I still have nightmares about dental floss threaders. I had to wear braces for a good portion of my teenage years and those miserable threaders were a constant feature of my life.
My teeth were particularly bad and my mom was really adamant that I take extra good care of my teeth. I flossed with a threader twice daily for years. It's a wonder that I floss at all now. I'm brace free but the memory of those threaders does not go away quickly.