Short Answer: 24-karat Gold, Grade-1 Titanium or Zirconia (in certain cases)
Long Answer: There are many materials crowns and fillings can be made from: Fillings, for example, can be made from a composite resin (basically hard plastic), amalgam (mercury metal filling), porcelain (there are many types) and cast metals (gold or non-precious alloys). But with so many to choose from, the “best” one depends a lot on your budget, tolerance for things not-white in your mouth, patience for longer or multiple appointments and priority placed on the “healthiest” materials. This post focuses on the latter, but I will briefly address the pros and cons of the other materials. Incidentally, crowns can be made from the same materials as fillings, but typically they are made of porcelain or a gold alloy fused to porcelain (also known as a “porcelain-fused-to-metal” crown). Here is a brief and quick summary of the different materials available:
This post could literally go on forever in order to cover the full scope of the available materials. For practical purposes, I will say that the healthiest materials to put in your mouth continue to be Grade-1 titanium (the kind dental implants, artificial joints, etc are made from) and pure gold. This is based on many studies that show the level certain metals have on cell health (cytotoxic) and what kind of immune reaction they illicit. Gold and titanium are generally the gold standards (yes, pun intended) for bio-compatible materials.
As for gold crowns, it is quite rare to have one made out of pure 24k gold. This is because gold is soft and pliable and it would be hard to work with and would wear very quickly in the mouth in a pure form. So usually gold is mixed with other metals, most often they are palladium, silver, copper, zinc, iridium, platinum and more. Depending on the actual content, a dental metal is classified as being “high noble, titanium, noble or a base alloy”. See below:
The chart above shows metals in the order I would choose when having crowns in my own mouth (when purely considering bio-compatibility). Although high noble alloys are at least 40% gold, I generally recommend alloys that have more than 60% pure gold. Naturally, this is expensive to make when compared to other options. But the more gold in an alloy, the less there is of “other” metals. Titanium would be my next choice and I would forgo noble and non-precious alloys. Many people get what are known as “PFM” or “porcelain fused to metal” crowns which are basically thin gold crowns covered with a white porcelain material. Most porcelains are generally safe although they may contain aluminum oxide and even heavy metals (such as cobalt, barium or cadmium). The main disadvantage of a PFM is that the porcelain coating can break off the gold center piece over time. Also, the porcelain is abrasive and hard which causes teeth that oppose it to wear faster than normal. So, if a gold/metal crown was not an option, I would select a pure zirconia oxide material as the most bio-compatible of the porcelains. Zirconia is very strong and has been found to be highly bio-compatible in many studies and some dental implants are now being made of the material (a good sign that the body tolerates it well).
But sticking to the topic of metal crowns, when it comes to dental billing, some unscrupulous dentists will charge you and your insurance for a “high noble” crown but then have the laboratory make one using a lower grade and much cheaper metal. Some dentists even have a laboratory in China or other foreign country make their crowns, places where it is extremely difficult to verify what they are actually making the crowns from. To make matters worse, some laboratories will actually tell an honest dentist they used a high noble metal, when in fact, they did not. All this happens for obvious reasons and it happens more than some people think. That’s because it is is extraordinarily hard to know for sure what it is you got without testing it and it’s extremely easy to fudge the truth. I wish I had some easy foolproof way to detect this type of fraud, but it is very difficult. Some people who are sensitive to base metals will develop gum irritations around the crown edges and this might be a sign of a problem. Also, color alone is not an indicator because even crowns with hardly any gold at all can be made to look gold in color.
Ultimately, you have to trust your dentist and make it very well known that the subject concerns you. Fully expect to get a high noble metal crown if that’s what you or your insurance is paying for. I would also recommend asking your dentist where the crowns are made, and at minimum, I would insist on a US-based laboratory. I personally charge a little extra if a patient requests a crown with gold content beyond 60% because my costs go up accordingly, but the conversation is always open and honest.
So to answer the original question, I don’t think any one thing to put in your mouth is perfect except for your original enamel. But if a crown is required, ideally it would be made from a high noble alloy with more than 60% gold. If a white crown was preferred, I would select a zirconia material.