Cavities are caused by bacteria in the mouth that, when exposed to sugar, produce an acid that eats away at the enamel on the teeth. To prevent them, you should:
• Limit the sticky, sugary foods your kids eat. Cavities aren't as much about what you eat but how long sugar remains on the teeth afterward. This means avoiding gooey foods that can stick to the teeth for hours, such as chewy fruit snacks, or foods that douse the mouth in sugar for extended periods of time, like soda or lollipops.
• Make teeth more cavity-resistant with fluoride (found in drinking water, in toothpaste, or in supplements) and dental sealants.
• Remove the sugar on your child's teeth with regular brushing and flossing. Start with an age-appropriate toothpaste approved by the American Dental Association. Kids under 2 should use fluoride-free toothpaste; after that give your kid a pea-sized dollop of the fluoridated kind (toddlers can't rinse and spit efficiently and end up swallowing most of the toothpaste). By age 4 you can start using a little more toothpaste and allow your kid to start participating more in the brushing.
Toothbrush quality is also important. Have your child choose only from brushes made by a major dental brand (which means no brushes from the toy store) and make sure the bristles are soft, since kids' teeth don't need a lot of abrasive scrubbing. If your toddler or older child wants to use an electric or battery-operated brush, that's fine. Just make sure that it's designed for children. Adult electric toothbrushes rotate much faster than kids' versions and are far more abrasive.