimetry while weight loss and degree of discoloration were used to assess the photostability after UV irradiation whereas references heat and UV absorbers were applied for comparison. The plasticizing effect of each glucose‐fatty acid ester at 20% by weight on the mechanical properties of modified PVC was determined and referenced to diethylhexylphthalate. The results revealed that the mechanical properties as well as the thermal stability of plasticized modified PVCs were enhanced. Plasticizers migration from the polymeric matrix was also determined and the results showed low extent of migration of the prepared plasticizers. So, modified plasticized PVC samples exhibited improved physicochemical properties. Antimicrobial properties of all samples, using disc diffusion agar method, were evaluated against some Gram +ve bacteria like Staphylococcus aureus and Streptococcus mutans and Gram −ve bacteria like Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa and fungi strains used were Candida albicans, Aspergillus niger, and Aspergillus ochraceous. All investigated compounds showed improved antibacterial and antifungal activities.Highlights PVC was chemically modified with two halo‐benzothiazoles to obtain antimicrobial PVC. Glucose‐fatty acids esters were prepared as eco‐friendly plasticizers for PVC. Halo‐benzothiazoles improved both the thermal‐ and photo‐stability of PVC. Glucose‐fatty acid plasticizers enhanced the mechanical properties of PVC. The extent of migration of prepared plasticizers is lower than that of reference plasticizer.

Thermochemical modification of beech wood with ammonium hydroxide

Four variants of the thermochemical modification were conducted on beech wood at a temperature of 130 °C, employing NH4OH concentrations of 5% or 10% for durations of either 12 or 24 h. The weight% gain (WPG) and bulking coefficient (BC) were initially calculated. Subsequently, the wood’s degree of discoloration was assessed using the CIELAB-colour-system. Chemical structure alterations were determined through Fourier transform infrared spectroscopy (FTIR), while the compressive strength of the wood parallel to the grain was measured. As the NH4OH concentration increased and the treatment duration extended, the samples displayed simultaneous weight increase and volume reduction. The ΔE* values of the samples ranged from 19.33 to 21.09 units, indicating significant color alteration. FTIR analysis revealed differences between the spectra of the unmodified control sample and the NH4OH-treated samples. The modification reduced in hydroxyl and carboxyl groups within the main and side chains of hemicelluloses. Additionally, a decrease in the absorption peak intensity of the unconjugated carbonyl group at 1740 cm− 1 indicated a relative reduction in hemicellulose content. Compressive strength tests showed that the thermochemical modification improved the modulus of elasticity, increasing it from 10,898 MPa (in the control sample) to a range of 11,663 − 13,390 MPa. Similarly, the compressive strength increased from 77.10 MPa to 81.56-107.19 MPa. Interestingly, this improvement was more pronounced with higher concentrations of NH4OH and prolonged modification durations.

Investigating the role of chlorogenic acids and coffee type in coffee-induced teeth discoloration

Objective Coffee is one of the most popular beverages in the world, with millions of people consuming it every day. The effect of coffee on teeth discoloration has long been a concern for both coffee drinkers and dental professionals. To address this concern, this study aimed to investigate the role of chlorogenic acids (CGAs) and the type of coffee in coffee-induced teeth discoloration. Materials and Methods High-performance liquid chromatography with a photodiode array detector was used to determine the CGA contents of instant coffee produced by five manufacturers (Starbucks, Dunkin’ Donuts, Kanu, Ediya, Coffee Bean). A total of 180 bovine tooth specimens were immersed in the coffee samples for varying durations (3, 9, 24, 48, and 72 h), and the discoloration levels were measured using a spectrophotometer. A linear mixed-effects model analysis was used to determine the significance of L*, a*, and b* values in relation to the duration of coffee immersion and coffee type. Results Both immersion time and coffee type had significant effects on tooth discoloration (p < 0.001), with some types of coffee being more strongly associated with tooth discoloration than others. The amount of CGAs present in coffee was found to be positively correlated with the degree of discoloration (p = 0.030). Conclusions Prolonged exposure to coffee can exacerbate teeth staining, and different types of coffee can cause varying degrees of discoloration. Furthermore, coffee with higher levels of CGAs may lead to greater tooth discoloration.

