Fluoridated water and occasional low-dose supplement tablets are the clear reason why I didn't have a single major cavity until I was nearly 50, in spite of a lifetime of very haphazard, on-again off-again brushing habits. (yes, I've since standardized my brushing!). My parents and other relatives aren't especially genetically resistant to tooth decay or anything, so I'm pretty sure it was the fluoride that gave me such a cavity-free first five decades. That certainly saved me money, but it saved the public health system even more. Meanwhile I still did my part to keep dentists in business with yearly cleaning and checkups.