Bleaching effectiveness and cytotoxicity of new experimental formulation of niobium-based bleaching gel.

OBJECTIVES: The development of new bleaching agents with minimum concentration of hydrogen peroxide (HP), without adverse effects, and with bleaching effectiveness, has great clinical relevance. The aim of this study was to evaluate the bleaching efficacy and cytotoxicity of a new niobium-based bleaching gel, compared to already available HP-based gels. MATERIALS AND METHODS: For the bleaching efficacy analysis, 40 bovine incisors were randomly divided into 4 groups according to the established bleaching protocol: control, untreated; 35HP, 35% HP bleaching gel; 6HP, 6% HP bleaching gel; NbHP, niobium gel associated with 3% HP gel. The color variation was measured in a spectrophotometer and the values of ΔL, Δa, Δb, and ΔE obtained. For the cell viability assay by MTT, MC3T3 cells were exposed to bleaching gel extracts (1:500, 1:250, 1:125 dilutions; immediately and 24 h). Statistical tests were performed (P < 0.05). RESULTS: The color alteration for all bleaching gels was significant compared to control (P < 0.05), but the NbHP gel showed a significant ΔE than other gels, with expressive color alteration at 14 days (P < 0.05). The 35HP showed high cytotoxicity regarding control and the most groups in all periods and extracts analyzed (P < 0.05), while the NbHP showed greater cell viability than control in the immediate period, dilution of the 1:500 and superior to 6HP in the most extracts at 24 h. CONCLUSION: The new experimental niobium-based gel has bleaching efficacy similar to that of gels with a high concentration of HP, and it has high cytocompatibility. CLINICAL RELEVANCE: The use of this new generation of niobium-based whitening gel associated with a low concentration of hydrogen peroxide represents the possibility of a tooth whitening with lower dentin sensitivity.

Manganese oxide increases bleaching efficacy and reduces the cytotoxicity of a 10% hydrogen peroxide bleaching gel.

OBJECTIVE: The study aims to assess the effects of a 10% H2O2 bleaching gel with different MnO2 concentrations on the bleaching efficacy (BE), degradation kinetics (DK) of H2O2, and trans-amelodentinal cytotoxicity (TC). MATERIALS AND METHODS: Standardized bovine enamel/dentin disks (n = 96) were placed in artificial pulp chambers, and the bleaching gels were applied for 45 min. Thus, the following groups were established: (G1) no treatment (negative control/NC); (G2) 35% H2O2 (positive control/PC); (G3) 10% H2O2; (G4) 10% H2O2 + 2 mg/mL MnO2; (G5) 10% H2O2 + 6 mg/mL MnO2; and (G6) 10% H2O2 + 10 mg/mL MnO2. After analyzing bleaching efficacy (ΔE00 and ΔWI), the degradation kinetics of H2O2 and trans-amelodentinal cytotoxicity were determined (n = 8, ANOVA/Tukey; p < 0.05). RESULTS: G6 presented BE (ΔE00 and ΔWI) statistically similar to G2, which represented conventional in-office bleaching (p = 0.6795; p > 0.9999). A significant reduction in the diffusion of H2O2 occurred in G3, G4, G5, and G6 compared to G2 (p < 0.0001). The highest DK of H2O2 occurred in G6 (p < 0.0001), which had the lowest TC in comparison with all other bleached groups (p ≤ 0.0186). CONCLUSION: The addition of 10 mg/mL of MnO2 in a 10% H2O2 bleaching gel potentiates the degradation of this reactive molecule, which increases the BE of the product and decreases TC. CLINICAL SIGNIFICANCE: Replacing a 35% H2O2 gel commonly used for conventional in-office dental bleaching by a 10% H2O2 gel containing 10 mg/mL of MnO2 reduces the cytotoxicity of this professional therapy, maintaining its excellent esthetic efficacy.

Pro-inflammatory mediators expression by pulp cells following tooth whitening on restored enamel surface.

