Carbamide Peroxide Research Articles

CLAREAMENTO DENTAL DE CONSULTÓRIO: UMA REVISÃO DE LITERATURA

White teeth are considered ideal for an aesthetic smile. In this way, the search for teeth whitening became the most searched dental procedure for patients. For that, the technique of teeth whitening provides fast results and comfort for the patients. This work treats a narrative literature review that searches to describe techniques of teeth whitening in the clinic, with the bibliographical survey in the following databases BVS, MEDLINE e Google Scholar, in the years of 2014 to 2024. From the selected studies, it was evaluated that the success of the teeth whitening is related to the properties of the whitening agent to infiltrate the dental structure and at the time the substance acts. For this, the most common substances are the hydrogen peroxide and the carbamide peroxide, varying in concentrations according to the technique indicated by the dentist. The clinic's teeth whitening is a procedure safe and efficient and the main disadvantage is the sensibility, which can be treated with the use of methods of desensitizers and laser.

Mechanism of microwave-assisted coal desulfurization with urea peroxide

To effectively remove organic sulfur from coal for higher resource efficiency, an innovative microwave-assisted urea peroxide for desulfurization system was designed. The experimental group with different microwave frequencies and the conventional pyrolysis control group were set up to prove the desulfurization effect of microwave in coordination with urea peroxide. The experimental results showed that under 1000 W microwave irradiation and the promotion of urea peroxide, the desulfurization efficiency can reach 67.29 %, with an increase of 38.32 % while the conventional pyrolysis is only 28.97 %. According to the Fourier transform infrared (FTIR) analysis, the effectiveness of microwave coordination with urea peroxide for desulfurization is explained from macroscopic point of view. Benzylidene thiol, dibenzyl sulfide, and dibenzyl disulfide were selected as model compounds for the quantum chemical calculation. The simulation results demonstrated that the changes in the pathway energy barriers for desulfurization align with the experimental material transformations, confirming the accuracy of the simulation. The sulfur-containing bonds of mercaptans will be destroyed to form hydrogen sulfide, and the undestroyed bonds will remain in the organic matter. After being oxidized, the sulfur-containing bond will break to form a water-soluble sulfonic acid free radical. The unoxidized sulfur bonds of thioethers will be destroyed to generate unstable phenyl free radicals and free sulfur radicals. To achieve stability, phenyl free radicals can pair to form diphenylethane or combine with other radicals (such as •H). In contrast, sulfur free radicals can only react with hydrogen radicals to form hydrogen sulfide. However, the limited availability of hydrogen radicals in the system restricts the desulfurization efficiency. After oxidation by urea peroxide, the thioethers will form sulfones. The sulfur-containing bonds will be fractured and directly generate phenyl and sulfur dioxide, which reduces the dependence on hydrogen free radicals. The three-dimensional desulfurization path of microwave collaboration with urea peroxide experiment was simulated and converted to the analytical bond breaking and formation mechanism. This study proved that microwave synergizes with urea peroxide can intensify the desulfurization process. It provides a high-efficiency method for the clean and green utilization of coal, which is conducive to supporting environmentally sustainable development.

Effectiveness of violet LED with or without a bleaching gel: a 12-month randomized clinical trial

IntroductionThe present interventional, controlled, randomized, blind clinical study aimed to evaluate the effectiveness of an in-office bleaching procedure with violet LED associated or not with 37% carbamide peroxide, considering as response variables the degree of change and color stability over 12 months and dental sensitivity over a month.MethodsForty participants, according to the inclusion and exclusion criteria, were randomly divided into 2 groups (n = 20) according to the bleaching protocol conducted, in two sessions, with a 7-day interval: vLED—violet LED, without gel; vLED/CP—37% carbamide peroxide photocatalyzed with violet LED (control group). In the vLED group, in each session the bleaching was carried out by 2 consecutive irradiation cycles of 25’ each (10 × 2’ LED + 30” interval), with 5’ interval between cycles. In the vLED/CP group, the gel was applied 5 times in the bleaching session and photocatalyzed 3 times for 2’ with 30” intervals (7’30” per gel application), totaling 37’30” per session. Dental sensitivity was assessed using a visual analog scale (VAS) and the effectiveness of bleaching as a function of the degree of change and color stability (ΔE) with a spectrophotometer. The data were tabulated and submitted to statistical tests (p < 0.05).ResultsThe VAS analysis showed that some individuals from both groups had mild pain (1 ≤ VAS < 4) during the time intervals evaluated, being more prevalent in the vLED/CP group. Regarding the degree of color change, the groups behaved differently over time (p < 0.0001). The ΔE observed for the vLED/CP group was superior in comparison to the vLED group at all evaluated moments.ConclusionsOver 12 months, the vLED/CP group was more effective in relation to the bleaching effect compared to the vLED group. Both groups showed low levels of sensitivity in the studied time intervals. Clinical Trial Registration[https://ensaiosclinicos.gov.br/rg/RBR-6rc23h], identifier [U1111-1253-8850].

