CnoX Is a Chaperedoxin: A Holdase that Protects Its Substrates from Irreversible Oxidation.

Bleach (HOCl) is a powerful oxidant that kills bacteria in part by causing protein aggregation. It inactivates ATP-dependent chaperones, rendering cellular proteins mostly dependent on holdases. Here we identified Escherichia coli CnoX (YbbN) as a folding factor that, when activated by bleach via chlorination, functions as an efficient holdase, protecting the substrates of the major folding systems GroEL/ES and DnaK/J/GrpE. Remarkably, CnoX uniquely combines this function with the ability to prevent the irreversible oxidation of its substrates. This dual activity makes CnoX the founding member of a family of proteins, the "chaperedoxins." Because CnoX displays a thioredoxin fold and a tetratricopeptide (TPR) domain, two structural motifs conserved in all organisms, this investigation sets the stage for the discovery of additional chaperedoxins in bacteria and eukaryotes that could cooperate with proteins from both the Hsp60 and Hsp70 families.

Titanium dioxide nanotubes in a hydrogen peroxide-based bleaching agent: physicochemical properties and effectiveness of dental bleaching under the influence of a poliwave led light activation.

OBJECTIVES: The effects of different concentrations of titanium dioxide (TiO2) into 40% hydrogen peroxide (HP) were evaluated as regards the effectiveness of dental color change either associated with activation by polywave LED light or not. MATERIALS AND METHODS: TiO2 (0, 1, 5, or 10%) was incorporated into HP to be applied during in-office bleaching (3 sessions/40 min each). Polywave LED light (Valo Corded/Ultradent) was applied or not in activation cycles of 15 s (total time of 2 min). The color of 80 third molars separated into groups according to TiO2 concentration and light activation (n = 10) was evaluated at baseline and at time intervals after the 1st, 2nd, and 3rd bleaching sessions. RESULTS: WID value was significantly higher when using HP with 5% TiO2 in the 2nd session than the values in the other groups (p < 0.05). After the 2nd and 3rd sessions, the ΔEab value was significantly higher when activated with light (p < 0.05) for all agents containing TiO2 or not. Zeta potential and pH of the agents were not modified by incorporating TiO2 at the different concentrations. CONCLUSIONS: The 5% TiO2 in the bleaching agent could enhance tooth bleaching, even without light application. Association with polywave LED light potentiated the color change, irrespective of the presence of TiO2 in the bleaching gel. CLINICAL SIGNIFICANCE: HP with 5% TiO2 could lead to a greater tooth bleaching response in the 2nd clinical session, as well as the polywave light can enhance color change.

Prognosis in home dental bleaching: a systematic review.

OBJECTIVES: The aim of this systematic review was to evaluate the prognosis of at-home dental bleaching using low concentration bleaching products. MATERIALS AND METHODS: This review was conducted was performed following the recommendations of the 2020 PRISMA statement and was registered in the International Prospective Register of Systematic Reviews (PROSPERO-CRD42022360530). The PICO question was "What is the prognosis of home teeth whitening treatment?". An advanced electronic search was made in three databases: PubMed, Web of Science, and Embase. RESULTS: The database search led to the retrieval of 225 articles. After elimination of duplicate references, the titles and abstracts of the articles were analyzed with respect to the eligibility criteria, and 24 studies were included for the development of the systematic review. CONCLUSIONS: Most authors state that the color remains stable between 1 and 2.5 years regardless of the type of bleaching agent or the forms of administration, and color stability in cases of severe discolorations presents a higher degree of recurrence. CLINICAL RELEVANCE: Given the growing demand for dental cosmetic treatments, the following systematic review may aid the clinician's continuing education and evidence-based practice by providing knowledge on the field of at-home dental bleaching agents and their long-term effects.

Whitening efficacy and tooth sensitivity in a combined in-office and at-home whitening protocol: A randomized controlled clinical trial.

