The conversation about fluoride’s health benefits has exploded after a US federal toxicology report, court ruling and independent scientific review all called for updated risk-benefit analysis. Ian Sample hears from Catherine Carstairs, professor of history at the University of Guelph in Canada, about how attitudes to fluoridation have evolved, and Oliver Jones, professor of chemistry at RMIT University, Melbourne, about where the science stands today You can support the Guardian at theguardian.com/fullstorysupport