This isn't even to the level of a hypothesis yet, but I think periodontal disease, which effects a great deal of people, may be significantly ameliorated by taking an NSAID like ibuprofen 20-40 minutes prior to brushing and flossing, due to the reduced gum inflammation decreasing periodontal pocket depth and allowing access to the pathogenic bacteria.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.