Penetration of Intracoronal Bleaching Agents Across a Calcium Silicate-Based Coronal Barrier in Pulpless Immature Permanent Teeth: An In Vitro Study.

Tooth bleaching procedures on nonvital teeth have been performed for crown discoloration caused by regenerative endodontic therapy (RET). However, leakage of bleaching agents across the root canal can be detrimental. This study aimed to assess and compare the penetration levels of hydrogen peroxide (HP) from different bleaching agents across calcium silicate-based coronal barriers in immature permanent teeth. Fifty extracted single-rooted human teeth were randomly divided into four groups (n = 10): Group I (HH)-35% hydrogen peroxide (HP); Group II (SS)-a mixture of sodium perborate (SP) powder and saline; Group III (SH)-a mixture of SP powder and 30% HP liquid; Group IV (CP)-10% carbamide peroxide gel. The control group (Group V, CC) was treated with distilled water. The bleaching agent was replaced on the 4th day, and penetration analysis was performed on the 7th day using ferro thiocyanate (FTC) method and a UV-spectrophotometer at a wavelength of 480 nm. Compared with the control group, the SH group (SP mixed with HP) showed a significant difference, indicating substantial HP penetration across the root canal space (p value < 0.0001). Intergroup comparisons also revealed a significant difference between the SS and SH groups (p value < 0.0001), suggesting that the SS group had less penetration. Compared with other bleaching agents, SP mixed with saline/water resulted in the lowest HP penetration in the pulp canals of the RET-simulated tooth models. This study is the first to investigate HP penetration from different bleaching agents in teeth that have undergone RET, identifying the safest bleaching agent for use in these cases. This study also provides a foundation for further research to develop precise guidelines for nonvital tooth bleaching protocols in RET-treated teeth.

Procedures And Adverse Effects Of Teeth Whitening

Now a days people are giving much more importance to perfect smiles. Expectations about aesthetic appearance has been increasing day by day in the recent times. Aesthetic smiles including tooth colour and appearance is very important to patients. So teeth whitening procedures are one of the most frequently demanded treatment options by public. Besides oral health and hygiene, there is an increasing number of oral care products that focus on teeth whitening. There are various reasons for people to choose teeth whitening as a treatment option which includes: staining of teeth which may include extrinsic or intrinsic stains, to improve their smiles etc. Among all of these, teeth discolouration is the most common cause. Discolouration of teeth are mostly associated with staining. Therefore, excellent approach to discolouration of teeth is teeth whitening techniques. There are various procedures of teeth whitening. Here we are going to discuss about vital and non-vital teeth whitening techniques which is also called bleaching and the adverse effects associated with these procedures. Both vital and non-vital teeth whitening procedures come up in in either at-home technique or in-office procedure and over-the- counter modalities. carbamide peroxide, hydrogen peroxide or sodium perborate are the different types of chemical agents that are being used for these procedures which are going to be discussed in the coming sections. These procedures not only produce excellent whitening effects but also some of the adverse effects which are discussed in this paper. Finally, the result of the treatment is whiter teeth and perfect smiles. Dentist plays an important role to bring about a perfect smile on people’s face

Biological action of bleaching agents on tooth structure: A review.

