Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups

Effect of deproteinization and tubular occlusion on microtensile bond strength and marginal microleakage of resin composite restorations

Dentin adhesion procedure presents limitations, especially regarding to lifetime stability of formed hybrid layer. Alternative procedures have been studied in order to improve adhesion to dentin. OBJECTIVE: The aim of this study was to evaluate in vitro the influence of deproteinization or dentin tubular occlusion, as well as the combination of both techniques, on microtensile bond strength (µTBS) and marginal microleakage of composite resin restorations. MATERIAL AND METHODS: Extracted erupted human third molars were randomly divided into 4 groups. Dentin surfaces were treated with one of the following procedures: (A) 35% phosphoric acid gel (PA) + adhesive system (AS); (B) PA + 10% NaOCl + AS; (C) PA + oxalate + AS and (D) PA + oxalate + 10% NaOCl + AS. Bond strength data were analyzed statistically by two-way ANOVA and Tukey's test. The microleakage scores were analyzed using Kruskal-Wallis and Mann-Whitney non-parametric tests. Significance level was set at 0.05 for all analyses. RESULTS: µTBS data presented statistically lower values for groups D and B, ranking data as A>C>B>D. The use of oxalic acid resulted in microleakage reduction along the tooth/restoration interface, being significant when used alone. On the other hand, the use of 10% NaOCl alone or in combination with oxalic acid, resulted in increased microleakage. CONCLUSIONS: Dentin deproteinization with 10% NaOCl or in combination with oxalate significantly compromised both the adhesive bond strength and the microleakage at interface. Tubular occlusion prior to adhesive system application seems to be a useful technique to reduce marginal microleakage

Evaluation by scanning electron microscopy of cleaning and deformation of rotary instruments after use

O presente estudo teve como objetivo avaliar, por meio da microscopia eletrônica de varredura (M.E.V.), a remoção de detritos e deformação superficial sofrida pelos sistemas endodônticos rotatórios de NiTi BioRace (BR); Protaper (PT) e Twisted File (TF) após cada uso, totalizando cinco usos, simulando as condições clínicas. Um total de 75 molares superiores humanos extraídos cuja raiz disto-vestibular apresentava curvatura de 0 a 5° e mésio-vestibular entre 20 e 30° de acordo com o método de Weine, foram selecionados e divididos em três grupos com 25 espécimes. Para o grupo I: realizou-se instrumentação com o sistema BR; para o grupo II com o sistema PT e para o grupo III, com o TF. Foram utilizadas cinco caixas de cada sistema rotatório para instrumentar os canais mesio e distovestibulares. Inicialmente os instrumentos foram fotografados em M.E.V. com aumento de 35 vezes, utilizados uma vez e em seguida passaram por um protocolo de limpeza baseado no proposto por Parashos, Linsuwanont e Messer (2004) previamente a esterilização e, em seguida eram analisados em M.E.V., antes do uso seguinte. Esses procedimentos foram realizados até o último uso. Os dados de limpeza foram submetidos ao teste estatístico de Kruskal Wallis para comparação global e ao teste de Dunn para comparação individual dos grupos, enquanto para análise da deformação foram submetidos ao teste estatístico do Qui-quadrado para comparação global e ao