Bleaching Effect Research Articles

Microleakage effect of in-office bleaching on two types of nanohybrid composites with or without surface sealer.

Bleaching is a highly common method used nowadays to treat tooth discolouration because it is a significant cosmetic issue, particularly with anterior teeth, however bleaching itself results in microleakage. This study aims to evaluate the impact of in-office bleaching on class V restoration microleakage with type 1 and type 2 composite restorations. Three hundred and twenty healthy, caries-free removed human anterior teeth were used in this in-vitro study. All extracted teeth had their buccal and lingual surfaces uniformly prepped for class V cavities. The 120 removed teeth were divided into two groups, with Group 1 receiving Tetric N-Ceram nanohybrid composite restorations and Group 2 receiving 3 M Filtek Z350 XT nanohybrid composite restorations. Groups 1 and 2 were further broken into four more subgroups of four each. The restorations were sealed with a G-Coat Plus resin. The p-value was kept at 0.005 for the data analysis using the Chi-square and Fisher exact tests. Allocating microleakage among 320 study models revealed that 141 (44.1%) study samples had no microleakage, whereas 20 (6.3%), 54 (16.9%), and 105 (32.8%) study samples had microleakage up to, between, and greater than two-thirds of cavity depth. With a statistically significant p-value of 0.001, no microleakage was discovered in 85 (53.1%) lingual surfaces with Tetric N-Ceram nanohybrid composite restoration and 56 (35%) buccal surfaces with 3M Filtek Z350 XT nanohybrid composite restoration. 19.1% of samples of N-Ceram that were sealed and not bleached had no microleakage, according to analysis of microleakage across several groups. With a p-value of 0.001, the distribution of microleakage among various clusters was statistically notable. According to the findings of the study, hydrogen peroxide bleaching has an enhanced impact on micro escape during dye dispersion. Both with and without bleaching, resin coating can be utilised to minimise marginal microleakage.

The Potential Teeth Bleaching and Halitosis Prevention Effects of Pediococcus inopinatus THK-30, a Kimchi-Derived Lactic Acid Bacterium: In Vitro Study.

Recent developments in addressing dental aesthetic concerns, encompassing issues like teeth discoloration and halitosis, underscore the demand for safer alternative solutions. This study aims to confirm the effects of lactic acid bacteria (LAB) from kimchi on artificial teeth bleaching and their potential impact in terms of preventing halitosis-related bacteria. To evaluate the antimicrobial effects against oral pathogens, disc diffusion tests and broth microdilution methods were used. Additionally, crystal violet analysis was performed to confirm the biofilm inhibition effect. The bleaching effects on stained artificial teeth were analyzed using the CIEDE2000 colorimetric method. Statistical analyses were performed using GraphPad Prism 9 with one-way and two-way ANOVA, with the significance level set at α < 0.05. The strain THK-30, isolated from kimchi, exhibited antibacterial activity against Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum, and was identified as Pediococcus inopinatus. Moreover, THK-30 showed a synergistic antibacterial effect against Gram-negative oral pathogens with 8% sodium hexametaphosphate (SHMP). In the stained artificial teeth bleaching test and artificial teeth biofilm inhibition test, the cell-free supernatant of THK-30 displayed significant teeth bleaching effects and caused the inhibition of biofilm formation, both independently and in combination with SHMP 8%. This study has demonstrated the potential applicability of LAB in teeth discoloration and halitosis. These findings are poised to provide a foundation for the development of research pertaining to the control of oral bacteria.

Effect of aging and bleaching on the color stability and surface roughness of a recently introduced single-shade composite resin