This paper aimed to assess the influence of adhesive restoration interface on the diffusion of hydrogen peroxide (H2O2), indirect toxicity, and pro-inflammatory mediators expression by odontoblast-like cells, after in-office tooth whitening. Dental cavities prepared in bovine enamel/dentin discs were adhesively restored and subjected or not to hydrolytic degradation (HD). A whitening gel with 35% H2O2 (WG) was applied for 45 min onto restored and non-restored specimens adapted to artificial pulp chambers giving rise to the groups: SD- intact discs (control); SD/HP- whitened intact discs; RT/HP- restored and whitened discs; and RT/HD/HP- restored and whitened discs subjected to HD. The extracts (culture medium + WG components diffused through enamel/dentin/restoration interface) were collected and applied to odontoblast-like MDPC-23 cells. The study evaluated the amount of H2O2 in the extracts, as well as the cell viability (CV), cell morphology (CM), and gene expression of inflammatory mediators (TNF-α and COX-2) by the pulp cells exposed to the extracts (ANOVA and Tukey tests; 5% significance). All whitened groups presented lower CV than SD (control; p<0.05). The highest CV reduction and gene expression of TNF-α and COX-2 was observed in the RT/HD/HP group in comparison with SD/HP and RT/HP (control; p<0.05). CM alterations occurred in all whitened groups. The intensity of these cell side effects was directly related with the amount of H2O2 in the extracts. We concluded that adhesive restoration of dental cavity increases the H2O2 diffusion after in-office whitening, enhancing the indirect toxicity of this therapy and trigger pro-inflammatory overexpression by MDPC-23 cells.

Strategy for reducing cytotoxicity and obtaining esthetic efficacy with 15 min of in-office dental bleaching.

OBJECTIVES: Evaluate in vitro the esthetic efficacy and cytotoxicity of a bleaching gel containing 35% hydrogen peroxide (BG-35%H2O2), applied for different time intervals, on enamel coated or not with polymeric biomaterials. MATERIALS AND METHODS: Nanofiber scaffolds (NSc) and a primer catalyst (PrCa) were used to coat the bovine enamel/dentin discs before the application of BG-35%H2O2, according to the following groups: G1-negative control (NC, without treatment); G2, G3, and G4-BG-35%H2O2 applied for 3 × 15, 2 × 15, and 15 min; G5, G6, and G7-BG-35%H2O2 applied on enamel coated with NSc and PrCa for 3 × 15; 2 × 15, and 15 min, respectively. The culture medium with components of gel diffused through the discs was applied on MDPC-23 cells, which were evaluated regarding to viability (VB), integrity of the membrane (IM), and oxidative stress (OxS). The quantity of H2O2 diffused and esthetic efficacy (ΔE/ΔWI) of the dental tissues were also analyzed (ANOVA/Tukey; p < 0.05). RESULTS: Only G7 was similar to G1 regarding VB (p > 0.05). The lowest value of H2O2 diffusion occurred in G4 and G7, where the cells exhibited the lowest OxS than G2 (p < 0.05). Despite G5 showing the greatest ΔE regarding other groups (p < 0.05), the esthetic efficacy observed in G7 was similar to G2 (p > 0.05). ΔWI indicated a greater bleaching effect for groups G5, G6, and G7 (p < 0.05). CONCLUSION: Coating the dental enamel with polymeric biomaterials reduced the time and the cytotoxicity of BG-35%H2O2. CLINICAL SIGNIFICANCE: Coating the dental enamel with polymeric biomaterials allows safer and faster BG-35%H2O2 application.

Influence of smoking on oral cells genotoxicity after at-home bleaching using 22% carbamide peroxide: a cohort study.

OBJECTIVE: This study evaluated the influence of smoking on the oral cells genotoxicity before and after at-home bleaching using 22% carbamide peroxide (CP). MATERIALS AND METHODS: This is a prospective observational analytics cohort study which evaluated nonsmokers (NS; n = 24) and smokers (S; n = 16) patients. At-home bleaching was performed using 22% CP gel in individual trays for 1 h per day for 14 days in both groups. Scrapped cells from marginal gums were collected before the bleaching treatment (D0-baseline) and 1 day (D1), 15 days (D15), and 1 month (D30) after its finishing. Cells were stained with Giemsa 10%, and the micronucleus (MN) and metanuclear alterations (MA) were counted by a trained operator in 1000 cells per patient. The collections and data analysis occurred blindly. Data was analyzed by Kruskal-Wallis, Dunn, and Mann-Whitney test (α = 0.05). RESULTS: MN frequency was not influenced by smoking or bleaching. An increase of MA was observed between D0 and D30 for both groups (p < 0.001); however, no statistical difference was found between NS and S (p > 0.05) in the evaluation times. CONCLUSION: Smoking associated with 22% carbamide peroxide gel for at-home bleaching does not show genotoxic potential analyzed by the MN counts. However, a significant increase of MA was found for smokers and nonsmokers. CLINICAL RELEVANCE: Despite of the increase in MA, smoking associated with 22% CP peroxide at-home bleaching showed no important genotoxic potential (MN) for oral cells. Therefore, at-home bleaching treatment is safe for nonsmokers and smokers even with a high carbamide peroxide concentration of 22%.

Photothermal-Enhanced Fenton-like Catalytic Activity of Oxygen-Deficient Nanotitania for Efficient and Safe Tooth Whitening.

