Article

A study of hydrogen peroxide chemistry and photochemistry in tea solution with relevance to clinical tooth whitening

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Abstract

Objective: Tooth whitening using hydrogen peroxide is a complex process, and there is still some controversy about the roles of pH, temperature, chemical activators, and the use of light irradiation. In this work the basic interactions between whitening agents and stain molecules are studied in simple solutions, thus avoiding the physics of diffusion and light penetration in the tooth to give clarity on the basic chemistry which is occurring. Method: The absorbance of tea stain solution at 450 nm was measured over a period of 40 min, with various compositions of whitening agent added (including hydrogen peroxide, ferrous gluconate and potassium hydroxide) and at the same time the samples were subjected to blue light (465 nm) or infra-red light (850 nm) irradiation, or alternatively they were heated to 37°C. Results: It is shown that the reaction rates between chromogens in the tea solution and hydrogen peroxide can be accelerated significantly using ferrous gluconate activator and blue light irradiation. Infra red irradiation does not increase the reaction rate through photochemistry, it serves only to increase the temperature. Raising the temperature leads to inefficiency through the acceleration of exothermic decomposition reactions which produce only water and oxygen. Conclusion: By carrying out work in simple solution it was possible to show that ferrous activators and blue light irradiation significantly enhance the whitening process, whereas infra red irradiation has no significant effect over heating. The importance of controlling the pH within the tooth structure during whitening is also demonstrated.

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... 5,6 This sensitivity may be related to the use of high-concentrated bleaching agents. 7 However, there are other factors that are associated to the bleaching-induced tooth sensitivity, such as the presence of restorations, 5 application time, 8 chemical process 9 and pH [10][11][12] of bleaching agents. ...
... 11,[16][17][18] Theoretically, these factors may facilitate the passage of hydrogen peroxide to the pulp and thus may be partially responsible for the higher levels of tooth sensitivity observed with more acid bleaching gels. 19 In contrast, products with neutral or alkaline pH produce greater bleaching efficacy under in vitro studies, 9,10 which may be related to the fact that hydrogen peroxide dissociation is a constant in an alkaline pH. Additionally, these bleaching agents do not alter the enamel roughness or produce deleterious effects on the enamel surface. ...
... In other words, the more alkaline the bleaching agent is, the higher number of free radicals will be formed to oxidize the organic content of the tooth, 27 improving the efficacy. 9,16,25 However, other studies indicate that the pH of the product does not affect the whitening effectiveness of hydrogen peroxide in high concentrations. 12,19,20 This was similar to this study, which demonstrated a similar color change in all the experimental groups. ...
Article
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Objective In‐office bleaching gels are usually marketed in different pHs. This study is aimed at evaluating the efficacy, enamel surface morphology and concentration of hydrogen peroxide (HP) in the pulp chamber of teeth bleached with 40% HP with different pHs. Materials and Methods Forty premolars were randomly divided according to bleaching gel pH: 5.1, 6.3, 7.0, and control (no bleaching). Teeth were prepared, an acetate buffer was placed in the pulp chamber and teeth were bleached with two 20‐minutes applications. The amount of HP was determined on a UV‐VIS spectrophotometer. Color change was assessed by using a digital spectrophotometer before and 1 week after bleaching treatment. Five additional premolars were divided into four parts, assigned to the same groups above for analysis under scanning electron microscope. Data were subjected to anova and Tukey's tests (alpha = 0.05). Results The group pH 5.1 showed the highest HP diffusion in the pulp chamber (P < .001). No significant difference was detected in color change (P = .51). All groups presented the same pattern of enamel demineralization. Conclusions The bleaching agent with pH 5.1 presented the highest HP amounts in the pulp chamber, but color change and enamel morphology were similar among groups. Clinical significance Regardless of the pH, the bleaching effect can be observed in teeth submitted to high concentrations of HP, but a higher permeability of HP was found in the pulp chamber of teeth bleached with more acidic bleaching agents. Based on that, we suggest the use of alkaline gels for in‐office bleaching to minimize damage to the pulpal tissue.
... Plaque may also serve as a reservoir for pathogens that are significant causes of pneumonia [11] and other systemic diseases [12]. Denture staining is an aesthetic problem that can affect appearance and interpersonal communication [13][14][15][16]. ...
... Through multiple logistic regression analysis (MLRA), Visschere et al. [17] determined that institutional management practices were the only risk factor for denture plaque in patients receiving long-term care in Belgian institutions. Denture staining is reportedly affected by smoking [14,18,19], coffee [20,21] and tea [13][14][15] consumption, duration of denture use [14], and cleaning method [14][15][16]. However, most studies have used monofactorial analyses to investigate factors influencing denture plaque or staining. ...
... Previous univariate analysis have shown that denture staining was associated with smoking [14,18,19], tea consumption [13][14][15], duration of denture use [14], and cleaning method [14][15][16]. Our findings are in accordance with these results. ...
Article
Full-text available
Removable dentures are subject to plaque and/or staining problems. Denture hygiene habits and risk factors differ among countries and regions. The aims of this study were to assess hygiene habits and denture plaque and staining risk factors in Chinese removable denture wearers aged >40 years in Xi'an through multiple logistic regression analysis (MLRA). Questionnaires were administered to 222 patients whose removable dentures were examined clinically to assess wear status and levels of plaque and staining. Univariate analyses were performed to identify potential risk factors for denture plaque/staining. MLRA was performed to identify significant risk factors. Brushing (77.93%) was the most prevalent cleaning method in the present study. Only 16.4% of patients regularly used commercial cleansers. Most (81.08%) patients removed their dentures overnight. MLRA indicated that potential risk factors for denture plaque were the duration of denture use (reference, ≤0.5 years; 2.1-5 years: OR = 4.155, P = 0.001; >5 years: OR = 7.238, P<0.001) and cleaning method (reference, chemical cleanser; running water: OR = 7.081, P = 0.010; brushing: OR = 3.567, P = 0.005). Potential risk factors for denture staining were female gender (OR = 0.377, P = 0.013), smoking (OR = 5.471, P = 0.031), tea consumption (OR = 3.957, P = 0.002), denture scratching (OR = 4.557, P = 0.036), duration of denture use (reference, ≤0.5 years; 2.1-5 years: OR = 7.899, P = 0.001; >5 years: OR = 27.226, P<0.001), and cleaning method (reference, chemical cleanser; running water: OR = 29.184, P<0.001; brushing: OR = 4.236, P = 0.007). Denture hygiene habits need further improvement. An understanding of the risk factors for denture plaque and staining may provide the basis for preventive efforts.
... Several studies have shown that bleaching in acidic pH can produce changes in chemical composition and surface morphology, calcium loss, and reduction in hardness and fracture resistance. [13][14][15][16][17] On the other hand, studies of dental bleaching agents with alkaline pH have shown an increased bleaching efficacy, 18 reducing its deleterious effects on enamel surface properties. 19 However, there is a lack of literature in relation to the influence of pH on bleaching of chromogens commonly found in the oral cavity that are responsible for tooth darkening, such as wine and tobacco. ...
... Thus, an in vitro method for testing the action of peroxide on chromogens without the use of tooth substrate is simple, and a larger number of combinations can be assessed, avoiding the complexities resulting from chemical diffusion and optical transmission within the tooth. 18 When we use tooth structure, other variables are present, such as tooth age, mineralization status, initial color, diameter and number of dentin tubules, and differences in the numbers of organic and inorganic compounds. ...
... To evaluate the bleaching effect of hydrogen peroxide in vitro, its action on the colored dye solutions containing known chromogens was measured by a reflectance spectrophotometer (CM 2600d, Konica Minolta, Osaka, Japan), as proposed by Maiolo and others 20 and Young and others. 18 Wine (Santome, Itupeva, Sã o Paulo, Brazil) and an alcoholic solution of tobacco (Nicotianatabacum L.) were used as chromogen agents. 21,22 To prepare the solution, a portion of 80 g of dry tobacco was mixed and chopped into slices of 7 mm (maximum) in 100 mL of alcohol 548Gay-Lussac. ...
Article
Objective: To evaluate the influence of pH on the bleaching effect of hydrogen peroxide on chromogen agents. Method: Hydrogen peroxide 50% was mixed with red wine or with an alcoholic solution of tobacco in glass cuvettes, resulting in final peroxide concentrations of 16.97% and 21.12%, respectively. The pH of this mixture was measured and adjusted with 3.3 M HCl solution or 2.5 M NaOH solution to obtain the final pH values of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0. After mixing, the color of these solutions was evaluated in a reflectance spectrophotometer; readings were repeated after 10 minutes for the wine solution and 20 minutes for the tobacco solution. Ten samples were prepared for each solution at each pH. Color changes (Delta E) were calculated. The data were statistically analyzed using analysis of variance one-way and Tukey tests, with a significance level of 5%. Results: There were significant differences among the different pH values for the wine and tobacco solutions (p=0.0001). The Tukey test showed that for both solutions, pH 9.0 resulted in a significantly greater bleaching effect than the other values tested. Conclusion: The efficacy of hydrogen peroxide bleaching is directly proportional to the increase in its pH.
... Reactive oxygen species (ROS) such as superoxide anion ( 1 O 2 · − ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical (·OH) are responsible for many physiologic cellular disorders in humans. [1][2][3][4] Of a particular concern is the interconvertibility [4][5][6] of the reactions that involve the production of these destructive chemical entities which also causes synergetic effects on the weights of damage inflicts on susceptible cellular targets. For example, superoxide anion converts to hydrogen peroxide readily in the presence of suitable hydrogen ion donors [1,7,8] while hydrogen peroxide transforms to reactive hydroxyl and hydro-peroxyl radicals in the presence of Fe 2+ and Fe 3+ ions, respectively, under Fenton reaction mechanism. ...
... For example, superoxide anion converts to hydrogen peroxide readily in the presence of suitable hydrogen ion donors [1,7,8] while hydrogen peroxide transforms to reactive hydroxyl and hydro-peroxyl radicals in the presence of Fe 2+ and Fe 3+ ions, respectively, under Fenton reaction mechanism. [5,6,8] However, among these ROS, H 2 O 2 seems to have attracted considerable attention. This is attributed to the fact that, its presence could be linked to the existence of other ROS [1,4,8,9] or some chemical agents (e.g., glucose or cholesterol) [10][11][12][13] responsible for the promotion of certain physiologic diseases. ...
... [4] The major factor responsible for the utility of drugs over many cycles is incomplete therapies due to administration of lower doses. [21] Many HPCPs are susceptible to degradation under different light [6] and heat [5] conditions, which further lower their required concentrations for effective therapeutic functions [5] and thus subsequently promote their extensive usage over time. As a result, it is essential to monitor the levels of H 2 O 2 in commercially-available HPCPs to safeguard against overexposure to H 2 O 2 contamination and thus possible cellular oxidative stress. ...
