Influence of the photoactivation method on the hardness of a composite resin

Authors

  • Monique Mori Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP
  • Carlos Alberto Kenji Shimokawa Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP
  • Paula Mendes Acatauassú Carneiro Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP
  • Tamile Rocha da Silva Lobo Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP
  • Míriam Lacalle Turbino Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, SP

DOI:

https://doi.org/10.11606/issn.2357-8041.clrd.2014.77662

Keywords:

Infl uence of the photoactivation method on the hardness of a composite resin

Abstract

Objective: to evaluate the hardness of a composite resin polymerized with two different methods, continuous and soft-start, by varying the distance between the activator tip and the composite resin (7 mm and 0 mm). Materials and Methods: Twenty test specimens were fabricated, in which the irradiated and the opposite surfaces were analyzed, totaling 40 surfaces divided into 4 groups (n = 10): Group 1, continuous method + irradiated surface; Group 2, continuous method + opposite surface; Group 3, soft-start method + irradiated surface; Group 4, soft-start method + opposite surface. The test specimens were prepared using black polypropylene matrices, with a diameter of 4 mm and thickness of 2 mm, Z350 composite resin (3M ESPE), shade AO3, and the Elipar Freelight 2 curing unit (3M ESPE). The test specimens were subjected to the Vickers hardness test in an HMV-2000 microhardness tester (Shimadzu). Five indentations were made per surface with a load of 50 gf for 45 seconds. The ANOVA and Tukey tests were used for the statistical analysis. Results: No statistically signifi cant difference between the evaluated methods was found in the irradiated surfaces; however, in the opposite surfaces, there were differences between protocols, in that the soft-start protocol achieved the lowest hardness values. When comparing the different depths, there was a reduction in hardness values for both activation methods, so that the maximum hardness percentage of 80% was not achieved in the opposite surface. Relevance: The dentist should be knowledgeable of the photoactivation method applied to his/her restorations, since it may reduce the polymerization quality, especially in depths of 2 mm when using opaque resins.

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Published

2014-09-28

Issue

Vol. 20 No. 3 (2014)

Section

Original Research

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