A cavity is a hole that can grow bigger and deeper over time. Cavities are also called dental caries (say: KARE-eez), and if you have a cavity, it's important to get it repaired. But why would your tooth develop a hole? Blame plaque.
Some people feel sensitivity after they receive a filling. The tooth may be sensitive to pressure, air, sweet foods or cold. Composite fillings often cause sensitivity, but other types of filling materials can, too.