ObjectivesTo assess the effects of aging and bleaching procedures on the color stability and surface roughness of a new single-shade composite versus multi-shade composite resins. MethodsA single-shade composite resin (Charisma Diamond One, CDO) and 3 multi-shade composite resins (Tetric NCeram, Filtek Z350 XT, Clearfil Majesty Posterior) were tested. Thirty specimens of each material were subjected to one of the aging procedures respectively: immersion in distilled water (12 days/37 °C), immersion in coffee (12 days/37 °C), or water thermocycling (10,000 cycles/5–55 °C). All specimens underwent in-office bleaching after aging. Kruskal-Wallis tests and analysis of variance were used for statistical analysis (α=0.05). ResultsAll materials exhibited a change of color (ΔE00), translucency (RTP), whiteness (WID) and surface roughness parameters (Sa,Sv) after aging and bleaching procedures. CDO showed the highest ΔE00 among all resins with the highest RTP value, regardless of the aging procedures. Immersion in coffee led to the significantly highest ∆E00 values and lowest RTP values for nearly all resins. Positive ΔWID1 (WID(bleaching)−WID(baseline)) values were found in distilled water immersion and thermocycling groups, while negative ΔWID1 values were found in the coffee immersion group for all materials. Besides, positive ΔWID2 (WID(bleaching)−WID(aging)) values were found in all aging groups for nearly all materials. All materials showed an increasing trend in Sa and Sv after bleaching. ConclusionsCDO showed more pronounced discoloration than multi-shade composite resins. Although the whiteness of all resins increased after bleaching, none was completely restored in the coffee immersion group. Bleaching significantly increased the surface roughness of all materials. Clinical significanceCharisma Diamond One is more susceptible to discoloration, which may affect its long-term success rate. Bleaching could partially reduce the color change of the composite resins but did not return them completely to their original state. The roughness of the resins increased after bleaching, prompting dentists to repolish them after bleaching.

Investigation of seaming performance of dyed and finished polyester/viscose fabrics

Seaming performance of a fabric is an important property because seams on a garment play a major role in determining the quality of the garment. Seam efficiency is calculated by the ratio of seam strength to fabric tensile strength. Seam strength and fabric strength are affected by the fabric-related properties and the stitch-related parameters. Therefore, as well as the effects of seaming parameters, dyeing, finishing, and laundering processes that the fabric is exposed to before the seaming processes have an effect on the seam efficiency. Polyester/viscose blended fabrics, which are frequently preferred in textiles, are used in this study, and the effects of bleaching, dyeing, finishing, laundering, and seaming processes on seam strength and seam efficiency, fabric tensile strength and fabric tensile elongation, air permeability, and thickness properties of these fabrics are examined. After the processes, there will be an increase or decrease in the properties depending on which process is examined in detail. The results are evaluated statistically. According to the results obtained, it has been observed that the mentioned processes are effective on seam efficiency. It can be said that seam strength and seam efficiency values are affected by the processes in different ways, and also that seam parameters are effective on seam strength values. Different effects of fabric direction on tensile strength and seam strength values were also observed. As explained in the study, these processes affect the other features differently.

Do Different Tooth Bleaching-Remineralizing Regimens Affect the Bleaching Effectiveness and Enamel Microhardness In Vitro?

Tooth bleaching may negatively affect the enamel surface properties, such as reduction in hardness values, and remineralizing agents can reverse these effects. This study evaluated the effect of remineralizing agents before, during, and after the bleaching process on enamel's whitening effectiveness and microhardness. The initial color of 104 bovine incisors after immersion in tea solution was recorded, and then, the teeth were randomly divided into eight groups (n = 13). Group 1 (NC) was considered the control with no treatment, and Group 2 (B) was bleached with 40% hydrogen peroxide gel. The 3% fluorohydroxyapatite (FHA) and 2% sodium fluoride (NaF) were applied before (FHA/B, NaF/B), during (FHA + B, NaF + B) and after (B/FHA, B/NaF) the bleaching process in other groups. The final color and microhardness in three depths of 20-30, 50-60, and 100-120 µm were measured. Data were analyzed using Shapiro-Wilk, one-way ANOVA, Tukey, Games Howell, repeated measurement, and LSD tests. The FHA + B presented the lowest ΔE, significantly lower than other groups, except B/FHA. The ΔE in B/FHA was significantly lower than B/NaF. The bleaching significantly reduced the enamel hardness in three depths. The highest microhardness values were reported for B/NaF and NaF + B, which have no noticeable difference with NC, while FHA/B showed the lowest hardness in three depths, which was significantly lower than NC. The application of NaF before, during, and after the bleaching improved the microhardness of bleached enamel as the unbleached one with no adverse effect on whitening effectiveness.

