Cracks in gold crowns cemented on amalgam restorations

Twenty-seven gold crowns, removed from patients with problems such as diffuse pain and metallic taste, have been examined. The gold crowns were made of an ordinary casting gold alloy, type III. The crowns were built on amalgam cores or big amalgam fillings. Eight of these crowns had cracks beginning at the cervical margin and propagating occlusally. The crowns were examined in a scanning electron microscope equipped with an energy-dispersive detector. The study showed that the cracks propagated along the grain boundaries within the gold alloy. In the cracks corrosion products usually found on amalgam were identified. The cracks could be due to intercrystalline stress corrosion or overloading.