teste exato de Fisher para as comparações individuais, todos com significância de 5%. Os resultados apontaram diferenças estatisticamente significantes quanto à limpeza para o sistema BR com maior quantidade de detritos remanescentes do processo de fabricação em relação ao PT e TF; após os 5 usos, os sistemas BR e PT apresentavam-se mais limpos em relação ao início do experimento, enquanto o TF permaneceu com quantidade semelhante de detritos superficiais. Ocorreu deformação em 40% do sistema BR, sendo 5% fratura e, 100% do TF, sendo 40% fratura. O sistema PT não sofreu danos consideráveis de acordo com os critérios avaliados. Por meio dos resultados obtidos neste estudo, concluiu-se que o protocolo de limpeza utilizado não proporcionou superfícies completamente limpas tanto no decorrer quanto ao final do experimento e quanto a deformação superficial, o sistema TF apresentou o pior resultado, seguido do BR, enquanto o PT que não apresentou qualquer deformação quanto aos critérios avaliados.The aim of this study was to evaluate by scanning electron microscopy (SEM) the debris removal and deformation surface by rotary NiTi endodontic systems BioRace (BR), Protaper (PT) and Twisted File (TF) before each use, total five uses, simulating clinical conditions. A total of 75 extracted human molars whose disto-vestibular roots had curvature between 0 and 5 degrees and mesio-vestibular roots had curvature between 20 and 30 degrees according to the Weine method were selected and divided into three groups of 25 specimens. In the Group I: was used the BR system, group II was used the PT system and group III was used the TF system to shaping the mesio and distovestibular molars canals. Were used a total of five boxes to each rotary system. Initially, the instruments were examined by SEM at a magnification of 35x, then used into root canals and submitted through the cleaning protocol based on proposed by Parashos, Linsuwanont and Messer (2004) prior to sterilization for further examination by SEM, before the next use. These procedures were carried out until the last use. The cleaning data were analysed using statistical Kruskal Wallis test for global comparison and the Dunn test for individual groups comparison. The deformation data were analysed using Chi-square test for overall comparison and Fisher exact test for individual comparisons, both with 5% significance. The results showed the following statistically significant differences regarding cleaning to BR system with highest amount of debris remaining from the manufacturing process in relation to the PT and TF; after the five uses, the BR and PT systems were cleaner in relation to the initial experiment, but the TF system had the same debris amount. The deformation occurred in 40% of the BR system, with 5% fractured and 100% of the TF, with 40% fractured. The PT system has not suffered considerable damage in accordance with the criteria evaluated. The results of this study showed that the protocol did not provide cleaning surfaces completely free of debris, especially in the TF system, while for the BR and PT, resulting in cleaner surfaces at the end of the experiment compared with the dirt initial (immediately removed from their packaging). The surface deformation of TF system presented the worst results, followed by the BR and PT did not show any deformation on the criteria evaluated

