Effect of penetrating resin on the surface structure, microhardness and color of enamel after bleaching / 中华口腔医学杂志

Objective: To investigate the effect of permeable resin on the surface structure, microhardness and color of tooth enamel after bleaching. Methods: Premolars extracted for orthodontic needs were selected (provided by the Department of Oral and Maxillofacial surgery of the first affiliated Hospital of Zhengzhou University) and randomly divided into A, B and C 3 groups. Each group was randomly divided into control subgroup, resin subgroup, bleaching subgroup and combined subgroup. Samples in the control subgroup did not receive any treatment. Those in the bleaching subgroup and combined subgroup were treated with cold light whitening. Those in the resin group and combined group were treated with permeable resin. Samples in the group A were observed by scanning electron microscope immediately after treatment and 2 weeks after treatment, and the microhardness of samples in the group B was measured before treatment, immediately after treatment and 2 weeks after treatment (the sample size of each time point was 8 in each subgroup). In group C, chromaticity was measured and chromatic aberration (ΔE value) was calculated before treatment, immediately after treatment and 1 and 2 weeks after treatment (10 samples in each subgroup). Results: Scanning electron microscope showed that the enamel surface of the resin subgroup and the combined group was smooth immediately after treatment, which was basically the same as that of the control subgroup, but covered with resin, and microporous defects and mineral deposits could be seen on the surface of the bleaching subgroup. Two weeks after treatment, the enamel surface of each subgroup was smooth, there was no obvious difference. Immediately after treatment, the microhardness of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were (354±33), (364±21), (411±30) and (350±17) HV, respectively (F=9.39,P<0.05). The microhardness of the bleaching subgroup was significantly higher than that of the other subgroups (P<0.05). There was no significant difference in microhardness among the four subgroups before treatment and 2 weeks after treatment (F=0.34, 2.75, P>0.05). Immediately after treatment, the ΔE values of the control subgroup, resin subgroup, bleaching subgroup and combined subgroup were 0.00±0.00, 2.29±1.86, 7.20±1.94 and 8.00±0.88, respectively (F=74.21,P<0.05); except that there was no significant difference between bleaching subgroup and combined subgroup (P>0.05), there were significant differences among the other subgroups (P<0.05). There was no significant difference in ΔE value among control subgroup, resin subgroup and bleaching subgroup at each time point (F=1.66, 0.30, 0.96, P>0.05). The difference in the combined subgroup immediately after treatment was significantly higher than that at 1 and 2 weeks after treatment (t=4.73, 4.23,P<0.05), but there was no significant difference between 1 and 2 weeks after treatment (t=0.75, P>0.05), and the color tended to be stable. Conclusions: When whitening healthy enamel, simple cold light whitening or cold light whitening combined with permeation resin can achieve whitening effect.

Effects of bleaching using 10% carbamide peroxide with calcium or amorphous calcium phosphate on enamel mineral content and hardness / Asociación entre la severidad de Hipomineralización Incisivo-Molar (HIM) y lesiones cavitadas de caries en escolares

ABSTRACT This study evaluated enamel mineral content and surface microhardness before and after bleaching treatment using 10% carbamide peroxide (CP) containing calcium (Ca) or amorphous calcium phosphate (ACP). Thirty-six bovine slabs were randomly allocated into 3 groups (n = 12) according to bleaching treatment: G1 - Opalescence PF 10% (CP), G2 -NiteWhite ACP (CP+ACP), and G3 - Opalescence PF (10%) with calcium (CP+CA). The bleaching agent was applied on enamel surface for 6 h/day over a period of 21 days. Enamel surface was evaluated by Knoop microhardness (KNH) and micro energy-dispersive X-ray fluorescence spectrometry (p-EDXRF) at baseline and at after bleaching treatment. Data were statistically analyzed by repeated measures ANOVA and Tukey's test (a = 0.05). There was a significant decrease in microhardness after bleaching treatments for all study groups, but no difference between bleaching gels. There was no difference in the Ca/P ratio measured by p-EDXRF for all groups at the study times, but the mean value was lower in group CP+CA than in group CP+ACP. Group CP was similar to both CP+ACP and CP+CA. It can be concluded that enamel microhardness decreased after the bleaching process, regardless of the presence of calcium or ACP, but there was no significant change in the Ca/P ratio of enamel after bleaching for each tested gel. This indicates that the bleaching gels have erosive potential, causing softening of enamel without promoting surface loss, regardless of the presence of calcium of ACP ions.

