O objetivo deste estudo foi realizar uma revisão crítica da literatura sobre os fatores que podem interferir nos resultados do teste de microtração de sistemas adesivos ao esmalte ou dentina. Foram utilizados trabalhos publicados nas bases de dados eletrônicas MEDLINE e BBO, em inglês, espanhol ou português, entre julho de 1994 e setembro de 2009, referências destes artigos, além de dissertações e teses disponíveis em bancos de dados eletrônicos de universidades brasileiras enfocando o estudo das variáveis que podem influenciar cada fase da execução do ensaio de microtração. A estratégia de busca incluiu os termos: microtração e teste; microtração e ensaio; microtensile e test e parameters; microtensile e test e factors; microtensile e specimen; microtracción e espécimen. Os 25 artigos selecionados demonstraram que mesmo após a padronização de parâmetros do ensaio, as alterações encontradas na dentina podem ser responsáveis pela variação do resultado. Uma maneira de reduzir esta influência seria utilizar os valores de resistência coesiva da dentina adjacente à interface adesiva como padrão de comparação, porém mais estudos são necessários. Aspectos relativos à análise dos dados devem ser levados em consideração quando se compara os estudos.

The aim of this study was to provide a critical review of the literature regarding factors that can interfere with microtensile test results for enamel and dentin adhesive systems. Primarily, reports in English, Spanish, or Portuguese that were published between July 1994 and September 2009 and are catalogued in MEDLINE and BBO were used. Additionally, we compiled relevant articles found in the references of these articles and dissertations and theses available in electronic databases of Brazilian universities that examined factors that can influence implementation of the microtensile test at each stage. The search strategy included searching for the following key term groups: microtensile and test; microtensile and assay; microtensile and test and parameters; microtensile and test and factors; microtensile and specimen; microtraccón and especimen. We reviewed 25 selected articles and found that they showed that even after adjustment of test parameters, changes found in the dentin could be responsible for variations observed amongst results. This influence could potentially be reduced by using the cohesive strength value of dentin adjacent to the adhesive interface as a standard for comparison, but more studies are needed to confirm whether such an approach would be reliable. Data analysis methodology should be taken into account when comparing studies.

OBJETIVO: Avaliar a resistência ao cisalhamento de adesivo autocondicionante e adesivo convencional ao esmalte e dentina bovinos. METODOLOGIA: As superfícies vestibulares de 28 incisivos mandibulares bovinos foram lixadas, sob refrigeração, para obtenção de superfícies de esmalte ou dentina planas. Um adesivo autocondicionante de passo único e um convencional de três passos foram utilizados de acordo com as instruções dos fabricantes (Adper Easy One and Adper Scotchbond, respectivamente). Um cilindro de resina composta foi confeccionado sobre a camada adesiva usando um molde de silicone (2 mm de diâmetro × 3 mm altura). Os espécimes foram armazenados a 37°C em água destilada por 24 h. A resistência de união foi mensurada através de máquina de ensaios universal à velocidade de 0.1 mm/min. Teste t de Student comparou os resultados de resistência de união entre os adesivos com nível de confiança de 95%. RESULTADOS: Para os espécimes de esmalte, Adper Scotchbond apresentou valores significativamente maiores que Adper Easy One (P=0.007). Para espécimes de dentina, não houve diferenças significativas entre os adesivos (P=0.12). CONCLUSÃO: Adper Easy One mostrou menor resistência ao cisalhamento do que Adper Scotchbond no esmalte. Para dentina, Adper Easy One mostrou resistência de união similar ao Adper Scotchbond.

PURPOSE: To evaluate the shear bond strength of a self-etch adhesive and an etch-and-rinse adhesive when bonded to bovine enamel and dentin. METHODS: The labial surfaces of 28 bovine mandibular incisors were wet ground to achieve a flat enamel or dentin surface. A 1-step self-etch adhesive and a 3-step etch-and-rinse adhesive were bonded to enamel or dentin according to the manufacturer's instructions (Adper Easy One and Adper Scotchbond, respectively). A composite resin cylinder (Filtek Z350 XT) was built upon the adhesive layer using a silicon mold (2 mm in diameter × 3 mm high). The specimens were stored in 37°C distilled water for 24 h. The bond strength was measured by a universal testing machine at a crosshead speed of 1.0 mm/min. Student's t-test was used to compare bond strength values between adhesives at the 95% confidence level. RESULTS: For the enamel specimens, Adper Scotchbond had significantly higher values of bond strength than Adper Easy One (P=0.007). For the dentin specimens, there were no statistically significant differences between adhesives (P=0.12). CONCLUSION: Adper Easy One showed lower shear bond strength than Adper Scotchbond on enamel. For dentin, Adper Easy One showed bond strength similar to Adper Scotchbond.

