Acids such as citric acid are also very safe, but definitely not in the context of brushing teeth as they dissolve enamel. There simply isn't enough safety data _in that context_ for dentists to start recommending EDTA vs regular fluoride toothpaste. In one in vitro study I found, EDTA is shown to cause erosion https://www.medigraphic.com/pdfs/odon/uo-2012/uoi121b.pdf so I'd say more studies are required.