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Revista Portuguesa de Estomatologia, Medicina Dentária e Cirurgia Maxilofacial
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Inicio Revista Portuguesa de Estomatologia, Medicina Dentária e Cirurgia Maxilofacial Effect of Light-Curing in the Microhardness of Resin Cements of Dual Polymerizat...
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Vol. 51. Issue 3.
Pages 133-138 (July - September 2010)
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Vol. 51. Issue 3.
Pages 133-138 (July - September 2010)
Open Access
Effect of Light-Curing in the Microhardness of Resin Cements of Dual Polymerization
Isabel Gomes
Corresponding author

Correspondência para.
, Luis Pires Lopes**
* Professor and Chair Department of Prosthodontics, School of Dentistry, University of Lisbon, Portugal
** Department of Prosthodontics, School of Dentistry, University of Lisbon, Portugal
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The aim of this study was to evaluate the influence of the type of the light curing unit, exposure time and absence of light-curing in the microhardness of two resin cements of dual polymerization.

Materials and Methods

Disc-shaped samples were prepared for each resin cement. The samples were light-cured with Visilux 2500 or with Elipar FreeLight 2 for 20 or 40 seconds. In addition, samples that had not been light cured were prepared for each cement studied. Measurements of Knoop microhardness were made after 15 minutes and 24 hours. The average value of Knoop microhardness was determined to each group and the results were submitted to analysis of variance ANOVA and Tukey test (α=0.05).


Differences have been detected between light-cured and non light-cured samples, with these showing significantly lower results. Samples with 20 seconds exposure time and measurements undertaken 15 minutes post-exposure showed statistically significant lower values, compared to samples with 40 seconds exposure time and measurements made 24 hours post-exposure time. No statistically significant difference was found between the results obtained with the two light-curing units.


Light-curing with second generation LED systems did not show higher results, comparatively to conventional Halogen light units. For both cements, microhardness was significantly higher when light-curing was undertaken and there was a significant increase in microhardness after light exposure. Dental practitioners should consider that a LED whit high intensity doesn’t mean a short polymerization time nor a better polymerization in regard to a conventional halogen.

Resin cements
Light curing units
Post-exposure polymerization
Knoop hardness

Este estudo avalia a influência do tipo de fotopolimerizador, do tempo de exposição e da ausência de fotopolimerização na microdureza de cimentos de resina de polimerização dupla.

Materiais e Métodos

Foram preparadas amostras em forma de disco a partir de dois cimentos de resina de polimerização dupla. As amostras foram fotopolimerizadas com Visilux 2500 ou com Elipar FreeLight 2 durante 20 ou 40 segundos. Adicionalmente, foram realizadas amostras dos dois cimentos que não foram fotopolimerizadas. Medições de microdureza Knoop foram realizadas após 15 segundos e 24 horas. O valor médio de microdureza Knoop foi determinado para cada grupo e os resultados foram analisados com ANOVA e teste de Tukey (α=0,05).


As amostras não fotopolimerizadas apresentaram resultados significativamente inferiores comparativamente a todas as amostras fotopolimerizadas. Para um tempo de exposição de 20 segundos e para medições realizadas após 15 minutos foram encontrados valores significativamente inferiores, comparativamente ao tempo de exposição de 40 segundos e às medições realizadas após 24 horas. Não foi encontrada diferença estatisticamente significativa entre os dois fotopolimerizadores em estudo.


a fotopolimerização com LED de segunda geração não apresenta resultados superiores, comparativamente ao halogéneo convencional. Para ambos os cimentos em estudo a microdureza foi significativamente superior quando se realizou fotopolimerização, ocorrendo uma significativa polimerização química após a fotopolimerização. O clínico deve considerar que a polimerização com LED de alta intensidade não significa um menor tempo de exposição nem uma melhor polimerização comparativamente a um halogéneo convencional.

Cimentos de resina
Tempo de fotopolimerização
Polimerização pós-fotopolimerização
Microdureza Knoop
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(Gomes I, Lopes LP. Effect of Light-Curing in the Microhardness of Resin Cements of Dual Polymerization. Rev Port Estomatol Med Dent Cir Maxilofac 2010;51:133–138)

Copyright © 2010. Sociedade Portuguesa de Estomatologia e Medicina Dentária
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