RESUMO Este estudo avaliou o conteúdo mineral do esmalte e a microdureza superficial antes e após o tratamento clareador, utilizando peróxido de carbamida 10% (PC) contendo cálcio (Ca) ou fosfato de cálcio amorfo (ACP) em sua composigao. Trinta e seis espécimes de esmalte bovino foram alocados aleatoriamente em 3 grupos (n = 12) de acordo com os tratamentos clareadores: G1 - Opalescence PF 10% (CP), G2 -NiteWhite (CP+ACP); e G3 - Opalescence PF (10%) com cálcio (CP + CA). O agente clareador foi aplicado na superficie do esmalte por 6 h/dia por um periodo de 21 dias. A superficie do esmalte foi avaliada por microdureza Knoop (KNH) e espectrometria de fluorescencia de raios X micro-dispersiva (p-EDXRF) no inicio e após o tratamento clareador. Os dados foram analisados estatisticamente pelo teste ANOVA de medidas repetidas e Tukey (a = 0,05). Houve uma diminuigao significativa da microdureza após os tratamentos clareadores para todos os grupos estudados, mas nao houve diferenga entre os diferentes géis. Nao houve diferenga da relagao Ca/P mensurada por p-EDXRF para todos os grupos nos tempos estudados; no entanto, o grupo CP+CA apresentou menor valor comparado ao grupo CP+ACP. O grupo CP foi similar aos grupos CP+ACP e CP+CA. Portanto, pode-se concluir que houve redugao significativa da microdureza do esmalte após o clareamento, independente da presenga de cálcio ou APC na composigao dos géis, embora nao tenha havido alteragao significando na relagao Ca/P do esmalte após o clareamento. Isto indica um potencial erosivo dos géis clareadores, causando o amolecimento sem perda da estrutura do esmalte, independente da presenga dos íons cálcio e ACP.

Influence of Prolonged Tooth Bleaching on Enamel Mass Variation / Influencia del Blanqueo Dental Prolongado en la Variación de Masa del Esmalte Dental

ABSTRACT: The objective evaluate was the influence of prolonged tooth bleaching with 10 % carbamide peroxide (10CP) on tooth enamel mass variation. Ten healthy bovine incisor teeth were divided (n = 5) into G1 - storage in distilled water and G2 - storage in artificial saliva. The samples were weighed in an electronic analytical balance at the following times: T0 - before application of the bleaching gel, T1 - after 14 days of bleaching (the time recommended by the manufacturer), T2 - after 21 days of bleaching (50 % increase in the time recommended by the manufacturer), and T3 - after 28 days of bleaching (100 % increase in the time recommended by the manufacturer). The data were subjected to ANOVA for related samples (p = 0.05). The highest mean was observed in G2 (0.5982 g) and the lowest mean was observed in G1 (0.3074 g) at T2 and T3, respectively. Significant differences were observed between the groups at all times. Overall, 10CP caused variation in the enamel mass after a 100 % increase in the use time recommended by the manufacturer, with a decrease in mass when distilled water was used as the storage medium and an increase when artificial saliva was used.

