It's stating the obvious to say that spotting a brown patch on a tooth is concerning. Teeth should be white, or off-white, although some teeth may be more yellow than they should. Brown discoloration suggests advanced decay, as though the tooth's deterioration is so severe that you're in danger of losing the tooth. What can be especially puzzling is when you know that the tooth needed some attention in the past, but as far as you're concerned, those problems were solved when a dental crown was fitted to the tooth.

Many Years of Service

It's difficult to give the precise length of time a dental crown will last. There are so many different factors to consider, such as your own level of oral hygiene, the amount of pressure (wear and tear) that the tooth experiences, along with the material used to make the crown. Some crowns are even acrylic (plastic), which can become tarnished quite easily. You can assume that a crown will last (as a very rough average) for around ten years. With a high standard of care, a crown can last even longer. Since it may have been many years ago, you might not even remember what type of crown was fitted.

Porcelain and Metal

When a brown patch develops on a tooth with a dental crown, it may be due to the composition of the crown. If your dentist thought that porcelain fused to metal (PFM) crown was the best choice to suit your needs, then this is what would have been fitted. These crowns involve a porcelain shell fused over a metal frame. These crowns offer fantastic functionality, even when they eventually begin to show their age. 

Thinning Out

As the porcelain shell over the metal frame experiences all the wear and tear, friction, and bite pressure that a crown might expect, that porcelain shell begins to thin out. This is entirely expected, but as the porcelain thins, the underlying metal becomes visible. This is the brown patch—it is metal becoming more visible as the porcelain thins out. 

Good News and Bad News

The good news is that your crown is likely to still be in perfect working order—still doing precisely what it's supposed to. The bad news is that the appearance of the metal frame cannot be reversed, and it will become more prominent in the coming years. This isn't a simple discoloration of natural dental enamel, so it's not as though this issue can be corrected with whitening toothpaste or a teeth whitening kit.

Upgrading Your Crown

What happens next is up to you, but you may wish to have the crown assessed, if only for esthetic purposes. All porcelain crowns offer the necessary strength to serve your purposes, so it might be time to have your PFM crown replaced. Although any dental crown will experience some wear and tear, as the new crown is entirely porcelain, you won't experience the same problem in the years to come.

It's not an urgent matter (since the crown remains totally functional), but discoloration around a PFM crown suggests it's time for an upgrade.

Contact a local dentist to learn more about porcelain crowns and other crown materials.