Article
In this report, a facile system consisting of iron (III) meso-tetrakis(4-hydroxyphenyl)porphyrin-methylene blue dye hybrid immobilized on a disposable paper strip was used to detect and sense H2O2 in aqueous solutions via a low-cost pixelometric imaging technique. The new technology was employed to evaluate the level of H2O2 in a self-administering 30%-labeled commercial H2O2 disinfectant solution. The result showed that the concentration of H2O2 in the tested pharmaceutical sample solution deviated from the label by 92.37%. The current approach provides a simple low-cost resolution for the rapid detection and quantification of H2O2 in aqueous solution and pharmaceutical fluids.
... Whereas several in vitro and clinical trials have indicated that light activation does not affect the change in color produced by whitening, [2][3][4][5][6] other studies have provided evidence that it significantly enhances the degree of lightening and the reduction of chroma. [7][8][9][10][11][12] This controversy is partly based on our current lack of knowledge of the basic mechanism underlying tooth whitening, with respect to both the hydrogen peroxide diffusion into the enamel and dentin, and the interaction of peroxide radicals with particular chromogens in the tooth. It has been speculated that light activation may lead to direct whitening by breaking bonds in the chromogen when sufficient energy is transferred. ...
... Alternatively, the absorption of photons could raise the energy status of conjugated bonds in the chromogens, making these molecules more reactive to hydrogen peroxide molecules and radicals. 12 Energy absorption by chromogens is dependent on the spectrum that are present, with yellow chromogens absorbing light at 425 nm, and other dyes having their own characteristic frequency of absorption, depending on where they fall in the color spectrum. 13 Based on the theory of Young and colleagues, 12 yellow stains should absorb more photons from a light-activating unit with a peak wavelength of 466 nm than a red or blue stain and the latter would preferably absorb photons at peak wavelengths of 504 and 625 nm, respectively. ...
... This also supports the theory of Young and colleagues that yellow stain may absorb energy transferred from the light source and thus may be particularly susceptible to tooth whitening by hydrogen peroxide. 12 An interesting aspect of this study was the observation of differences in the extent of the change in color with respect to the artificial stains. Yellow and orange stains have been reported to respond well to tooth whitening, whereas grayish-blue stains have not. ...
Article
There is still controversy as to the efficacy of light activation used in tooth whitening. The purpose of this study was to evaluate the effect of light activation on tooth color change relative to the artificial dye color. Extracted human third molars (160) were randomly distributed into eight groups of 20 specimens each based on artificial staining and use of light activation. All groups received three 45-minute sessions of in-office whitening at 3-day intervals. Color measurements were performed with an intraoral spectrophotometer at baseline prior to staining (T0 ), after artificial staining (T1 ), 1-day-(T2 ), and 1-week-(T3 ) post-whitening. Color differences were calculated relative to after artificial staining color parameters (L*1 , a*1 , b*1 ) with the use of a software analysis program enabling synchronization of two images. Within the same staining groups, the light-activated samples exhibited a greater color change than their nonlight-activated counterparts. However, only in the case of the yellow-stained samples at 1-day post-whitening was there a significant difference between the nonlight-activated and light-activated groups (Tukey's post hoc multiple comparison test for pairwise comparisons, p < 0.05). Light activation is a valid method for enhancing the efficacy of tooth whitening with respect to overall color change and works best with yellow stains. Light activation is a valid method for enhancing the efficacy of tooth whitening with respect to overall color change and works best with yellow stains. © 2015 Wiley Periodicals, Inc.
... Additionally, the penetration rate will vary depending on the concentration and time of H 2 O 2 application, and other minor defects to the tooth structure, especially if it involves a restored tooth [17]. H 2 O 2 is proposed to remove stain via the production of short-lived free radicals such as hydroxyl radical (OH − ) [18,19] which acts as strong oxidising agents that breaks carbon double bonds often found in the colour staining chromophore, such as heteroatoms, carbonyl, or phenyl rings [19]. However, as highly chemically unstable molecules, these peroxide derived free radicals are able to react indiscriminately with other organic molecules, including proteins, lipids, carbohydrates and nucleic acids (reviewed in [20]). ...
... The underlying mechanism by which H 2 O 2 results in bleaching of the chromogen is complex. In solution H 2 O 2 decomposes to form hydrogen ions (H + ) and perhydroxyl ions (HOO − ) resulting in a weak acidic solution [18,19]. The perhydroxl ion interacts with further H 2 O 2 to produce highly reactive oxygen species such as hydroxyl radicals perhydroxyl radicals. ...
... As strong oxidising bleaching agents, the free radicals are able to break chemical bonds within the phenyl structure of the chromogen. Raising the pH has been shown to increases the production of perhydroxyl ions which has been attributed to increasing its effectiveness as a tooth whitening product [18,19]. In addition through the Fenton reaction, H 2 O 2 can react with exogenous ferrous ions (Fe 2+ ) to produce hydroxyl radicals. ...
Article
Objectives: Dietary stains can be adsorbed into the dentin of teeth. Using Orange II as a model dietary stain, this study investigated the strength of its interaction with the mineral and protein components of dentin matrix and how hydrogen peroxide (H2O2) treatment influences this interaction. Methods: Dentin slices were prepared from human teeth and were either deproteinized (5.6% sodium hypochlorite, 12 days), demineralised (0.5 M EDTA, 3 days) or left as intact control samples. Samples were stained with Orange II for 1-168 h, during which staining intensity was quantified by image analysis. Similarly, uptake of stain by deproteinized / demineralized samples treated with 10 or 30% H2O2 was investigated. Using surface plasmon resonance technology, real-time binding kinetics were determined assessing the interaction of orange II with the dentin matrix protein constituents, collagen type I, biglycan, decorin, dentin sialoprotein and osteopontin. Results: Deproteinization of dentin matrix reduced the uptake of the orange II compared to the intact control. Conversely, demineralization of dentin samples increased the uptake of the dye. Treatment of samples for 48 h with H2O2 reduced subsequent uptake of the orange II. Real-time kinetic analysis indicated moderate strength of binding for Orange II with collagen type I, weak binding with decorin and biglycan and negligible binding with dentine sialoprotein and osteopontin. Conclusion: These results indicate a predominant role for collagen type I, which accounts for 90% of the organic protein matrix of teeth, for attracting dietary stains. Binding analyses indicate that the interaction is highly dissociable, and further binding is reduced following H2O2 treatment. Clinical significance: This study provides new information regarding adsorption of dietary stains into tooth dentin, suggesting that they are attracted and moderately bound to the collagen type I matrix. This study also contributes valuable information for discussion for considering the effect of H2O2 on bleaching teeth and its influence on subsequent uptake of dietary stains following whitening treatments.
... Violet illumination can cause pigments breakdown through dissociation of the weaker O-O and HO-OH bonds. 42 The light can penetrate enough in the tooth surface to remove the superficial staining of the teeth and may act on odontoblastic nerve terminals without increasing the tooth sensitivity to pain. Light-based techniques can also be used to quantify the effect of whitening treatments, as they provide objective and real-time assessment of biological tissues. ...
... Young et. al. 42 have explained the chemistry of the stain molecules breakdown by hydrogen peroxide and the synergic whitening photochemistry when the peroxide is combined with blue light. The enhancement provided by the illumination is also present in our study, where light from 2.97 eV (398 nm) to 3.12 (418 nm) eV is used to cleave covalent bonds of the stain molecules and increase the energy states of the conjugated bonds C=O, C=C and C=C-C=C to be targeted by the hydrogen peroxide. ...
... This agrees with the hypothesis of Young et. al. 42 for the photochemistry of the light illumination, since light would be responsible for breaking O-O and HO-OH bonds, generating OH and OOH radicals and shortening the chain of organic molecules. Then, polar and non-polar products of the reaction can be removed by cleaning and washing the teeth. ...
Article
Objective : To evaluate the effectiveness of the whitening and washing steps of a treatment using violet illumination (VI) alone or combined with hydrogen peroxide gel. In addition, we evaluated the color change after cleaning the tooth with and without mineral oil. Methods : First, 16 bovine teeth were extracted and stored in 5% thymol solution. Next, the teeth were collected and cleaned. Then, the teeth were stained with instant coffee solution for 24 h. The teeth were divided in four groups: control, VI without 35% hydrogen peroxide gel (VI), VI with 35% hydrogen peroxide gel (VI + gel), and VI without 35% hydrogen peroxide gel and cleaned with mineral oil before washing (VI + oil). Results : The whitening treatment VI + gel was able to completely restore the teeth whiteness and make the teeth 31.2% less yellow than prior coffee staining. The VI + oil treatment led to about 3.7 times the whiteness and yellowness changes observed in the VI treatment and restored 51% of the whiteness lost by staining. Conclusions : The VI + gel treatment can be recommended against coffee stains and should be further investigated for other types of tooth stains. In addition, cleaning the tooth surface with mineral oil could be an alternative to increase the performance of whitening treatments.
... Under alkaline pH, the formation of free radicals is more quick and intense than under acidic pH. [10][11][12][13][14][15] Additionally, some enzymes and salts of transition metals, such as Fe, Cu, Cr, or Mn, can act as catalyzers or intensifiers, promoting the dissociation of hydrogen peroxide molecules and formation of free radicals. 11,[16][17][18][19][20][21][22] Previous studies have shown that the association of metallic salts and bleaching gels was able to improve the dental bleaching effect. ...
... Although previous studies showed that the addition of FG significantly increased the bleaching effect, 10,34 in this study, it was not effective in improving the bleaching effect for all concentrations tested, nor in preventing the yellowish regression, as observed for FS and FC. It is possible that the reactivity of the ferrous ion inside the complex is lower than the free ions obtained from the other sources. ...
... Many studies have shown that the pH in which the bleaching reaction with hydrogen peroxide occurs can influence the efficiency of the process, improving the bleaching effect. [10][11][12][13][14] In higher pH, a higher amount of peri-hydroxyl ions are formed, which increases the formation of free radicals. 13,38,52 However, as can be seen in Table 2, the addition of the catalyst in all formulations did not significantly interfere with the pH of the alkaline solutions or bleaching gels, indicating that the variation of the effects can be due the action of the metallic ions and not because of the pH. ...
Article
The objective of this study was to evaluate the effects of different types and concentrations of chemical catalysts on the efficiency of 35% hydrogen peroxide gel on dental bleaching. Enameldentin disks were obtained from bovine incisors and the initial color was assessed. The groups were divided according to the type and concentration of catalyst added to an experimental gel: ferrous sulphate (FS) (0.001, 0.002 and 0.003%); ferrous gluconate (FG) (0.01, 0.02 and 0.03%); ferric chloride (FC) (0.01, 0.02 and 0.03%); manganese gluconate (MG) (0.01, 0.02 and 0.03%); and manganese chloride (MC) (0.01, 0.02 and 0.03%). The positive control (PC) group received the bleaching gel without any catalyst, while in the negative control (NC) the specimens remained in artificial saliva. Three applications of the bleaching gels were performed for 10 minutes each, repeated after 7 days. Color assessments were performed 7 days after the first session and 7 days after the second. The specimens were stored in artificial saliva and assessed again after 1 year. The data were analyzed by parametric analysis of variance and Tukey's test. Some of the chemical catalysts tested were effective in reducing the yellowish color of the samples in relation to the positive control group after 1 and 2 applications and diminished the color relapse over time. After 1 year, the FS was the most effective catalyst tested. We concluded that some chemical catalysts increased the efficiency of dental bleaching. How to cite this article Torres CRG, Guimarães CA, Ribeiro ZEA, Borges AB. Influence of Different Types and Concentrations of Chemical Catalysts on Dental Bleaching Efficiency. J Contemp Dent Pract 2015;16(11):893-902.