RESUMEN: El objetivo fue investigar la influencia del blanqueamiento dental prolongado con peróxido de carbamida al 10 % (10CP) sobre la variación de masa del esmalte dental. Las muestras se dividieron en dos grupos: G1, diez dientes sanos de los incisivos bovinos (n = 5) en agua destilada, y G2, almacenamiento en saliva artificial. Las muestras se midieron en una escala analítica electrónica de precisión en los siguientes tiempos: T0-antes de la aplicación del gel blanqueador, T1-después de 14 días de blanqueo (el tiempo recomendado por el fabricante), T2-después de 21 días de blanqueo (aumento de 50 % en el tiempo recomendado por el fabricante), y T3-después de 28 días de blanqueo (aumento de 100 % en el tiempo recomendado por el fabricante). Los datos se presentaron al ANOVA para las muestras relacionadas (P = 0,5). La media más alta se observó en G2 (0,5982 g) y la media más baja se observó en G1 (0,3074 g) en T2 y T3, respectivamente. Se observaron diferencias significativas entre los grupos en todo momento. En general, la 10 CP causó variación en la masa del esmalte después de un aumento de 100 % en el tiempo de uso recomendado por el fabricante, con una disminución en la masa cuando el agua destilada se utilizó como medio de almacenamiento y aumentó cuando se usó saliva artificial.

Effect of at-home bleaching on oxygen saturation levels in the dental pulp of maxillary central incisors

Abstract The present study assessed oxygen saturation (SaO2) levels before, during, and after at-home bleaching treatment in the pulps of healthy maxillary central incisors. SaO2 levels were measured in 136 healthy maxillary central incisors using a pulse oximeter. The bleaching protocol consisted of 10% carbamide peroxide gel placed in individual trays and used for four hours daily for 14 days. SaO2 levels were assessed before bleaching (T0), immediately after the first session (T1), on the 7th day of treatment (T2), on the 15th day (the day following the last session) (T3), and 30 days after completion of the bleaching protocol (T4). Data were statistically analyzed using generalized estimating equations (GEE), Student's t test (p<0.05) and Pearson's correlation. Mean pulp SaO2 levels were 85.1% at T0, 84.9% at T1, 84.7% at T2, 84.3% at T3, and 85.0% at T4. Gradual reductions in SaO2 levels were observed, with significant differences (p<0.001) during the course of home bleaching treatment. However, 30 days after the end of the bleaching protocol, SaO2 levels returned to baseline levels. Home bleaching caused a reversible transient decrease in SaO2 levels in the pulps.

Resumo Este estudo verificou o grau de saturação de oxigênio (SaO2) pulpar antes, durante e após o clareamento dental caseiro em incisivos centrais superiores hígidos. O nível de SaO2 foi verificado em 136 incisivos centrais superiores hígidos usando oxímetro de pulso. A técnica de clareamento empregou peróxido de carbamida 10% em moldeira individual por quatro horas diárias durante 14 dias. Os níveis de SaO2 foram analisados antes do clareamento (T0), imediatamente após a primeira sessão (T1), no sétimo dia de tratamento (T2), no décimo quinto dia (um dia após a última sessão) (T3) e 30 dias após o término do clareamento dental (T4). A análise estatística utilizou o modelo de equações de estimações generalizadas (GEE), teste t de Student (p<0,05) e correlação de Pearson. Os níveis médios de SaO2 pulpar foram 85,1% em T0, 84,9% em T1, 84,7% em T2, 84,3% em T3 e 85,0% em T4. Foi observada uma redução gradual dos níveis de SaO2, com diferenças significantes (p<0,001) durante o clareamento dental caseiro. No entanto, 30 dias após o término do clareamento dental, houve retorno aos valores iniciais. O clareamento dental caseiro provocou uma diminuição transitória reversível no grau de SaO2 pulpar.

