In 2012, a number of county jail inmates filed a $500 million lawsuit against Westchester County in New York State, after being denied dental floss, claiming that the result was dental decay and gum disease. There have been reports that prisoners escaped using ropes braided out of dental floss (yes, it’s really happened, and many times. See 1001 Uses #1 for the report. There have also been stories of prisoners using the floss to strangle each other, to saw through jail cell bars, with tooth paste as the abrasive that would do the job (questionable, really, and it would probably take years of sawing if this could really work), and the floss container as well as tooth brushes can be modified for use as a weapon. Some inmates are very creative, and I suppose they’ve got a lot of time on their hands to think these things up and then do them. Jail officials cite these security issues, saying there’s more at stake than oral hygiene.
I haven’t seen any news about how this lawsuit worked out. So far, as far as I know, there’s no constitutional amendment that mandates the right to bear floss. All the paperwork probably gave these convicts a chance to get the guards with papercuts, though, or maybe escape on a giant taped-together paper airplane.