OBJECTIVE: This controlled randomized clinical trial determined the whitening efficacy and the intensity and absolute risk of tooth sensitivity in dual whitening when prefilled at-home whitening trays were used between in-office whitening intervals. MATERIALS AND METHODS: An in-office whitening agent containing 35% hydrogen peroxide was used. A prefilled tray with a whitening agent containing 6% hydrogen peroxide was used for at-home whitening. Sixty-six subjects were randomly assigned to three groups. Group I: at-home whitening was performed 10 times between the in-office whitening treatments. Group II: at-home whitening was performed five times between the in-office whitening treatments. Group III: only in-office whitening was performed. The tooth color changes were evaluated using a spectrophotometer. A visual analog scale was used to express the pain intensity. RESULTS: All the groups showed increased ΔE*ab, ΔE00 , and ΔWID with increased whitening sessions. Group I at the 3rd whitening session showed significantly higher ΔE*ab, ΔE00 , and ΔWID than group III. Tooth sensitivity showed higher values up to 24 h after whitening. CONCLUSIONS: Although dual whitening with the prefilled tray and in-office whitening had higher whitening ability than in-office whitening alone, the intensity and absolute risk of tooth sensitivity was similar. CLINICAL RELEVANCE: The dual whitening might produce faster and stronger whitening effects than in-office whitening alone.

Anti-Melanogenic and Antioxidant Activity of Bifidobacterium longum Strain ZJ1 Extracts, Isolated from a Chinese Centenarian.

Melanin produced by melanocytes protects our skin against ultraviolet (UV) radiation-induced cell damage and oxidative stress. Melanin overproduction by hyperactivated melanocytes is the direct cause of skin hyperpigmentary disorders, such as freckles and melasma. Exploring natural whitening agents without the concern of toxicity has been highly desired. In this study, we focused on a Bifidobacterium longum strain, ZJ1, isolated from a Chinese centenarian, and we evaluated the anti-melanogenic activity of the distinctive extracts of ZJ1. Our results demonstrated that whole lysate (WL) and bacterial lysate (BL) of ZJ1 ferments efficiently reduce α-melanocyte-stimulating hormone (α-MSH)-induced melanin production in B16-F10 cells as well as the melanin content in zebrafish embryos. BL and WL downregulate melanogenesis-related gene expression and indirectly inhibit intracellular tyrosinase activity. Furthermore, they both showed antioxidant activity in a menadione-induced zebrafish embryo model. Our results suggest that ZJ1 fermentation lysates have application potential as therapeutic reagents for hyperpigmentary disorders and whitening agents for cosmetics.

Effects of Dental Bleaching Agents on the Surface Roughness of Dental Restoration Materials.

Background and Objectives: This study aimed to evaluate the surface roughness evolution of several finished and polished composites when bleaching materials are applied. The research was conducted on four microhybrid or nanofilled composites that are used in dental restorations. Materials and Methods: For each composite type, 5 samples were selected for control, 5 samples were subjected to the bleaching protocol "office bleach" with 40% hydrogen peroxide, and 5 other samples were subjected to the "home bleach" protocol with 16% carbamide peroxide, resulting in a total number of 60 samples. The surfaces of all the samples were tested for roughness, and the values of the most relevant parameter (Ra), were collected. Comparisons between composites and samples were performed using one-way ANOVA (in Statistical Package for Social Sciences). Results: After the bleaching protocol with 40% hydrogen peroxide gel, it was found that the roughness of the group increased considerably compared to the control group, so the highest roughness was found at GC Gradia direct anterior group, and the lowest value was registered for the 3M ESPE Valux Plus group. Following the bleaching protocol with 16% carbamide peroxide (home bleach), it was noted that the sample surfaces were not as affected. In this case, the lowest roughness was found at 3M ESPE Valux Plus group, and the highest roughness was registered for the GC G-aenial anterior group. Following the interpretation of the results, all four types of dental composites tested showed significant surface roughness differences between the groups subjected to bleaching protocols and those kept as control (p < 0.05). Conclusions: The surfaces of the samples were affected by the bleaching protocols by increasing the roughness compared to the control samples.