OBJETIVO: Este estudo procurou verificar se o tratamento térmico influencia na microdureza Knoop (KHN) de resinas compostas, e observar se existem diferenças entre áreas fotoativadas antes e depois da aplicação do calor. METODOLOGIA: Oitenta e quatro amostras retangulares transversais (10 × 2 mm × 2 mm) foram preparadas, 14 por resina composta. Após fotoativação (600 mW/cm² - 40), sete espécimes por compósito foram tratados termicamente (170 ºC/10 min), enquanto os demais permaneceram sem tratamento térmico (controle). Os dados de KHN foram obtidos em três áreas de cada amostra, de acordo com a distância a partir da superfície irradiada (mais próxima, intermediária e mais distante). Os dados foram analisados por ANOVA a dois critérios e teste de Tukey a 5%. RESULTADOS: O aumento da KHN foi dependente dos compósitos estudados. Os valores da KHN da TE-Econômico, Natural Look e Prisma foram significativamente melhorados por tratamento térmico (P < 0,05), enquanto que na FillMagic e Glacier permaneceram inalterados (P > 0,05) após o aquecimento. A área mais distante irradiada influenciou significativamente a KHN para todos os compósitos, independentemente da aplicação de tratamento térmico (P < 0,05). Quanto mais próximo da superfície irradiada, maior foi a KHN observada (P < 0,05). CONCLUSÃO: A escolha do compósito é importante quando é proposta a melhora da KHN por aquecimento. Quanto mais próximo da fonte de irradiação, maior a dureza mesmo após tratamento térmico.

PURPOSE: The mechanical properties of direct composites may be improved by heat treatment. This study aimed to verify whether heat treatment influences the Knoop microhardness (KHN) of direct composites and whether there are differences among photoactivated areas before and after the application of heat. METHODS: A total of 84 rectangular cross-sectional specimens (10 × 2 × 2 mm) was prepared, 14 per composite. After photoactivation (600 mW/cm² - 40 s), seven specimens per composite were heat-treated (170 ºC/10 min), whereas the others remained unheated (control). KHN values were obtained for three sites on each specimen at specified distances from the irradiated surface (0.2, 1.0, and 2.0 mm). The data were analyzed by two-way ANOVA and Tukey's test at with a significance level set to 5%. RESULTS: The improvement in the KHN values depended on the composites studied. The KHN values of TE-Economic, Natural Look, and Prisma were significantly improved by heat treatment (P < 0.05), whereas FillMagic and Glacier remained unchanged (P > 0.05) after heating. The distance from the irradiated area significantly influenced the KHN of all of the composites, regardless of heating application (P < 0.05). Sites that were closer to the irradiated surface exhibited a higher KHN (P < 0.05). CONCLUSION: The choice of the composite is important when intending to improve the KHN by heating. Sites that are closer to the irradiation source exhibit greater hardness, even after thermal treatment.

OBJETIVO: A associação de resinas compostas de uso direto com tratamentos térmicos pode melhorar as propriedades mecânicas destes materiais. No entanto, a temperatura ideal de aplicação está na dependência do comportamento térmico individual, como a temperatura de transição vítrea (Tg) e a temperatura inicial de degradação. Com o objetivo de propor uma metodologia de aplicação do tratamento térmico, o objetivo deste trabalho foi caracterizar cinco resinas compostas de uso direto usando calorimetria exploratória diferencial (DSC) e termogravimetria (TGA). METODOLOGIA: Corpos-de-prova cilíndricos (3×2 mm) foram fotoirradiados utilizando um aparelho de fotopolimerização (600 mW/cm² - 40s). As análises térmicas foram realizadas nas temperaturas de 25 ºC a 900 ºC. RESULTADOS: Os valores de Tg após análise de DSC foram: 130,6 ºC para FillMagic, 129 ºC para Glacier, 143,5 ºC para Te-Econom, 147,5 ºC para Prisma APH e 143,7 ºC para Natural Look. Para todos os materiais estudados a degradação iniciou-se por volta de 270 ºC. CONCLUSÃO: Considerando a aplicação do tratamento térmico em resinas compostas de uso direto, é possível sugerir que a temperatura efetiva é dependente do material em uso.

