I get this question a lot from patients. The answer is one of two things: It is either decay that has set in under the crown or the patient is seeing the metal that is underneath the porcelain.
Yes crowns can get decay under them. I am still surprised at the number of my patients that believe once a tooth has been crowned that it is fixed forever. However, this isn't the case. The tooth that is under the crown can still become decayed. It is important to brush thoroughly at the gum line and floss as most cavities under crowns occur between your teeth. I recommend some type of fluoride treatment to my patients that have 5 or more crowns. This will help keep the tooth under the crown from decaying.
What about the metal? I thought this was a porcelain crown? Up until recent years, most crowns placed were of a type that the inner portion was a metal appearing silver with porcelain applied on the outer part of it. These can be noticeable if the gum recedes over time. Today, the trend in dentistry is moving towards crowns that are metal free. This is due to a number of reasons I won't get into here. But what is worth noting is that these crowns are metal free, are stronger, don't wear the opposing teeth as severely, and are superior esthetically. The fit can be just as good or better using modern digital technology.
Notice the light blue line and even the blue gum around one of these front teeth. This is a porcelain crown with metal underneath.
These are four all-ceramic crowns. Much more esthetic and even stronger that the metal-porcelain.
Dr. Derrick Gregory is a general dentist in Lebanon, TN. His practice is focused on using the latest technologies and materials in dentistry. For more information visit his website at Gregory Dental Group or call (615) 444-0322.