Babies tend to get cavities on the front teeth, especially if they are given a bottle to sleep with. Even milk contains sugar that can harm teeth. This is referred to as baby bottle tooth decay. Children tend to get cavities on the chewing surfaces as well as in-between teeth. Adults can be at risk for both new and recurrent cavities.New cavities tend to form between teeth as well as on the root surfaces. The cavities that form between teeth are typically related to a lack of flossing. Cavities on the root surfaces of teeth generally occur because this area is not covered with enamel and is softer and more prone to cavities. The exposed root may be the result of hard brushing or bone loss related to gum disease. Cavities that reoccur form next to existing restorations such as fillings, crowns, bridges, etc. As restorations get old, the filling material can shrink or wear away, causing the possibility of a small space forming between the tooth and the restoration. This provides a prime area for bacteria to accumulate and breed decay. Click the link to do an experiment with fluoride to see how it helps fight cavities.