| Dental Gold |
Because of its bio-compatibility, malleability and resistance to corrosion, gold has been used in dental work for nearly three thousand years. The Etruscans in the seventh century BC used gold wire to hold in place substitute teeth, usually from a cow or calf, when their own were knocked out. The first printed book on dentistry published in Leipzig in 1530 recommends gold leaf for filling cavities.
Preparing dental gold on
bridgework
(Credit: World Gold Council)
The
technique has not entirely disappeared. Gold leaf of 999.9
fineness is still compressed into pellets and
packed into small cavities in teeth that are otherwise sound, with the aid of
a hand mallet or mechanical condenser. This restoration has great durability
against the chemical attack of oral fluids but the gold must be in cavities
exposed to little wear because it is soft.
Thus the main application
of gold in modern dentistry is alloys, which are a mixture of gold and the noble
metals platinum, palladium or silver plus copper and zinc. The aim is an alloy
that is easy for the dentist to manipulate but is strong, stiff, durable and
resistant to tarnish and corrosion. These alloys are used for inlays, crowns
and bridges. The gold content of the alloy will vary from 620-900 fine according
to the precise application. A typical crown and bridge alloy may contain 62-78
per cent gold, with silver, platinum and palladium added to make at least 75
per cent noble metals, plus copper and zinc.
Although the rising cost of gold in the 1970s and 80s lead to a proliferation of inferior alloys, sometimes with gold content as low as twelve per cent, and an increasing use of palladium in some countries, dental use has grown slowly in recent years towards seventy tonnes annually. Dental applications were also curtailed by a tightening up of social security payments for gold work, notably in Germany and Japan. The improvement in consumption has been helped by growing concern, especially in the United States, about the possible side-effects of alloys lacking a high precious metal content and by prosperity in such Asian countries as Indonesia, Malaysia, South Korea and Thailand where high quality imported dental alloys are more widely used. Actual fabrication of dental alloys continues to be mainly in Japan, Germany and the United States, which alone account for almost seventy per cent of all manufacture, although South Korea now ranks as the fifth largest dental fabricator.