I'm 36, and I've had 32 cavities filled in my lifetime. I can't stand the procedure every time, and it's been heartbreaking for me not to be able to pinpoint why I've had so many cavities. I'm vegetarian, and I don't drink soda or alcohol. I brush regularly but should probably floss more. I do drink a lot of coffee and a lot of water. I completely avoid any candy and processed sugar (except for the occasional bit of something sweet in a restaurant dessert once or twice a year). I also eat a lot of acidic fruits and vegetables like tomatoes, lemons, limes, and pineapples.
Most were in my early teens (I had eight filled at once one time) so I was convinced it was the dentist racketeering and my parents wouldn't let me out of getting them filled. I should note my parents have a similar diet and a similar amount of major dental work. The handful of cavities I've had in adulthood have been major blows to my mental health.