I've heard dentists say that flossing might be even more important than brushing as far as dental health is concerned. Dental floss was apparently invented in 1819 and was made of silk. In the US, flossing became more popular around World War II when nylon floss was developed.
The floss picks that I'm trying to use, plastic prongs that hold a short length of floss, have their origin in the late 19th century in a complicated sort of notched toothpick. As far as I can tell from my package of picks, the newest innovation is the "Patented Fold-Away Pick Protector" that "provides greater safety." I can only imagine what flossing will be like in the future.