Alpha-tocopherol: An alternative solution for the adverse effects of dental bleaching on dentin adhesion

PurposeThis study evaluated the effect of solutions of different concentrations of alpha-tocopherol on hybrid layer formation and microtensile bond strength of endodontically treated teeth bleached with 38% hydrogen peroxide. Materials and methodsSixty bovine incisors were randomly distributed into six groups (n = 10). In the control group (CONT), no intervention was performed. In the 38HP group, only bleaching with 38% hydrogen peroxide was conducted. In the 15AT, 20AT, 25AT, and 10SA groups, bleaching with 38% hydrogen peroxide was followed by the application of alpha-tocopherol at 15%, 20%, 25%, or 10% sodium ascorbate, respectively. Subsequently, bond strength was performed using the microtensile test, and the formation of the hybrid layer was examined through scanning electron microscopy. The obtained data were subjected to Kruskal-Wallis and Dunn tests (α = 0.05). ResultsFor bond strength, groups CONT and 20AT displayed higher values compared to HP. There were no significant differences in the other groups compared to the control. 38HP, 10SA, 20AT and 25AT exhibited a predominance of adhesive failures, while CONT and 15AT presented more cohesive failures in dentin. In the evaluation of the hybrid layer, the CONT group showed greater formation of longer resin tags than 38HP and 15AT, which presented a predominance of few and short resin tags (p < 0.05). ConclusionAlpha-tocopherol at 20% is capable of minimizing the deleterious effects of dental bleaching on the hybrid layer formation and bond strength to dentin.

Ultrasound bleaching and quality evaluation of rice bran oil

AbstractRice bran oil (RBO) contains rich nutrients that are beneficial to the human body, but RBO suffers from severe nutrient loss due to bleaching difficulties. This article investigates low‐power ultrasound‐assisted bleaching as a new method for RBO during the bleaching process, which could potentially reduce nutrient loss and lipid oxidation. First, florisil (FL), magnesium trisilicate (MAT), and activated blending earth (ABE) were selected to use a mixture design for formula optimization from six adsorbent types, and then, central composite design was employed to optimize the parameters of the bleaching process for the ultrasound‐assisted adsorbent formula. The results showed that the optimal formula was 66% FL, 10% MAT, and 24% ABE, the highest L* value and the lowest a* value is obtained at ultrasound power of 50 W for 9 min. The various parameters of RBO were subjected to comparison before and after ultrasound‐assisted bleaching. Following this bleaching procedure, the color and quality of RBO experienced notable enhancements, all the while maintaining micronutrient and fatty acid compositions within acceptable ranges. The characterization analysis of the adsorbent by FT‐IR spectroscopy and atomic force microscopy confirmed its adsorption of pigments and other substances. The results indicate that the low‐power ultrasound‐assisted bleaching is effective for RBO bleaching and may provide a promising alternative to the adsorption‐based bleaching method.Practical ApplicationsRBO is made from pressed rice bran and has high nutritional value, such as fatty acids, vitamin E, sterols, and oryzanol, with over 90% absorption by the body. The dark color of RBO makes it difficult to produce clear, transparent, and light‐colored rice bran oil, and even if bleaching is achieved, it results in significant nutrient losses. Conventional bleaching methods are commonly inefficient while emerging technologies cannot be applied industrially. Three adsorbents were selected for formulation optimization based on the fact that the bleaching effect of a single adsorbent is not obvious. Low‐power ultrasound‐assisted bleaching was performed to reduce nutrient loss and lipid oxidation. The aim is to find new bleaching methods that achieve bleaching results with acceptable nutrient losses.

Investigating the Effect of Internal Bleaching With 10% Carbamide Peroxide on the Color Change of Three Types of Common Endodontic Sealers.