Impact of different intraorifice barriers on fracture resistance of non-vital bleached teeth.

Background and Aim: This study aimed to evaluate the effects of bleaching agents on the fracture resistance of endodontically treated teeth using different intraorifice barrier (IOB) materials. Materials and Methods: The endodontic treatment was performed for 160 mandibular premolars, and then, the teeth were divided into four groups according to the IOB: Ionoseal, Biodentine, ProRoot MTA, and TheraBase. Then, these teeth were subdivided into four subgroups (n = 10) based on the bleaching agents as distilled water (control), hydrogen peroxide 35% (HP), sodium perborate (SP), and carbamide peroxide 37% (CP). The access cavities were restored with composite resin after applying the bleaching agents for 7 days. The fracture resistance test was performed using a universal testing machine. Data were statistically analyzed, and the significance level was set at 5%. A scanning electron microscope was used to evaluate the effect of bleaching agents on the surfaces of IOBs. Results: The highest fracture resistance values were observed in Biodentine groups with significant differences compared to Ionoseal and ProRoot MTA (P <.05). The distilled water groups showed significantly the highest fracture resistance compared to SP and HP groups (P <.05). There was no significant difference between SP, HP, and CP groups (P >.05). It was demonstrated that the morphological surface of the intact IOBs (control) was different from the surface of IOBs treated with bleaching agents. Conclusion: The intracoronal bleaching procedures affected negatively the fracture resistance of the endodontically treated teeth.

Helicobacter pylori senses bleach (HOCl) as a chemoattractant using a cytosolic chemoreceptor.

The gastric pathogen Helicobacter pylori requires a noncanonical cytosolic chemoreceptor transducer-like protein D (TlpD) for efficient colonization of the mammalian stomach. Here, we reconstituted a complete chemotransduction signaling complex in vitro with TlpD and the chemotaxis (Che) proteins CheW and CheA, enabling quantitative assays for potential chemotaxis ligands. We found that TlpD is selectively sensitive at micromolar concentrations to bleach (hypochlorous acid, HOCl), a potent antimicrobial produced by neutrophil myeloperoxidase during inflammation. HOCl acts as a chemoattractant by reversibly oxidizing a conserved cysteine within a 3His/1Cys Zn-binding motif in TlpD that inactivates the chemotransduction signaling complex. We found that H. pylori is resistant to killing by millimolar concentrations of HOCl and responds to HOCl in the micromolar range by increasing its smooth-swimming behavior, leading to chemoattraction to HOCl sources. We show related protein domains from Salmonella enterica and Escherichia coli possess similar reactivity toward HOCl. We propose that this family of proteins enables host-associated bacteria to sense sites of tissue inflammation, a strategy that H. pylori uses to aid in colonizing and persisting in inflamed gastric tissue.

Supplement Individual Article: Algorithm for Pre-/Post-Procedure Measures in Racial/Ethnic Populations Treated With Facial Lasers, Nonenergy Devices, or Injectables.

BACKGROUND: Cosmetic procedures with lasers, nonenergy devices, and injectables are increasing in popularity among patients with skin of color. Published algorithms address measures to reduce side effects related to aesthetic procedures; however, none focus on reducing adverse events in skin of color. METHODS: An expert panel of dermatologists and plastic surgeons conducted face-to-face and online meetings to develop an algorithm for measures before, during, and after using aesthetic devices (energy and nonenergy-based) and injectable treatments based on the best available evidence for skin of color. Published algorithms and literature searches for aesthetic procedures provided guidance for the current algorithm. A modified Delphi method was used to reach a consensus to apply outcomes of literature searches, along with expert opinion, resulting in the current algorithm. RESULTS: The four sections of the algorithm outline an approach to optimize outcomes with specific before, during, and after procedure considerations. Pre-procedural consultation includes the development of a specific treatment plan based on individual patient goals and risk profile (including history and signs that may predict a higher risk for pigmentary or scarring complications). Before the procedure, sun avoidance and sunscreen use are emphasized; herpes simplex virus 1 prophylaxis and bleaching agents are administered if indicated. During the procedure, skin cleansing products are addressed, along with judicious techniques to minimize unintended cutaneous injury or inflammation. Post-procedural sunscreen and gentle skincare that may include skin-lightening agents or formulations designed to prevent infection and promote optimum healing are advised. CONCLUSIONS: The algorithm strives to optimize treatment outcomes for patients with skin of color by providing their physicians with guidance on measures before, during, and after office-based medical aesthetic procedures. J Drugs Dermatol. 2022;21:9(Suppl 1):s3-10.