Toxicidade do peróxido de carbamida 16% adicionado de nanopartículas de hidroxiapatita / Carbamide peroxide toxicity added 16% hydroxyapatite nanoparticles

O clareamento dental é um dos tratamentos mais realizados nos consultórios odontológicos a fim de melhorar a aparência do sorriso. O procedimento consiste na aplicação de um gel clareador, a base de peróxido de carbamida ou de hidrogênio, sobre os dentes a serem clareados. A sensibilidade dentária é o efeito adverso mais frequentemente relatado no clareamento dentário e é a principal causa de desmotivação dos pacientes. O mecanismo pelo qual se produz a sensibilidade após clareamento dentário ainda não foi completamente elucidado; no entanto, parece estar associado à rápida difusão dos agentes clareadores através do esmalte e dentina que, devido ao seu grau de citotoxicidade, podem agir agredindo as células pulpares, causando sensibilidade. O objetivo deste estudo foi avaliar a biocompatibilidade de nanopartícula de hidroxiapatita adicionada ao gel clareador peróxido de carbamida 16% com flúor e sem flúor e, para tanto, foram realizados testes de citotoxidade empregando MTT. Como resultados verificou-se que as nanopartículas de hidroxiapatita, quando comparadas aos géis de peróxido de carbamida a 16% com e sem flúor, foram as menos citotóxicas (p< 0.05). As diluições citotóxicas convertidas para 70% das amostras testadas também foram comparadas através do teste de Anova com tukey. Foi possível observar que as partículas de nanoHap quando adicionadas nos géis de clareamento com e sem flúor reduziu significativamento a citotoxidade. Concluímos que o novo material proposto nesta investigação apresenta melhor biocompatibilidade do que o gel sem hidroxiapatita, acompanhado da redução da citotoxidade, tais aspectos sugerem que as nanopartículas de hidroxiapatita podem ter aplicações clínicas futuras em tecidos mineralizados em procedimentos de clareamento dental, contribuindo para a redução da sensibilidade dentária.

The dental bleaching is one of the most procedures performed at dental offices to improve the appearance of the smile. The procedure consists of the application of a bleching gel, based on carbamide peroxide or hydrogen over the teeth to be whitened. Tooth sensibility is the frequently reported adverse effect on tooth whitening and is the leading cause of demotivation by the patients. The mechanism that provides the sensibility after tooth whitening has not already been fully elucidated; however, it appears to be associated with the rapid diffusion of bleaching agents through the enamel and dentin that, because of their degree of cytotoxicity, may act attacking pulp cells, causing the sensibility. The aim of this study was to evaluate the biocompatibility of hydroxyapatite nanoparticles added to whitening gel of 16% carbamide peroxide with and without fluoride and, therefore, cytotoxicity tests were performed using MTT. As a result, it was found that the hydroxyapatite nanoparticles, compared to the gels of 16 % carbamide peroxide with and without fluoride, were less cytotoxic (p <0.05). Cytotoxic dilutions converted to 70 % of the tested samples were compared using ANOVA test with Tukey. We concluded that the new material proposed in this research has a better biocompatibility in comparison with the gel without hydroxyapatite, followed by a reduction of cytotoxicity. These aspects suggest that the hydroxyapatite nanoparticles may have clinical future applications in mineralized tissues when dental bleaching procedures are performed, contributing to the reduction of tooth sensitivity. We conclude that the new material proposed in this research has a better biocompatibility of the gel without hydroxyapatite, accompanied by a reduction of cytotoxicity, these aspects suggest that the hydroxyapatite nanoparticles may have future clinical applications in mineralized tissues in dental bleaching procedures, contributing to a reduction tooth sensitivity.

