When I suggest a patient have a gold crown or filling, even in the last molars, the responses are comical and predictable these days. “You think I want to look like a rapper?” is the most common answer I get.
Gold dental treatment was not always regarded with such suspicion by the public. Hundreds of years after the first use of gold for filling teeth, you might be surprised to learn that gold is still considered the longest lasting material ever invented for fillings and crowns! It was taught as the “premium option” when I attended dental school in the late 1970s. Even our modern plastic polymers and exotic ceramics cannot compare to the longevity of gold when properly used in the mouth. If you look in the mouths of most US dentists (including mine), gold is the most common material you will see!
Why is gold so durable in teeth? Well, we know that gold is a very noble metal, meaning it does not combine with other elements like oxygen. Gold placed in a Pharaoh’s tomb 3000 years ago and uncovered will look pretty much like it did the day it was put there. The mouth is a crucible of different chemicals, including various acids, enzymes, bacterial toxins, and sulfur compounds. An inert element like gold survives this hostile environment better than most materials mankind has invented.
While compressed gold fillings, rarely done anymore, were 100% pure gold, the gold used for cast fillings (“inlays”) and partial crowns, and crowns is alloyed with other metals to increase hardness. Additions to gold include indium, platinum, and palladium. When bridges are made of cast gold, more strength is needed, and the percent of gold is lowered a bit. However, I rarely use gold alloys with less than 70% gold.
Another fine property of gold is that it can be cast to a very thin edge, and burnished to fit the tooth even more accurately. Tight marginal fit is a key feature that makes dental restorations last. Inaccurate margins are the main reason resin fillings and porcelain crowns fail. When there is a microscopic gap between where the restoration ends and the tooth begins, bacteria can enter and eventually cause new decay.
Metal, including gold alloys, can be strong even when cast very thin. Ceramic materials must be at least twice as thick as gold alloys to have enough strength to last in the mouth. If not made thick enough, the usual result is porcelain fracture, especially on second molars. Think about it. Hammer on a thin porcelain dish and a thin sheet of metal. Which one will shatter into pieces? Thick crowns mean having to reduce more tooth structure, which frequently results in pulp deaths and root canals.
Are Metals Safe in the Mouth?
You can’t believe everything you read. You will hear “holistic” healers claim you must get all the metal out of your body to achieve perfect health. This is a bizarre recommendation, as the hemoglobin that carries oxygen in our red blood cells is based on the element iron. Last time I heard, iron is a metal. Other essential trace nutrients that are metals include copper, zinc, chromium, and manganese. We cannot live without these metals.
There is no scientific basis for avoiding metals in dental restorations. True metal allergies are very rare. The only one I have encountered has been to nickel. To my knowledge, no gold dental alloys have any nickel content.
Think about this also. Humans routinely have joint replacements. Many are made of various metal alloys. Our highly biocompatible dental implants are made out of titanium, after early experimentation with crystalline ceramics resulted in implant fractures. Why would metal be safe for joint replacements and dental implants, but unsafe for dental crowns and fillings? The admonition to “get the metal out of our bodies” just does not make any sense.
What Would We Do Without Gold?
Don’t get me wrong. I really appreciate recent advances in resin and ceramic technology. In esthetically critical areas of the mouth, resin and all-ceramic systems have allowed me to more easily match natural tooth color while reducing less tooth structure. With zirconia crowns, we finally have a white material for 2nd molars that resists breakage. (But they have the problem of being hard to bond, and coming loose.) Still, nothing beats the tensile strength of metal alloys, even at relatively small thicknesses. Gold alloys add the important advantages of easy castability and ductility to achieve tight marginal fit. In all the years of its use, nothing has beat gold alloys for tooth restoration in areas that don’t readily show in the smile.
Patients always think about looks and cost, and dentists always think about durability, and for good reason. Doing a quality gold filling once results in far less trauma to the pulp than replacing a resin filling six times during a patient’s lifetime. Although gold fillings, crowns, and bridges may seem expensive at first, they often save patients money and root canals over their life.
Kim Henry, D.M.D.
December 15, 2016