MILLENIAL-SCALE TIME AVERAGING INFERRED BY DISCOLORED SHELLS IN BEACH DEATH ASSEMBLAGES

ABSTRACT Molluscan death assemblages occurring on present-day beaches frequently consist of secondary-colored shells, with yellow to brown and gray to black colors. It is hypothesized that this secondary coloration can be related to postmortem age and to conditions in the taphonomically active zone, altering shells to black and gray tones in reducing conditions, and then becoming yellowish or brownish in oxidizing settings. In this study, we assessed whether the variability in the degree of shell discoloration of two species of the infaunal bivalve Mactra collected in beach death assemblages from a temperate siliciclastic beach in Uruguay is a function of postmortem age, and whether this variability in discoloration can be linked to differences in their elemental composition, microstructure, and provenance. Although we did not detect any differences in mineralogy or elemental composition among shells differing in discoloration, we show that modern (younger than a century) beach shells are not secondary-colored, but have remained white, but some white shells are also old (millennial). In contrast, yellow and gray shells are consistently older than 1,000 years, indicating that this degree of discoloration requires millennial residence times in the taphonomically active zone and suggesting that discoloration can be used as an indicator of time averaging. Discolored shells are derived from subtidal death assemblages.

An experimental study on quenching of metallic spheres in seawater

Motivated by quenching of melt droplets and debris particles in seawater during a hypothetical severe accident of light water reactors (LWRs), the quenching process of stainless-steel spheres in a seawater pool was investigated in the present study. The polished spheres were pre-heated up to 1000℃ in an induction furnace with inserted atmosphere, and then immersed into the subcooled water pool in a chamber made of transparent quartz. A thermocouple was embedded in the center of the sphere to measure the history of the sphere’s temperature, while a high-speed camera was employed to record the quenching process and vapor film dynamics. Quantitative data, e.g. film thickness and oscillation, of the vapor film evolution during the quenching process were obtained through an image processing program developed on the MATLAB platform.The experimental results indicated that the quenching rate was higher in seawater than in deionized water, and the vapor film collapsed at a temperature higher than the Leidenfrost temperature in deionized water. The trend appeared more significant with increasing subcooling of water. The comparison of the quenched spheres suggested the surface of the sphere in seawater achieved higher degree of discoloration and roughening than that in deionized water, probably due to the additives of salt which change water properties. The image processing and analysis revealed that the vapor film had different thickness profile along the upper and lower hemispheres, and the averaged film thickness was smaller in seawater than in de-ionized water during the stage of stable film boiling. The vapor film was thinning and oscillating with time, and its fluctuations appeared different frequencies and amplitudes at the upper and lower locations, which may explain the mechanism of the earlier collapse of vapor film in the quenching process of a high-temperature sphere in seawater.

Degradation of the Chromophore Functions of Dyes in Irradiated Solutions

Radiolysis damages the system of conjugated bonds and thus leads to the degradation of the chromophore functions of dyes in aqueous solutions. Ten representatives of quinophthalone, indigo, triphenylmethane, and azo dyes exhibited the same type of correlations between the absorbed dose and the degree of discoloration. It was shown using the method of competing scavengers that the color of aerated solutions decreased mainly due to the addition of OH radicals to the dyes. The radiation-chemical yields of discoloration ranged from 0.03 to 0.11 μmol/J and increased depending on the length of bond conjugation in the dye molecules. For practical electron-beam discoloration of dye solutions with a concentration of 20 mg/dm3, anabsorbed dose of 1–1.5 kGy was sufficient.

Evaluation of the amount of superoxide anion radicals generated by ultrasonic cavitation in a TiO2 suspension

In this study, the amount of radicals generated by high-intensity ultrasound irradiation of TiO2 suspensions was evaluated through image processing to determine the degree of discoloration of methylene blue added to the suspension. It was found that 40 ml of distilled water, 0.2 g of H2O2 with a concentration of 50 mM, 5 g of TiO2 pellets with an average diameter of 3.85 mm, and 20 min of irradiation with ultrasound with an acoustic intensity of 22.7 × 103 W m−2 were the most efficient conditions for activating the generation of radicals.