Background and purpose Color change caused by materials used for endodontic treatment is an important clinical issue. The current research examined the impact of internal bleaching with 10% carbamide peroxide on discolored teeth resulting from various types of sealers. Materials and methods In this study, 36 anterior teeth were cut from 1 mm beneath the cementoenamel junction (CEJ), and the samples were divided into three groups of 12. Then, AH26 (Tulsa Dental, Tulsa, OK), Endofill (Herpo Produtos Dentários Ltda, Petrópolis, Brazil), and AH Plus (DentsplyDeTrey, Konstanz, Germany) color change potential sealers were placed inside the pulp chamber. The cervical access cavity was covered with a thin layer of glass ionomer. After one month, the material was removed, and bleaching was done with 10% carbamide peroxide. The color of the samples was measured by a spectrophotometer before bleaching, one week after bleaching, and one week after bleaching again. The data were subjected to statistical analysis using the Statistical Package for Social Sciences (SPSS)software version 16 (IBM SPSS Statistics, Armonk, NY), with a significance level set at P<0.05. Results The results showed that the factor of time and material used and the opposing effect of these two on the amount of L and ΔE were statistically significant (P<0.05). After one to two weeks of internal bleaching, all groups showed some degree of reduction in sealer-induced discoloration. In addition, in all groups, the largest difference in L was related to the difference in L0 and L2 (before bleaching and one week after bleaching again), and the lowest difference was related to the difference in L0 and L1. Also, the highest ΔE(T0,T1) belonged to the Endofill group, and this significantly differed from the AH26 group. AH26 showed the lowest value of ΔE(T0,T1), and after two weeks, the ΔE of all groups was higher than the clinically observable limit. The highest ΔE(T2,T0) among the groups belonged to the Endofill group. The ΔE(T2,T0) of AH26 and Endofill was significantly higher than AH Plus. Among all ΔE values, the AH Plus group had the lowest values. Conclusion Color change caused by Endofill and AH26 sealers showed a better response to internal bleaching than the AH Plus sealer.

Energy spectrum and optical properties in a double parabolic quantum ring: Effects of the impurity, the magnetic field and the spin–orbit interaction

In this letter, the energy spectrum in a concentric double quantum rings(CDQRs) with a parabolic confinement under the influence of the spin–orbit interactions (SOIs), the magnetic field and the hydrogenic donor impurity has been investigated by diagonalizing the Hamiltonian matrix and applying the perturbation theory. Then the optical absorption coefficients (OACs) are calculated through the scheme of compact density-matrix formalism. A discussion of the different intensity of the two SOIs is conducted. Meanwhile, the effects of different factors on the total OACs with different incident light polarization angles have also been investigated, in which the bleaching effects are found.

Effect of strontium fluorophosphate bioactive glass on color, microhardness and surface roughness of bleached enamel.

Undesirable effects of tooth bleaching can alter the biomechanical properties of enamel. To determine the influence of strontium fluorophosphate bioactive glass (Sr-FPG) on color, microhardness and surface roughness of enamel bleached with 35% hydrogen peroxide. The labial enamel of 36 extracted intact human anterior teeth were divided into 3 groups (n= 12), group 1 (HP): bleaching with 35% hydrogen peroxide only, group 2 (Sr-HP): bleaching with Sr-FPG incorporated 35% hydrogen peroxide and group 3 (HP-SrFPG): bleaching with 35% hydrogen peroxide followed by remineralization with Sr-FPG. Four consecutive eight-minute applications of the bleaching gel were done twice in all the groups. Color change (ΔE), microhardness and surface roughness were evaluated at baseline, post-bleaching and post-remineralization using spectrophotometer, Vickers hardness tester and profilometric analysis respectively. The mean ΔE among the groups was statistically similar (p> 0.05). Bleaching with HP significantly reduced microhardness (p< 0.05), whereas bleaching with Sr-HP and HP-SrFPG did not (p> 0.05). Post-bleaching microhardness in Sr-HP was significantly higher than HP-SrFPG (p< 0.05). An increased surface roughness was seen in Sr-HP bleached samples (p< 0.05). The addition of Sr-FPG to hydrogen peroxide significantly improved enamel microhardness than its use post-bleaching. An increase in surface roughness was seen post-bleaching with HP and Sr-HP.

