This refers to a filling that is made from an impression or by an indirect method. Its purpose is to make the tooth stronger by holding it together by bonding to the natural tooth structure while having it's own pleasing esthetic tooth color.
These fillings are made from an impression and fabricated in a lab and therefore take two visits to complete. They are quite durable and can last from 10-20 years. While a conventional silver filling can make a tooth more prone to fracture, a bonded inlay or onlay can actually increase the tooth's strength by 75%. Their advantages are their pleasing esthetic value and their strength.