Depending on the area of decay or the size of the existing filling some teeth can be restored with bonded composite (plastic) resin filling.
Composite resin fillings are tooth coloured so they look better, are durable and bonded to the tooth structure so they provide a measure of support and strength for the restored tooth.
They are often smaller and more conservative than other fillings materials because only the decayed portion needs to be eliminated. This helps to preserve the tooth structure for years to come.
See Why We Don’t Use Any Mercury / Silver Fillings
If a patient wish is for a longer lasting restoration or if the size of the fillings is greater than 40-50% of the biting surface of the tooth then a porcelain or gold inlay or onlay may be chosen.