Bleaching can decrease the surface hardness of resin-based composites but may not change the hardness of ceramics, according to a new study to be presented at the upcoming International Association for Dental Research (IADR) meeting in Barcelona, Spain, July 14-17.
Researchers from the University of Passo Fundo evaluated the effect of two bleaching products (16% carbamine peroxide and 7.5% hydrogen peroxide) on the hardness of two composite resins (Filtek Z350 and Filtek Supreme, 3M ESPE) and two feldspathic ceramics (VM7 and VM13) after 3, 6, 13, 20, 28, 34, and 41 days.
They fabricated 20 disk-shaped specimens from each material and submitted them to bleaching. The hardness values were then evaluated using a hardness tester.
"Both ceramics showed no statistical differences in mean hardness values, but both resin composites significantly decreased in hardness after bleaching with any of the protocols," the authors concluded.
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