The risk of dental fluorosis development is related to the systemic exposure to fluoride during enamel formation. Currently, diet and fluoride toothpastes are the main sources of fluoride to children at the age-risk for fluorosis development. However, when estimating the risk of fluorosis from toothpaste inadvertently ingested, it has not been considered the systemic fluoride bioavailability. Since some toothpaste formulations may contain part of fluoride as insoluble salts, the hypothesis behind this study is that only soluble fluoride in toothpastes would be absorbed when they are inadvertently ingested. To test that, adult volunteers will ingest a standardized dose of total fluoride from commercially available toothpastes, which present different concentrations of soluble fluoride. Fluoride systemic bioavailability will be assessed by the release of fluoride in saliva up to 3 hours after ingestion (as an indicator of blood fluoride) and by urinary fluoride excretion.