Evaluation by scanning electron microscopy of cleaning and deformation of rotary instruments after use

O presente estudo teve como objetivo avaliar, por meio da microscopia eletrônica de varredura (M.E.V.), a remoção de detritos e deformação superficial sofrida pelos sistemas endodônticos rotatórios de NiTi BioRace (BR); Protaper (PT) e Twisted File (TF) após cada uso, totalizando cinco usos, simulando as condições clínicas. Um total de 75 molares superiores humanos extraídos cuja raiz disto-vestibular apresentava curvatura de 0 a 5° e mésio-vestibular entre 20 e 30° de acordo com o método de Weine, foram selecionados e divididos em três grupos com 25 espécimes. Para o grupo I: realizou-se instrumentação com o sistema BR; para o grupo II com o sistema PT e para o grupo III, com o TF. Foram utilizadas cinco caixas de cada sistema rotatório para instrumentar os canais mesio e distovestibulares. Inicialmente os instrumentos foram fotografados em M.E.V. com aumento de 35 vezes, utilizados uma vez e em seguida passaram por um protocolo de limpeza baseado no proposto por Parashos, Linsuwanont e Messer (2004) previamente a esterilização e, em seguida eram analisados em M.E.V., antes do uso seguinte. Esses procedimentos foram realizados até o último uso. Os dados de limpeza foram submetidos ao teste estatístico de Kruskal Wallis para comparação global e ao teste de Dunn para comparação individual dos grupos, enquanto para análise da deformação foram submetidos ao teste estatístico do Qui-quadrado para comparação global e ao teste exato de Fisher para as comparações individuais, todos com significância de 5%. Os resultados apontaram diferenças estatisticamente significantes quanto à limpeza para o sistema BR com maior quantidade de detritos remanescentes do processo de fabricação em relação ao PT e TF; após os 5 usos, os sistemas BR e PT apresentavam-se mais limpos em relação ao início do experimento, enquanto o TF permaneceu com quantidade semelhante de detritos superficiais. Ocorreu deformação em 40% do sistema BR, sendo 5% fratura e, 100% do TF, sendo 40% fratura. O sistema PT não sofreu danos consideráveis de acordo com os critérios avaliados. Por meio dos resultados obtidos neste estudo, concluiu-se que o protocolo de limpeza utilizado não proporcionou superfícies completamente limpas tanto no decorrer quanto ao final do experimento e quanto a deformação superficial, o sistema TF apresentou o pior resultado, seguido do BR, enquanto o PT que não apresentou qualquer deformação quanto aos critérios avaliados.The aim of this study was to evaluate by scanning electron microscopy (SEM) the debris removal and deformation surface by rotary NiTi endodontic systems BioRace (BR), Protaper (PT) and Twisted File (TF) before each use, total five uses, simulating clinical conditions. A total of 75 extracted human molars whose disto-vestibular roots had curvature between 0 and 5 degrees and mesio-vestibular roots had curvature between 20 and 30 degrees according to the Weine method were selected and divided into three groups of 25 specimens. In the Group I: was used the BR system, group II was used the PT system and group III was used the TF system to shaping the mesio and distovestibular molars canals. Were used a total of five boxes to each rotary system. Initially, the instruments were examined by SEM at a magnification of 35x, then used into root canals and submitted through the cleaning protocol based on proposed by Parashos, Linsuwanont and Messer (2004) prior to sterilization for further examination by SEM, before the next use. These procedures were carried out until the last use. The cleaning data were analysed using statistical Kruskal Wallis test for global comparison and the Dunn test for individual groups comparison. The deformation data were analysed using Chi-square test for overall comparison and Fisher exact test for individual comparisons, both with 5% significance. The results showed the following statistically significant differences regarding cleaning to BR system with highest amount of debris remaining from the manufacturing process in relation to the PT and TF; after the five uses, the BR and PT systems were cleaner in relation to the initial experiment, but the TF system had the same debris amount. The deformation occurred in 40% of the BR system, with 5% fractured and 100% of the TF, with 40% fractured. The PT system has not suffered considerable damage in accordance with the criteria evaluated. The results of this study showed that the protocol did not provide cleaning surfaces completely free of debris, especially in the TF system, while for the BR and PT, resulting in cleaner surfaces at the end of the experiment compared with the dirt initial (immediately removed from their packaging). The surface deformation of TF system presented the worst results, followed by the BR and PT did not show any deformation on the criteria evaluated

Influence on the bond strength of glass fiber posts with and without mechanical retentions depending of materials used for cementing: push-out test