The growing demand for charming smiles has led to the popularization of tooth bleaching procedures. Current tooth bleaching products with high-concentration hydrogen peroxide (HP, 30-40%) are effective but detrimental due to the increased risk of enamel destruction, tooth sensitivity, and gingival irritation. Herein, we reported a less-destructive and efficient tooth whitening strategy with a low-concentration HP, which was realized by the remarkably enhanced Fenton-like catalytic activity of oxygen-deficient TiO2 (TiO2-x). TiO2-x nanoparticles were synthesized with a modified solid-state chemical reduction approach with NaBH4. The Fenton-like activity of TiO2-x was optimized by manipulating oxygen vacancy (OV) concentration and further promoted by the near-infrared (NIR)-induced photothermal effect of TiO2-x. The TiO2-x sample named BT45 was chosen due to the highest methylene blue (MB) adsorption ability and Fenton-like activity among acquired samples. The photothermal property of BT45 under 808 nm NIR irradiation was verified and its enhancement on Fenton-like activity was also studied. The BT45/HP + NIR group performed significantly better in tooth whitening than the HP + NIR group on various discolored teeth (stained by Orange II, tea, or rhodamine B). Excitingly, the same tooth whitening performance as the Opalescence Boost, a tooth bleaching product containing 40% HP, was obtained by a self-produced bleaching gel based on this novel system containing 12% HP. Besides, negligible enamel destruction, safe temperature range, and good cytocompatibility of TiO2-x nanoparticles also demonstrated the safety of this tooth bleaching strategy. This work indicated that the photothermal-enhanced Fenton-like performance of the TiO2-x-based system is highly promising in tooth bleaching application and can also be extended to other biomedical applications.

Effect of different bleaching techniques on DNA damage biomarkers in serum, saliva, and GCF.

Bleaching agents containing a high concentration of H2O2 in the dental market lead to formation of reactive oxygen species, which have genotoxic effects. However, ozone bleaching, one of the most effective oxidants known, stimulates blood circulation and immune response and thus it has strong antimicrobial activity against viruses, bacteria, fungi, and protozoa. For these reasons, one of our hypothesis was ozone bleaching would reduce local and systemic DNA damage in the body. Hence, we aimed to determine the oxidative DNA damage biomarker levels in serum, saliva, and gingival crevicular fluid (GCF) by measuring 8-hydroxy-2'-deoxyguanosine (8-OHdG) after different bleaching methods.Forty-eight volunteers who requested dental bleaching were divided into three treatment groups (n = 16). Group 1: ozone bleaching with the ozone-releasing machine; Group 2: chemical bleaching with 40% hydrogen peroxide (H2O2) gel; Group 3: 40% H2O2 gel activated with the diode laser. Initial and post-operative (immediately after bleaching and two weeks later) color measurements were performed with a spectrophotometer. The color changes were calculated with the CIEDE2000 (ΔE 00) formula. 8-OHdG levels in serum, saliva, and GCF samples were determined with ELISA. All three treatments resulted in efficient and statistically similar bleaching. The 8-OHdG levels in the serum and saliva were not affected by all bleaching methods (p > 0.05), but a temporary increase was observed in the GCF for chemical and laser-assisted groups except the ozone group (p > 0.05). According to the findings, chemical and laser-assisted bleaching can affect DNA damage locally but not systemically. Bleaching with ozone may eliminate this local DNA damage.

Influence of Tooth Pigmentation on H2O2 Diffusion and Its Cytotoxicity After In-office Tooth Bleaching.

CLINICAL RELEVANCE: Pigments in tooth structures affect the diffusion of H2O2 through enamel and dentin. The bleaching methodology can be impacted. SUMMARY: Objective: The aim of this study was to evaluate the influence of the presence of pigments in tooth structures on the trans-enamel and trans-dentin diffusion of hydrogen peroxide (H2O2) and its cytotoxicity after carrying out an in-office bleaching therapy.Methods and Materials: A bleaching gel with 35% H2O2 was applied for 45 minutes (three times for 15 minutes) on enamel and dentin discs (n=6), either previously submitted to the intrinsic pigmentation protocol with a concentrated solution of black tea, or not, defining the following groups: G1, unbleached untreated discs (control 1); G2, unbleached pigmented discs (control 2); G3, bleached untreated discs; G4, bleached pigmented discs. The discs were adapted to artificial pulp chambers, which were placed in wells of 24-well plates containing 1 mL culture medium (Dulbecco's modified Eagle's medium [DMEM]). After applying the bleaching gel on enamel, the extracts (DMEM + components of bleaching gel that diffused through the discs) were collected and then applied on the cultured MDPC-23 odontoblast-like cells. Cell viability (methyl tetrazolium assay and Live & Dead, Calcein AM, and ethidium homodimer-1 [EthD-1] probes), the amount of H2O2 that diffused through enamel and dentin (leuco-crystal violet product), and the H2O2-mediated oxidative cell stress (SOx) and components of degradation were assessed (analysis of variance/Tukey; α=0.05).Results: There was no significant difference between the groups G1 and G2 for all the parameters tested (p>0.05). Reduction in the trans-enamel and trans-dentin diffusion of H2O2 occurred for G4 in comparison with G3. Significantly lower cell viability associated with greater oxidative stress was observed for G3 (p<0.05). Therefore, in-office tooth bleaching therapy performed in pigmented samples caused lower cytotoxic effects compared with untreated samples submitted to the same esthetic procedure (p<0.05).Conclusion: According to the methodology used in this investigation, the authors concluded that the presence of pigments in hard tooth structures decreases the trans-enamel and trans-dentin diffusion of H2O2 and the toxicity to pulp cells of an in-office bleaching gel with 35% H2O2.

