The type of filling (restorative) material used has a minor effect on how long they last. The majority of clinical studies indicate the annual failure rates (AFRs) are between 1% and 3% with tooth colored fillings on back teeth. Note that root canaled (endodontically) treated teeth have AFR's between 2% and 12%. The main reasons for failure are cavities that occur around the filling and fracture of the real tooth. These are related to personal cavity risk and factors like grinding teeth (bruxism).