Some Romans brushed their teeth with tooth powder mixed with water, very similar to how modern toothpaste is made. It was called dentrificium in Latin (you can see the root dens- in there, cf "dental"). From Pliny we get the impression that it was made up of powdered dry ingredients and they brushed or gargled with liquid. It's easiest if you just read what he writes here. There is clearly an abrasive element (like modern toothpaste) and a medicinal element for gums or whitening. He also mentions using a small animal bone to pick at the gums. In Diodorus, Agathocles tyrant of Syracuse uses a "quill" or bird's feather (Greek πτερόν) to pick his teeth after eating, like a modern toothpick. But tooth powder is the subject, famously, at Apuleius Apologia 6 as well, where he also mentions the most famous toothcare-related mention of all: Catullus poem 39, where he suggests that civilized peoples (in Italy) brush their teeth puriter ("cleanly"), but Celt-Iberians in Hispania brush their teeth with their own piss!