Though the floss trick does seem to work in the short-term, it’s best used as a quick fix rather than an actual long-term solution to frizz. In other words, if you’re about to head into a special event or your friend wants to snap a selfie and you notice that the top of your head is sprouting flyaways, a few passes of dental floss could help temporarily.
If you rely on this trick too often, though, you could cause a buildup of—you guessed it—wax on your hair, which will cause it to look dull and flat. Not to mention, because you have to use a lot of tension to slide the floss down your hair, this could cause breakage or damage.
TL;DR: Using dental floss on your strands might make for a fun party trick and can perhaps even be helpful if you’re in a pinch, but it’s not meant for regular use.