Effect of whitening dentifrices: a double-blind randomized controlled trial

Abstract The aim of this clinical study was to evaluate tooth color changes (ΔE) and tooth sensitivity (TS) associated with whitening dentifrices. Sixty participants were selected according to inclusion and exclusion criteria and then allocated to three groups (n = 20): Colgate Luminous White (G1), Close Up White Now (G2) and Sorriso dentifrice (G3-control). The participants were instructed to use only the provided dentifrice and toothbrush in standardized oral hygiene procedures for 4 weeks. ΔE was assessed by spectrophotometry (CIELab System) whereas TS was determined by a visual analog scale at baseline and weekly using four assessment points. The data were analyzed by two-way ANOVA and Tukey's post-hoc test and Friedman test (α = 0.05). ΔE (baseline-assessment point 4) showed no significant difference (p>0.05) across the groups: G1 (ΔE = 5.1), G2 (ΔE = 6.8), and G3 (ΔE = 4.4). Δb (baseline-assessment point 4) was significantly different (p < 0.05) in G2 (3.8) when compared to G1 (-0.2) and G3 (0.3). There was no significant difference (p > 0.05) in TS at baseline. Both the control and whitening dentifrices caused similar tooth color changes (ΔE). There was no significant TS during the study period.

In vitro evaluation of the whitening effect of mouth rinses containing hydrogen peroxide

The aim of this study was to evaluate the bleaching effect of two mouth rinses containing hydrogen peroxide. Thirty premolars were randomly divided into two groups (n = 15): Listerine Whitening (LW) and Colgate Plax Whitening (PW). The teeth were fixed on a wax plate and with acrylic resin, at a distance of 5 mm between each other, exposing the buccal surfaces. All teeth were stored in artificial saliva for 45 days, being removed twice a day to be immersed for 1 min in each mouthwash, followed by 10-second washing in tap water. The pH of each product was measured. Digital images of each tooth were captured under standardized conditions. These images were cut in areas previously demarcated and analyzed in Adobe Photoshop 7.0 using the CIEL*a*b* color space system. Data were statistically analyzed by a paired t test and an independent samples t test (p < 0.05). The pH values were 5.6 and 3.4 for LW and PW, respectively. Both treatment groups showed a decrease in the b* parameter (p < 0.01), but a decrease of a* was observed only for PW (p < 0.01). While the LW group showed an improvement in lightness (L*) (p = 0.03), the PW group had a decrease in the L* parameter (p = 0.02). Within the limitations of this study, it is possible to conclude that both products caused some degree of whitening; however, extreme care should be taken when using Colgate Plax Whitening, since its decline in luminosity might be due to its lower pH.

Physical-chemical characteristics of whitening toothpaste and evaluation of its effects on enamel roughness

This in vitro study evaluated the physical-chemical characteristics of whitening toothpastes and their effect on bovine enamel after application of a bleaching agent (16 percent carbamide peroxide). Physical-chemical analysis was made considering mass loss by desiccation, ash content and pH of the toothpastes. Thirty bovine dental enamel fragments were prepared for roughness measurements. The samples were subjected to bleaching treatments and simulated brushing: G1. Sorriso Dentes Brancos (Conventional toothpaste), G2. Close-UP Whitening (Whitening toothpaste), and G3. Sensodyne Branqueador (Whitening toothpaste). The average roughness (Ra) was evaluated prior to the bleaching treatment and after brushing. The results revealed differences in the physical-chemical characteristics of the toothpastes (p < 0.0001). The final Ra had higher values (p < 0.05) following the procedures. The mean of the Ra did not show significant differences, considering toothpaste groups and bleaching treatment. Interaction (toothpaste and bleaching treatment) showed significant difference (p < 0.0001). The whitening toothpastes showed differences in their physical-chemical properties. All toothpastes promoted changes to the enamel surface, probably by the use of a bleaching agent.

Effect of a bleaching agent on the color stability of a microhybrid composite resin / Efeito de um agente de clareamento na estabilidade de cor de uma resina composta micro-híbrida

