A Maryland bridge consists of a porcelain tooth bonded onto a metal framework. The framework has metal wings which are bonded to the lingual side (inside surfaces) of the two adjacent teeth. In order to bond properly, that metal has to be etched. The etching produces microscopic irregularities in the surface that make the metal bond well to dental bonding resins. And there are two ways to make that metal etchable.
One is to use an alloy that contains 1-2% beryllium. Usually that metal also contains nickel and chromium as primary components, but it doesn’t have to. The problem with such an alloy is that about 10% of the population will have an allergy or sensitivity to the alloy. That allergy could be to any of these three components, or all of them, as all are known to provoke sensitivity reactions in some people.
The other way to create an etchable surface on the metal is to plate the metal with tin. When that is done, a semi-precious alloy can be used—one that is made of maybe palladium and silver. Such an alloy is hypoallergenic. The alloy itself isn’t etchable, but the tin plating is. So that is an option for you.
A final option would be to make the bridge out of zirconia. Zirconia is a metal oxide, a compound of the metal zirconium plus oxygen, and is extremely strong. It is a ceramic and is white and translucent, similar to porcelain. Some people call it “ceramic steel.” And it can be etched so that it bonds to dental bonding resin. This, to me, is a better way to go. Not only does it eliminate the sensitivity problem, it is more esthetic since there is no metal to darken the adjacent teeth.
– Dr. Hall
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