How does a Cavity Form?
There are many factors involved in the formation of a cavity. For example, genetics, the structural integrity of the tooth itself, the shape of the tooth in terms of deep grooves or not, the alignment of teeth in terms of crowding and overlapping, your flow of saliva, diet, the presence of fluoride or not, the bacteria in your mouth, and the length of time the tooth is under attack by the bacteria in your mouth.
Brush, floss, visit your hygienist regularly and your dentist should be able to give you good checkups. If there are problems, the earlier you let your dentist have a turn at fixing the problem, the easier and less expensive it is for you!