Efeitos de dentifrícios contendo carvão ativado no esmalte dental: uma revisão da literatura

ABSTRACT The increased demand for white teeth has intensified the commercialization of new bleaching products, particularly those that can be accessed easily, do not require the direct supervision of a dentist, and are affordable. Among these new products, several dentifrices publicized as bleaching products have been developed, most recent of them being the activated charcoal toothpaste, which entered the market promising to whiten teeth. While it is portrayed as a healthy and ecological product, there is a paucity of scientific evidence supporting its alleged benefits. Therefore, this literature review aimed to evaluate activated charcoal containing oral hygiene products on their bleaching ability and effects on enamel. After analyzing several in vitro studies on the subject, it can be concluded that these products do not have a bleaching effect per se, but act by removing the extrinsic pigments from the teeth. However, most of the products containing activated charcoal could have abrasive effects on the surface of the enamel. Therefore, it is suggested caution about the indication of these dentifrices, especially for individuals predisposed to dental wear, such as gingival recession, reduced salivary flow, and high risk of caries or dental erosion.

Biomaterials based on advanced oxidation processes in tooth whitening: fundamentals, progress, and models.

The increasing desire for aesthetically pleasing teeth has resulted in the widespread use of tooth whitening treatments. Clinical tooth whitening products currently rely on hydrogen peroxide formulations to degrade dental pigments through oxidative processes. However, they usually cause side effects such as tooth sensitivity and gingival irritation due to the use of high concentrations of hydrogen peroxide or long-time contact. In recent years, various novel materials and reaction patterns have been developed to tackle the issues related to H2O2-based tooth whitening. These can be broadly classified as advanced oxidation processes (AOPs). AOPs generate free radicals that have potent oxidizing properties, which can thereby increase the oxidation power and/or reduce the exposure time and can probably minimize the side effects of tooth bleaching. While there have been several reviews on clinical tooth whitening and the application of novel nanomaterials, a review based on the concept of AOPs in tooth bleaching application has not yet been conducted. This review describes the common types and mechanisms of AOPs, summarizes the latest research progress of new tooth bleaching materials based on AOPs, and proposes a model for tooth bleaching and a rate control step at the molecular level. The paper also reviews the shortcomings and suggests future development directions.

At-home bleaching versus whitening toothpastes for treatment of tooth discoloration: a cost-effectiveness analysis.

This study aimed to analyze the cost-effectiveness of whitening toothpastes and at-home bleaching for the treatment of tooth discoloration. A cost-effectiveness economic analysis was conducted, and eight randomized clinical trials were selected based on the whitening agent product used: blue covarine dentifrices (BCD), hydrogen peroxide dentifrices (HPD), dentifrices without bleaching agents (CD, negative control), and 10% carbamide peroxide (CP10, positive control) for at-home bleaching. The consumer/patient perspective was adopted, macro-costing techniques were used and a decision tree model was performed considering the costs in the American and Brazilian markets. The color change evaluation (ΔE*ab) was used to calculate the effectiveness of tooth bleaching. A probabilistic analysis was performed using a Monte Carlo simulation and incremental cost-effectiveness ratios were obtained. CP10 resulted in the highest cost-effectiveness compared to the use of dentifrices in both markets. In Brazil, HPD was more cost-effective than BCD and CD. In the US, the increased costs of HPD and BCD did not generate any whitening benefit compared to CD. CP10 was more cost-effective than BCD and HPD for tooth bleaching from the perspectives of the Brazilian and American markets. Decision-making should consider the use of CP10 for treating tooth discoloration.

Evaluation of the Effect of Intra-Coronal Bleaching after Using C-Phycocyanin as a Photosensitizing Agent- In vitro Study.

Evaluation of the Effect of Intra-Coronal Bleaching after Using C-Phycocyanin as a Photosensitizing Agent- In vitro Study.

Effect of at-home and in-office bleaching on microleakage of class V composite resin restorations using different types of universal adhesives: An in vitro study.