... At present, manufacturers have paid their attention to the acidity of bleaching gels, because low-pH can produce various harmful effects on the structure and properties of the tooth, such as changes in chemical composition, surface morphology, reduction in hardness and fracture resistance [11][12][13][14][15] . Conversely, previous studies have shown that alkaline bleaching agent improved the bleaching efficacity 10,16) while minimizing the detrimental modifications on enamel surface 8) . Despite the advantages, high-pH of bleaching products raise concerns about the safety of the soft tissues as they cause mild irritation to severe ulcerations. ...
... One experiment measuring the color of the solution containing chromogens (wine and tobacco solution) reported that the efficacy of H 2O2 bleaching was directly proportional to the pH of the solution 10) . Similar results were obtained in another study 16) , investigating the chemical activity of H2O2 on chromogens of a tea solution by measuring the absorbance of the solution as a function time. An increase in the speed of the reaction between pH 8.0 and pH 9.0 16) was found. ...
Article
Full-text available
This study investigated the effect of pH of bleaching agent, photo-irradiation time or application times on bleaching action using hematoporphyrin-stained papers (HSPs) and artificially stained bovine-teeth (BT). 23% H2O2 with pH 5.5, 6.0, 7.0, 8.0 and 9.0 were applied on the specimens. HSP was photo-irradiated for 1, 3 and 5 min. BT were photo-irradiated for 10 min and the bleaching was repeated ten times (n=10). CIE L*a*b* of the specimens were measured before and after the procedure. Data were analyzed by repeated-measures ANOVA followed by multiple comparisons with Bonferroni correction. For the HSP, longer irradiation time and higher pH yielded significantly higher color difference (ΔE). As for BT, increasing application times and higher pH resulted in higher ΔE. It was concluded that the pH of the bleaching agent significantly improved the bleaching effect with increased photo-irradiation time for HSP and with an increase of repeated application times for BT.
... Our results supported similar studies that hydrogen peroxide is more potent on P. fluorescens in both acid and alkaline pH than at neutral conditions [36][37][38]. Similar studies reported that alkaline H 2 O 2 has a higher bleaching efficacy without an obvious surface erosion or modification [39,40], due to generation of perhydroxyl anion and active powerful hydroxyl radicals from hydrogen peroxide at alkaline pH [41][42][43], but since H 2 O 2 is more stable in acidic conditions, many products have an acidic pH to maintain H 2 O 2 stability [43]. ...
... On the other hand, it was demonstrated that the efficacy of H 2 O 2 solutions is increased at more acidic pH ranges [44], but the disadvantage is that bleaching at acidic conditions is found to be harmful to surfaces [39,40,[45][46][47][48][49]. It was also reported that bacterial resistance to H 2 O 2 increases at low pH values, regardless of catalase activity [50]. ...
Thesis
The aim of thesis was to understand the alterations in cellular oxidative processes, antioxidant defense mechanisms, cell ultrastructure and morphology underlying the synergistic bacterial control effects of selected pH values alone (pH 8.2 and 5.0) and peracetic acid, H2O2, dodecyltrimethylammonium chloride DTACl (cationic surfactant), C10 linear alkyl chain alcohol ethoxylate C10/EO8 (non-ionic surfactant) and novel combination of hydrogen peroxide + peracetic acid + non-ionic surfactant with bleach activator sodium nonanoyloxybenzenesulfonate (NOBS) at mild alkaline conditions (pH 8.2), and of linear alkylbenzene sulfonate LAS (anionic surfactant) at acidic milieu (pH 5.0) in Pseudomonas fluorescens ATCC 13525 by measuring the intracellular antioxidant molecules and oxidative stress biomarkers levels, antioxidant enzymes activities, and characterizing the cell morphology and ultrastructure. The minimum inhibitory concentrations (MICs) of peracetic acid, hydrogen peroxide, dodecyltrimethylammonium chloride, linear alkyl chain alcohol ethoxylate and combination of hydrogen peroxide + peracetic acid + non-ionic surfactant with bleach activator at pH 8.2, and MIC of linear alkylbenzene sulfonate at pH 5.0 were used during the stationary growth phase of planktonic cells grown in tryptic soy broth liquid medium to test free radicals generation, catalase, superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx) and glucose-6-phosphate dehydrogenase (G6PDH) specific activities, malondialdehyde (lipid peroxide), protein carbonyls (protein oxidation product), total thiols and low molecular weight thiols (LMWT) levels, and total glutathione/glutathione disulfide (tGSH/GSSG) ratio in addition to analysis of cell ultrastructure and morphology. Hydrogen peroxide and peracetic acid decomposition kinetics by the selected bacterial strain were also investigated. The analyses were performed by UV/VIS spectrophotometer and electron paramagnetic resonance (EPR), and cellular visualization was carried out by transmission electron microscope (TEM). Alkaline conditions (pH 8.2) alone mainly elevated protein carbonyls level, decreased the levels of LMWT and tGSH/GSSG ratio which could potentiate the effect of hydrogen peroxide, peracetic acid, cationic and non-ionic surfactants and selected combination, while acidic environment (pH 5.0) alone mainly decreased total thiol level that could facilitate anionic surfactant action. Free radicals have been detected in highly diluted samples of anionic surfactant and peracetic acid only (10 µg/ml total soluble protein), which explain the higher efficacy of anionic surfactant and peracetic acid when compared to tested disinfectants. Hydrogen peroxide and peracetic acid increased the levels of malondialdehyde and protein carbonyls, while reduced the total thiols and LMWT levels which could explain the oxidative damage of these oxidants to cells. Hydrogen peroxide and peracetic acid were also found to stimulate SOD specific activity and inhibit catalase specific activity which suggest a late stage of oxidative stress. Peracetic acid and hydrogen peroxide increased GR, GPx and G6PDH specific activities which suggests disruption of cellular redox status as a result of oxidation. Cationic surfactant targeted the cell membrane, which was reflected by elevation in malondialdehyde levels. SOD and catalase specific activities were increased, while GPx and G6PDH specific activities were decreased with cationic surfactant. The decrease of GR specific activity also contributed to the effect of cationic surfactant. Non-ionic surfactant caused protein denaturation reflected by increment in total thiol level which is the main target of non-ionic surfactant. Moreover, non-ionic surfactant was found to increase SOD specific activity and decrease the catalase specific activity which suggest cell oxidative damage. Non-ionic surfactant stimulated GR and G6PDH specific activities, while GPx specific activity was not changed suggesting overall imbalance of cell homeostasis. Combination of hydrogen peroxide + peracetic acid + non-ionic surfactant + bleach activator reduced the tGSH/GSSG ratio that explains the bacterial control effects of combination. The same combination was also found to increase GR specific activity, and lower both GPx and G6PDH specific activities as a consequence of oxidative stress. Anionic surfactant increased the levels of protein carbonyls which is a biomarker of protein oxidation, while decreased the total thiol level and tGSH/GSSG ratio. Anionic surfactant was also found to increase SOD specific activity, decrease catalase specific activity, inhibit GR specific activity, while found to stimulate GPx and G6PDH specific activities which altogether impairs the redox status of cell. Each treatment has shown distinct alterations and disruption in cell morphology and cytoplasmic structures as reported by TEM, which result in bacterial control effects. Moreover, the selected bacterial strain decomposed hydrogen peroxide by catalase and peroxidase activities, but did not degrade peracetic acid, due to the lack of cellular enzymes that break down peracetic acid which explains the higher efficacy of peracetic acid in respect of hydrogen peroxide. In conclusion, we suggest that treating bacteria with the tested oxidizing agents and surfactants at the selected pH values probably caused a high production of free radicals which developed intricate oxidative processes and antioxidant defense mechanisms causing an imbalance of the cell redox homeostasis that resulted in deformity and collapse of cellular ultrastructure and morphology at late stage of oxidative damage that led to controlling the growth of Pseudomonas fluorescens. In addition, hydrogen peroxide + peracetic acid + non-ionic surfactant + bleach activator tested combination was found to provide synergistic action for enhanced removal of biological soil and control of bacterial growth.
... This reaction is complex, so it has not clearly documented, up to now, how this whitening process functions [33]. In addition, the bleaching response seems to be differently influenced by each particular colorant, because their composition is not similar [34,35]. Therefore, the response of each stain to the various bleaching protocols is not predictable. ...
... Experimental models, which simulate clinical conditions, have been designed through the years to study the efficiency of whitening methods on stained teeth. The most commonly used stains are coffee, red wine, tea, blood and chlorhexidine [16,[35][36][37][38]. ...
Article
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Objective: In vitro investigation of four bleaching protocols efficiency, on artificially tea-stained human teeth, up to 24-month post-treatment. Methods: 100 intact, extracted, human incisors were randomly divided (n=4x25/group) and underwent black tea staining. The bleaching protocols applied per group were: 1. (BH, at-home) 10%CaP for 5 days (120min/day), repeated twice, 2. (BO1, in-office) 40%HP for 3 successive applications (15 min/application), repeated twice, 3. (BO1, in-office) 40%HP for 3 successive applications (15 min/application), repeated 3 times and 4. (BH+BO1, at-home/in-office) starting with BH, interval of 2 days, followed by BO1. The color was measured before bleaching(t0), right after staining(t1), after each bleaching procedure(t2), 3(t3), 6(t4) and 24 months(t5) after treatment, with a colorimeter (Braive Instruments) in CIEL*a*b*system. ΔΕ*values were calculated relative to t0. Statistical analysis was performed by Mann-Whitney U and Friedman and Wilcoxon Signed Ranks tests (a=0.01). Results: All bleaching protocols, at t2 induced increase in L*, return of a* to before-staining values, shifting of b* to blue (BO1, BO2) and improvement of tooth color (ΔΕ*) with no statistically significant difference among protocols. All color coordinates presented gradual rebound at t3. Regarding ΔΕ*, tooth color reached after-staining values for BH, BO1, BO2 up to 24 months, while bleaching effect was partially preserved for BH+BO1 group. Conclusion: At-home and in-office bleaching protocols provided similar whitening effect on tea-stained teeth, immediate after application. However, rebound effect started at 3 and progressed up to 24 months post-treatment. The combination of at-home and in-office treatment showed relative better potential in bleaching color preservation.
... Tooth surface stains develop due to an interaction and a subsequent precipitation reaction between human salivary proteins and dietary pigments [1][2][3][4]. The major protein constituent of saliva is a group of proteins that consists of multiple repeats of an unusual amino acid sequence containing a large number of proline residues that are commonly referred to as salivary proline-rich proteins (PRPs). ...