Effect of calcium silicate-based endodontic sealers on tooth color: A 3-year in vitro experimental study

ObjectiveTo analyze the change in tooth color produced by two hydraulic and one resin-based sealers by means of spectrophotometry for 3 years. MethodsForty maxillary anterior teeth were selected (n = 10 per group). Root canals were prepared by rotary instrumentation and irrigation was performed with NaOCl, which was also used in the final irrigation, followed by saline and activated with Endoactivator. Root canals were then filled using single cone technique. Negative control (NC): gutta-percha filling; Positive control: gutta-percha and AH Plus; experimental groups: gutta-percha and Bioroot RCS/TotalFill BC Sealer. Gutta-percha was cut 2 mm below the cementoenamel junction, the pulp chamber was sealed with flowable composite. The teeth were kept in PBS. Color was measured in the cervical and incisal halves before root canal treatment (RCT), one and six months after RCT, and after one, two and three years, with the Vita EasyShade spectrophotometer; positioned using an individualized splint. ΔEab and ΔE00 were calculated. Two-way ANOVA repeated measures test followed by Bonferroni post-test were performed to analyze the ΔL, Δa*, Δb*, ΔEab, and ΔE00, considering treatment groups and evaluation periods. Statistical significance was set at p < 0.05. ResultsIn the incisal half, in decreasing order of darkening, the groups at three years were ordered according to the ΔEab: AH Plus > NC > TotalFill > Bioroot. ΔE00 values were: 1.38 ± 0.61 NC, 2.37 ± 0.70 AH Plus, 1.86 ± 0.60 BioRoot and 1.53 ± 0.85 TotalFill. In the cervical half, the ΔEab values, showed the same descending order, except for Bioroot and TotalFill which alternated the order. The ΔE00 values were 1.86 ± 0.61 NC, 3.01 ± 0.70 AH Plus,1.89 ± 0.58 Bioroot and 1.65 ± 0.41 TotalFill, with no significant differences between groups and times in both locations. ConclusionsAll groups presented some degree of discoloration. Lightness and b* component were the most influential. Calcium silicate-based cements (Bioroot RCS and TotalFill BC Sealer) produced acceptable levels of discoloration at the end of follow-up.

Research of the activity of Fe-pillared montmorillonites in aqueous dye solution

High specific surface area, large micropore volume, concentration of surface acid sites, and increased density of sorption sites make montmorillonite pillared as an excellent adsorbent and catalyst to remove contaminants from wastewater. The studies are aimed at establishing the adsorption and catalytic activity of Fe pillared montmorillonite based on Krantau and Navbakhor bentonite in relation to dyes from solutions. It has been shown that the introduction of Fe3+ ions into the interlayer space of a natural sample increases the activity with respect to the anionic dye by more than 2 folds. Despite the large specific surface area of the original Navbakhor clay, compared to Krantau clay, the activity for Congo red is greater in the pillar of the latter. It has been established that Fe-pillared materials are active catalysts for the oxidation of dyes by hydrogen peroxide in aqueous solutions and lead to its 100% conversion. An increase in the temperature of catalytic oxidation ranged from 25 to 55°C increases the discoloration degree of Congo red solution under homogeneous conditions by 1.5 folds or more, and under conditions of heterogeneous catalysis at least three folds.

Switchable aptamer-fueled colorimetric sensing toward agricultural fipronil exposure sensitized with affiliative metal-organic framework

Persistent usage of pesticides in agriculture has posed serious damage to overall ecosystem and human health, and thereby it is imperative to develop sensitive and efficient tools to evaluate residual pesticides in food and environmental setting. Herein, we reported a switchable colorimetric probe toward fipronil residue sensitized with aptamer-fueled catalytic activity of affiliative ZIF-8. Innovatively, it was found that the attached aptamer preferred to adsorb 3,3′,5,5′-tetramethylbenzidine (TMB) rather than 2,2-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) (ABTS), greatly promoting catalytic oxidation of ZIF-8 toward TMB for further improving sensitivity. Aiding with smartphone-based image acquisition, fipronil-responsive discoloration degree was converted into the ratio of green and blue (G/B) with limit of detection as low as 0.036 μM (0.016 μg·g−1). Moreover, it allowed for fipronil analysis in water, soil and vegetable samples with good recovery between 87 % and 110 %, verifying extension application prospect of the aptamer-fueled colorimetry for on-field pesticide evaluation in food safety supervision.

Coronal discoloration induced by calcium silicate-based cements used in full pulpotomy in mature permanent molars: a randomized clinical trial.

