Activation mode effects on the shear bond strength of dual-cured resin cements.

OBJECTIVES: This study evaluated the immediate (10-minute) and delayed (24-hour) bond strength of dual-cured resin cements that are light-activated either immediately or delayed (after five minutes) or chemically-activated only. MATERIALS AND METHODS: Three dual-cured resin cements were evaluated: RelyX ARC, Panavia F and Enforce. Cylinders of resin cement were built up over resin composite blocks following the manufacturers' instructions for each luting agent. The cements were mixed, inserted into the molds and light-activated either immediately or after five minutes (delayed light activation). When no light activation was performed, the materials were protected from light exposure until testing. Half of the samples were tested at 10 minutes; the remaining samples were stored at 100% relative humidity for 24 hours when they were then tested (n = 10). Data were submitted to three-way ANOVA and post-hoc Tukey's tests (alpha = 0.05). The failure mode was evaluated under SEM. RESULTS: RelyX ARC presented the highest values of shear bond strength, followed by Enforce. Panavia F showed the lowest values. Both immediate and delayed light activation caused the cements to present the highest means of shear bond strength. There was an improvement in bond strength after 24 hours of storage. CONCLUSIONS: RelyX ARC produced the highest bond strength, which was improved by light activation and storage for 24 hours.

Variability of shear and microtensile bond strength tests to enamel and dentin / Variabilidade de testes de cisalhamento e microtração ao esmalte e à dentina

Purpose: This study aimed to provide guidelines about the coefficient of variation (CV) of shear (SBS) and microtensile (µTBS) bond strength to enamel and dentin. Methods: A search of the English language peer-reviewed literature was conducted using the PubMed database from 2000 to 2009. Only bond strength studies (SBS and µTBS) that have tested both enamel and dentin substrates were selected. The following information was gathered from the 103 papers selected: groups mean and standard deviation (SD), repetition number, and type of statistical analysis. The CV of each study was calculated by using its mean and SD values, the normality of shear and microtensile CV was analyzed using Shapiro-Wilk test, and a CV classification was established for each variable. Results: According to the CV classification proposed, values below 10.3% and 11.3% could be considered low for shear bond strength to enamel and dentin, respectively; and values below 15.4% to enamel and 16.4% to dentin could be considered low for the microtensile test. Values higher than 46.8% and 62.1% (shear bond strength to enamel and dentin) and 45.9% and 45.5% (microtensile bond strength to enamel and dentin) showed a very high variability. Conclusion: Such classification can be useful for future experiments on adhesive materials to estimate statistical power and data precision.

Objetivo: Este estudo se propôs a fornecer diretrizes sobre o coeficiente de variação (CV) de ensaios de resistência ao cisalhamento (SBS) e à microtração (µTBS) em esmalte e dentina.Metodologia: Uma busca de artigos publicados de 2000 a 2009 foi realizada na base de dados PubMed. Apenas estudos (SBS e µTBS) que testaram esmalte e dentina foram considerados elegíveis. As seguintes informações foram coletadas dos 103 artigos selecionados: média e desvio-padrão (DP) dos grupos, número de repetições e análise estatística. O CV de cada estudo foi calculado utilizando-se média e DP, a normalidade dos CV de cada teste foi analisada pelo teste de Shapiro-Wilk e classificações para os CV foram estabelecidas. Resultados: De acordo com a classificação proposta, valores menores que 10,3% e 11,3% são baixos para estudos de cisalhamento ao esmalte e dentina, respectivamente. Para estudos de microtração, baixa variabilidade é obtida com CV menores que 15,4% (esmalte) e 16,4% (dentina). Experimentos com CV maiores que 46,8% e 62,1% (cisalhamento no esmalte e dentina) e 45,9% e 45,5% (microtração no esmalte e na dentina) apresentam variabilidade muito alta. Conclusão: Esta classificação pode ser útil para futuros experimentos em Odontologia adesiva para estimar o poder estatístico dos testes e a precisão dos dados.

Influence of fiber-post translucency on the degree of conversion of a dual-cured resin cement.

This study evaluated the degree of conversion of one dual-cured resin cement when used to lute fiber posts with different translucencies. To measure the degree of conversion, polyvinylsiloxane molds were prepared to simulate root canals. The posts, Aestheti-Post or Light-Post, were cemented in these molds and, after photoactivation, were removed to obtain the resin cement spectrum by FT-Raman spectroscopy. Spectra were acquired at three depths: superficial, medium, and deep. For Light-Post, the resin cement at deep depth showed the lowest degree of conversion and no significant difference in degree of conversion was found between the other depths. For Aestheti-Post, the superficial depth presented a higher degree of conversion values than those in the medium and deep depths, which were not significantly different from each other. Light-Post exhibited a higher degree of conversion than that of Aestheti-Post only at medium depth. Light-Post effectiveness regarding the degree of conversion is dependent on the depth.

Microleakage study of three adhesive systems

O objetivo deste estudo foi avaliar a eficácia de 3 sistemas adesivos hidrófilos na redução da microinfiltração de restaurações classe II. Foram selecionados 60 dentes molares humanos. Foi realizado em cada dente dois preparos classe II do tipo "slot vertical" nas superfícies mesial e distal, com margem cervical em dentina. As 120 cavidades foram sorteadas aleatoriamente em 3 grupos (n = 40), de acordo com o sistema adesivo testado G1: OptiBondo SOLO® (Kerr); G2: Amalgambond Plus® (Parkell); G3: Etch & Prime 3.0® (Degussa). As cavidades foram restauradas com resina composta Z 100 (3M/ESPE). As amostras foram termocicladas 2000 vezes (5 ± 1ºC e 55 ± 1ºC), durante 1 min em cada banho. Após a termociclagem, os dentes foram imersos em uma solução de azul de metileno a 2%, pH 7,0, durante 4 h, seccionados e observados em microscópio ótico MEIJI 2000 (35X). A avaliação foi realizada utilizando-se escores (0-4) e os resultados expressos através da soma das ordens. G1: 1994.00; G2: 2294.00; G3: 2972.00. Os 3 grupos foram significativamente diferentes. Os resultados indicaram que o sistema adesivo auto-condiconante Etch & Prime 3.0 foi menos efetivo no controle da microinfiltração marginal. Já o sistema adesivo OptiBond SOLO foi o mais efetivo no controle da microinfiltração quando comparado com o Amalgambond Plus e o Etch & Prime 3.0.

Microleakage study of three adhesive systems.

The purpose of this in vitro study was to evaluate the efficacy of three hydrophilic dentin adhesive systems to reduce class II restoration microleakage. A total of 60 human molar teeth were used in which two box cavities were made on the distal and mesial surfaces, with a cervical margin in dentin. These cavities were randomly divided into 3 groups (n = 40 each), according to adhesive system tested: G1: OptiBond SOLO; G2: Amalgambond Plus; G3: Etch & Prime 3.0. The cavities were restored with the composite resin Z-100. The groups were thermocycled 2000 times (5 +/- 1 degrees C and 55 +/- 1 degrees C) with a dwell time of 1 min. The teeth were then immersed in 2% methylene blue, pH 7.0, for 4 h, sectioned and observed with a stereomicroscope MEIJI 2000 (35X). The evaluation was made using scores (0-4) and the results were expressed through the sum of the ranks. G1 = 1994.00; G2 = 2294.00; G3 = 2972.00. The three groups were significantly different. The self-etching adhesive system Etch & Prime 3.0 was less effective in preventing microleakage. The OptiBond SOLO adhesive was the most effective in reducing microleakage in dentin margins when compared with Amalgambond Plus and Etch & Prime 3.0.