... The potential of CPs for TF readsorption control was investigated by comparing of the amount of TF adsorption and readsorption on different thicknesses of films, which were as follows: [1] native Db-CN film before hydrolysis, [2] residual Db-CN/TF film after hydrolysis, and [3] residual native Db-CN film after hydrolysis. Native Db-CN film was catalyzed with a concentration of 0.25 mM enzyme with the conditions described above. ...
Article
Theaflavin (TF) from the black tea can react to human salivary proline-rich proteins (PRPs) to form stains on exposed dental surfaces. Here, we employed a model of protein/pigment film using TF and dephosphorylated bovine β-casein (Dβ-CN), which has an extended conformation, similar to that of salivary PRPs, on a sensor surface to assess the efficacy of cysteine proteases (CPs) including papain, stem bromelain, and ficin, on removing TF bound to Dβ-CN and the control TF readsorption on the residual substrate surfaces was also measured. The protein/pigment complex film was built by using a quartz crystal microbalance with dissipation (QCM-D). The efficacies of CPs were assessed by Boltzman equation model. The surface details were detected by grazing angle infrared spectroscopy spectra, atomic force microscopy images, and contact angles. The efficacy order of CPs on hydrolyzing protein/pigment complex film is ficin>papain>bromelain. The results from grazing angle infrared spectroscopy spectra, atomic force microscopy images, and contact angles demonstrated that TF bound on the Dβ-CN was effectively removed by the CPs, and the amount of TF readsorption on both the residual film of the Dβ-CN/TF and the Dβ-CN was markedly decreased after hydrolysis. This study indicates the potential application of the CPs for tooth stain removal and suggests that these enzymes are worthy of further investigation for use in oral healthcare.
... Because HO • is a much more potent bleaching agent, this will enhance the bleaching efficiency. However, as mentioned before, caution has to be taken when using UV light [29,36,37]. ...
... Of course, in this case HO • will also be formed due to photolysis of HP. Again, using UV light is not advisable in oral applications [29,36,37]. ...
Article
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The use of optical radiation for the activation of bleaching products has not yet been completely elucidated. Laser light is suggested to enhance the oxidizing effect of hydrogen peroxide. Different methods of enhancing hydrogen peroxide based bleaching are possible. They can be classified into six groups: alkaline pH environment, thermal enhancement and photothermal effect, photooxidation effect and direct photobleaching, photolysis effect and photodissociation, Fenton reaction and photocatalysis, and photodynamic effect.
... This thermal stability is important, because exothermal reactions on dental tissues are known-depending on their intensity-to be capable of generating irreversible damage to pulp cells.33,34 Studies have demonstrated that products with low pH cause superficial demineralization of tooth enamel, with consequent reduction in its hardness and increase in porosity, which could favor the diffusion found in the dental market present low pH values, that prevent their fast degradation, improving the stability and extending the shelf lifetime of such commercial products.35,36,39 Young et al39 reported that the alkalinity of bleaching agents accelerated the reaction of H 2 O 2 when it came into contact with an organic substrate. ...
... Studies have demonstrated that products with low pH cause superficial demineralization of tooth enamel, with consequent reduction in its hardness and increase in porosity, which could favor the diffusion found in the dental market present low pH values, that prevent their fast degradation, improving the stability and extending the shelf lifetime of such commercial products.35,36,39 Young et al39 reported that the alkalinity of bleaching agents accelerated the reaction of H 2 O 2 when it came into contact with an organic substrate. The authors showed that the esthetic efficacy of the product was directly proportional to the pH of the medium in which it was applied. ...
Article
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Evaluate the kinetics of hydrogen peroxide (H2O2) degradation, esthetic efficacy and cytotoxicity of a bleaching gel with 35%H2O2 applied on enamel previously covered or not with polymeric nanofibrillar scaffold (SNan), polymeric primer catalyst (PPol), and both. Standardized enamel/dentin discs (n = 128) obtained from bovine teeth were adapted to pulp chambers. After covering enamel with the polymeric products, the bleaching gel was applied for 45 min, establishing the following groups: G1: no treatment (negative control); G2: 35%H2O2 (positive control); G3: SNan; G4: PPol; G5: SNan + PPol; G6: SNan + 35%H2O2; G7: PPol + 35%H2O2; G8: SNan + PPol + 35%H2O2. The kinetics of H2O2 degradation (n = 8), bleaching efficacy (ΔE/ΔWI; n = 8), trans-amelodentinal cytotoxicity (n = 8), and cell morphology (n = 4) were assessed (ANOVA/Tukey test; p < 0.05). Greater H2O2 degradation occurred in G7 and G8. Bleaching efficacy (ΔE) was higher in G6, G7, and G8 in comparison with G2 (p < 0.05). However, no difference was observed for ΔWI (p > 0.05). G8 presented the lower level of trans-amelodentinal diffusion of H2O2, oxidative stress, and toxicity to the MDPC-23 cells (p < 0.05). Polymeric biomaterials increased the kinetics of H2O2 decomposition, as well as maintained the esthetic efficacy and minimized the cytotoxicity caused by a bleaching gel with 35%H2O2. Clinical Significance Application of a bleaching gel with 35%H2O2 on enamel previously covered by polymeric biomaterials maintains the esthetic efficacy and reduces the cytotoxicity caused by a single session of in-office dental bleaching.
... Moreover, there is inconsistent data available on the effect of hydrogen peroxide on enamel hardness. Especially, the influence of the pH of peroxide solutions on tooth hardness changes and wear has largely been unexplored [27]. According to reviews conducted by Attin et al. [13] and Joiner [6] on the effect of peroxide on enamel and dentine properties, there are conflicting results between the findings of different researchers on the impact of bleaching agents on the microhardness of the enamel. ...
... Especially, a comparison of hardness and wear behaviour of bovine with human tooth is needed as bovine enamel has been reported to have significantly higher porosity and tendency to lower fracture resistance than human enamel [62,63]. Whereas it is important to do peroxide treatments at a physiological mouth temperature to exploit the whitening efficacy [27] (teeth were treated in this study at 37 1C), temperature has shown to have no significant effect on measured tooth wear rates [36], which justifies the chosen wear test temperature (22 1C). ...
... Our results supported similar studies that hydrogen peroxide is more potent on P. fluorescens in both acid and alkaline pH than at neutral conditions [36][37][38]. Similar studies reported that alkaline H 2 O 2 has a higher bleaching efficacy without an obvious surface erosion or modification [39,40], due to generation of perhydroxyl anion and active powerful hydroxyl radicals from hydrogen peroxide at alkaline pH [41][42][43], but since H 2 O 2 is more stable in acidic conditions, many products have an acidic pH to maintain H 2 O 2 stability [43]. ...
... On the other hand, it was demonstrated that the efficacy of H 2 O 2 solutions is increased at more acidic pH ranges [44], but the disadvantage is that bleaching at acidic conditions is found to be harmful to surfaces [39,40,[45][46][47][48][49]. It was also reported that bacterial resistance to H 2 O 2 increases at low pH values, regardless of catalase activity [50]. ...
Article
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Peracetic acid (PAA) and hydrogen peroxide (H 2 O 2) were more potent at pH 8.2, while linear alkylbenzene sulfonate (LAS) showed higher potency at pH 5.0 against Pseudomonas fluorescens ATCC 13525. The aim was to understand the changes in the cellular redox status, ultrastructure and morphology underlying the synergistic bacterial control effects of selected pH values alone and treatments. The minimum inhibitory concentrations of PAA and H 2 O 2 at pH 8.2, and MIC of LAS at pH 5.0 were tested during the stationary growth phase of planktonic cells. pH 8.2 alone mainly elevated the protein carbonyls level and decreased the levels of low molecular weight thiols (LMWT), which could potentiate the effect of H 2 O 2 and PAA, while pH 5.0 alone largely decreased the total thiol level that could facilitate LAS action. Free radicals were only detected with LAS and PAA treatments. H 2 O 2 and PAA increased the levels of protein carbonyls, while reduced LMWT levels. LAS increased the levels of protein carbonyls, while reduced the total thiol level. H 2 O 2 , PAA and LAS were also found to increase SOD and decrease catalase specific activities. Each treatment showed distinct alterations and disruption in cytoplasmic structures. We suggest that exposing bacteria to the test oxidants and LAS at the selected pH ranges resulted in high generation of reactive species which activated complex oxidative processes and antioxidant defense pathways causing an imbalance of the cellular redox homeostasis that led to deformity and collapse of ultrastructure at late stage of oxidative damage, and eventual control of bacterial growth.
... The absorption of photons by peroxide leads to the formation of free radicals that will cleave the chromophore molecules. In addition, the absorption of photons increases the reactivity of the chromophore molecules to the peroxide because of the increase in the energy of its C ¼O bonds, C¼ C, and C ¼C-C ¼C [9]. ...
Article
The tooth whitening process is intended to restore the original color of teeth. It consists of the application of oxidizing agents, including hydrogen peroxide. Although these products considerably improve the color of teeth, their effects on other properties of enamel are not fully understood. This work aimed to study the effects of hydrogen peroxide concentration on hydrophilicity, roughness, morphology, and mechanical and tribological properties of human tooth enamel. Human teeth were subjected to bleaching sessions with 6%, 15%, and 35% hydrogen peroxide to achieve a similar level of whitening. The enamel roughness and morphology were characterized by atomic force microscopy and scanning electron microscopy. Vickers microindentation hardness data were obtained. The hydrophilicity was determined using the captive bubble method. Reciprocating, ball-on-flat friction, and wear tests were conducted in artificial saliva using zirconia as the ball and polished enamel as the flat specimens. Although all three test solutions improved tooth color, they also changed the properties of the enamel. Morphological and roughness changes were observed, and there was a decrease in hardness and wear resistance. The wettability was nearly unaffected. It was found that the 15% hydrogen peroxide solution damaged the enamel the least. It was concluded that there is an ideal concentration of hydrogen peroxide for whitening treatments.
... Pirolo et al. [30] also agreed with these results when he stored bleached dental specimens in cola and coffee, and suggested that the degree of staining is dependent on the type of chromogen. The higher chromogenic effect of black tea was explained by Young et al. [31] who stated that black tea contains a mixture of chromogens that are mainly composed of reddish brown colors that easily reflect yellow and reddish colors in visible light. This was confirmed by Téo et al. [26] who found that black tea caused more color relapse than cola in a study that used the same products used in this study. ...
... 1 Whitening outcome is believed to be a consequence of H 2 O 2 decomposition, which generates free radicals that interact with chromophores present in dentin substrate. 2 Instead of being considered a strong oxidant agent, H 2 O 2 is the reactive oxygen species (ROS) with the lowest oxidative potential 3 . Therefore, to achieve effective dental color alteration in short periods, highly concentrated H 2 O 2 bleaching gels (35-40%) have been traditionally used for professional tooth-bleaching. 1 However, many studies have shown that such esthetic therapy allows diffusion of high amounts of H 2 O 2 through enamel and dentin, 4,5 causing in vitro [6][7][8][9][10][11] and in vivo [12][13][14][15] toxicity to pulp cells. ...