Present status and future directions - Managing discoloured teeth.

Managing tooth discolouration involves a range of different protocols for clinicians and patients in order to achieve an aesthetic result. There is an increasing public awareness in the appearance of their teeth and management of tooth discolouration may be inter-disciplinary and involve both vital and nonvital teeth. Vital teeth can be easily treated with low concentration hydrogen peroxide products safely and effectively using an external approach and trays. For endodontically treated teeth, the walking bleach technique with hydrogen releasing peroxide products is popular. However, there is an association with external cervical root resorption with higher concentrations of hydrogen peroxide of 30%-35%. There are also regulatory considerations for the use of hydrogen peroxide in certain jurisdictions internationally. Prosthodontic treatments are more invasive and involve loss of tooth structure as well as a life cycle of further treatment in the future. This narrative review is based on searches on PubMed and the Cochrane library. Bleaching endodontically treated teeth can be considered a safe and effective protocol in the management of discoloured teeth. However, the association between bleaching and resorption remains unclear although there is likely to be a relation to prior trauma. It is prudent to avoid thermocatalytic approaches and to use a base/sealer to cover the root filling. An awareness expectations of patients and multidisciplinary treatment considerations is important in achieving the aesthetic result for the patient. It is likely that there will be an increasing demand for aesthetic whitening treatments. Bleaching of teeth has also become increasingly regulated although there are international differences in the use and concentration of bleaching agents.

Clinical comparison of diode laser- and LED-activated tooth bleaching: 9-month follow-up.

This study aims to evaluate the effect of diode laser- or LED-activated tooth bleaching on color change, tooth sensitivity(TS), temperature variation, and gingival irritation (GI) for 9 months. Thirty-five subjects having anterior teeth with a color of A2 or darker were enrolled in the study. In a split-mouth design, one side of each arch was activated by a diode laser (Epic X, Biolase), and the other side was activated by an LED (Radii Plus, SDI) in conjunction with a bleaching agent (35%, Whiteness HP). The color change was evaluated by subjective (VitaClassic/Vita3D Master Bleachguide) and objective (spectrophotometer, Vita Easyshade) methods for up to 9 months. TS and GI were assessed by visual analogue scale (VAS) and gingival index, respectively, at the same recall periods. During the bleaching, the temperature variation was also recorded using a thermocouple. Statistical analyses were performed (p < 0.05). In the color evaluation, no statistically significant difference was found between diode laser and LED (p > 0.05), except for the 6-month spectrophotometric assessment (ΔE00, ΔEab), where higher values were obtained with the laser (p < 0.05). The temperature difference and maximum temperature with diode were found to be significantly higher than LED (p < 0.05). Higher values were obtained with LED when the mean temperatures were compared (p < 0.05). There was no difference between the two activation methods in terms of TS and GI at any of the recalls (p > 0.05). The bleaching activated either with diode laser or LED performed similar clinical performance in terms of effective color change, tooth sensitivity, and gingival irritation with minimum temperature variations.

The effect of two different prophylaxis paste applying processes on color stability in-office bleaching: 24-month clinical follow-up.

