I have heard about orally consuming fluoride and rinsing with a solution containing fluoride to help prevent cavities, but I've also heard some claims that fluoride is bad for peoples' health. What health concerns are there and does it matter how the fluoride is taken (e.g. swallowed vs spitting out after a minute)?
According to Wikipeidia it seems fluoride is safe but according to this article and this article it is not. I don't consider Wikipedia a reliable source and the other two articles don't speak directly about reasons why fluoride may be harmful to adults.