Fluoride became a weapon against tooth decay when it was discovered children who lived in areas with fluoride-rich drinking water had fewer cavities than children who lived in regions without fluoride in the water. Fluoride originally gets into the teeth before birth and in the early years of childhood. It gets into the teeth as they are first forming and gives them strength.
Now that you are older, you can have fluoride placed on your teeth by a dentist or use toothpastes with fluoride to continually give them strength and reduce your chances of tooth decay.
If you have children, check with your local water authority to make sure you have fluoride in your drinking water. If you don’t, then your dentist or family doctor can give fluoride tabs for your children.