OBJECTIVE: The purpose of this study was to examine the effect of applying two different prophylaxis pastes with various protocols on the degree of bleaching and color stability in the office bleaching process with a bleaching agent containing 40% hydrogen peroxide. MATERIAL AND METHOD: The 300 teeth of 15 (9 female, 6 male) patients were included in our study, and 5 different study groups were randomly formed. The bleaching process with Ultradent Opalescence Boost (Ultradent, South Jordan, USA) was performed according to the manufacturer's instructions. Two different prophylaxis pastes, Ultrapro (Ultradent, Cologne, Germany) and Cleanic (Kerr, Rastatt, Germany), were applied with protocols determined according to the groups. The effect on color stability at 6-, 12-, and 24-month follow-up was determined using the CIE L* a* b* color system. The changes in the parameters were analyzed using the one-way ANOVA, chi-square, and Tukey test (p > 0.05). RESULTS: The evaluation rate of the treatments was 100% at the end of 24 months. Control group 6-month ΔE (0-6) and 12-month ΔE (0-12) values were higher than 24-month ΔE (0-12) values. UU + UU, KC + KC, and UU group 6-month ΔE (0-6) values were higher than 12-month ΔE (0-12) values. In addition, 6-month ΔE (0-6) and 12-month ΔE (0-12) values were higher than 24-month ΔE (0-24) values. KC group 6-month ΔE (0-6) and 12-month ΔE (0-12) values were higher than 24-month ΔE (0-24) values. Control, UU + UU, KC + KC, UU, and KC group ΔE (1-6) values at 6 months were lower than 12-month ΔE (1-12) and 24-month ΔE (1-12) values in all groups. In addition, 12-month ΔE (1-12) values were lower than 24-month ΔE (1-24) values. According to the study data, there was no statistically significant difference between the groups according to the prophylaxis paste and prophylaxis procedure (p > 0.05). However, it was observed that whiteness decreased in all groups over time. CONCLUSIONS: Discoloration was observed at 6 months, 12 months, and 24 months after bleaching. However, at the end of 24 months, the tooth color was significantly whiter than the initial color. CLINICAL RELEVANCE: Pre-bleaching prophylaxis application and pre-bleaching and post-bleaching prophylaxis application have no effect on color stability.

Evaluation of bleaching efficacy, microhardness, and trans-amelodentinal diffusion of a novel bleaching agent for an in-office technique containing hexametaphosphate and fluoride.

OBJECTIVE: This study evaluated in vitro the effects of calcium gluconate (CaGlu), sodium fluoride (NaF), sodium hexametaphosphate (HMP), and NaF/TMP added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color change, enamel hardness, and trans-amelodentinal diffusion. MATERIALS AND METHODS: Enamel discs/bovine dentin (n = 150) were divided according to the bleaching gel: 35% H2O2 (H2O2); 35% H2O2 + 0.1% NaF (H2O2/NaF); 35% H2O2 + 1% HMP (H2O2/HMP); 35% H2O2 + 0.1% NaF + 1% HMP (H2O2/NaF/HMP), and 35% H2O2 + 2% CaGlu (H2O2/Caglu). The bleaching gels were applied three times (40 min/session) at 7-day intervals between each application. Then, color alteration (ΔE), whitening index (ΔWID), percentage of surface hardness loss (% SH), cross-sectional hardness (ΔKHN), and trans-amelodentinal diffusion were determined. Data were submitted for analysis of variance (ANOVA), followed by the Student-Newman-Keuls test (p < 0.05). RESULTS: All bleaching gels showed significant color changes after treatment (p < 0.001). ΔE and ΔWID were similar among the evaluated gels. Mineral loss (% SH and ΔKHN) and trans-amelodentinal diffusion of hydrogen peroxide were lower for H2O2/NaF/HMP; the H2O2/CaGlu group presented the highest values about the other groups (p < 0.001). CONCLUSION: It is possible to conclude that the addition of NaF/HMP to the in-office bleaching agent did not interfere with the bleaching efficacy and reduced enamel demineralization and H2O2 diffusion. CLINICAL SIGNIFICANCE: The association of NaF/HMP to the bleaching gel can be used as a novel approach for minimizing the adverse effects of H2O2 by-products and with similar clinical efficacy.

