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1.
Dent Mater ; 28(4): e27-34, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22336142

RESUMO

OBJECTIVES: To purpose a method for predicting the shrinkage stress development in the adhesive layer of resin-composite cylinders that shrink bonded to a single flat surface, by measuring the deflection of a glass coverslip caused by the shrinkage of the bonded cylinders. The correlation between the volume of the bonded resin-composite and the stress-peak was also investigated. METHODS: A glass coverslip deflection caused by the shrinkage of a bonded resin-composite cylinder (diameter: d=8 mm, 4 mm, or 2 mm, height: h=4 mm, 2 mm, 1 mm, or 0.5 mm) was measured, and the same set-up was simulated by finite element analysis (3D-FEA). Stresses generated in the adhesive layer were plotted versus two geometric variables of the resin-composite cylinder (C-Factor and volume) to verify the existence of correlations between them and stresses. RESULTS: The FEA models were validated. A significant correlation (p<0.01, Pearson's test) between the stress-peak and the coverslip deflection when the resin-composites were grouped by diameter was found for diameters of 2 and 4 mm. The stress-peak of the whole set of data showed a logarithmic correlation with the bonded resin-composite volume (p<0.001, Pearson's test), but did not correlate with the C-Factor. SIGNIFICANCE: The described method should be considered for standardizing the stress generated by the shrinkage of resin-composite blocks bonded to a single flat surface.


Assuntos
Resinas Compostas/química , Colagem Dentária , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Vidro , Teste de Materiais , Polimerização , Estresse Mecânico , Propriedades de Superfície
2.
Braz Dent J ; 20(3): 205-10, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19784465

RESUMO

The aim of this study was to verify the influence of an experimental heat treatment (170 masculineC/10 min) using a casting furnace on the mechanical properties (hardness and flexural strength) of 2 commercial direct resin composites (TPH Spectrum and Filtek P60) compared to a commercial indirect resin system (BelleGlass). Heat treatment temperature was determined after thermal characterization by thermogravimetry (TG) and differential scanning calorimetry (DSC). Data was analyzed by ANOVA and Tukey's test at 5% significance level. There was statistical significance for the main factor heat treatment (p=0.03) and composite (p=0.02), for flexural strength. For Knoop hardness, only the main factor composite was statistically significant (p=0.00). P60 presented higher hardness than TPH. No statistically significant correlation between mechanical properties tested was detected. Based on these results, it was possible to conclude that heat treatment influenced flexural strength of direct composites, while it was not observed for hardness. The association of direct composites with a simple post-cure heat treatment may be an alternative for current indirect composite systems, although more studies are needed to verify other properties of the composites for this application.


Assuntos
Resinas Compostas/química , Técnica de Fundição Odontológica , Temperatura Alta , Maleabilidade , Análise de Variância , Análise do Estresse Dentário , Dureza , Humanos , Teste de Materiais , Metacrilatos/química , Estatísticas não Paramétricas , Estresse Mecânico
3.
Braz. dent. j ; 20(3): 205-210, 2009. graf, tab
Artigo em Inglês | LILACS | ID: lil-526411

RESUMO

The aim of this study was to verify the influence of an experimental heat treatment (170ºC/10 min) using a casting furnace on the mechanical properties (hardness and flexural strength) of 2 commercial direct resin composites (TPH Spectrum and Filtek P60) compared to a commercial indirect resin system (BelleGlass). Heat treatment temperature was determined after thermal characterization by thermogravimetry (TG) and differential scanning calorimetry (DSC). Data was analyzed by ANOVA and Tukey's test at 5 percent significance level. There was statistical significance for the main factor heat treatment (p=0.03) and composite (p=0.02), for flexural strength. For Knoop hardness, only the main factor composite was statistically significant (p=0.00). P60 presented higher hardness than TPH. No statistically significant correlation between mechanical properties tested was detected. Based on these results, it was possible to conclude that heat treatment influenced flexural strength of direct composites, while it was not observed for hardness. The association of direct composites with a simple post-cure heat treatment may be an alternative for current indirect composite systems, although more studies are needed to verify other properties of the composites for this application.


O objetivo deste estudo foi avaliar a influência de um tratamento térmico experimental (170ºC/10 min), em um forno de fundição, sobre as propriedades mecânicas (dureza e resistência à flexão) de 2 resinas compostas comerciais de uso direto (TPH Spectrum e Filtek P60), em relação a uma resina comercial indireta (BelleGlass). A temperatura de tratamento térmico foi determinada após caracterização térmica por termogravimetria (TG) e calorimetria exploratória diferencial (DSC). Os dados foram analisados por análise de variância, que mostrou, para a resistência à flexão, diferença estatística para os fatores principais tratamento térmico (p=0,03) e material (p=0,02). Para a dureza Knoop, somente o fator principal material foi estatisticamente significante (p=0,00). A P60 apresentou maiores valores de dureza em relação à TPH Spectrum. Não foi detectada nenhuma correlação estatisticamente significante entre as propriedades mecânicas avaliadas. Baseado nos resultados foi possível concluir que o tratamento térmico influenciou na resistência à flexão das resinas compostas de uso direto, enquanto, para a dureza, o mesmo não foi observado. A associação de resinas compostas a um simples tratamento térmico de pós-cura pode ser uma alternativa para os sistemas indiretos atuais. Entretanto, mais estudos são necessários para verificar outras propriedades das resinas compostas para esta aplicação.


Assuntos
Humanos , Resinas Compostas/química , Técnica de Fundição Odontológica , Temperatura Alta , Maleabilidade , Análise de Variância , Análise do Estresse Dentário , Dureza , Teste de Materiais , Metacrilatos/química , Estatísticas não Paramétricas , Estresse Mecânico
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