Two main ways cavities attack teeth.
The first is through the pits and fissures on molars and premolars, which are grooves that are visible on the top biting surfaces. These pits and fissures are thin areas of enamel that contain recesses that can trap food and plaque to form a cavity. The cavity starts from a small point of attack, and spreads widely to invade the underlying dentin.
In a smooth surface cavity, acid attack is from a smooth surface, which is between, or on the front or back of teeth. The acid must travel through the entire thickness of the enamel. The area of attack is generally wide, and comes to point or converges as it enters the deeper layers of the tooth.