Effect of bleaching agents on enamel demineralization and elastic modulus of bovine dentin organic matrix

Orientadores: Marcelo Giannini, Cinthia Pereira Machado TabchouryTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O objetivo geral deste estudo foi avaliar o efeito de géis clareadores contendo cálcio ou fosfato de cálcio amorfo (ACP) no módulo de elasticidade da dentina bovina desmineralizada e desmineralização do esmalte hígido ou com lesão inicial de cárie artificial. Capítulo 1: Este estudo avaliou o efeito de agentes clareadores no módulo de elasticidade (ME) da matriz orgânica da dentina bovina. Oitenta e cinco fatias foram obtidas de dentes bovinos e separadas em 5 grupos: grupo controle - sem tratamento (GC), peróxido de hidrogênio 4% (PH4), PH4+0,05% Ca (HP4/Ca), PH 7,5% + ACP (PH7,5) e peróxido de carbamida 10% (PC10). Os grupos PH4, PH4/Ca e PC10 foram tratados com os géis clareadores por 8 horas / dia durante 14 dias, enquanto as amostras do grupo PH7,5 foi submetida ao clareador por 30 minutos, 2 vezes ao dia, durante 14 dias. O esmalte das amostras foi removido e foram preparados 17 espécimes (0,5 x 1,7 x 7,0 mm) por grupo. Em seguida, estas foram desmineralizados em solução de ácido fosfórico 10% por 5 horas e o ME foi mensurado: 24 horas, 7 e 14 dias após o clareamento, utilizando o teste de micro-flexão de 3 pontos. Os dados foram submetidos a ANOVA e teste de Fisher (p<0,05). As amostras clareadas após 24 horas e 7 dias mostram menor ME que o GC. Os grupos clareados foram similares ao GC após 14 dias, exceto o grupo PH7,5. O uso de peróxidos pode promover diminuição do módulo de elasticidade da matriz orgânica da dentina bovina. Capítulo 2: O propósito nesta parte da tese foi avaliar o efeito de um clareador experimental e um comercial no esmalte sadio (ES) ou esmalte com lesão inicial de cárie artificial (LC), utilizando microscópio confocal laser de varredura (CLSM). Oitenta blocos (4 x 5 x 5 mm) de esmalte bovino foram usados, sendo que quarenta destes foram desmineralizados com ciclagem de pH para induzir a lesão inicial de cárie artificial. Oito grupos experimentais foram formados a partir dos produtos clareadores e a condição do esmalte dental (ES ou LC), com n=10: Grupos ES: G1 - sem tratamento (controle); G2 - peróxido de hidrogênio 4% (PH4); G3: PH4 contendo 0,05%Ca (Ca); G4 - peróxido de hidrogênio 7,5% (PH7,5) contendo fosfato de cálcio amorfo (ACP). Grupos LC: G5 - não clareado; G6 - PH4; G7 - PH4 contendo Ca; G8 - PH7,5 contendo ACP. Os grupos G2, G3, G6 e G7 foram tratados com o gel clareador por 8 horas/dia durante 14 dias, enquanto as amostras dos grupos G4 e G8 foram submetidas ao clareador por 30 minutos/duas vezes ao dia, durante 14 dias. Os blocos de esmalte foram corados com solução de rodamina e área fluorescente de desmineralização foi quantificada utilizando CLSM. Os dados foram submetidos a ANOVA e teste de Fisher (p<0,05). Para ES, os tratamentos clareadores aumentaram significativamente a área de desmineralização quanto comparado com os grupos não clareados, entretanto, para LC não foi observado diferença estatística significante entre os grupos. A adição de ACP e Ca na composição dos géis clareadores não resultou em redução da desmineralização promovida