Este estudo teve como objetivo avaliar a influência na resistência de união de pinos de fibra de vidro (PFV) com retenções mecânicas (CRM) e sem retenções (SR), associados a três materiais: RelyX ARC cimento resinoso convencional dual com sistema adesivo Adper Single Bond (ASB), convencional de 2 passos; RelyX U200 cimento resinoso auto condicionante dual e resina flow SDR foto ativada, com sistema adesivo Prime & Bond 2.1 (PB), convencional de 2 passos; nos terços cervical (C), médio (M) e apical (A), por meio do teste de push-out. Sessenta incisivos bovinos foram selecionados, tiveram as coroas seccionadas para padronizar 17mm de raiz e foram submetidas ao tratamento endodôntico, para posterior cimentação do PFV. Foram divididas aleatoriamente em 2 grupos (N=30), quanto ao tipo de PFV: CRM - com retenções mecânicas (Glassix+plus no2) e SR - sem retenções (Exacto no2). Todos os PFV apresentavam formato cônico. Cada grupo foi subdividido em 3 (N=10), quanto ao tipo de material: cimento RelyX ARC+ASB; cimento RelyX U200 (auto condicionante) e resina SDR+PB. Todas as orientações dos fabricantes para tempo de manipulação e foto ativação do material foram rigorosamente respeitadas. As raízes foram mantidas em saliva artificial e decorridas 24h da cimentação dos PFV, foram seccionadas perpendicularmente ao longo eixo, obtendo 9 fatias de aproximadamente 1mm, cuja identificação foi feita de acordo com o terço correspondente. O teste de push-out foi realizado em máquina de ensaio universal com célula de carga de 50N; velocidade de 0,5mm/min, da direção apical para a cervical da fatia até que o pino fosse deslocado, respeitando o formato cônico do canal radicular. Todos os espécimes foram analisados em microscopia óptica, aumento de 200 vezes, quanto aos tipos de falha ocorrido. Os dados foram tabulados considerando as variáveis dos diferentes materiais utilizados para a cimentação, presença ou não de retenções mecânicas nos PFV e terços radiculares. Os valores de resistência de união (Ru) obtidos foram submetidos ao teste de normalidade Kolmogorov- Smirnov, à análise de variância a três critérios (ANOVA) e ao teste LSD de Fisher (p<0,05). Os resultados mostraram diferença estatisticamente significante nos terços C, M e A, respectivamente para os cimentos ARC com pino Glassix+plus, média e desvio padrão (MPa) a seguir, 8,50 (4,76); 6,99 (3,55); 4,71 (2,13) e U200 com pino Exacto: 9,40 (4,93); 8,02 (4,67); 4,67 (1,86); a resina SDR não interagiu significativamente com os PFV CRM 6,78 (2,72); 5,97 (2,45); 2,67 (1,55) e SR 7,24 (3,55); 6,86 (2,84); 4,10 (1,90). A análise microscópica mostrou predominância de falhas adesivas entre cimento e dentina e mista para todos os grupos. O cimento U200 com pino Exacto apresentou o melhor desempenho, seguido do ARC com pino Glassix+plus. A resina SDR teve desempenho semelhante para ambos os PFV. Todos os grupos apresentaram valores de Ru maiores no terço cervical, intermediários no terço médio e menores no terço apical.This study aimed to evaluate the influence on the bond strength of glass fiber posts (GFP) with mechanical retention (WMR) and without retentions (NR), associated with three materials: RelyX ARC total-etching resin cement dual cure with Adper Single Bond (ASB) adhesive system, conventional 2 steps; RelyX U200 self-etching resin cement dual cure, and flowable resin SDR, activated by light, with Prime & Bond 2.1 adhesive system conventional 2 steps in the cervical (C), medium (M) and apical (A) thirds by the \"push-out\" test. Were selected sixty bovine incisors, had the crowns sectioned to root was standardized 17mm, were submitted to endodontic treatment, for cementing the GFP later. Were randomly divided into 2 groups (N=30), according to the GFP: WMR - with mechanical retentions (Glassix+plus &#x2260;2) and NR - without retentions (Exacto &#x2260;2). All GFP had conic shape. Each group was divided into 3 (N=10), according to material: RelyX ARC+ASB, RelyX U200 (self-etching) and flowable resin SDR+PB. All guidelines of manufacturers to handling time and cure time of the material were strictly adhered. The roots were kept in artificial saliva and 24 hours after GFP cementing it were sectioned perpendicular to the long axis, obtaining nine slices of approximately 1mm, which identification was done according to the corresponding third. The \"push-out\" test was performed with a universal test machine, 50N load cell; crosshead speed of 0.5 mm/min, the load was applied in an apical to cervical direction until the post dislodged from the specimen, respecting the conical shape of the root canal. Subsequently, all specimens were analyzed with optical microscopy 200 times increase to evaluate failure modes. Data were tabulated considering the materials used for cementing, presence or absence of mechanical retentions in GFP and root thirds. The bond strength values (BS) were submitted to Kolmogorov-Smirnov normality test, three-way ANOVA and Fisher\'s LSD test (p<0.05). The values showed statistically significant differences in thirds C, M and A, respectively for the ARC with Glassix+plus, average and standard deviation (MPa): 8.50 (4.76); 6.99 (3.55); 4.71 (2.13) and U200 with Exact post: 9.40 (4.93); 8.02 (4.67); 4.67 (1.86). SDR resin does not significantly interacted with GFP WMR 6.78 (2.72); 5.97 (2.45); 2.67 (1.55) and NR 7.24 (3.55); 6.86 (2.84); 4.10 (1.90). The microscopic analysis showed predominance of failure between cement and dentine and mixed for all groups. U200 cement with Exacto post had the best performance, followed by ARC with Glassix+plus post, SDR resin has similar performance for both GFP. All groups showed BS values higher in the cervical third, intermediate in the middle third and smaller in the apical third