Increased whitening efficacy and reduced cytotoxicity are achieved by the chemical activation of a highly concentrated hydrogen peroxide bleaching gel.

OBJECTIVE: This study was designed for the chemical activation of a 35% hydrogen peroxide (H2O2) bleaching gel to increase its whitening effectiveness and reduce its toxicity. METHODOLOGY: First, the bleaching gel - associated or not with ferrous sulfate (FS), manganese chloride (MC), peroxidase (PR), or catalase (CT) - was applied (3x 15 min) to enamel/dentin discs adapted to artificial pulp chambers. Then, odontoblast-like MDPC-23 cells were exposed for 1 h to the extracts (culture medium + components released from the product), for the assessment of viability (MTT assay) and oxidative stress (H2DCFDA). Residual H2O2 and bleaching effectiveness (DE) were also evaluated. Data were analyzed with one-way ANOVA complemented with Tukey's test (n=8. p<0.05). RESULTS: All chemically activated groups minimized MDPC-23 oxidative stress generation; however, significantly higher cell viability was detected for MC, PR, and CT than for plain 35% H2O2 gel. Nevertheless, FS, MC, PR, and CT reduced the amount of residual H2O2 and increased bleaching effectiveness. CONCLUSION: Chemical activation of 35% H2O2 gel with MC, PR, and CT minimized residual H2O2 and pulp cell toxicity; but PR duplicated the whitening potential of the bleaching gel after a single 45-minute session.

Comparison of diffusion, cytotoxicity and tissue inflammatory reactions of four commercial bleaching products against human dental pulp stem cells.

Multiple side effects related to bleaching were found to occur in the dental pulp tissue, including decreased cell metabolism and viability. In this work we evaluated the in vitro diffusion capacity, cytotoxicity and biocompatibility of four commercial bleaching products on stem cells from human dental pulp (hDPSCs). Two commercial bleaching gels hydrogen peroxide-based (HP), Norblanc Office 37.5% (Nor-HP) and Opalescence Boost 40% (Opal-HP) were applied for 30 min to enamel/dentine discs. Another two gels from the same manufacturers, 16% carbamide peroxide-based (CP), Norblanc Home (Nor-CP) and Opalescence CP 16% (Opal-CP), were applied for 90 min. The diffusion of HP was analysed by fluorometry. Cytotoxicity was determined using the MTT assays, the determination of apoptosis, immunofluorescence assays and intracellular reactive oxygen species (ROS) level. Tissue inflammatory reactions were evaluated histopathologically in rats. Statistical differences were performed by one-way ANOVA and Bonferroni post-test (α < 0.05). Normon products showed lower cytotoxicity and diffusion capacity than the Ultradent products. A high intracellular ROS level was measured in hDPSCs after exposure to Opal-HP. Finally, a severe necrosis of both coronal and radicular pulp was observed with Opal-HP. Similar concentrations of hydrogen peroxide and carbamide peroxide in a variety of bleaching products exhibited different responses in cells and dental pulp tissue, suggesting that bleaching products contain unknown agents that could influence their toxicity.

Chronic exposure to 35% carbamide peroxide tooth bleaching agent induces histological and hematological alterations, oxidative stress, and inflammation in mice.