pelos tratamentos clareadoresAbstract: The aim of this study was to evaluate the effect of bleaching agents containing calcium or amorphous calcium phosphate (ACP) on the elastic modulus of demineralized bovine dentin and demineralization in sound enamel or early artificial caries lesion. Chapter 1: This study evaluated the effect of tooth whitening agents on the elastic modulus (EM) of bovine dentin organic matrix. Eighty?five slices were obtained from bovine teeth and divided into five groups: unbleached control group (CG), 4% hydrogen peroxide (4HP), 4HP+0.05% Ca (4HP/Ca), 7.5% HP (7.5HP) and 10% carbamide peroxide (10CP). The 4HP, 4HP/Ca and 10CP groups were treated with the whitening agents for 8 hours/day during 14 days, while the samples of 7.5HP group were exposed to peroxides for 30 minutes twice a day during 14 days. The enamel of the samples was removed and 17 dentin specimens (0.5 x 1.7 x 7.0 mm) were prepared per group. The specimens were demineralized in 10% phosphoric acid solution for 5 hours and E was assessed using a micro-flexural three-point bend method at 24 hours, 7 and 14 days post-bleaching. The mean values of EM for each group were statistically analyzed using ANOVA and Fisher's test (p<0.05). Bleached specimens tested after 24 hours and 7 days showed lower EM than CG. The bleached groups were similar to CG after 14 days, except for the 7.5HP group. The use of peroxides can promoted decrease of EM of bovine dentin organic matrix. Whitening agents can significantly affect of the dentin organic matrix and irreversible damage is observed for selected agents. Chapter 2: The purpose of this study was evaluated to effect of experimental and one commercial bleaching agents on the sound enamel (SE) and with early artificial caries lesions (CL) enamel using confocal laser scanning microscopy (CLSM). Eighty blocks (4 mm thickness x 5 wide x 5 length) of bovine enamel were used and half of them were demineralized with a pH cycling to induce artificial caries lesions. Eight experimental groups were investigated following the bleaching treatments or not and SE or CL (n=10): SE groups: G1 - unbleached (control); G2 - 4% hydrogen peroxide (4HP); G3 - 4HP containing 0.05% Ca (Ca); G4 - 7.5% hydrogen peroxide (7.5HP) containing amorphous calcium phosphate (ACP). CL groups: G5 - unbleached; G6 - 4HP; G7 ? 4HP containing Ca; G8 ? 7.5HP containing ACP. The G2, G3, G6, G7 groups were treated with the bleaching agents for 8 hours/day during 14 days, while the samples of G4 and G8 groups were exposed to bleaching agent for 30 minutes twice a day during 14 days. The enamel blocks were stained with rhodamine solution and the quantification of fluorescence demineralization areas of the samples were evaluated using a CLSM. Data were analyzed using ANOVA and Fisher's tests (p<0.05). For the SE, the bleaching treatments significantly increased the demineralization area when compared to unbleached group, however, in CL no statistically significant difference was observed among the groups. The addition of ACP or Ca in the composition of the whitening products did not result in the decreasing of the enamel demineralization promoted by bleaching treatmentsDoutoradoMateriais DentariosDoutor em Materiais Dentário