Article
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Objective: This study was designed for the chemical activation of a 35% hydrogen peroxide (H2O2) bleaching gel to increase its whitening effectiveness and reduce its toxicity. Methodology: First, the bleaching gel - associated or not with ferrous sulfate (FS), manganese chloride (MC), peroxidase (PR), or catalase (CT) - was applied (3x 15 min) to enamel/dentin discs adapted to artificial pulp chambers. Then, odontoblast-like MDPC-23 cells were exposed for 1 h to the extracts (culture medium + components released from the product), for the assessment of viability (MTT assay) and oxidative stress (H2DCFDA). Residual H2O2 and bleaching effectiveness (DE) were also evaluated. Data were analyzed with one-way ANOVA complemented with Tukey's test (n=8. p<0.05). Results: All chemically activated groups minimized MDPC-23 oxidative stress generation; however, significantly higher cell viability was detected for MC, PR, and CT than for plain 35% H2O2 gel. Nevertheless, FS, MC, PR, and CT reduced the amount of residual H2O2 and increased bleaching effectiveness. Conclusion: Chemical activation of 35% H2O2 gel with MC, PR, and CT minimized residual H2O2 and pulp cell toxicity; but PR duplicated the whitening potential of the bleaching gel after a single 45-minute session.
... 10,12 Moreover, previous studies have reported that H 2 O 2 at a higher pH decreased deleterious effects on the enamel surface, including demineralization, loss of the aprismatic layer, calcium loss, and an increase in surface roughness. 13,14 However, the increased shelf-life of H 2 O 2 -based products and the stability of the H 2 O 2 molecule require a lower pH. 10 The authors are unaware, however, of studies that have evaluated the behavior of hydrogen peroxide at 35% gel under different pH values on the tooth structure with high or low staining. ...
Article
Objective: This study aimed to evaluate the effect of 35% hydrogen peroxide at different pH values and the degree of tooth staining on whitening efficacy and enamel microhardness. Materials and methods: 90 enamel-dentin specimens were obtained from bovine incisors. They were randomly divided into 2 groups (n = 45), 1 group was immersed in a staining broth for 14 days, and another group was not stained and kept in distilled water at 37°C. Twenty-four hours after the staining procedure, each group was distributed into 3 subgroups that were whitened by 35% hydrogen peroxide with different pH values (5, 7, and 8.4) for 30 minutes. The color was measured at baseline and 7 days after whitening. Microhardness was measured at baseline, immediate, 24 hours, and 1 month after the whitening procedure. Data were submitted to 2-way analysis of variance (ANOVA) and the Tukey test for multiple comparisons for color analysis. Repeated measures ANOVA and the Tukey test were used to analyze microhardness data. Results: The color change of the stained groups (ΔE00 = 4.6) was significantly higher than that of the nonstained groups (ΔE00 = 3.7). Microhardness value decreased significantly immediately after whitening for all subgroups and did not return to initial values. For each measurement time, microhardness was not significantly different among subgroups with different pH values. Conclusions: Despite the effectiveness of 35% hydrogen peroxide, changes on gel pH did not affect the whitening efficacy, and the enamel was superficially demineralized, regardless of pH values. Clinical significance: Independently of the pH value of whitening gel, enamel undergoes superficial demineralization and with a reduction in superficial microhardness that does not return to the initial values. However, using hydrogen peroxide with different pH values does not alter the whitening effect.
... As such, it will be important to understand the roles of pH, chemical activators, temperature, and light activation at various wavelengths. 52 The rate of decomposition and the type of active oxygen formed are dependent on the temperature and concentration of the peroxide, as well as on the pH and the presence of co-catalysts and metallic reaction partners. 53 In addition, depending on which chemical bond breaks, hydrogen peroxide can give rise to a number of reactive oxygen species. ...
Article
PurposeThis review integrated the current literature on diffusion of whitening agents, their interactions with stain molecules, and changes to the surface, with the aim of establishing a better understanding of the mechanism underlying tooth whitening.Materials and Methods An electronic PubMed database search, with combinations of the following terms was performed: Tooth Bleaching, Tooth Bleaching Agent, Hydrogen Peroxide, Pharmacokinetics, Tooth Permeability, Oxidation-Reduction, Tooth Demineralization, and Color.ResultsTooth whitening is a dynamic process that involves diffusion of the whitening material to interact with stain molecules and also involves micromorphologic alterations on the surface and changes within the tooth that affect its optical properties. The interaction seems not to be limited to stain molecules, but rather an affinity-based interaction process that also accompanies effects on sound enamel and dentin structures.Conclusions This review underlines that supervision by dental health professionals as recommended by the American Dental Association (ADA) Council on Scientific Affairs is critical to achieving a successful and safe whitening outcome.Clinical SignificanceThe mechanism that underlies tooth whitening with the use of peroxide-based materials is a complex phenomenon encompassing diffusion, interaction, and surfaces changes within the tooth. Therefore, supervision by dental health professionals as recommended by the ADA Council on Scientific Affairs is imperative to achieve a successful and safe whitening outcome.
... Additionally, there is a high risk of irritation and burns in gums and overheating of the tooth pulp which can lead to loss of its vitality, b) the dentists: contemporary data do not support the use of bleaching devices. Since similar results can be achieved with less aggressive methods 29 and taking into account the principle of "primum non nocere" ("the first thing is to do no harm"), dentists are recommended to abstain from using them 30 . ...
... Acrylic resin teeth are used widely in the fabrication of dentures than porcelain teeth, studies confirmed that the acrylic resin teeth must be used in fabrication of dentures in most cases [10] .Plastic teeth collected stain more than another type of artificial teeth such as porcelain that cause change in color. There were various reasons caused staining of dentures [11,12] denture staining affected appearance so it consider one of esthetic problems .Smoking consider as one of cause of stain of acrylic teeth [9] . The most apparent feature of tobacco smoker is brown to black discoloration of denture .Tobacco stain was brownish, yellow, tar-like deposit this discoloration of tooth surface among smoker result by the nicotine, tar and the other chemicals that found in cigarette [2] . ...
Conference Paper
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Acrylic dentures were subject to staining problems ,one of the causative factors that had relation with staining of acrylic teeth resin was smoking cigarette , which was most of the commonly used tobacco habits The study subjected to assess dental staining in smoking wearer removable complete acrylic denture ,their aged between 40-70 years and to study the relation of the stain to: age, gender, period of wearing the denture, and number of cigarette smoking per day on acrylic resin teeth among smoking wearer complete denture. Methods :62patients who wear removable complete(acrylic)denture ,were examined clinically in dental chair by mirror and probe to assess dental stain, examination findings were recorded by stain index according to the criteria of stain index. No radiographs were taken ,questionnaire were administrated to these patients Result: show there was highly significant differences between the number of cigarette and dental stain, P<0.01, also show the relation between the gender and dental stain ,there was significant differences between dental stain and the gender P<0.05, but the relation between the: period of wearing denture and age with dental stain ,there were no significant differences between dental stain and :the period of wearing denture and age P>0.05. INTRODUCTION:
... Testing the whitening effect in a tooth model implies, besides the stain whitener interaction, the diffusion phenomena through the enamel. To avoid the diffusion step, the action of whitening agents upon the absorbance of tea and coffee stain solutions has been previously used as a model [22]. However, these solutions contain not only polyphenols but different types of compounds (e.g., melanoidins or sugars) that could be interacting with the whitening agent complicating the spectrophotometric and voltammetry measurements and results interpretation and making it difficult to control the stain concentrations as well as the reaction's stoichiometry. ...
Article
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Objectives It is widely accepted that current tooth whitening treatment effect is based on the oxidizing action of peroxides, even if the mechanism of action remains still unclear. Treatments are claimed to be safe, but several secondary effects have been described, since long application times and high concentrations are needed. A faster whitening ingredient which permits the use of lower concentrations and shorter application times could potentially overcome this problem. In this work, a different approach based on a reducing agent, sodium metabisulfite (MBS), is explored. Materials and methods The reaction between tannic acid (TA) with carbamide peroxide (CP), MBS, and potassium persulfate (PS), as an oxidizing agent, was monitored for 48 hours by measuring its absorbance, comparing their different whitening effects. The reduction process between TA and MBS was confirmed by cyclic voltammetry. An in vitro test was used to observe if MBS whitens also stained teeth. Results It is shown that MBS bleaching effect is faster and higher than CP’s effect over time. PS produced a darkening effect after the 3rd hour because of the strong absorbance of the oxidation metabolite. Cyclic voltammetry showed a progressive increase in the intensity of the TA anodic peak when MBS was present, demonstrating that a reduction is taking place. In vitro, MBS showed a faster whitening performance than CP, using lower concentrations. Conclusions Using a TA solution as a staining model, it was possible to show that MBS has a visible bleaching effect through a reduction reaction, faster than CP, both in solution and in vitro. Low concentrations of MBS are effective in whitening. Clinical significance This work shows MBS as a promising candidate to develop novel whitening treatments, which is acting by reducing mechanism instead of oxidation.
... Although H2O2 itself does not have any deleterious effects on the enamel, but the low pH of bleaching agent can adversely affect the enamel integrity 20) . The higher pH prevents the demineralization of dental surface 31) as pH of the bleaching agent with higher than pH 6.0 can prevent the damage to dental tissues 11) . The average pH of in-office bleaching gels available in the market is around pH 5.5. ...
Article
Full-text available
This study evaluated the alterations of surface topography of the bovine enamel caused by different pH of in-office bleaching agents. 23% H2O2 with pH 5.5, 7.0 and 8.5 were applied on the bovine tooth specimens (n=10) and photo-irradiated for 10 min. The bleaching procedure was repeated three times and specimens were subjected to linear surface roughness (Ra) and Vickers microhardness test (VHN) at baseline and after three consecutive applications. The morphological alterations were observed before and after third bleaching application. Data were analyzed by two-way ANOVA followed by Tukey’s HSD. The pH of the bleaching agent significantly affects the Ra and VHN (p<0.05). Low pH yielded a significant increase in Ra and decrease in VHN. All the groups showed morphological alterations and profound effect was found in pH 5.5 group. It was concluded that the pH of the bleaching agent can affect Ra, VHN and surface morphology.
... Vasluianu et al. [42], studying the changes induced in HAP by HP whitening treatments, observed a decrease in the reflectance and an hypsochromic shift for the main FITR peaks of HAP; they related it, again, to the shortening of P-O, even if the pH of the treatments was 7.4. In our experiment, CP pH was 8 as in the commercial treatments, since its effectiveness is increased at this pH [46]. Accordingly, a decrease in the reflectance (PC1) and an hypsochromic shift (PC3) were observed. ...
