Fiber Post Etching with Hydrogen Peroxide: Effect of Concentration and Application Time

AbstractIntroductionEtching is necessary to expose the fibers and enable both mechanical and chemical bonding of the resin core to the fiber post. This study evaluated the effect of concentration and application time of hydrogen peroxide on the surface topography and bond strength of glass fiber posts to resin cores.MethodsFiber posts were etched with 24% or 50% hydrogen peroxide for 1, 5, or 10 min (n = 10). Posts without any treatment were used as a control. After etching, the posts were silanated and adhesive resin was applied. The posts were positioned into a mold to allow a self-cured resin core to be inserted. The post/resin assembly was serially sectioned into five beams that were subjected to a tensile bond strength test. Data were subjected to two-way ANOVA and Tukey test (α = 0.05). The surface topography was analyzed using scanning electronic microscopy.ResultsNon-etched post presents a relatively smooth surface without fiber exposure. Application of hydrogen peroxide increased the surface roughness and exposed the fibers. All experimental conditions yielded similar bond strength values that were higher than those obtained in the control group.ConclusionBoth 24% and 50% hydrogen peroxide exposure increased the bond strength of resin to the posts, irrespective of the application time

Influência de substâncias irrigadoras endodônticas nas propriedades mecânicas da dentina radicular

The aim of this study was to evaluate the influence of different endodontic irrigants on the cohesive and flexural strength of the root dentin. One hundred of bovine incisor roots were selected, instrumented and randomly divided into 10 experimental groups (n = 10), according to the irrigation solution used: Control - physiological solution; N1 - sodium hypochlorite 1.0%; N5 - sodium hypochlorite 5.25%; N1EDTA - sodium hypochlorite 1.0% associate to EDTA 17%; N5EDTA - sodium hypochlorite 5.25% associate to EDTA 17%; Sclx chlorhexidine gluconate solution 2.0%; Gclx - chlorhexidine gluconate gel 2.0%; SclxEDTA - chlorhexidine gluconate solution 2.0% associate to EDTA 17%; GclxEDTA - chlorhexidine gluconate gel 2.0% associate to EDTA 17% and EDTA - EDTA 17%. The roots were axially sectioned in two halves. Half of them were used for the microtensile cohesive strength test: six 1.0mm thick slices were trimmed to produce hourglass shaped samples with a test area of 1mm2. The other halves were used in a 3-point bend flexural strength by means of dentine bars with 1X1X12 mm. Each sample remained two hours in contact with the irrigant solutions, except for EDTA, which remained for five minutes. After irrigants treatment, samples were rinsed with distilled water, and tested. Specific devices for each test were used, in a universal testing machine with a load cell of 20Kgf, and a crosshead speed of 0.5 mm/minute. Date were recorded and statistically analyzed with one-way ANOVA and Tukey test. Significant reduction in the ultimate cohesive strength and flexural strength was verified only for the groups that used sodium hypochlorite irrespective of the concentration and additional solution, differing significant from the group control. The use of chlorhexidine and EDTA separately did not cause alteration in the mechanical properties of root dentine.Mestre em OdontologiaO objetivo desse estudo foi avaliar a influência de diferentes irrigantes endodônticos na resistência coesiva e flexural da dentina radicular. Cem raízes de incisivos bovinos foram selecionadas, instrumentadas e divididas aleatoriamente em 10 grupos experimentais (n= 10), de acordo com a substância irrigadora utilizada: Controle - solução fisiológica; N1 - hipoclorito de sódio a 1,0%; N5 - hipoclorito de sódio a 5,25% ; N1EDTA - hipoclorito de sódio a 1,0% associado à EDTA a 17%; N5EDTA - hipoclorito de sódio a 5,25% associado à EDTA a 17%; Sclx - solução de gluconato de clorexidina a 2,0%; Gclx - gel de gluconato clorexidina a 2,0%; SclxEDTA - solução de gluconato clorexidina 2,0% associado à EDTA a 17%; GclxEDTA - gel de gluconato clorexidina a 2,0% associado à EDTA a 17% e EDTA - EDTA a 17%. As raízes foram axialmente seccionadas em duas metades. Uma metade foi utilizada para ensaio de microtração, da qual foram obtidas seis fatias de 1,0mm de espessura que receberam constrições na face externa, determinando área de teste de 1mm2. A outra metade foi utilizada no ensaio de flexão de 3-pontos, da qual foi extraída uma barra de dentina com dimensões de 1X1X12 mm. Cada amostra permaneceu duas horas em contato com a substância irrigante endodôntica com exceção do EDTA, que atuou por cinco minutos. Após o tratamento com os irrigantes, procedeu-se a lavagem com água destilada, e em seguida executados os ensaios mecânicos. Foram utilizados dispositivos específicos para cada ensaio, acoplados à máquina de ensaio mecânico, utilizando célula de carga de 20Kgf, com velocidade de 0,5 mm/minuto até a fratura da amostra. Os dados obtidos foram submetidos à análise de variância e teste Tukey. Verificou-se redução significativa na resistência máxima coesiva e flexural apenas para os grupos que empregaram o hipoclorito de sódio independe da concentração e associação com outra substância, diferindo estatisticamente do grupo controle. O uso de clorexidina e EDTA isoladamente não alterou as propriedades mecânicas da dentina radicular