Objectives: To evaluate the effect of Opalescence™ PF home bleaching gel on the color stability ofAmelogen™ Plus microhybrid composite resin. Material and method: Thirty disks were fabricated fortesting using three different shades (A1, A2 and A3.5) of Amelogen™ Plus composite. Standardized L*a*b*parameters were determined and the specimens were subjected to 15% carbamide peroxide. The L*a*b*parameters were measured again and the color change (ΔE) in the composite disks were calculated. Thedata were analyzed using the One-way ANOVA and Tukey tests. (α = 0.05) Results: In all specimens themean of ΔE was more than 3.3. There was a signifi cant difference between shade A3.5 and A2 and withshade A1, as A1 showed the lowest values of color change with bleached composites being lightened incomparison with the unbleached specimens. The greatest change occurred in the red-green (a*) parameter.Conclusion: 15% carbamide peroxide bleaching gel (Opalescence® PF) caused a clinically detectable colorchange with each of three different shades (A1, A2 and A3.5) of Amelogen™ Plus (ΔE> 3.3) tested. Thegreatest color change occurred with the A3.5 shade and the least change was associated with the A1 shade.

Objetivos: Avaliar o efeito do gel de clareamento doméstico Opalescente® na estabilidade de cor do microcompósitoAmelogen® Plus. Material e método: Parâmetros L*a*b* foram determinados e os espécimes foram sujeitos a peróxidode carbamida a 15%. Os parâmetros L*a*b* foram medidos novamente e a alteração de cor (ΔE) nos discos de compósitofoi calculada. Os dados foram analisados pelos testes One-way ANOVA e Tukey (α = 0.05). Resultados: Emtodos os espécimes o valor médio de ΔE foi maior do que 3.3. Não houve diferença signifi cante entre cores A3,5, e A2A1. A1 mostrou o mais baixo valor, sendo mais claros os compósitos submetidos ao agente clareador em comparaçãoaos espécimes não submetidos. A maior alteração ocorreu no parâmetro vermelho-verde (a*). Conclusão: O gelde peróxido de carbamida a 15% (Opalescente® PF) causou uma alteração de cor clinicamente detectável em cadauma das diferentes cores (A1, A2 e A3,5) do compósito Amelogen® Plus testado. A maior alteração de cor ocorreucom a cor A3.5 e a menor foi associada à cor A1.

The effect of carbamide peroxide bleaching agents on the microhardness of dental ceramics

This study examined the effect of 10% and 16% carbamide peroxide bleaching agents on the surface microhardness of micro-particulate feldspathic ceramics (VM7 and VM13, Vita Zahnfabrik). Forty specimens (8-mm diameter, 2-mm thickness) were divided into four groups (n=10): G1- VM7 + 10% Whiteness, G2- VM7 + 16% Whiteness, G3- VM13 + 10% and G4- VM13 + 16% Whiteness. The home-use bleaching agents were applied for 8 hours on 15 days, and the specimens were stored in distilled water at 37°C. The Vickers hardness number (HV) was determined for each specimen. Data were analyzed by the Wilcoxon and Mann- Whitney tests (p<0.05). The microhardness values before exposure were: g1- 433 (57); g2- 486 (22); g3- 509 (28); g4- 518 (24), and after exposure: G1- 349 (32); G2- 496 (95); G3- 519 (38); G4- 502 (81). G2 exhibited a higher and significant difference than G1 in VM7 groups, and the effect of bleaching concentration was shown to be significant by the Mann-Whitney test. And for VM13, both the Wilcoxon and Mann-Whitney tests showed no significant differences. When using 10% carbamide peroxide, the microhardness of VM7 ceramic was affected, and there were no effect on the microhardness between VM7 and VM13 ceramics when 16% carbamide peroxide was used.