Article
Objectives To compare the side effects of typical whitening treatments (by means of oxidation) compared to the new treatment developed by the authors through reduction. The aim is to provide information about the chemical interactions of the encapsulated reductant agent (metabisulfite, MBS) with the enamel structure compared with carbamide peroxide (CP) and to study their penetration in the hydroxyapatite (HAP) and the changes produced in the mineral and its hardness. Methods Chemical imaging is performed by synchrotron-based micro Fourier transformed infrared spectroscopy (SR-µFTIR). Continuous Stiffness Measurements (CSM) were used to determine the depth reached by the treatments in order to delimitate the area of study. Results The SR-µFTIR studies showed that MBS treatments softened the first 10 µm of enamel, as happens in the initial stages of tooth decay. Principal component analysis (PCA) showed that the main differences between treatments were found in the intensity of the ν3 PO4³⁻ peak related to tooth demineralization. CP and MBS promoted different changes in the HAP mineral, observed as opposite shifts of the peak: CP shortened the P-O bond while MBS seemed to elongate it. Moreover, MBS promoted the loss of carbonates while CP did not, which is probably related to the solution’s pH. When comparing MBS and MBS Liposomes, it was observed how liposomes favoured the diffusion of MBS to inner layers, since the effects of MBS were observed in deeper enamel. Thus, the encapsulated MBS whitening effect is highly improved in terms of time when compared to MBS alone or CP. Significance The obtained results indicated that using oxidizing (CP) or reducing (MBS) treatments, promote different HAP mineral changes, and that liposomes favour the diffusion of MBS into the enamel. It is the first time that synchrotron light is used to map the bovine incisor’s enamel chemically, and to determine the effect of a whitening treatment in terms of chemical HAP modifications, and the extent in deep of these effects.
... As demonstrated in the literature, the decomposition of H 2 O 2 into different ROS with higher oxidation potential is relatively slow when H 2 O 2 is not catalyzed. 31,32 This makes reduction of the chroma (scale that refers to the quantity of saturation of the hue) occur in a gradual manner. 12,15,21 These data may perhaps explain, even if only partially, the fact that the in-office bleaching procedure assessed in this study had also caused an important cytotoxic effect, even when the procedure was used in teeth pigmented with black tea. ...
Article
Clinical Relevance Pigments in tooth structures affect the diffusion of H2O2 through enamel and dentin. The bleaching methodology can be impacted.
... Calatayud et al. (25) also showed that diode laser usage combined with 35% hydrogen peroxide had better clinical efficiency than other bleaching protocols. Similarly, Young et al. (20) and Hayward et al. (76) found that the use of light in addition to the bleaching gel will enhance bleaching efficacy and produce lighter color than chemical bleaching protocol. The disagreement between these results and the current study might be attributed to the different concentrations of bleaching gel used, and the baseline color of the tested teeth and the exposure time to bleaching gel. ...
... Torres et al. 25 (2014), demonstraram que a efetividade do H 2 O 2 em oxidar substratos orgânicos é proporcional ao pH da solução, sendo observado pico de efetividade no pH 8,0 a 9,0. Este efeito tem sido associado ao aumento na formação de espécies reativas derivadas do oxigênio (EROs) em pH alcalino, as quais efetivamente promovem o clareamento dental 25,26 . ...
Article
Full-text available
INTRODUÇÃO A hipersensibilidade dental tem sido considerada como pro-blemática central das terapias clareadoras, sobretudo do clare-amento de consultório 1,2. Sabe-se que o H 2 O 2 livre não reagido proveniente dos agentes clareadores é capaz de se difundir pelas estruturas dentais mineralizadas até atingir o tecido pulpar, cau-sando dano oxidativo e reação inflamatória, com consequente ativação de nociceptores 3-7. Por essa razão, terapias clareadoras alternativas têm sido pesquisadas e desenvolvidas para mini-mizar os efeitos nocivos mediados pelos agentes clareadores de consultório tradicionais sobre o complexo dentino-pulpar 8,9. Dentre essas estratégias, pesquisadores têm proposto o em-prego de agentes dessensibilizantes e remineralizantes previa-mente, durante ou após as terapias clareadoras, como fluore-tos, nitrato de potássio e fosfato/gluconato de cálcio 10-14. Já foi demonstrado que géis clareadores contendo cálcio e flúor na sua composição resultam na formação de depósitos minerais na superfície dental após clareamento, o que foi associado a me-nores alterações na estrutura de esmalte 15-17. Acredita-se que a deposição desta camada mineral durante o clareamento minimize a difusão de H 2 O 2 residual para a câmara pulpar 12,13. Um interessante estudo clínico randomizado demonstrou que géis RESUMO Objetivo: Avaliar a citotoxicidade de um agente clareador contendo 2% de gluconato de cálcio (GC) sobre células pulpares humanas (HDPCs). Materiais e Métodos: Discos de esmalte-den-tina adaptados em câmaras pulpares artificiais (CPAs) foram posicionados em compartimentos de forma que a dentina per-maneceu imersa em meio de cultura, enquanto que o esmalte foi submetido ao clareamento com géis a 20% de H2O2 contendo ou não GC, durante 1x 45, 1x15 ou 1x5 minutos. No controle positi-vo foi realizado clareamento com 35% de H2O2 aplicado por 1x 45 minutos, sendo que no controle negativo nenhum tratamen-to foi realizado sobre o esmalte. A viabilidade celular (teste do MTT) e a difusão trans-amelodentinária de H2O2 (violeta leuco-cristal/peroxidase) foram avaliadas (ANOVA/Tukey α = 5%; n = 8). Resultados: Foi observada redução significativa na viabili-dade celular em todos os grupos clareados quando comparados ao controle negativo (p < 0,05); no entanto, os grupos expostos aos géis contendo 20% de H2O2, com ou sem GC, apresentaram valores de viabilidade celular significativamente superiores ao controle positivo (p < 0,05). A redução da viabilidade celular e a difusão de H2O2 residual para os grupos clareados com 20% de H2O2 foi proporcional ao tempo de contato dos produtos com a superfície dental, sendo que a presença de GC resultou em minimização significativo do efeito tóxico/difusão de H2O2 para os protocolos 1x 15 e 1x 5 min (p < 0,05). Conclusão: A presença de 2% de GC nos géis com 20% de H2O2 resulta em redução da difusão de H2O2 residual pela estrutura dental e do efeito citotóxico sobre células pulpares humanas, quando o produto é aplicado por curtos períodos sobre a superfície dental.
... For visible light irradiation these can be summarized in two main hypotheses of enhanced bleaching: Controlled in vitro studies are most suitable for investigating the mechanism of LAW. Bleaching of extrinsic colorants, such a tea solutions, shows a light dose dependent peroxide bleaching rate [9]. However, dietary stains employed in such studies represent only a part of the chromophores that accumulate in human teeth over time, and miss the natural intrinsic chromophores. ...
Article
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Objective To test the hypotheses that blue light accelerates whitening through either (1) direct photobleaching or (2) photon-assisted oxidation using sequential longitudinal bleaching. Methods Thirty extracted human tooth samples having natural life accumulated color were divided over five groups: A. 9h light + 10h 6% H2O2 gel + 6h light & 6% H2O2 combined; B. 9h 6% H2O2 gel + 10h light + 6h light & 6% H2O2 combined; C. 11 h light & 6% H2O2 combined; D. 8.45h 25 %H2O2 gel + 10h of light only + 6h light & 25% H2O2 combined E. 10.45 h light & 25 %H2O2 combined. Blue light (456nm) was used at 190 mW/cm². Color change (ΔE) was measured over time, and reported after 48h color stabilization. Results Groups A, B and D reached saturation in the first phase (at 9h) at a ΔE of 4.3 ± 0.7, 4.9 ± 1.3 and 10.9 ± 2.2, respectively. Groups C and E achieved in the same time a significantly higher ΔE of 14.2 ± 1.7 and 15.6 ± 1.9, respectively. Subsequently adding the opposite single modality to groups A, B and D for 10h did reach an end stage at 8.1 ± 1.3, 8.8 ± 1.8 and 10.8 ± 1.4 ΔE, respectively. The final 6h treatment combining light and H2O2 showed in these groups a statistically significant step in ΔE reaching 12.9 ± 1.4, 10.7 ± 2.5 and 15.3 ± 1.7, respectively. Conclusions Blue light significantly increases bleaching rate and final achievable ΔE. This sequential whitening study provides a first indication that this enhanced bleaching is the result of the hypothesized light mechanisms acting in parallel to hydrogen peroxide bleaching. Clinical significance This study shows that blue light can accelerate whitening, within the limits of an in-vitro model. The findings help the clinician explain to their patients that in light accelerated whitening the light not merely accelerates the bleaching process, but that it attacks more stain compounds than peroxide alone does.
... Reversely, the degradation was quicker in the neutral condition, i.e. 69.4% at pH 7.4 versus 21.3% at pH 5.0 (Figure 2(c)), which is attributed to oxidation of more perhydroxyl anions with H 2 O 2 in pH 7.4 buffer [32]. Our observation is consistent with other research using plant polyphenols, which are PDA analogues [33,34]. Therefore, the Cur release would be also promoted in the intracellular environment particularly in the neutral cytoplasm where there is a high level of H 2 O 2 in colon cancer cells [35]. ...
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Immunotherapy has made great progress in recent years while most cancer patients cannot benefit from it. Photochemotherapy combination strategy holds great promise for developing novel immunotherapy for the patients bearing immunosuppressive tumors such as colon cancer. In this research, a novel core/shell-structured polydopamine (PDA)-based nanoplatform is constructed to load two Food and Drug Administration (FDA)-approved cytotoxic drugs, i.e. immunostimulatory doxorubicin (Dox) and immunomodulatory curcumin (Cur) to achieve immunostimulatory photochemotherapy of primary colon tumors upon 808 nm near infrared (NIR) irradiation (1 W/cm ² for 5 min) and subsequent prevention of rechallenged distant colon tumors. The experimental data have shown that PDA-mediated photothermal therapy (PTT) synergized two therapeutic drugs in inducing colon cancer cell death and very efficiently inhibited the primary tumor growth (by ∼92%) at very low doses of therapeutics (0.25, 5, and 30 mg/kg of Dox, Cur, and PDA, respectively). More significantly, the combined photochemotherapy promoted strong adaptive antitumor immune responses and successfully prevented tumorigenesis in the setting of tumor rechallenge model. Our research has thus demonstrated the promising efficacy of this photochemotherapeutic nanoformulation for colon cancer treatment and provided a way to improve immunostimulatory effects of conventional chemotherapeutic drugs.
... Not surprisingly, the 35% HP showed slightly acidic pH (6.7) while the 6% HP + LED/laser showed basic pH (8.2) due to their concentrations [6,59,60]. The alkaline pH of low concentration HP can represent less damage to the tooth structure and high potential to ions dissociation, since the dissociation constant (pKa) of HP is approximately 11.62 and pH values closer to that means more chemical reactions [61][62][63]. ...
