Discolored fillings that do not match the natural color of our teeth lower the esthetic appeal of our smile. For fear of a tooth damage we don’t want to change it in every case. If there is no caries under the filling, we can cover it with the new esthetic layer. Such ‘improvement’ is not harmful. On the contrary, it improves the esthetic appeal. If, however, furrows are visible, we can change the whole filling not because of ugly look but in order to prevent bacteria from getting under the filling and damaging (at the beginning in painless way) the tooth.