PURPOSE: The association of direct resin composites with simple thermal treatments may improve the mechanical properties of these materials. However, the ideal temperature for heat application depends on the thermal behavior of each material, such as glass transition (Tg) and initial degradation temperatures. To propose a heat treatment methodology, this study evaluated the thermal behavior of five commercial direct resin composites using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). METHODS: Photo-irradiation was achieved in cylindrical specimens (3×2 mm) using a photo-activator source (600 mW/cm² for 40 s). Thermal analyses were performed by DSC and TGA using a temperature range from 25 ºC to 900 ºC. RESULTS: Tg values obtained by DSC were 130.6 ºC for FillMagic, 129 ºC for Glacier, 143.5 ºC for Te-Econom, 147.5 ºC for Prisma APH and 143.7 ºC for Natural Look. A moderate weight loss began at around 270 ºC for all materials, which represented the initial degradation temperature. Conclusion: Regarding the heat treatment itself, it was concluded that the effective temperature for heat treatment is material dependent.

The aim of this study was to compare the surface roughness achieved by different finishing/polishing systems on two composite resins for direct use after thermic treatment. The specimens (n = 40 per group (G); G1 = Filtek™ P60; G2 = Fill Magic®) were set up on a matrix of stainless steel with circular internal niches (Ø = 10.0 mm; h = 2.0 mm). Next, they were subjected to thermal treatment in a heated chamber at 170 °C for 10 minutes. They were then divided randomly into four subgroups (Sg) to receive the surface treatment according to the finishing/polishing systems tested (n = 10): Sg A: Control; Sg B: Diamond® felt disc + Diamond Excel® diamond paste; Sg C: Sof-Lex® discs; and Sg D: Enhance™ silicon tips. The mean roughness (Ra) was determined using a digital surface roughnes tester. Data was analyzed by two-way ANOVA and Tukey's post-hoc test (α = 0.05). Differences between the surface treatments were found on both resins (p < 0.05). In G1, the lowest mean Ra values were observed using Sg C (0.07 μm) and the highest for Sg D (0.12 μm) (p < 0.05). There was no difference between Sg B (0.08 μm) and Sg C (0.07 μm) (p = 0.076). In G2, there was a progressive increase in mean Ra values from Sg D (0.05 μm) to Sg C (0.06 μm) and to Sg B (0.07 μm) (p < 0.05). It was concluded that the finishing/polishing systems modified Ra on both resins.

The purpose of this study was to evaluate the flexural strength of a direct composite, for indirect application, that received heat treatment, with or without investment. One indirect composite was used for comparison. For determination of the heat treatment temperature, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed, considering the initial weight loss temperature and glass transition temperature (Tg). Then, after photoactivation (600 mW/cm² - 40 s), the specimens (10 x 2 x 2 mm) were heat-treated following these conditions: 170ºC for 5, 10 or 15 min, embedded or not embedded in investment. Flexural strength was assessed as a means to evaluate the influence of different heat treatment periods and investment embedding on mechanical properties. The data were analyzed by ANOVA and Tukey's test (α = 0.05). TGA showed an initial weight loss temperature of 180ºC and DSC showed a Tg value of 157°C. Heat treatment was conducted in an oven (Flli Manfredi, Italy), after 37°C storage for 48 h. Flexural strength was evaluated after 120 h at 37°C storage. The results showed that different periods and investment embedding presented similar statistical values. Nevertheless, the direct composite resin with treatments presented higher values (178.7 MPa) compared to the indirect composite resin (146.0 MPa) and the same direct composite submitted to photoactivation only (151.7 MPa). Within the limitations of this study, it could be concluded that the heat treatment increased the flexural strength of the direct composite studied, leading to higher mechanical strength compared to the indirect composite.