The use of bleaching agents to remove stains is one of the main dental procedures to improve the aesthetics of teeth. This review presents the main agents used for tooth whitening, existing clinical protocols, and the structural changes that may occur through their use. The main bleaching agents consist of hydrogen peroxide and carbamide peroxide, which are used in bleaching techniques for vital teeth. These techniques can be performed in the office by a professional or by the individual in a home en-vironment under professional guidance. Bleaching agents come in a variety of concentrations and there are over-the-counter products available on the market with lower concentrations of hydrogen peroxide. Due to the chemical characteristics of the agents, changes in the organic and inorganic content of the tooth structure can be observed. These changes are related to morphological changes characterized by in-creased permeability and surface roughness, such changes compromise the mechanical resistance of the tooth. Furthermore, bleaching agents can promote molecular changes after reaching the dental pulp, resulting in oxidative stress of pulp cells and the release of pro-inflammatory mediators. Despite the bleaching effectiveness, tooth sensitivity is considered the main side effect of use. Therefore, among the heterogeneity of protocols, those that used the bleaching agent for a prolonged time and in lower con-centrations presented more harmful effects on the tooth structure.

Development and experimental investigation of a new direct urea fuel cell

This study concerns the development and experimental investigation of Direct Urea-Hydrogen Peroxide Fuel Cells (DUHPFC), with a particular emphasis on electrode preparation using nickel zinc iron oxide coated on stainless steel foil via the electrochemical deposition method, and the performance evaluation of single cells under varying operational conditions is also performed. This electrochemical deposition helps achieve a uniform and stable anode coating, which exhibits the high catalytic activity and stability, resulted in significantly enhanced urea oxidation reaction. The research further identifies an optimal performance for a single cell at 25 °C with 9 M KOH and 0.5 M urea, achieving a peak power density of 46.38 mW/cm2. The single cell demonstrates an open circuit voltage (OCV) of 0.72 V. Both energy and exergy efficiencies are further investigated for the cell performance and found to be 58% and 24%, respectively, at 5 M KOH. The electrochemical impedance spectroscopy (EIS) results reveal a significant reduction in impedance, from 30-Ωcm2 at 25 °C to 15-Ωcm2 at 65 °C, indicating an enhanced ionic conductivity and a reduced resistance. The present study results suggest that optimizing the electrode composition and operational parameters significantly improves the DUHPFC's performance, offering valuable insights for future fuel cell development.

Use of amazonian fruits in dental bleaching

Natural products stand out for their chemical diversity, thus plants are important candidates for screening new bioactive compounds. This study evaluated the effect of plant extracts combined with 16% carbamide peroxide (PC16%) on tooth whitening. Bovine teeth and composite resin blocks were randomly assigned to pigmentation and whitening protocols. For pigmentation, they were immersed in diluted coffee (14 days), and whitening was performed by mixing 1g of plant extract from each species and 0.5mL of PC16% (9 days). The extracts were prepared from fruits of species occurring in the Amazon biome: Myrciaria dubia (Myrtaceae), Bactris gasipaes (Arecaceae), Euterpe oleracea (Arecaceae), Theobroma grandiflorum (Malvaceae), and Paullinia cupana (Sapindaceae). PC16% was used alone as control, and a group without whitening was also included. Color analysis was performed using ΔE2000, ΔE1976, and WhiteIndex through an EasyShade Advanced 4.0 spectrophotometer before and after the protocols. The pH of the extracts at a concentration of 10% and micrographs after whitening were analyzed. Data were analyzed by one-dimensional ANOVA and Tukey's post-hoc test. Pigmentation showed significance only for bovine teeth (p 0.05). The pH of the pupunha and guaraná-de-maués extracts approached that of PC16%. Micrographs show that only the cupuaçu group had no surface alteration. Further research is needed to investigate variation factors, particularly given the study's limitations.

In-Office Dental Bleaching Using 37% Carbamide PeroxideVersus 35% Hydrogen Peroxide: A Randomized, Double-Blind Clinical Trial.

Compare the tooth sensitivity (TS) and bleaching efficacy(BE) of in-office dental bleaching performed with 35% hydrogen peroxide (HP) or 37% carbamide peroxide (CP). Sixty-six participants were randomly divided into two groups according to the bleaching gel applied to the right hemiarch: 35% HP, or 37% CP. TS was recorded immediately after, up to 1, 24, and 48 h after bleaching, using the VAS and NRS scales. BE was assessed before bleaching and 1 month after using color guide units (ΔSGUs) and a spectrophotometer (ΔEab, ΔE00, and ΔWID). TS was assessed using McNemar's and paired t-test (VAS) or Wilcoxon signed rank (NRS). The paired t-test was used to analyze BE (α = 0.05). TS risk and intensity were lower for the 37% CP (p = 0.003 and p < 0.005). Despite significant differences between the groups after 1 month (ΔSGU and ΔE00; p < 0.05), the color measurements of both groups exceeded the 50%:50% perceptibility/acceptability threshold. In-office dental bleaching using 37% CP resulted in reduced risk and TS intensity, without prejudice to the BE. The use of 37% CP for in-office dental bleaching could decrease TS risk and intensity without affecting BE. ClinicalTrials.gov identifier: RBR-683qhf.