Previous studies have demonstrated the side effects of tooth whiteners on the gastric mucosa. However, the impact of dental bleaching products on the liver, kidney, and heart remains obscure. The present study investigated the toxic potential of 35% carbamide peroxide (CPO) containing tooth whitening product (TWP) on the liver, kidney, heart, and stomach of mice, pointing to the role of oxidative stress and inflammation. Mice received 250 or 500 mg/kg body weight CPO-TWP orally for 3 weeks and samples were collected for analyses. Both doses of CPO-TWP induced a significant increase in circulating liver, kidney, and heart function markers. CPO-TWP-administered mice showed several histological alterations and a significant increase in liver, kidney, heart, and stomach lipid peroxidation levels along with diminished glutathione, superoxide dismutase, and catalase. In addition, administration of CPO-TWP provoked anemia, leukocytosis, and a significant increase in circulating levels of pro-inflammatory cytokines. In conclusion, exposure to 35% CPO-TWP induced functional, histological, and hematological alterations, oxidative stress, and inflammation in mice. Therefore, the frequent use of tooth bleaching agents should be monitored very carefully to avoid the application of excess amounts as well as the intake.

Evaluation of biochemical changes in dental tissues after different office bleaching methods.

The color of the teeth is an important topic for many people and can be influenced by intrinsic and extrinsic stains. There is an increasing demand for whitening of the teeth year by year. The most popular way of whitening is "bleaching," which is the result of the breakdown of pigments located in the enamel and/or the dentin, caused by reactive oxygen species (ROS) released from bleaching agents. These bleaching agents could increase matrix metalloproteinase (MMP)-mediated collagen degradation in dentin. The aim of this study was to compare biochemical changes and oxidative stress levels of the human premolar dentin-pulp complex after three different bleaching methods containing hydrogen peroxide (H2O2) bleaching agents. Individuals, whose first four premolars were extracted for orthodontic purposes, included into the study. Group 1-Laser: bleaching gel containing 46% H2O2 (LaserWhite20 whitening gel, Biolase Technology Inc., San Clemente, CA, USA) and a diode laser activation (Ezlase 940 nm system). Group 2: 35% H2O2 containing whitening gel (Whiteness HP Maxx, FGM) and halogen light source activation (Optilux 501, Kerr, Orange, CA, USA). Group 3: 35% H2O2 containing whitening gel (Whiteness HP Maxx, FGM). Group 4-Control: No whitening treatment. According to the test results, there were no significant differences among groups in the values of cathepsin B and MMP proteolytic activities ( p > 0.05). The total ROS values released from the dentin tissue were higher than those obtained from the pulp tissue ( p < 0.05). There were significant differences among the bleaching groups in the ROS values released from the dentin tissue.

Increased whitening efficacy and reduced cytotoxicity are achieved by the chemical activation of a highly concentrated hydrogen peroxide bleaching gel

Abstract Objective This study was designed for the chemical activation of a 35% hydrogen peroxide (H2O2) bleaching gel to increase its whitening effectiveness and reduce its toxicity. Methodology First, the bleaching gel - associated or not with ferrous sulfate (FS), manganese chloride (MC), peroxidase (PR), or catalase (CT) - was applied (3x 15 min) to enamel/dentin discs adapted to artificial pulp chambers. Then, odontoblast-like MDPC-23 cells were exposed for 1 h to the extracts (culture medium + components released from the product), for the assessment of viability (MTT assay) and oxidative stress (H2DCFDA). Residual H2O2 and bleaching effectiveness (DE) were also evaluated. Data were analyzed with one-way ANOVA complemented with Tukey's test (n=8. p<0.05). Results All chemically activated groups minimized MDPC-23 oxidative stress generation; however, significantly higher cell viability was detected for MC, PR, and CT than for plain 35% H2O2 gel. Nevertheless, FS, MC, PR, and CT reduced the amount of residual H2O2 and increased bleaching effectiveness. Conclusion Chemical activation of 35% H2O2 gel with MC, PR, and CT minimized residual H2O2 and pulp cell toxicity; but PR duplicated the whitening potential of the bleaching gel after a single 45-minute session.

Análise de citotoxicidade, desmineralização e potencial clareador de géis clareadores experimentais, baseado em peróxido de carbamida 15% adicionados de nano-hidróxiapatita / Analysis of cytotoxicity, demineralization and bleaching potential of experimental bleaching gels, based on 15% carbamide peroxide added with nanohydroxyapatite