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Background Tooth whitening protocols with low concentration hydrogen peroxide (HP) appear to minimize the microstructural effect on teeth. In addition, light sources have been used to enhance bleaching efficiency. This study evaluated the color change and microhardness of a protocol with 6% HP photoactivated by LED/laser in comparison with 35% HP. Methods Twenty bovine incisors were randomized in two groups: 6% HP + LED/laser and 35% HP (n=10). Teeth were submitted to staining using dark tea. Three whitening sessions were carried out according to the manufacturer's instructions. Enamel microhardness (VHN) and color change evaluation (∆L*, ∆a*, ∆b*, ∆E00 [CIEDE2000], and WID) before 24 hours and 7 days after the last whitening session were performed. Two-way repeated ANOVA and Bonferroni post-test was used (α = 0.05). Results Both groups showed perceptible color changes, being more pronounce for 35% HP. Differences were observed for ∆a*, ∆b* and ∆E00 (p≤0.027), except for ∆L* (p>0.05). Differences were also found in the comparison among the evaluation times within the same group (p≤0.027), except for ∆a* results (p>0.05). WID showed that 35% HP exhibited high whiteness values. Regarding microhardness, the groups did not show significant differences (p>0.05). However, 35% HP showed decreased values after 7 days of the last whitening session compared to the baseline (p≤0.027). Conclusions 6% HP + LED/laser promoted perceptible color change, but not comparable with 35% HP. No differences on enamel microhardness were observed between the whitening protocols. However, 35% HP showed decreased hardness after 7 days of whitening compared to baseline.
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Background: Tooth discoloration can be treated with dental bleaching using Hydrogen peroxide (H2O2). Dental bleaching may interfere with the shear bond strength of composite resins because the remaining free radicals can affect bonding polymerization. Epigallocatcehin-3-gallate (EGCG) as an antioxidant can neutralize the free radicals produced during bleaching process. Purpose: Analyze the role of EGCG antioxidants in increasing the shear bond strength of composite resin after bleaching.. Reviews: Of the seven journals included in this literature review, six journals reported significant difference, and one journal noted no significant difference in the shear bond strength of composite resin following the EGCG application. Conclusion: The use of EGCG can increase the shear bond strength value of post-bleaching composite resin restorations.
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Purpose: To evaluate the whitening efficacy of a new two-layer technology in-office system compared to a conventional gel-type system and determine hydrogen peroxide penetration (HPP) into the pulp cavity. Materials and methods: Extracted molars (n = 60) were assigned to group NC: glycerol gel; group QPRO: 20% HP varnish (Zoom Quick Pro, Philips Oral Healthcare); group ZOOM_NL: 25% HP gel (Zoom Chairside Whitening); and group ZOOM_WL: 25% HP gel (Zoom Chairside Whitening) with light-activation. HPP levels were estimated with leucocrystal-violet and horseradish-peroxidase. Instrumental color measurements were performed at baseline (T0 ), 1-day post first whitening (T1 ), 1-day post second whitening (T2 ), 1-day post third whitening (T3 ), and 1-month post whitening (T4 ). One-way analysis of variance followed by post hoc Tukey's HSD test was performed to detect difference in ΔE* and HP penetration levels (α = 0.05). Results: ΔE* of NC was lower than other groups, whereas ΔE* of ZOOM_WL was greater than the other three groups, at T3 and T4 . Mean HPP level obtained from ZOOM_WL (1.568 ± 0.753 μg/mL) was significantly greater than those obtained from the other groups, whereas the mean HPP level observed in NC group (-0.131 ± 0.003 μg/mL) was significantly lower than the other groups. Conclusions: Tooth whitening efficacy and HPP levels vary based on whitening systems used. Clinical significance: The two-layer technology in-office varnish system may be an alternative whitening option to reduce chair time in the office. (J Esthet Restor Dent 28:313-320, 2016).
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Objectives This split‐mouth, double‐blind, randomized clinical trial evaluated the 1‐year bleaching efficacy produced by two hydrogen peroxide gels with different pHs. Materials and Methods Twenty‐eight patients were divided into two groups corresponding to two different products: Pola Office (pH = 2.0/SDI) and Pola Office Plus (pH = 7.0/SDI). The treatment was assessed during and after the bleaching procedure up to 12 months post‐treatment. The assessment consisted of two bleaching scales shade guide units (ΔSGU) and spectrophotometric device (ΔE, ΔE00, and Whiteness Index) of both maxillary quadrants. Results for ΔSGUs in both scales and ΔE00 and Whiteness Index were compared using Mann Whitney test and ΔE measurements through the t‐Student test for paired samples in each evaluation time. The color rebound (1‐ vs 12‐month postbleaching data) was evaluated with Wilcoxon test (alpha = .05). Results During the different times of evaluation, the color variation was similar for both products (P > .05), both for subjective (ΔSGUs) and objective assessments (ΔE, ΔE00, and Whiteness Index). Also, both products showed a slight rebound after 12‐month postbleaching (P > .05). Conclusions Concerning the stability of color, in‐office dental whitening with two hydrogen peroxide gels of different pHs produced similar results, with no significant of regression, for 12 months postwhitening. Clinical Significance Bleaching using a neutral (pH = 7.0) in‐office gel demonstrated similar stability and rebound effect than an acidic one (pH = 2.0).
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Objective This study evaluated physicochemical properties of bleaching agents incorporated with titanium dioxide (TiO2) nanotubes, and the effects on tooth color change at different periods. Methodology 40 premolars were treated according to the following groups (n=10): CP - 10% carbamide peroxide (1 hour daily/21 days); CPN - CP incorporated into TiO2; HP - 40% hydrogen peroxide (three 40-minute sessions/7 days apart); HPN - HP incorporated into TiO2. Color shade was evaluated at five different periods (baseline, after 7, 14 and 21 days of bleaching, and 7 days after end of treatment) according to Vita Classical, CIELab and CIEDE2000 scales. Mean particle size (P), polydispersity (PO) and zeta potential (ZP) were evaluated using dynamic light scattering. Data on the different variables were analyzed by mixed model tests for measures repeated in time (ZP e L*), generalized linear models for measures repeated in time (P, PO, Vita Classical and b*), and Friedman and Mann-Whitney tests (a* and color change/ΔE and ΔE00). Results CP and CPN presented higher P, higher PO and lower ZP than HP and HPN (p≤0.05). All groups showed a significant decrease in Vita Classical color scores after 7 days of bleaching (p<0.05), and HPN presented a greater significant reduction than the other groups. L* increased in TiO2 presence, in all groups, without any differences (p>0.05) in bleaching time. A significant reduction occurred in the a* and b* values for all the groups, and HPN presented lower a* and b* values (p<0.05) than CPN. ΔE was clinically noticeable after 7 days, in all groups, and all groups resulted in a perceptible color change according to ΔE00. Conclusion TiO2 did not influence physicochemical properties of the bleaching agents. HPN presented more effective tooth bleaching than CPN.
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Light-activated bleaching is a method of tooth whitening. The authors conducted a study to compare the whitening effects and tooth temperature changes induced by various combinations of peroxide bleaches and light sources. The authors randomly assigned 250 extracted human teeth halves into experimental groups (n = 10). A placebo gel (control), a 35 percent hydrogen peroxide or a 10 percent carbamide peroxide bleach was placed on the tooth surface and was irradiated with no light (control); a halogen curing light; an infrared, or IR, light; an argon laser; or a carbon dioxide, or CO2, laser. Color changes were evaluated immediately, one day and one week after treatment using a value-oriented shade guide and an electronic dental color analyzer. The outer enamel and inner dentin surface temperatures were monitored before and immediately after each 30-second application of light using a thermocouple thermometer. Color and temperature changes were significantly affected by an interaction of the bleach and light variables. The application of lights significantly improved the whitening efficacy of some bleach materials, but it caused significant temperature increases in the outer and inner tooth surfaces. The IR and CO2 laser lights caused the highest tooth temperature increases. Dentists performing an in-office bleaching technique with the use of an additional light source to accelerate tooth whitening should consider the specific bleaching agent being used, as well as the potential risks of heating teeth. A specific combination of bleach and light that demonstrates good color change and little temperature rise should be selected for in-office tooth bleaching.
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Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.
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Reaction rate constants of (−)-epigallocatechin gallate (EGCG) and (+)-catechin with the hydroxyl radical (·OH) were measured using the rapid flow ESR method. The rate constant of EGCG was larger twice than that of the pyrogallol or gallic acid, they are the model compounds of the B ring of EGCG. It was explained by the quantum-chemical calculation of the bond dissociation energy (BDE) of the phenolic hydroxyl group (ϕ-OH) and the spin densities of EGCG radical. The energy of the EGCG radical was lowered by the hydrogen bonding between the radical part on the B ring and the hydroxyl group on the gallate group, leading to the lowering of BDE. Linear relationship between the relative activation energy and BDE of all the polyphenols measured was observed (Evans-Polanyi equation), showing that the reaction with ·OH occurs in the same manner.
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The strength of the O−O bond is of fundamental importance in a variety of chemical processes. Traditionally, a value of 34 kcal/mol has been ascribed to a generic O−O bond dissociation energy. The present, high-level ab initio calculations indicate that the average O−O bond energy is significantly higher, ca. 45 kcal/mol, and that the bond energy is sensitive to the bonding environment. Calculations at the G2 level of theory give bond dissociation enthalpies at 298 K of 50 kcal/mol for HOOH, 45 kcal/mol for CH3OOH, 39 kcal/mol for CH3OOCH3, and 48 kcal/mol for HC(O)OOH and CH3C(O)OOH. The G2(MP2) results are similar and, additionally, give bond dissociation enthalpies of 38 kcal/mol for diacetyl peroxide, 49 kcal/mol for trifluoroperoxyacetic acid, 23 kcal/mol for isopropenyl hydroperoxide, and 22 kcal/mol for peroxynitrous acid.
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The decomposition of alkaline hydrogen peroxide solutions at 20°C has been studied in the presence of both supported iron catalysts and in systems with iron initially in solution. Studies with an iron-alumina supported catalyst showed the decomposition reaction was first order with respect to total peroxide concentration, while studies with alkaline Fe3+ produced more complex behavior. This has been attributed to the presence of at least two distinct catalytically active iron species. The first species is highly active and gives rise to high initial rates of reaction. A decrease in concentration of this species is observed together with an increase in concentration of a second, less active, iron species. The catalytic behavior of this “aged” iron species was found to be very similar to that of the supported iron catalyst.
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Aqueous solutions of coumarin have been used to detect the hydroxyl radicals produced as a result of gamma radiolysis. Reverse-phase chromatography and fluorescence measurements show that the 7-hydroxycoumarin (umbelliferone) is produced. The hydroxycoumarin isomers of 3OH-, 4OH-, 5OH-, 6OH- and 8OH-coumarin are also produced although the fluorescence emission of these products is negligible compared to that of 7-hydroxycoumarin. The radiation chemical yield of 7-hydroxycoumarin has been studied in different gas conditions.