Effect of carbamide peroxide treatment on the ion release of different dental restorative materials

BackgroundTo predict the long-term performance of restorative materials in the oral environment, it is important to evaluate their resistance to chemical and mechanical degradation and to know the toxic potential of the type and amount of ions eluted from the filling material. In this study, home bleaching was applied to dental materials with different contents and it was aimed to determine the type and amount of ions released from these materials.MethodsIn this study, amalgam, posterior composite resin, anterior composite resin, bulk fill composite resin, indirect composite resin, hybrid ceramic and all-ceramic were used as restorative materials. 10 specimens of each material were prepared according to the manufacturer’s instructions. Each material group was divided into two subgroups as the bleached group and the control group. After bleaching, all specimens were stored in 1 ml of 75% ethanol/water solution. Solutions were renewed after 1, 14 and 28 days. The type and amount of ions released from the materials were determined using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Data were analyzed using the Friedman, Wilcoxon Signed Ranks, and Mann-Whitney U tests (α = 0.05).ResultsIt was determined that the amount of ions release from the restorative materials decreased over time (p < 0.05). According to the results of the Mann-Whitney U test, there was no difference between the bleaching and control groups in most of the restorative materials (p > 0.05).ConclusionWithin the limits of this study, home bleaching system does not have a significant effect on ion release from restorative materials.

Effect of Bleaching Treatments on the Mechanical Properties of the Dentin Matrix and on Collagen Biodegradation by Endogenous Protease.

This study evaluated the mechanical properties of demineralized dentin matrix submitted to different bleaching treatments, as well as the changes in mass and collagen biodegradation brought about by endogenous protease. Dentin collagen matrices were prepared to receive the following treatments (n=12): no bleaching treatment (C-control), 10% carbamide peroxide (CP-Opalescence PF, Ultradent, South Jordan, UT, USA) 10%/8 hours/ day/14 days, and 40% hydrogen peroxide (HP-Opalescence Boost, Ultradent), 40 minutes per session/3 sessions. The dentin matrices were evaluated for elastic modulus and mass before and after treatments and ultimate tensile strength after treatments. The solution collected during storage was evaluated for hydroxyproline release. There was no statistically significant difference between CP and C in terms of the elastic modulus (p=0.3697) or mass variation (p=0.1333). Dentin beams treated with HP and C presented significant mass loss after the first session (p=0.0003). HP treatment led to complete degradation of collagen matrices after the second bleaching session. After the second session, CP showed higher hydroxyproline concentration than C (p<0.0001). Ultimate tensile strength was lower for CP than C (p=0.0097). CP did not affect the elastic modulus or the dentin collagen matrix mass but did promote hydroxyproline release by endogenous protease and reduce the ultimate tensile strength. HP significantly affected the mechanical properties of dentin and promoted complete degradation of the demineralized dentin collagen matrix.

Evaluation of the Surface Roughness and Solubility of Newer Self-blending Composite Resin following Home-bleaching and Brushing-mouth Rinsing Cycle

Objective(s): To evaluate the effect of tooth brushing and mouth rinsing after bleaching with 16% carbamide peroxide (16% CP) on the surface roughness and solubility of newer self-blending resin composite. Materials and Methods: About 70 specimens were fabricated with Estelite sigma-quick composite resin and subjected to bleaching using custom-tray with 16%CP gel for 6hours except 10 samples to serve as control group and divided into seven groups (n=10) as follows: group 1: no bleaching (control), group 2: 16% CP, group 3: brushing, group 4: brushing+Listerine mouth rinse, group 5: brushing +Colgate Plaxmouth rinse, group 6: Listerine, group 7: Colgate Plax. Electric tooth brushing was done using toothpaste slurry for 3min, immersed in mouth-rinse of respective groups for 1min and placed in artificial saliva for 24hrs. This was done for a total period of 21 days followed by surface roughness and solubility testing. Data were statistically analyzed using one-way ANOVA and post hoc Tuckey tests (p&lt;0.05). Results: Group 4 (Brushing + Listerine) showed greater surface roughness and solubility followed by group 6 (Listerine). No significant difference was found between group1 with group3 and group 5. Conclusion (s): Along with brushing, Listerine mouth rinse has a determining effect on surface roughness and solubility of newer self-blending composite resin following bleaching with 16% Carbamide peroxide.