Enamel susceptibility to red wine staining after 35% hydrogen peroxide bleaching

Concern has been expressed regarding the staining of enamel surface by different beverages after bleaching. This study investigated the influence of 35% hydrogen peroxide bleaching agents on enamel surface stained with wine after whitening treatments. Flat and polished bovine enamel surfaces were submitted to two commercially available 35% hydrogen peroxide bleaching agents or kept in 100% humidity, as a control group (n = 10). Specimens of all groups were immersed in red wine for 48 h at 37°C, immediately, 24 h or 1 week after treatments. All specimens were ground into powder and prepared for the spectrophotometric analysis. Data were subjected to two-way analysis of variance and Fisher's PLSD test at 5% significance level. The amount of wine pigments uptake by enamel submitted to bleaching treatments was statistically higher than that of control group, independently of the evaluation time. Results suggested that wine staining susceptibility was increased by bleaching treatments

Influence Of Surface Treatments And Adhesive Systems On Lithium Disilicate Microshear Bond Strength

The purpose of this study was to evaluate the microshear bond strength of ceramic prosthetic structures reinforced by lithium disilicate cemented with resin cement under conditions of different surface treatments and adhesive systems. Seventy-two rectangular blocks of lithium disilicate (6.5 mm long × 5 mm wide × 1 mm thick) were fabricated, air abraded with 50-&#956;m Al2O3 particles and divided into six groups (n=12) depending on the surface pretreatments. The groups were as follows: 10HF/S/SBM: 10% hydrofluoric acid etched for 20 s (10HF) + silane (S) + Adper Scotchbond Multi-Purpose (SBM); 10HF/S/SB: 10HF + S + Single Bond Universal (SB); 10HF/SBM; 10HF/SB; S/SBM and S/SB. Two 1-mm-long plastic tubes were placed on the specimens, filled with RelyX ARC resin cement and cured for 20 s per tube. The plastic tube was removed, and the microshear bond strength was tested. Data were submitted to analysis of variance and Tukey's tests (&#945;=0.05). Fractured specimens were observed under optical microscopy. For both adhesives, the bond strengths (MPa) of groups treated with acid-etching and silane (10HF/S/SB: 24.82, 10HF/S/SBM: 24.90) were higher (p&lt;0.001) than those of groups treated with acid-etching (10HF/SB: 16.47, 10HF/SBM: 19.94) only or only silane (S/SB: 18.42, S/SBM: 13.24). All groups showed a predominance of failure adhesive. The silanization should be a clinical step in cementing ceramic structures reinforced by lithium disilicate, even with the application of universal adhesive that contains silane in its formulation.27445846

Decomposition rate, pH, and enamel color alteration of at-home and in-office bleaching agents

This study evaluated the decomposition rate (DR), pH, enamel color alteration (DE) and whiteness index (DWI) promoted by at-home and in-office bleaching. Enamel surface was submitted to (n=10): at-home (10%, 15%, 20% carbamide peroxide - CP, 6% hydrogen peroxide -HP) and three 35% HP agents with light irradiation (LED, laser, and halogen) or no treatment (control). The DR and pH of agents were measured after 0, 2, 4, 6 and 8 h (at-home) or after 5, 15, 20, 30 and 40 min (in-office). Color parameters (L*, a*, b*, DE, DWI) were determined at baseline and after bleaching. DR, pH, L*, a*, b* data were analyzed by one-way (at-home) or two-way (in-office) repeated measures ANOVA and Tukey test. DE and DWI, by one-way (at-home) or two-way (in-office) ANOVA and Tukey test. DR of at-home agents was similar after 6 and 8 h (p>0.05), with pH close to neutral (6.5 to 6.9, CP) or acid 5.9 (6% HP). From 4 to 8 h, DE was higher for 15% and 20% CP compared with 10% CP (p0.05). One 35% HP showed alkaline pH, and the others, pH 0.05), com pH próximo ao neutro (6,5 a 6,9 - CP) ou ácido (5,9- HP 6%). De 4 a 8 h, a ∆E foi maior para CP 15% e 20% comparado ao CP 10% (p0.05). Um agente HP 35% exibiu pH alcalino, e os outros, pH<5.5. Os agentes clareadores caseiros poderiam ser aplicados por 2 h (15%, 20% CP e 6% HP) e 4 h (CP 10%), e os agentes clareadores de consultório, até 40 min em uma aplicação, sem lu

The impact of different surface treatments on the shear bond strength of orthodontic metal brackets applied to different CAD/CAM composites

To investigate the shear bond strength (SBS) of orthodontic metal brackets applied to different CAD/CAM composites treated with different surface treatments. Specimens of two CAD/CAM composites were obtained of Lava Ultimate (LU; n=60) and Brilliant Cri

Effect Of Sodium Hypochlorite And Peracetic Acid On The Surface Roughness Of Acrylic Resin Polymerized By Heated Water For Short And Long Cycles.

To evaluate the surface roughness of acrylic resin submitted to chemical disinfection via 1% sodium hypochlorite (NaClO) or 1% peracetic acid (C2H4O3). The disc-shaped resin specimens (30 mm diameter ×4 mm height) were polymerized by heated water using two cycles (short cycle: 1 h at 74°C and 30 min at 100°C; conventional long cycle: 9 h at 74°C). The release of substances by these specimens in water solution was also quantified. Specimens were fabricated, divided into four groups (n = 10) depending on the polymerization time and disinfectant. After polishing, the specimens were stored in distilled deionized water. Specimens were immersed in 1% NaClO or 1% C2H4O3 for 30 min, and then were immersed in distilled deionized water for 20 min. The release of C2H4O3 and NaClO was measured via visual colorimetric analysis. Roughness was measured before and after disinfection. Roughness data were subjected to two-way ANOVA and Tukey's test. There was no interaction between polymerization time and disinfectant in influencing the average surface roughness (Ra, P = 0.957). Considering these factors independently, there were significant differences between short and conventional long cycles (P = 0.012), but no significant difference between the disinfectants hypochlorite and C2H4O3 (P = 0.366). Visual colorimetric analysis did not detect release of substances. It was concluded that there was the difference in surface roughness between short and conventional long cycles, and disinfection at acrylic resins polymerized by heated water using a short cycle modified the properties of roughness.8533-