O clareamento dental é considerado um procedimento muito seguro, de efeito rápido e agradável, tornando-se um dos procedimentos mais realizados na odontologia. Contudo, o mesmo apresenta alguns efeitos colaterais, sendo o principal deles a sensibilidade dental, que pode ser causada pela citotoxidade, pela desmineralização, pela geração de espécies reativas do oxigênio na polpa dental e pela degradação da região interprismática facilitando o estimulo nos túbulos dentinários. Diante disso, a presente pesquisa avaliou a desmineralização, a citotoxidade e o potencial clareador de géis clareadores experimentais baseados em peróxido de carbamida (PC) 15%, adicionados de 5% e 10% de nano partículas de hidroxiapatita (n-Hap). Para a avaliação cromática foram utilizados 36 incisivos bovinos divididos em 3 grupos: Grupo1 PC 15%, Grupo 2 PC 15% adicionado 5% nHap e grupo 3 PC 15% com 10% n-Hap, mensurando a cor antes e depois do procedimento terapêutico clareador com auxilio de um espectrofotômetro. As coordenadas do CIELAB foram analisadas para verificação da diferença de cor (ΔE) obtida entre os grupos e dentro do próprio grupo (L*) e, após a analise estatística, foi verificado que todos os géis foram capazes de clarear e não houve diferenças entre os grupos. A citotoxidade foi verificada através da absorbância das células viáveis após o tratamento com o MTT e 1:800 das preparações de agente clareador e gel contendo 5% e 10% de n-Hap aplicadas sobre células L929. Nesse caso os grupos foram desiguais estatisticamente, apresentando o PC 15% como o mais tóxico, seguido do PC 15% adicionado de 10% de n-Hap e o melhor resultado foi obtido pelo gel acrecido de 5% de n-Hap. A análise do conteúdo mineral foi realizada pela fluorescência de raios X por dispersão de energia, onde foi necessário o uso de 15 dentes bovinos, que tiveram seus terços médios seccionados, embutidos em resina epóxi e planificados, e foram dividos em grupos de 5 CPs. Cada CP foi aferido em 8 pontos diferentes antes e depois, nos mesmos pontos da terapia clareadora. Foi então verificado que os géis experimentais apresentaram menor perda de Ca e P. No entanto, não houve diferenças estatísticas entre os grupos 2 e 3. Diante das limitações do presente estudo in vitro é possível concluir que os géis experimentais contendo n-Hap foram eficazes em reduzir a citotoxidade e desmineralização sem perder a eficácia da terapia clareadora

Dental whitening is considered a very safe, quick and pleasant procedure, making it one of the most accomplished procedures in dentistry. However, it has some side effects, the main one being sensibility, which can be caused by cytotoxicity, demineralization, oxygen arrival in the dental pulp and the degradation of the interprismatic region facilitating the stimulation in the dentin tubes. Therefore, the present study evaluated the demineralization, cytotoxicity and bleaching potential of 15% carbamide peroxide-based (PC) based bleaching gels added with 5% and 10% nano-hydroxyapatite (n-Hap) particles. For the chromatic evaluation, 36 bovine incisors were divided into 3 groups: Group 1 PC 15%, Group 2 PC 15% added 5% nHap and group 3 PC 15% with 10% n-Hap, measuring the color before and after the the CIELAB coordinates were analyzed to verify the color difference (Δe) obtained between the groups and within the group (L *). After the statistical analysis it was verified that all the gels were able to lighten and there were no differences between the groups. Cytotoxicity was verified by optical density of viable cells after treatment with MTT and 1: 800 of the bleach and gel preparations containing 5% and 10% nHap applied in L929 cells. In this case, the groups were statistically unequal, presenting 15% PC as the most toxic, followed by PC 15% added with 10% n-Hap and the best result was obtained by the 5% n-Hap increased gel. The mineral content analysis was performed by X-ray Fluorescence by energy dispersion, where it was necessary to use 15 bovine teeth, which had their middle sections sectioned, embedded in epoxy resin and planned, and were divided into groups of 5 CPs, each CP was measured at 8 different points before and after, at the same points of the bleaching therapy, then it was verified that the experimental gels presented a lower loss of Ca and P, however there were no statistical differences between groups 2 and 3. On the face of the limitations of the present in vitro study, it is possible to conclude that the experimental gels were effective in reducing the cytotoxicity and demineralization without losing the effectiveness of the bleaching therapy.

Hydrogen peroxide induces cell proliferation and apoptosis in pulp of rats after dental bleaching in vivo: Effects of the dental bleaching in pulp.

OBJECTIVE: This study provides an in vivo evaluation of the inflammatory response, levels of cell proliferation and apoptosis, and the presence of necrosis after dental bleaching with two concentrations of hydrogen peroxide (H2O2). DESIGN: Wistar rats were divided into Control (placebo gel), BLUE (20% H2O2, 1×50min), and MAXX (35% H2O2, 3×15min) groups. At 2 and 30days, the rats were killed (n=10). The jaws were processed for histology analysis and PCNA and Caspase-3-cleaved immunohistochemistry, and data were submitted to the Mann-Whitney or ANOVA test (P<0.05). RESULTS: At 2days, the MAXX group showed necrosis and the BLUE group revealed moderate inflammation on the occlusal third of the crown (P<0.05). At 30days, tertiary dentin had formed and there was an absence of inflammation. The level of cell proliferation was higher in the middle third of the BLUE group (P<0.05), and cervical of MAXX at 2days (P<0.05), decreasing at 30days. The apoptosis was present at 2days, particularly in the cervical third of the crown in the bleached groups (P<0.05), with a decrease only at 30days in the BLUE group (P<0.05). CONCLUSIONS: The concentration of H2O2 influences effects on the pulp tissue, where a higher concentration of H2O2 can cause necrosis in the pulp and a prolonged effect within the apoptotic process; lower concentrations of H2O2 provide moderate inflammation, cell proliferation and apoptosis with a reduction of these processes over time.