Effect of Successive At-home Bleaching Sessions on the Surface Properties, Biaxial Flexural Strength, and Reliability of CAD-CAM Monolithic Materials.

Although at-home bleaching can recover the optical properties of stained CAD-CAM monolithic materials, little is known about its impact on their surface and mechanical properties, especially when successive sessions are performed. This study evaluated the effect of successive at-home bleaching sessions on the microhardness, roughness, topography, biaxial flexural strength (BFS), and reliability of CAD-CAM monolithic materials. Disks from Lava Ultimate (LU), Vita Enamic (VE), and IPS Empress CAD (EMP) were fabricated and submitted to up to three bleaching sessions. At-home bleaching was performed with 10% carbamide peroxide, and each session consisted of one application for 10 hours/day for 14 days. The analyses of the aforementioned parameters were assessed before and after the first, second, and third bleaching sessions, except for BFS, which was evaluated at baseline and after the third session. The Weibull modulus was calculated from the BFS data. The microhardness of the three materials as well as the roughness of LU were not affected by the sessions, whereas the roughness of VE and EMP increased from the second session. All materials displayed topographic changes, which became more pronounced with the increase in the number of sessions. Although bleaching decreased the BFS of the materials, it did not adversely affect their reliability. Successive at-home bleaching sessions with the protocol used in the present study cannot be considered a safe procedure for the materials evaluated.

Comparison of various methods of restoring adhesion to recently bleached enamel

AimThis study compared the effectiveness of several techniques in restoring compromised bonding to recently bleached enamel.MethodsSeventy-five healthy bovine incisors were divided into five groups (n = 15). Fifteen teeth (Group 1) remained intact, whereas 60 (Groups 2 to 5) underwent at-home bleaching with 16% carbamide peroxide. The bonding procedures were as follows: Group 1: Bonding of resin composite to unbleached enamel; Group 2: Bonding immediately after bleaching; Group 3: Application of a 10% sodium ascorbate solution for 10 min before bonding; Group 4: Enamel removal to the depth of 0.5 mm; and Group 5: Increased curing time of the bonding agent to 80 instead of 20 s. After 24 h, the specimens were subjected to micro-shear testing, and the failure mode was determined.ResultsANOVA revealed a significant difference in bond strength among the groups (P < 0.001). The mean bond strength was significantly lower in group 2 than in other groups (P < 0.05), which showed comparable bond strength to each other (P > 0.05). Adhesive failure was the most predominant failure type in all groups. The mixed failure occurred with a frequency of 26.7% in groups 3 and 5. The Fisher’s exact test revealed a significant difference in failure modes among the groups (P = 0.047).ConclusionsThe three experimental procedures used in this study, including the application of 10% sodium ascorbate before bonding, enamel removal to the depth of 0.5 mm, and increasing the curing time of the bonding agent to 80 s, were effective in restoring the compromised bonding to recently bleached enamel.

Effects of Different Concentrations of Carbamide Peroxide on Color, Surface Roughness, and Hardness of CAD/CAM Dental Ceramics.