When bleaching agents contact dental structures, they act on restorative materials and adhesive interfaces. This study investigated the effect of "at-home" and "in-office" bleaching on the microleakage of composite resin restorations performed with different universal adhesives in self-etch and etch-and-rinse modes. Class V cavities were prepared in 132 premolars. The samples were divided into four groups (n=33). All Bond Universal adhesive was used in the first and second groups, and G-Premio Bond adhesive was used in the third and fourth groups. The total-etch mode was used in the first and third groups, and the self-etch mode was used in the second and fourth groups. The samples were divided into three subgroups (n=11). In the first subgroup, home bleaching was used, and in the second subgroup, office bleaching was used. In the third subgroup, bleaching was not performed. The specimens were examined under a stereomicroscope for microleakage. Ordinal regression analysis was applied (P<0.05). The adhesive type, application method, and margin type significantly affected microleakage (P<0.05). The amount of microleakage in All Bond Universal adhesive was significantly higher than in G-Premio Bond adhesive. The chance of microleakage in the self-etch mode was almost twice as high as in the etch-and-rinse mode. The bleaching method did not significantly affect microleakage (P>0.05). Based on the results of the microleakage test, bleaching after composite resin restorations did not significantly affect the microleakage of Class V restorations.

Application of an edible coating developed with Andean potato starch and carboxymethyl-cellulose for lipid reduction during frying

This work aimed to search for alternative uses for different varieties of Andean potatoes (Solanum tuberosum ssp andigenum) which have been reintroduced in north-western Argentina. Specifically, the development of simple and compound films made with hydrocolloids such as carboxymethyl-cellulose (CMC) and starch (S) extracted from Andean potatoes var. Runa, and its application as a cover in the deep frying of Andean potato chips var. Waycha was studied to minimize oil absorption. The effect of prior bleaching of the chips with different media was also evaluated: water, calcium chloride solution, and ascorbic acid. The coatings were applied to potatoes chips before being fried. The results showed that the type of oil used did not affect absorption by the chips. The bleaching treatments with calcium chloride and coating with S/CMC, showed a significant reduction in oil absorption (39.5 % ± 0.7), delayed its oxidation, and decreased the loss of tocopherols during the frying process. It also contributed to the physical and sensory characteristics of the final product, which presented high acceptability by consumers.

Effect of incorporation of calcium polyphosphate sub-microparticles in low-concentration bleaching gels on physical properties of dental enamel.

To evaluate the bleaching efficacy and effects on enamel properties of experimental gels with carbamide peroxide (CP; 10%) or hydrogen peroxide (HP; 6%) containing calcium polyphosphate sub-microparticles (CaPPs). A total of 216 bovine tooth specimens were divided for microhardness and color analyses (n = 108) and block randomized into nine groups (n = 12): (G1) commercial CP (Whiteness Perfect, FGM; Brazil); (G2) experimental CP; (G3) CP-0.5%CaPPs; (G4) CP-1.5%CaPPs; (G5) commercial HP (Potenza Bianco, PHS; Brazil); (G6) experimental HP; (G7) HP-0.5%CaPPs; (G8) HP-1.5%CaPPs; (G9) artificial saliva. The gels' pH values were determined with a bench pH meter. Color (ΔE, ΔE00, ΔWID) and microhardness variation were evaluated before and after the therapy. Part of the specimens used for microhardness was submitted to the scanning electron microscopy (SEM) (n = 3) and energy-dispersive X-ray spectroscopy EDX (n = 3) analyses. Statistical analyses were performed in the R statistical software (α = 0.05). Linear mixed models for repeated measures in time were used to analyze microhardness and L* values. Generalized linear models were used to analyze the a*, b*, ΔE, ΔE00, and ΔWID, considering a group effect. The EDX data were analyzed using a one-way ANOVA with Tukey's test. The gels' pH remained over 6,0. All gels effectively bleached the specimens and did not differ significantly. When compared to the control group, the hardness was significantly lower in the G1, G2, G6, and G7 groups. The G3, G4, G5, and G8 groups did not differ significantly (p > 0.05). The incorporation of CaPPs in low-concentration whitening gels reduces its negative effects on microhardness without interfering with their bleaching efficacy.