Este estudo examinou o efeito do agente clareador peroxido de carbamida a 10% e a 16% na microdureza superficial de ceramicas feldspaticas micro-particuladas (VM7 e VM13, Vita Zahnfabrik). Quarenta corpos-de-prova (8 mm de diametro, 2 mm de espessura) foram divididos em quatro grupos (n=10): G1- VM7 + 10% Whiteness, G2- VM7 + 16% Whiteness, G3- VM13 + 10% e G4- VM13 + 16% Whiteness. Os agentes clareadores foram aplicados por 8 horas durante 15 dias e os cp foram armazenados em agua destilada a 37°C. A dureza Vickers (HV) de cada cp foi determinada. Os dados foram analisados pelos testes de Wilcoxon e Mann-Whitney (p<0.05). Os valores da dureza antes da exposicao ao agente clareador foram: g1- 433 (57); g2- 486 (22); g3- 509 (28); g4- 518 (24), e depois da exposicao: G1- 349 (32); G2- 496 (95); G3- 519 (38); G4- 502 (81). G2 exibiu diferenca significante e microdureza maior comparado ao G1 nos grupos da VM7 e o efeito da concentracao do clareador foi significante, apresentados atraves dos testes Mann-Whitney. Para VM13, ambos testes, Wilcoxon e Mann-Whitney, nao apresentaram diferenca significante. Quando o peroxido de carbamida a 10% foi avaliado, a microdureza da ceramica VM7 foi afetada, e nao houve diferenca na microdureza entre as ceramicas VM7 e VM13 quando o peroxido de carbamida a 16% foi utilizado.

The use of ozone to lighten teeth: An experimental study

Tooth-whitening agents are available for therapeutic use in the dental office or at home. However, whitening more severe stains, such as those caused by systemic ingestion of tetracycline, constitutes a challenge. The aim of this study was to evaluate, in an experimental model of growing rats, the efficacy of using ozone to lighten tetracycline-stained incisors. At weaning, male Wistar rats (n=40) were randomly assigned to one of three groups. Two control groups, C21 and C60 (n=8, each) were used to document the usual age-related color. The third group (n=24) received 0.25 g% of oxytetracycline (O) until 60 days of age. These rats were subsequently divided into three further groups: O0, O3 and O5 (n=8, each). These rats were anesthetized; O3 and O5 groups received ozone application to the lower incisors for 3 (group O3) or 5 minutes (group O5), respectively; while O0 did not receive the ozone treatment. Teeth were then photographed and the incisors from the control (C60) and treatment groups (O0, O3 and O5) were cut, and compared to a standard color guide (there were eight shades numbered 0 to 7, lightest to darkest) to assess the hue visually. The teeth were then placed in phosphoric acid to quantify the color by spectrophotometry. The data (mean ± SD) were analyzed by One-Way Analysis of Variance (ANOVA) followed by Tukey's test or Dunnett test. The visual observation, analyzed blindly by one investigator, showed that O3 and O5 groups had diminished yellowing of the teeth as compared to the untreated O0 group (P<0.001). The color quantified by spectrophotometry also detected significant differences among groups (O3 < O0, P<0.01; O5 < O0,P < 0.001 and O5 < O3, P<0.01). C21 and C60 were significantly different among groups (P<0.001). This is the first experimental study to show that ozone can be successfully used for lightening the yellowish tinge of tetracycline- stained rat incisors. Further studies are required for its potential use in the dental clinic.

Los agentes blanqueadores dentales estan disponibles para tratamientos que se realizan en el consultorio odontologico o en el domicilio. Sin embargo, aclarar manchas severas, como las causadas por la ingestion sistemica de tetraciclina, constituyen un desafio. El objetivo de este estudio fue evaluar en un modelo experimental de ratas en crecimiento, la eficiencia del uso de ozono para aclarar los incisivos oscurecidos por el uso de tetraciclina. Ratas macho Wistar al destete (N=40) fueron asignadas aleatoriamente a uno de tres grupos. Dos de ellos grupos controles, C21 y C60 (N=8, cada uno), para documentar el color habitual de los incisivos, correspondiente a la edad del animal. El tercer grupo (N = 24) recibio 0,25 % de oxitetraciclina (O) hasta los 60 dias de edad. Entonces, el grupo O se dividio aleatoriamente en tres grupos O0, O3 y O5 (N = 8, cada uno) y las ratas se anestesiaron. Los grupos O3 y O5 recibieron en los incisivos inferiores la aplicacion de ozono durante 3 y 5 minutos, respectivamente; mientras que O0 no recibio tratamiento. Los incisivos de C60, O0, O3 y O5 fueron fotografiados. Luego se cortaron y se contrastaron con una guia estandar de ocho colores (ordenados de 0 a 7, desde el mas claro a mas oscuro) para cuantificar visualmente el color de los incisivos. Luego, se colocaron en acido fosforico para cuantificar el color por espectrofotometria. Los resultados (media ± SD) se analizaron por medio de ANOVA y prueba de Tukey o Dunnett (α =0.05) para determinar el efecto del tratamiento. El analisis visual de las imagenes mostro que los grupos O3 y O5 disminuyeron el color amarillo intenso respecto a O0. Dicha diferencia de color fue evaluada a traves de la guia (G) y cuantificada mediante espectrofotometria (E). Segun G, la mayor diferencia de color respecto a C60 fue para O0 (P<0.001), disminuyo en O3 (P<0.001) y aun mas en O5 (P<0.01). De acuerdo a E, O3

