Dental fillings replace tooth structure and restore a tooth that has been damaged by decay back to its normal shape and function.
Over time the seal between the tooth and the filling can break down, causing food debris and bacteria to seep down under the filling and cause more decay. If the decay is treated early, replacing the filling is adequate. If not, it can lead to a crown and even a root canal. The biggest mistake one can make is waiting to do something about a broken or unsealed filling until it is painful. Doing this could make the treatment more involved and often times much more expensive.
Regular dental exams and x-rays help to identify the condition of existing fillings so small problems can be fixed before they become major issues.