This study assessed the effects of 15% and 20% carbamide peroxide (CP) on color, surface roughness, and hardness of computer-aided design/computer-aided manufacturing (CAD/CAM) dental ceramics. This in vitro study was conducted on 120 Vita Mark II, Celtra Duo, and Suprinity CAD/CAM ceramic specimens. The ceramic specimens in each group (n = 40) were randomly assigned to two subgroups (n = 20) for polishing and glazing, and their baseline color, surface roughness (Ra), and hardness were assessed. In each subgroup, half of the specimens were exposed to 15% CP, while the other half were exposed to 20% CP. Their color change (ΔE), surface roughness, and hardness were then measured again. Surface roughness, hardness, and color were analyzed sequentially by profilometer, Vickers hardness tester, and spectrophotometer, respectively. Data were analyzed by repeated measures ANOVA, one-way ANOVA, and post hoc Bonferroni test (α = 0.05). The surface roughness of all groups significantly increased after bleaching treatment (p < 0.05). Surface hardness of all groups decreased after bleaching treatment, but this reduction was only significant in Vita Mark II subgroups (glazed, polished, 15%, and 20% CP). The ΔE was not clinically and visually perceivable in any group. The present results revealed that concentration of CP and type of surface treatment affected the surface properties of CAD/CAM ceramics. Type of surface treatment only affected the surface hardness of Vita Mark II ceramics (p < 0.05). Concentration of CP had a significant effect only on polished Vita Mark II.

A scanning electron microscope analysis on the effect of bleaching gel in combination with fluoro calcium phosphosilicate-based dentifrice on whitening of teeth and dentinal tubule occlusion – An in vitro study

Aim: The aim of this study is to investigate the use of 15% carbamide peroxide in combination with fluoro calcium phosphosilicate desensitizing dentifrice during bleaching to evaluate postoperative dentinal tubule occlusion. Materials and Methods: Premolars which were extracted and bleached using 15% carbamide peroxide with fluoro calcium phosphosilicate dentifrice were used in this investigation, and the shade change was assessed. They were subsequently divided into sections and examined with scanning electron microscope. The quantity of open tubules, fully obstructed as well as moderately obstructed tubules, was recorded for each specimen. The statistical analysis of shade changes was conducted using the paired t-test. The tubule numbers were statistically evaluated after being assigned a mean and standard deviation. Results: The mean values between test and control groups in completely blocked tubules are 81.370 ± 1.989 and 42.586 ± 11.316, respectively. In partially blocked tubules, the mean values were found to be 13.219 ± 1.747 and 32.264 ± 11.554, respectively. In open tubules, the mean values are 5.398 ± 1.260 and 25.149 ± 8.781. The mean values of shade comparison for test group and control group are 1.95 ± 2.78 and 3.40 ± 2.83, respectively. Conclusions: According to the findings of the study, dentinal tubules were blocked when fluoro calcium phosphosilicate dentifrice was administered with 15% carbamide peroxide, but the bleaching process was unaffected. The potential clinical advantage of using a single paste system for both bleaching and desensitizing was also emphasized.

Effect of C60 Fullerene on Muscle Injury-Induced Rhabdomyolysis and Associated Acute Renal Failure.

Rhabdomyolysis, as an acute stage of myopathy, causes kidney damage. It is known that this pathology is caused by the accumulation of muscle breakdown products and is associated with oxidative stress. Therefore, the present study evaluated the effect of intraperitoneal administration (dose 1 mg/kg) of water-soluble C60 fullerenes, as powerful antioxidants, on the development of rat kidney damage due to rhabdomyolysis caused by mechanical trauma of the muscle soleus of different severity (crush syndrome lasting 1 min under a pressure of 2.5, 3.5, and 4.5 kg/cm2, respectively). Using tensometry, biochemical and histopathological analyses, the biomechanical parameters of muscle soleus contraction (contraction force and integrated muscle power), biochemical indicators of rat blood (concentrations of creatinine, creatine phosphokinase, urea and hydrogen peroxide, catalase and superoxide dismutase activity), glomerular filtration rate and fractional sodium excretion value, as well as pathohistological and morphometric features of muscle and kidney damages in rats on days 1, 3, 6 and 9 after the initiation of the injury were studied. Positive changes in biomechanical and biochemical parameters were found during the experiment by about 27-30 ± 2%, as well as a decrease in pathohistological and morphometric features of muscle and kidney damages in rats treated with water-soluble C60 fullerenes. These findings indicate the potential application of water-soluble C60 fullerenes in the treatment of pathological conditions of the muscular system caused by rhabdomyolysis and the associated oxidative stress.

Effectiveness of desensitizing toothpastes in reducing tooth sensitivity after tooth bleaching: a systematic review.