Influence of intracoronal bleaching agents on the bond strength of MTA cements to composite resin and their surface morphology.

The objective of the present in vitro study was to evaluate micro-tensile bond strength (µSBS) of MTA cements to composite resin using a universal adhesive after internal bleaching procedure, and to examine surface characteristics of MTA cements exposed to bleaching agents. MTA specimens were divided into three subgroups according to the bleaching agent used which were, 37% carbamide peroxide (CP), 35% hydrogen peroxide (HP), and no exposure as a control group (n = 12). After exposure to bleaching agent, composite resins were applied to MTA surfaces using a universal adhesive in self-etch mode. The specimens were exposed to a shear force until failure to evaluate bond strength. MTA surfaces were investigated using scanning electron microscopy (SEM) to observe the effects of the bleaching agents. Differences between groups were analyzed using two-way ANOVA test and intergroup comparisons were assessed with Tukey test (p < 0.05). Although there was a slight difference in bond strength between bleaching agents (CP and HP), no significant difference was found, irrespective of MTA cement. After the HP application, the bond strength values decreased approximately by half compared with the controls. SEM results demonstrated distinct morphological differences between the intact MTA surface (control) and treated MTA surface. Distinct micro-cracks, surface irregularities, and capillary voids formed due to the superficial dissolution caused by peroxides. Exposure to the intra-coronal bleaching agents had a negative influence on the surface morphology of MTA cements and their bond strength to composite resin.

Over-the-counter bleaching agents can help with tooth whitening maintenance.

OBJECTIVE: This study evaluated the influence of over-the-counter agents on the maintenance of color and microhardness of the enamel after home bleaching protocol. MATERIALS AND METHODS: Specimens of bovine teeth (6 × 6 × 2 mm) were prepared, and color (Easyshade, VITA) and microhardness (HMV-2, Shimadzu) readings were performed. All the specimens were bleached using 22% carbamide peroxide (22%CP), except for the control group, and then separated into seven groups (n = 10) according to the interaction of toothpaste (whitening, conventional, and whitening with peroxide) and mouth rinse (whitening and conventional). The study simulated 1 year of toothbrushing (Pepsodent, MAVTEC) and mouth rinse by immersion. After that, final color and microhardness measurements were performed. Data were analyzed by one-way ANOVA, Tukey's test (P < .05). RESULTS: The group submitted to 22%CP + whitening toothpaste + whitening mouth rinse showed higher color maintenance (P < .05) than the control group. The perception of whitening of teeth (ΔWID ) was higher than the color change (ΔE00 ). There was a decrease in microhardness after treatment with 22%CP + conventional toothpaste + whitening mouth rinse. CONCLUSIONS: Over-the-counter products can help with the maintenance of tooth whitening after bleaching with carbamide peroxide; however, special attention should be given since the association of products can also reduce the microhardness of the dental enamel. CLINICAL SIGNIFICANCE: The association between whitening toothpastes and mouth rinses might be beneficial for maintaining color during 1 year after bleaching treatment.

Extraction and Concentration of Waste Pueraria lobata Stems with Antioxidants and Anti-Melanogenesis Activity as a Novel Skin Whitening Agent for Natural Cosmetic Prototypes.

The root of Pueraria lobata (Willd.) is used commercially in different products, including dietary supplements, cosmetics, and teas, but its stem part is rarely used and studied. Therefore, this study evaluated the antioxidant and anti-melanogenesis activities of the bioactive fraction of P. lobata stem and investigated whether the activated carbon decolorization technique would have an impact on its activity and chemical composition. We observed that the dichloromethane fraction of P. lobata stem (DCM-PLS) has excellent antioxidant and anti-melanin synthesis activity at a concentration of 50 µg/mL. For the investigation of the anti-melanogenesis mechanism, we evaluated the mRNA expression of tyrosinase, which was depressed by the DCM-PLS. Daidzin was identified as the main active ingredient in DCM-PLS by using a high-performance liquid chromatography-diode array detector-hyphenated with tandem mass spectrometry. In addition, the activated carbon decolorization technology has no negative impact on the main components and bioactivity of DCM-PLS. DCM-PLS also did not induce any skin response in the human skin safety test. Collectively, DCM-PLS could be used as a natural type of skin-whitening agent in skin care products.