Influence of enamel/dentin thickness on the toxic and esthetic effects of experimental in-office bleaching protocols.

OBJECTIVES: This paper aims to assess the whitening effectiveness and toxicity of tooth-bleaching protocols applied to enamel/dentin disks simulating mandibular incisors (ICs) and premolars (PMs). MATERIALS AND METHODS: A 10% hydrogen peroxide (H2O2) gel was applied for 3 × 15, 1 × 15, or 1 × 5 min to enamel/dentin disks simulating mandibular ICs and PMs, and the trans-enamel and trans-dentinal diffusion products were applied to human dental pulp cells (1 h). Professional therapy (35% H2O2-3 × 15 min) was used as positive control, and non-bleached samples were used as negative control. Cell viability and morphology, oxidative stress generation, and odontoblastic marker expression were assessed. The H2O2 diffusion and enamel color change (ΔE) were also analyzed. RESULTS: The 10% H2O2 gel induced significant cell viability reduction only when applied 3 × 15 min, with the intensity of oxidative stress and down-regulation of odontoblastic markers being higher in the IC group. The other experimental bleaching protocols caused slight alterations regarding the cell parameters evaluated, with intensity being related to enamel/dentin thickness. These effects were also correlated with higher H2O2 diffusion in the IC group. ΔE values similar as positive control were found for the 10% 3 × 15 and 1 × 15 protocols on IC group, after 4 and 6 sessions. CONCLUSION: Application of a 10% H2O2 bleaching gel for 15 or 45 min to thin dental substrate significantly minimizes cell toxicity in comparison with highly concentrated gels associated with similar esthetic outcomes by increasing the number of bleaching sessions. CLINICAL RELEVANCE: Bleaching gels with 10% H2O2 applied in small teeth for short periods may be an interesting alternative to obtain whitening effectiveness without causing toxicity to pulp cells, which may be able to reduce the tooth hypersensitivity claimed by patients.

Toxicity and efficiency study of plant extracts-based bleaching agents.

OBJECTIVES: Tooth bleaching is one of the most required dental esthetic treatments. However, it can generate side effects like oral irritation, enamel alteration, tooth sensitivity, especially caused by hydrogen peroxide, the main bleaching component of the commercial products. Therefore, development of new tooth bleaching agents, based on natural products, with comparable esthetic results and lower side effects is needed. The aim of this study was to evaluate the biological effects and bleaching efficacy of four experimental bleaching agents, derived from fruit juices, against the commercially available Opalescence (Ultradent, USA). MATERIALS AND METHODS: Organic acid composition of the gels was characterized by HPLC. Bleaching efficiency was tested by spectrophotometry on composite restorative materials. Biological testing was done in vitro, on human fibroblasts. Cells were exposed to dilutions of the bleaching gel-conditioned medium. Viability was measured by MTS, apoptosis by FACS-AnnexinV FITC/Propidium iodide, NF-kB activation by western blot, malondyaldehide, and superoxide dismutase activity by spectrophotometry. RESULTS: All gels exhibited physical stability and dental bleaching capabilities. Experimental gels induced significantly better viability and apoptosis rates, lower lipid peroxidation, and increased antioxidant defense, compared to Opalescence. CONCLUSIONS: The studied experimental gel formulations exhibited a good safety profile in vitro, as well as bleaching efficiency on restorative composite materials. CLINICAL RELEVANCE: These data open new possibilities for the use of new natural products in dental bleaching treatments that can insure significant esthetic results and lower side effects.

Inflammatory response of human dental pulp to at-home and in-office tooth bleaching.