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Dynamic behaviors of hydroxyl (OH) radical generation and consumption in photo-Fenton oxidation process were investigated by measuring OH radical concentration during the discoloration of azo-dye Orange II. The effects of operating parameters for photo-Fenton discoloration, i.e. dosages of H(2)O(2) and Fe, initial dye concentration, solution pH and UV irradiation, on the generation and consumption of OH radicals playing the main role in advanced oxidation processes were extensively studied. The scavenger probe or trapping technique in which coumarin is scavenger of OH radical was applied to estimate OH radical concentration in the photoreactor during the photo-Fenton discoloration process. The OH radical generation was enhanced with increasing the dosages of Fenton regents, H(2)O(2) and Fe. At the initial stage of photo-Fenton discoloration of Orange II, the OH radical concentration rapidly increased (Phase-I) and the OH radical concentration decreased after reaching of OH radical concentration at maximum value (Phase-II). The decrease in OH radical concentration started when the complete discoloration of Orange II was nearly achieved and the H(2)O(2) concentration became rather low. The dynamic behavior of OH radical concentration during the discoloration of Orange II was found to be strongly linked with the change in H(2)O(2) concentration. The generation of OH radical was maximum at solution pH of 3.0 and decreased with an increase of solution pH. The OH radical generation rate in the Fenton Process was rather slower than that in the photo-Fenton process.
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To examine the whitening efficacy of three whitening agents in combination with six different photoactivation systems. Bleaching techniques have achieved significant advances using photoactivation with coherent or incoherent radiation sources. Quick White, Ena White Power, and Opalescence Endo bleaching agents, all containing 35% hydrogen peroxide, were stimulated with halogen lamp, light-emitting diode (LED), low-power diode laser, and neodymium: yttrium-aluminum-garnet (Nd:YAG), second harmonic of Nd:YAG, and Er:YAG lasers. One hundred twenty-six extracted human incisors were treated, and color change, pulpal temperature, and enamel morphological alterations were evaluated. Only the groups that were photoactivated using a diode laser, halogen lamp, and LED showed statistically significant differences (p < 0.005) in color change when compared with the control group (without photoactivation). All whitening protocols were safe with regard to the increase in pulpal temperature. Scanning electron microscopy showed no evidence of effects on the integrity of enamel. The source of irradiation is more relevant than the bleaching agent for efficient tooth whitening. In addition, photoactivation with LED was found to be the best choice: it yielded significant change in color with only a minor increase in pulpal temperature.
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Accurately weighed bovine enamel slabs were individually immersed in 2 ml of 35% hydrogen peroxide for 1, 3, 5, 30, or 60 min. A control group was obtained by individual immersion of bovine enamel slabs in 2 ml of saline for 60 min. All samples were washed, dried, acid-etched with 37% phosphoric acid for 60 s, then washed and dried again. Two milliliters of double-distilled water were used for individual sample leaching. Leaching was done for 1, 5, 10, 20 min, or 7 days for the experimental groups and for 7 days for the control group. The samples of one of the experimental groups were leached for a second time for 1 min. A total of 112 samples was used in this study. Hydrogen peroxide was spectrophotometrically identified and quantified in all leaching solutions based on the oxidation reaction of leuco-crystal violet buffer solution by hydrogen peroxide, a reaction catalyzed by horseradish peroxidase. The results revealed a significant difference in the quantity of leached peroxide between bleached samples (irrespective of the duration of leaching) and control, saline-treated ones. No difference was observed in the quantity of leached peroxide between releached samples and control, saline-treated ones. However, these were small, random, and numerically insignificant. Statistically significant differences were also noted among some of the experimental groups. They were thought to hold no clinical significance. The results suggested that upon immersion, the complete leaching of peroxide from bleached enamel occurs rapidly.
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The impact of fluoride is being felt with a decline in caries incidence over the past 25 to 30 yr. Restorative dentistry is focusing a great deal more on cosmetic applications, among which is bleaching of stained vital teeth. Although studies have shown that vital bleaching procedures can severely inhibit pulpal enzymes, deleterious effects have been minimal. This study attempts to measure the quantity of H2O2 that reaches the pulp during a bleaching treatment. Roots of extracted maxillary anterior teeth were amputated approximately 3 mm apical to the cementoenamel junction and pulpal tissues were removed. A buffer solution was placed into the pulp chamber and the labial surface was exposed to 1, 10, or 30% H2O2 at 37°C for 15 min. Hydrogen peroxide uptake by the pulpal buffer solution was determined colorimetrically. Results showed significant amounts of H2O2 in the pulp chamber and uptake was greatly enhanced by the application of heat (50°C) along with the H2O2.
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Translucency of human dental enamel was determined by total transmittance of wavelengths from 400 to 700 nm. The transmission coefficient at 525 nm was 0.481 mm-1. Total transmission of light through human dental enamel increased with increasing wavelength. Human tooth enamel is more translucent at higher wavelengths. The translucency of wet human enamel and enamel after dehydration was also measured by total transmittance. The transmission coefficient at 525 nm decreased from 0.482 to 0.313 mm-1 after dehydration and was reversed on rehydration. The decrease in translucency occurred as a result of the replacement of water around the enamel prisms by air during dehydration.
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The authors tested the adjunctive use of light with a 15 percent peroxide gel as a single-visit, in-office tooth whitening system. Subject (N = 87) with stained (> shade D4, Vita Zahnfabrik, Bad Säckingen, Germany) anterior teeth were randomly assigned to test (peroxide and light), peroxide control (peroxide gel) or light control (placebo gel and light) groups and were treated for one hour. The researchers evaluated tooth shade, color and subject response at baseline and posttreatment and at three and six months posttreatment. The initial shade unit reduction of combined light and peroxide treatment (8.4) was greatest compared with that of peroxide alone (5.9) and of light alone (4.9). Approximately 88 percent of these effects persisted for six months. Lightness was increased and yellowness decreased to a significantly greater extent in the test group than in either control. These findings were corroborated by subject evaluation. One week after treatment, moderate to greatly increased tooth sensitivity occurred in 20 percent of test subjects, 21.7 percent of peroxide control subjects and none of the light control subjects. Neither tooth sensitivity nor gingival redness was present at the three- and six-month visits. Peroxide and light treatment significantly lightened the color of teeth to a greater extent than did peroxide or light alone, with a low and transient incidence of tooth sensitivity. Light can increase the tooth-whitening effect of peroxide, thereby increasing the effectiveness of tooth-whitening procedures.
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To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37 degrees C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to anova and Tukey's test (5%). Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 +/- 0.2003 micro g) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 +/- 0.3981 micro g). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.
Article
To investigate peroxide penetration from newer bleaching products into the pulp chamber. Fifty extracted human maxillary central incisor teeth were separated into five groups (n = 10). All the teeth were sectioned 3 mm apical to the cemento-enamel junction; the intracoronal pulp tissue was removed, and the pulp chamber filled with acetate buffer. Buccal crown surfaces of teeth in the experimental groups were subjected to either a whitening strip (containing 5.3% hydrogen peroxide-G1) or one of three paint-on liquid whiteners (containing 19% sodium percarbonate peroxide-G2, 18% carbamide peroxide-G3 and 8.7% hydrogen peroxide-G4). The teeth in the control group (G5) were exposed only to distilled water. The acetate buffer solution in each tooth was then transferred to a glass test tube after 30 min and leuco-crystal violet and enzyme horseradish peroxidase were added, producing a blue solution. The optical density of the resultant blue colour in the tubes was measured by a UV-visible spectrophotometer at a wavelength of 596 nm. The values were converted into microgram equivalents of HP using a spectrophotometric calibration curve. Data were analysed statistically using the Kruskal-Wallis Analysis of Variance and the Mann-Whitney U-test. Statistically significant differences were found between all of the groups (P < 0.05). Pulpal peroxide was not observed in the control group. The amount of hydrogen peroxide (microg) found in the pulp chamber of G1 (0.726 +/- 0.024) > G4 (0.443 +/- 0.017) > G3 (0.231 +/- 0.011) > G2 (0.175 +/- 0.012). The peroxides from the whitening strip and paint-on whiteners penetrated into the pulp chamber to varying degrees.
Article
To review current knowledge of tooth whitening with respect to external bleaching methods. The scope is the external bleaching of vital teeth and focuses on mechanisms; in vivo and in vitro measurement methods, and factors influencing the efficacy of the whitening process. "Medline" and "ISI Web of Science" databases from 1966 and 1974, respectively were searched electronically with key words tooth, teeth, colo*r, white*, bleach* and peroxide. The importance of tooth whitening for patients and consumers has seen a dramatic increase in the number of products and procedures over recent years, with a concomitant rise in publications on this topic. Literature suggests that the mechanisms of tooth whitening by peroxide occur by the diffusion of peroxide through enamel to cause oxidation and hence lightening of coloured species, particularly within the dentinal regions. A number of approaches are available for measuring changes in tooth colour. These include visual measurements by trained clinicians and instrumental measurements using spectrophotometry, chromameters and digital image analysis. The key factors that affect tooth whitening efficacy by peroxide containing products are concentration and time. In general, higher concentrations are faster than lower concentrations. However, lower concentrations can approach the efficacy of higher concentrations with extended treatment times. Alternative bleach systems to peroxide have received only minor attention. The efficacy of light activated systems versus non-light activated controls in clinical studies is limited and conflicting. Other factors which can influence tooth bleaching outcome include type of stain, initial tooth colour and subject age.
Article
This study examined whether an ultraviolet light enhanced the whitening efficacy of a peroxide gel containing a photo-Fenton activator. Fifty subjects were enrolled into the trial at two geographically separate sites. As directed by the randomization keys, teeth of half of the study subjects were concurrently exposed to the whitening lamp, while the gel was on their teeth, for a total light exposure of 45 minutes. The other half of the subjects received no light treatment. At each examination, clinical data were collected on the gingival index, shade score, and self-assessed dentinal hypersensitivity. Changes in tooth shade were significantly better (approximately 26% improvement; p < 0.05) for subjects exposed to the gel and dental whitening lamp (average = 7.7 shade changes) compared to subjects exposed to the gel only (average 6.1 shades) immediately after treatment. No reports of erythema, desquamation, ulceration of soft tissues, gross changes in teeth, gingiva, or restorations were documented. The relative changes in mean sensitivity scores were similar for both groups, with no significant differences between the Light and No-light groups at any interval. The whitening effect was improved by approximately 26% when the Zoom2 dental whitening lamp was used. It was demonstrated that the a photo-Fenton activator used with a bleaching light and 20% hydrogen peroxide gel is safe and effective for whitening teeth rapidly.
Article
External bleaching procedures utilizing highly concentrated 30-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures. Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review. Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 degrees C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation. Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.
Article
This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 microg) and human (2.27 +/- 0.41 microg) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.
Penetration of the pulp chamber from newer whitening products
  • O Gokay
  • A Mujdeci
  • Algin
Gokay O, Mujdeci A, Algin E. Penetration of the pulp chamber from newer whitening products. International Endodontic Journal 2005;38:516–20.
  • D J Lurie
  • J Mclay
  • I Nicholson
  • J R Mallard
Lurie DJ, McLay J, Nicholson I, Mallard JR. Journal of Magnetic Resonance 1991;95:1091-195.