Effect of application time and concentration of silver diamine fluoride on the enamel remineralization

Silver diamine fluoride has attracted attention because of its clinical success in arresting dental caries. Thus, the aim of this study was to evaluate the effect of different application times and concentrations of silver diamine fluoride (SDF) on decid

Effect of Fluoridated Solution based on Silver Nanoparticles Associated with High Fluoride Dentifrice on Dental Erosion

Objective: To investigate the effect of fluoridated solution based on silver nanoparticles (AgNano) associated or not with toothpaste containing high fluoride concentration (TP) on dental erosion. Material and Methods: Ninety-six enamel blocks from bovine incisors were prepared and analyzed for microhardness and initial roughness. Then, divided into 8 experimental groups (n = 12): G1 - brushing with water (H2O); G2 - brushing with TP; G3 - AgNano + TP; G4 - AgNano + H2O; G5 - SDF + TP; G6 - SDF + H2O; G7 - FV + TP; G8 - FV + H2O. SDF, AgNano, and FV were applied and, after 24 hours, all samples were submitted to erosive challenge with 0.3% citric acid (pH 2.6) and brushing with TP or H2O for 5 days. After treatments and erosion challenge, microhardness and roughness were again evaluated. The data were statistically analyzed by ANOVA followed by Tukey\u27s test (microhardness) and Kruskal-Wallis test (roughness), α=0.05. Results: There was no difference between treatments (AgNano, SDF, and FV), (p&gt;0.05); however, brushing with toothpaste with high fluoride concentration significantly decreases loss of enamel microhardness. Conclusion: AgNano associated or not with toothpaste containing high fluoride concentration was not able to reduce dental erosion in the enamel, as well as SDF and FV

Color stability of enamel treated with different antioxidant agents following at-home bleaching with 10% hydrogen peroxide

This study evaluated the color stability of enamel submitted to 10% hydrogen peroxide (HP) followed by antioxidants agents, and the pH and antioxidant activity (AA%) of these agents. Methodology: Bovine enamel-dentin blocks were randomly distributed into groups (n=10/group): GNC (negative control: no treatment); GPC (positive control: bleaching only); TOC_10% (HP+10% α-tocopherol); GT_10% (HP+10% green tea extract); GS_5% (HP+5% grape seed extract); SA_10% (HP+10% sodium ascorbate); QUI_10% (HP+10% quinoa extract); and QC_1% (HP+1% quercetin). Color (ΔE00) and whiteness index (ΔWID) changes were analyzed using a digital spectrophotometer. The pH and AA% were determined using a pH meter and the DPPH method, respectively. Data were analyzed by ANOVA/Tukey’s and Dunnett’s tests (α=0.05). Results: At 14 days post-bleaching, GNC promoted the lowest ΔWID&nbsp;and ΔE00 (p&lt;0.05), and no differences were found between GPC and the remaining groups submitted to the antioxidant agents (p&gt;0.05). QC_1% and QUI_10% exhibited acidic pH levels (3.64 and 4.75, respectively), whereas TOC_10% and GS_5% exhibited alkaline pH (7.07 and 7.64, respectively). No differences in AA% were found between the agents (p&gt;0.05), ranging from 92.6 to 97.6%. Conclusion: The antioxidant agents did not interfere in bleached enamel color stability, showing satisfactory antioxidant activity. However, QUI and QC gels displayed acidic pH. Clinical significance: The antioxidants evaluated showed high AA% and no impact on post-bleaching color stability, suggesting that their capacity to recover bond strength demonstrated elsewhere would not compromise the esthetic efficacy of tooth bleaching. However, those with acidic pH should be used with caution due to potential enamel damage. &nbsp