This study aimed to randomly compare in vivo coronal discoloration at 6 and 12months after full pulpotomy in mature permanent molars using MTA, Biodentine, and TotalFill and to investigate the effect of variables such as remaining buccal wall thickness and time to achieve hemostasis. One hundred eight teeth that met the inclusion criteria received full pulpotomy and were randomly divided into 3 groups via a block randomization technique according to the calcium silicate cement (CSC): ProRoot WMTA, TotalFill, or Biodentine. Assessment of tooth color was carried out using a spectrophotometric device (VITA Easyshade Compact) after composite placement (T0), at 6- and 12-month follow-up. Buccal wall thickness and time to hemostasis were recorded. The primary outcome measure (color change ΔE) was calculated, and the results were analyzed by three-way ANOVA and crosstabulations in relation to material type and effect of variables. Four cases were excluded after pulpotomy failure; 81 teeth were evaluated at 6months and 95 teeth at 12months. All CSCs caused tooth discoloration (defined as ΔE > 3.7); MTA significantly caused the highest color change at 6- and 12-month follow-up (76% (19/25) and 87.5% (28/32), respectively) compared to Biodentine (41% (9/22), 48% (13/27)) and TotalFill (44% (15/34), 53% (19/53)) (p = 0.022, p = 0.002), while no significant difference was found between the Biodentine and TotalFill groups (p = 0.813, p = 0.8). Buccal wall thickness (above or below 2.7mm) had a significant effect on the degree of discoloration (p = 0.004). The 3 CSCs caused tooth discoloration based on the threshold of ΔE > 3; the remaining buccal wall thickness was a significant factor. The use of Biodentine and TotalFill instead of MTA is encouraged to minimize discoloration. While experimental studies report coronal discoloration after CSCs use, clinical data is lacking. This study assessed discoloration using a spectrophotometric device. The use of materials with lower discoloration potential in pulpotomy is encouraged. The study was registered with clinical trial registration number: NCT04346849 on 14.4.2020.

Study of CaTiO3–ZnS heterostructure obtained by microwave-assisted solvothermal synthesis and its application in photocatalysis

We report herein the assembly of a calcium titanate (CTO)-zinc sulfide (ZnS) heterostructure through a microwave-assisted solvothermal (MAS) method and its respective characterizations to evaluate its material properties and applicability in heterogeneous photocatalysis. The CTO-ZnS heterostructure comprises a mixture of the orthorhombic crystalline phase of CTO and the cubic crystalline phase of ZnS. Scanning electron microscopy (SEM) images have revealed that the CTO consists of mesocrystals assembled from agglomerated microcubes. After applying a ZnS coating, it was possible to identify the formation of a cloud of particles around parts of the CTO mesocrystals, thus forming the heterostructure. The presence of ZnS on the CTO surface allowed for greater emission of photoluminescence, resulting in improved efficiency for photocatalytic applications. Photodegradation tests on Rhodamine B (RhB) dye in the presence of CTO, ZnS, and CTO-ZnS revealed that the heterostructure led to more extensive photocatalytic degradation (50.5%) within 30 min than CTO (10%). Moreover, the degradation efficiency over the CTO-ZnS increased to 95.7% after 180 min, indicating that the ZnS coating served to increase the degree of discoloration over time. These satisfactory results demonstrate that CTO-ZnS is a promising photocatalyst capable of accelerating the degradation of organic dyes, thus contributing to the decontamination of water resources. Scavenger tests revealed holes (h+) to be the main active species in the photocatalytic process with CTO, whereas electrons (e−), h+, and hydroxyl radicals (HO*) are all involved in the mechanism with both CTO-ZnS and ZnS.

Assessment of the Susceptibility of Aesthetic Orthodontic Brackets to Discoloration

The high aesthetic value of orthodontic appliance elements during treatment constitutes an important factor for an increasing number of adult patients. The aim of this study was to determine whether food dyes could significantly affect the color of both plastic and ceramic orthodontic brackets. Four brands of orthodontic brackets were investigated in the present study. Twenty-five samples of each kind were prepared. Five brackets of each series were stored in pure water, coffee, black tea and red wine for 1 h, 24 h, 7 days and 14 days. Total color change ΔE* of the samples was analyzed after storage with the use of the SpectroShade dental spectrophotometer (MHT, Verona, Italy) according to the CIE L*a*b* color scale. Correlations between bracket brand, kind of food dye and intensity of color change at the significance level p = 0.05 were investigated. After 1 and 24 h of incubation, water had the least influence on the color change of aesthetic orthodontic brackets, and tea had the greatest effect (p = 0.05). After 7 and 14 days of incubation of the samples, water still remained the environment influencing ΔE* change to the smallest extent, whereas storage in red wine changed the color of brackets to the significantly (p = 0.05) highest degree. The degree of discoloration of the assessed brackets depended on the type of material and the storage time in the environment of the individual food dyes (p = 0.05). The results of the present study show that, in the event of contact with food dyes, aesthetic orthodontic brackets discolor, the intensity of which can be influenced by the materials they are made of, the kind of food dye and the time of samples’ storage.