Abstract
Fluoride-releasing composites lose fluoride very slowly over time. An interesting question is the possible change in mechanical properties related to the F release. If this happens, it might be expected that the mechanical properties of the outer surface of a fluoridating composite are affected first. The purpose of this study was to investigate in vivo and in vitro the changes in surface microhardness and surface structure of three fluoride-releasing composites and a non-F-containing control after 28 days. In the in vitro experiment, the composites were stored in tap water at 37°C. The results show that all composites stored in water were significantly softened after 28 days.
In vivo, however, a very different picture emerged: The surface microhardness of the fluoride-releasing composites did not change significantly. In vitro, the data indicate that the amount of softening of the fluoridating composites is related to the amount of fluoride released. No relation was found between the amount of F released in one month in vitro and the microhardness changes in vivo. SEM micrographs of fluoridating composites do not reflect the microhardness changes mentioned.
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