The Optimization of Extraction Process, Antioxidant, Whitening and Antibacterial Effects of Fengdan Peony Flavonoids.

Flavonoids have important biological activities, such as anti-inflammatory, antibacterial, antioxidant and whitening, which is a potential functional food raw material. However, the biological activity of Fengdan peony flavonoid is not particularly clear. Therefore, in this study, the peony flavonoid was extracted from Fengdan peony seed meal, and the antioxidant, antibacterial and whitening activities of the peony flavonoid were explored. The optimal extraction conditions were methanol concentration of 90%, solid-to-liquid ratio of 1:35 g:mL, temperature of 55 °C and time of 80 min; under these conditions, the yield of Fengdan peony flavonoid could reach 1.205 ± 0.019% (the ratio of the dry mass of rutin to the dry mass of peony seed meal). The clearance of Fengdan peony total flavonoids to 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, hydroxyl radical and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical could reach 75%, 70% and 97%, respectively. Fengdan peony flavonoid could inhibit the growth of the Gram-positive bacteria. The minimal inhibitory concentrations (MICs) of Fengdan peony flavonoid on S. aureus, B. anthracis, B. subtilis and C. perfringens were 0.0293 mg/mL, 0.1172 mg/mL, 0.2344 mg/mL and 7.500 mg/mL, respectively. The inhibition rate of Fengdan peony flavonoid on tyrosinase was 8.53-81.08%. This study intensely illustrated that the antioxidant, whitening and antibacterial activity of Fengdan peony total flavonoids were significant. Fengdan peony total flavonoids have a great possibility of being used as functional food materials.

Evaluation of the penetration of intracoronal bleaching agents into the cervical region using different intraorifice barriers.

BACKGROUND: The present study aimed to make a comparison between the effects of 35% hydrogen peroxide gel (HP) and sodium perborate with distilled water (SP) bleaching agents on the sealing characteristics of glass ionomer cement (GIC), TheraBase, ProRoot MTA and Biodentine intraorifice barriers. METHODS: One hundred and twelve single-rooted mandibular human premolar teeth extracted from young patients (14-25 years) were chosen. Root cement and cementoenamel junction (CEJ) of teeth were examined under a stereomicroscope at 10 × magnification to ensure there was no cement defect or dentin gap in CEJ. After the endodontic access cavities were opened on the occlusal surfaces of the teeth, the working length was determined. Instrumentation of each root canal was performed with a ProTaper Gold rotary system in the determined working length and filled with gutta-percha + AH Plus with a single cone technique using. Root fillings were removed 3 mm short of the CEJ and sealed with one of the following intraorifice barrier materials (n = 30/group): 1. GIC; 2. TheraBase; 3. ProProot-MTA; 4. Biodentine. In each of the sub-groups, either HP or SP was used to perform intracoronal bleaching on days 1, 4, and 7. All outer surfaces of the specimens except the 3 mm cervical region were covered with nail polish and modeling wax layers. Specimens were immersed in a 5 ml Eppendorf tube that contained 2 mL of distilled water. The penetration of peroxide release was measured using the colorimetric ferric thiocyanate method. Statistical analysis of the data was performed with Three-way ANOVA and Tukey's test (P = 0.05). RESULTS: In the HP groups, GIC showed the greatest peroxide release when compared with other tested groups on day 1 (P < 0.05). Biodentine and ProRoot MTA displayed a significantly lower peroxide leakage when compared to GIC and TheraBase on days 1 and 4 (P < 0.05). While GIC and TheraBase were used, HP observed higher peroxide penetration when compared with SP on days 1 and 4 (P < 0.05). CONCLUSIONS: Peroxide diffusion was significantly influenced by the kind of intracoronal bleaching agents and intraorifice barrier materials used.