Evaluating the bonding of two adhesive systems to enamel submitted to whitening dentifrices

The aim of this study was to evaluate by micro-shear bond strength test, the bond strength of composite resin restoration to enamel submitted to whitening dentifrices. Forty bovine teeth were embedded in polystyrene resin and polished. The specimens were randomly divided into eight groups (n= 5), according to the dentifrice (carbamide peroxide, hydrogen peroxide and conventional dentifrice) and the adhesive system (Prime & Bond 2.1 and Adper Single Bond 2). Dentifrice was applied for 15 minutes a day, for 21 days. Thirty minutes after the last exposure to dentifrice, the samples were submitted to a bonding procedure with the respective adhesive system. After that, four buttons of resin were bonded in each sample using transparent cylindrical molds. After 24 hours, the teeth were submitted to the micro-shear bond strength test and subsequent analysis of the fracture mode. Data were submitted to analysis of variance and Fisher's PLSD test (α=0.05). The micro-shear bond strength showed no difference between adhesives systems but a significant reduction was found between the control and carbamide groups (p=0.0145) and the control and hydrogen groups (p=0.0370). The evaluation of the failures modes showed that adhesive failures were predominant. Cohesive failures were predominant in group IV. The use of dentifrice with peroxides can decrease bonding strength in enamel.

O objetivo deste trabalho foi avaliar, pelo metodo de microcisalhamento, a resistencia adesiva obtida em restauracoes de resina composta realizadas sobre o esmalte dental previamente exposto a diferentes dentifricios. Para isso, quarenta dentes bovinos foram incluidos em resina de poliestireno e polidos. Os dentes foram divididos aleatoriamente em 8 grupos (n=5) de acordo com o dentifricio utilizado (cremes contendo peroxido de hidrogenio, peroxido de carbamida ou dentifricio convencional) e sistema adesivo (Prime & Bond 2.1 ou Adper single Bond 2). Os dentes foram expostos por 15 minutos por dia durante 21 dias as suspensoes dos respectivos cremes dentais. Trinta minutos apos a ultima exposicao ao dentifricio, os dentes foram restaurados empregando os 2 diferentes sistemas adesivos e resina composta. Apos 24 horas os dentes foram submetidos ao teste de microcisalhamento e posterior analise do padrao de fratura. Os resultados obtidos foram submetidos a analise de variancia e teste de Fisher's PLSD (α=0.05). Nao foi detectada diferenca estatistica entre os adesivos, porem entre os tratamentos com dentifricios, houve reducao estatisticamente significante entre os grupos controle x carbamida (p=0.0145) e entre o grupo controle x hidrogenio (p=0.0370). Na avaliacao do tipo de fratura houve predominancia de falhas adesivas, com excecao do grupo IV que apresentou maior fratura coesiva em esmalte. Assim, a utilizacao de cremes dentais, contendo peroxidos em suas formulacoes, pode provocar uma reducao na resistencia de uniao ao esmalte.