Optical control of degradation of polytetrafluoroethylene films and its modification under electron irradiation

A method for monitoring the degradation of the optical density in polytetrafluoroethylene films and its modification, a copolymer of tetrafluoroethylene and ethylene, irradiated by electrons with energies of 100 keV and 10 MeV is described. The method is based on measuring the optical density of irradiated films in the photon energy range of 1-6 eV and is confirmed by established «dose-optical absorption» relationships. In particular, using the described method, a completely different nature of the radiation degradation of the optical properties of the two types of films under study was discovered. With an increase in the irradiation dose, «bleaching effect» in the region of 2-5 eV and the appearance of an absorption band at 5.6 eV are observed in polytetrafluoroethylene films. With a similar dose increase, three absorption bands at 4.0, 4.6 and 5.5 eV appear and grow in films of copolymer of tetrafluoroethylene and ethylene. The evidence of the critical role of the optical density of films in the functioning of space technology devices is given.

Effect of Different Desensitizer Treatments on the Shear Bond Strength of Orthodontic Metal Brackets Following In-Office Bleaching: An In Vitro Study.

One of the adverse effects of in-office bleaching is tooth hypersensitivity, which could be neutralized with a desensitizing agent. In-office bleaching and the application of desensitizing agents will affect the morphology of the enamel surface. These morphological changes have potential effects on the shear bond strength (SBS) and bonding of orthodontic brackets. This study analyzed the effects of fluoride and nonfluoride desensitizing agents after in-office bleaching on the SBS of metal brackets with resin composite cementation. Twenty-seven postextraction premolars (n = 27) were bleached with 37% hydrogen peroxide and then divided into three groups: control group (group 1), fluoride-based desensitizing agent (group 2), and nonfluoride-based desensitizing agent (group 3). After treatment, the brackets were bonded using Transbond, and then the SBS test was performed using a universal testing machine. The adhesive remnant index (ARI) was analyzed after the SBS test, whereas enamel morphological changes were observed under a scanning electron microscope. After this assessment, energy-dispersive X-ray spectroscopy was conducted to determine calcium and phosphorus elements in the enamel surface after treatments. SBS data were analyzed using the one-way analysis of variance, followed by the Tukey test, whereas ARI scores were subjected to the Kruskal-Wallis test and the Mann-Whitney test with a significance level of 5%. The SBS increased significantly in group 2 compared with groups 1 and 3 (p < 0.05). In group 2, an ARI of 2 (55.56%) was frequent, whereas in group 3, an ARI of 3 (55.56%) appeared most frequently. The application of the desensitizing agent fluoride after in-office bleaching increased the SBS and more adhesive remains on the tooth surface compared with that when nonfluoride desensitizing agents were applied on metal brackets with composite resin cementation.

Effect of Three Chemical Agents on Stain Removal from Dentin Caries Lesions Treated with Silver Diamine Fluoride

Introduction: This in vitro study aimed to evaluate the effect of three different chemical agents on stain removal and mineral uptake of artificial dentin caries (ADC) lesions treated with silver diamine fluoride (SDF). Methods: Baseline L*a*b* values were determined in polished human permanent dentin blocks, and ADC lesions were induced with an acid gel for 1 week. Samples were assigned to four groups; in three groups, half of each sample received SDF (30% SDF for 3 min), while the other half received SDF followed by a bleaching treatment protocol (garlic extract, bentonite, or 35% hydrogen peroxide). The fourth group had one SDF-treated half and one half without SDF. Color changes (ΔE) were measured by spectrometry, and transversal microradiography was used to quantify integrated mineral loss (ΔZ) 24 h after treatment (SDF or SDF + bleaching). A two-way mixed ANOVA was applied to thirty percent. Results: SDF application increased mineral uptake by ADC (p = 0.001). The type of chemical agent evaluated (p < 0.0001), time (p = 0.01), and their interaction (p < 0.0001) bleached the ADC treated with SDF. However, 35% hydrogen peroxide was the only compound with a bleaching effect (p < 0.001), without returning to baseline color. None of the compounds altered the mineral uptake effect of SDF (p = 0.30). Conclusion: This in vitro study showed mineral uptake effect in ACD within 24 h after SDF application and the ability of hydrogen peroxide to partially remove (reduction of 24%) the staining caused by SDF without affecting its mineral uptake effect.