Evaluation of bleaching agent effects on color and microhardness change of silver diamine fluoride-treated demineralized primary tooth enamel: An in vitro study.

BACKGROUND: The present study aimed to assess the impact of application of fluoridated- 10% carbamide peroxide (CP) with or without potassium iodide (KI) on silver diamine fluoride (SDF)-treated enamel surface in the primary teeth. METHODS: After stained-remineralized caries lesions (s-RCLs) creation, 96 teeth were randomly allocated to four experimental groups: Group 1:SDF-treated enamel followed by 8-h/day application of 10% CP for 2 weeks; Group 2: SDF-treated enamel followed by 15-min/day application of 10% CP for 3 weeks; Group 3: SDF + KI-treated enamel followed by 8-h/day application of 10% CP for 2 weeks; and Group 4: SDF + KI-treated enamel followed by 15-min/day application of 10% CP for 3 weeks. Enamel microhardness (EMH) test (n = 12) and spectrophotometric color assessment (n = 12) was performed at four stages: baseline (intact enamel), demineralized enamel, aged remineralized-stained enamel, and after final intervention. Sixteen samples were used for SEM evaluation. Data were analyzed with the paired t-test, one-way ANOVA, and Tukey's post-hoc test (p < 0.05). RESULTS: EMH values in all groups showed significant decrease after demineralization (all, p < 0.00001). All samples showed complete recovery of EMH values (%REMH) after SDF application compared to demineralization (%REMHSDF) (p = 0.971). Bleaching caused a slight decrease in %REMH for all groups. However, the differences were not statistically significant (p = 0.979). SEM findings revealed no changes in enamel porosity after bleaching. Bleaching application ameliorated the discoloration in all groups (all, p < 0.00001). All samples in Groups 2 and 4 had significantly lighter color after 21 days as compared to 14-day exposure to the bleaching material (both, p < 0.00001). CONCLUSIONS: SDF application on demineralized primary tooth enamel completely recovered enamel microhardness. 10% carbamide peroxide effectively bleached SDF stain without causing significant decrease in EMH values. Color improvement was more evident with the use of KI immediately after SDF application. Both 15-min and 8-h application of fluoridated CP resulted in statistically similar color enhancement in primary teeth.

Effect of high-concentration bleaching agents on dentin bonding: an in vitro study.

The aim of this in vitro study was to evaluate the effect of high-concentration hydrogen peroxide (HP) and carbamide peroxide (CP) bleaching solutions on the dentin-resin interface and the shear bond strength (SBS) of restorative materials. A total of 56 extracted human premolars were prepared with flat dentin windows and divided into groups according to the bleaching protocol: group A, bleached with 35% HP (n = 24); group B, bleached with 35% CP (n = 24); and group C, control, no bleaching (n = 8). Groups A and B were each divided into 3 subgroups according to the time of bonding: A0 or B0, bonded immediately after bleaching (n = 8); A1 or B1, bonded 1 week after bleaching (n = 8); and A2 or B2, bonded 2 weeks after bleaching (n = 8). The specimens in group C were bonded without prior bleaching. Scanning electron microscopic analysis was conducted to evaluate the length of the resin tags at the dentin-resin interface. For SBS testing, the specimens were loaded into a universal testing machine at a crosshead speed of 0.5 mm/min. The mean resin tag lengths of groups that were bonded immediately (A0 and B0) or after a 1-week delay (A1 and B1) were significantly shorter than that of group C (P < 0.001; Kruskal-Wallis test), but the differences between the 2-week delayed bonding groups (A2 and B2) and group C were not statistically significant. The SBS values of both the 35% HP and 35% CP groups increased significantly with delayed bonding time (P < 0.05; 1-way analysis of variance). When bonding was delayed until 2 weeks after bleaching, the mean SBSs of the bleaching and control groups were not significantly different (P > 0.05; Tukey test).