OBJECTIVE:: This study evaluated the inflammatory responses of human dental pulp after the use of two bleaching techniques. MATERIAL AND METHODS:: Pulp samples were collected from human third molars extracted for orthodontic reasons and divided into three groups: control - no tooth bleaching (CG) (n=7); at-home bleaching with 15% carbamide peroxide (AH) (n = 10), and in-office bleaching with 38% hydrogen peroxide (IO) (n=12). Pulps were removed and stained with hematoxylin-eosin for microscopic analysis of inflammation intensity, collagen degradation, and pulp tissue organization. Immunohistochemistry was used to detect mast cells (tryptase+), blood vessels (CD31+), and macrophages (CD68+). Chi-square, Kruskal-Wallis, and Mann Whitney tests were used for statistical analysis. The level of significance was set at p<.05. RESULTS:: The inflammation intensity and the number of macrophages were significantly greater in IO than in AH and CG (p<0.05). The results of CD31+ (blood vessels per mm2) were similar in CG (61.39±20.03), AH (52.29±27.62), and IO (57.43±8.69) groups (p>0.05). No mast cells were found in the pulp samples analyzed. CONCLUSION:: In-office bleaching with 38% hydrogen peroxide resulted in more intense inflammation, higher macrophages migration, and greater pulp damage then at-home bleaching with 15% carbamide peroxide, however, these bleaching techniques did not induce migration of mast cells and increased the number of blood vessels.

Inflammatory response of human dental pulp to at-home and in-office tooth bleaching

ABSTRACT Tooth bleaching is a technique of choice to obtain a harmonious smile, but bleaching agents may damage the dental pulp. Objective: This study evaluated the inflammatory responses of human dental pulp after the use of two bleaching techniques. Material and Methods: Pulp samples were collected from human third molars extracted for orthodontic reasons and divided into three groups: control - no tooth bleaching (CG) (n=7); at-home bleaching with 15% carbamide peroxide (AH) (n = 10), and in-office bleaching with 38% hydrogen peroxide (IO) (n=12). Pulps were removed and stained with hematoxylin-eosin for microscopic analysis of inflammation intensity, collagen degradation, and pulp tissue organization. Immunohistochemistry was used to detect mast cells (tryptase+), blood vessels (CD31+), and macrophages (CD68+). Chi-square, Kruskal-Wallis, and Mann Whitney tests were used for statistical analysis. The level of significance was set at p<.05. Results: The inflammation intensity and the number of macrophages were significantly greater in IO than in AH and CG (p<0.05). The results of CD31+ (blood vessels per mm2) were similar in CG (61.39±20.03), AH (52.29±27.62), and IO (57.43±8.69) groups (p>0.05). No mast cells were found in the pulp samples analyzed. Conclusion: In-office bleaching with 38% hydrogen peroxide resulted in more intense inflammation, higher macrophages migration, and greater pulp damage then at-home bleaching with 15% carbamide peroxide, however, these bleaching techniques did not induce migration of mast cells and increased the number of blood vessels.

Clinical Evaluation of Genotoxicity of In-office Bleaching.

OBJECTIVE: The aim of this study was to evaluate the genotoxicity of in-office bleaching with 35% hydrogen peroxide in epithelial cells from the gingival and lip tissues. METHODS AND MATERIALS: Thirty volunteers with central incisors shade A1 or darker were selected for this study. The gingival tissue of the teeth to be bleached was isolated with a light-polymerized resin dam, and the 35% hydrogen peroxide gel was administered during three 15-minute applications over the course of the 45-minute application period. Two bleaching sessions with a one-week interval in between were performed. Exfoliated oral mucosa gingival epithelial cells and upper lip lining were collected at baseline and one month after the in-office dental bleaching. The scraped cells were placed on clean glass slides and smears were prepared. After staining with Giemsa solution, two blinded examiners performed cell and micronuclei counts under a 100× optical microscope. Tooth sensitivity was evaluated using the Visual Analogue Scale (VAS). Shade evaluation was recorded before and one month after the bleaching treatment with the value-oriented shade guide Vita Bleachedguide 3D-MASTER and the spectrophotometer Vita Easyshade. Data from the shade guide units and the micronuclei (MN) frequency were subjected to a Mann-Whitney test (α=0.05). The overall difference between before and one month after the bleaching treatment (ΔE and ΔSGU), absolute risk, and intensity of tooth sensitivity (TS) were calculated, as was the 95% confidence interval (CI). RESULTS: The frequency of MN was not increased after bleaching with 35% hydrogen peroxide in both study groups (p>0.05). The absolute risk of TS of the participants was 93% (95% CI, 79%-98%), with a mean VAS intensity of 5.7 ± 2.9 (95% CI, 4.6-6.8). Meaningful whitening was observed after bleaching. The change in shade guide units in the Bleachedguide 3D-MASTER was 2.3 ± 1.4. In terms of ΔE, the change in color was 7.7 ± 3.5. CONCLUSIONS: The in-office bleaching did not induce DNA damage to the gingival and lip tissue during the bleaching period. Although effective whitening was observed, most of the participants experienced TS.