To evaluate the effectiveness of desensitizing toothpastes in reducing post-bleaching tooth sensitivity. A systematic review of randomized clinical trials was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. Electronic searches were conducted in the PubMed/MEDLINE, Scopus, Web of Science, The Cochrane Library and Embase databases, using the following terms: (dentifrices OR toothpaste) AND (sensitive OR sensitivity OR dental sensitivity) AND (dental bleaching OR tooth bleaching OR dental whitening OR tooth whitening). Five studies involving 387 individuals undergoing in-office or at-home teeth bleaching were reviewed. Desensitizing toothpastes reduced sensitivity effectively after home bleaching with 22% carbamide peroxide and single-session in-office bleaching with 35% hydrogen peroxide. However, they were ineffective for home bleaching with 16% carbamide peroxide and in-office bleaching across two sessions with 35% or 38% hydrogen peroxide. Desensitizing toothpastes are effective for home bleaching with high concentration carbamide peroxide and single-session in-office bleaching with highly concentrated hydrogen peroxide, but ineffective for home bleaching with low concentration carbamide peroxide and two-session in-office bleaching with concentrated hydrogen peroxide.

Synthesis, characterization, and a comparative study on the catalytic activity of the functionalized magnetic nanoparticles for the green oxidation of sulfides

AbstractIn the following research, meso‐tetrakis(4‐carboxyphenyl)porphyrinatomanganese (III) acetate (MnTCPP(OAc)) was immobilized onto the surface of two functionalized magnetic nanoparticles (MNPs) with different linker length via amide bond (Fe3O4@SiO2‐NH2‐MnTCPP(OAc) (A1) and Fe3O4@SiO2‐NHCO‐NH2‐MnTCPP(OAc) (A2)). The prepared catalysts were characterized by standard methods such as: atomic absorption spectroscopy (AAS), Ultra violet‐visible (UV‐Vis), Fourier‐transform infrared (FT‐IR), vibrating sample magnetometry (VSM), field emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) techniques and also the effect of the length of the linker on the catalytic activity of supported magnetic nanohybrids was investigated. The prepared magnetic nano‐catalysts with different linker lengths were participated in a comparative study of the clean oxidation of sulfides with urea hydrogen peroxide (UHP) in ethanol. The higher catalytic activity, selectivity and also reusability were achieved in the presence of the catalyst with longer linker length (A2) at ambient temperature. Moreover, the turnover number (TON) of catalytic reactions using A2 as catalyst was highly enough to consider the catalyst as an efficient material to oxidize various sulfides. Both A1 and A2 catalysts simply have accomplished 5 runs of recycling without significant decrease in the catalytic activity.

Whitening toothpastes with hydrogen peroxide concentrations vs. at-home bleaching.

To evaluate the effect of whitening toothpastes with different hydrogen peroxide (HP) concentrations on HP permeability, color change, and physicochemical properties, compared to at-home bleaching treatment. Forty-nine premolars were randomized into seven groups (n = 7): untreated (control); at-home bleaching with 10% carbamide peroxide gel (AH; 10% CP) with 14 and 28 applications of 180min each (AH [14 × 180min] and AH [28 × 180min]); three whitening toothpastes (3% HP; 4% HP and 5% HP) and 10% CP brushed 28 times for 90s each (TB [28 × 90s]). HP permeability was measured using a UV-VIS spectrophotometer and color change by a digital spectrophotometer (ΔEab, ΔE00, and ΔWID). Initial concentration, pH, and viscosity were measured through titration, digital pH meter, and rheometer, respectively. Statistical analysis included one-way ANOVA, Tukey's test, and Dunnett's test (α = 0.05). 4% HP group showed acidic pH, the lowest viscosity and the highest HP concentration into the pulp chamber (p < 0.05). The 10% CP groups had lower HP in the pulp chamber and greater color change than other groups (p < 0.05), except the 5% HP group in ΔEab and ΔE00. For ΔWID, the 10% CP AH groups showed greater whitening than other groups (p < 0.05). Whitening toothpaste with up to 5% HP resulted in higher HP permeability and less color change compared to 10% CP. Higher HP commercial concentrations in toothpaste increased whitening effect; however, acidic pH toothpastes exhibited greater HP permeability. Whitening toothpastes with high hydrogen peroxide concentrations were less effective than at-home bleaching, resulting in less color change and greater permeability of hydrogen peroxide, potentially increasing the risk of tooth sensitivity.