What? A crown can get a cavity on it?

I have heard this question a lot in my dental career. I don’t blame people for this seemingly dumb question because how would they know. They’re not dentists!

The answer is yes. And just to clarify another point, a tooth with a root canal and a crown can still get a cavity…..or fracture…..or infection. A lot of people think that if a tooth has a root canal and a crown, then there will be no further work needed on that tooth. They think it’s already had so much work to fix it, how could it ever need more work? Some even think they don’t need to brush and floss that tooth anymore. Wrong again!

A crown (or “cap”) covers the tooth to help protect if from fracture. A crown is necessary when a tooth is so heavily restored with fillings that the remaining tooth structure is weakened. At this point, we worry the tooth will fracture and need to be extracted, so we crown it. But even after a crown is done, there is still a margin where the ceramic of the crown meets the margin of the tooth (see picture). This micro-gap can be a large cave for bacteria, and they can hide out and cause decay below the crown. So please brush and floss your crown!

A tooth that has had a root canal AND crown can fail for several reasons. Sorry to say it, but you will most likely not have this tooth the rest of your life. A dental school professor once told me that teeth have 9 lives, just like cats. To me this means that after I have worked on a tooth roughly 9 times, there is no further heroics that can be done. Think about a tooth that needs a root canal and crown-this tooth most likely had a small cavity when you were a young kid. They had to do a filling on it. Years later that filling had to be replaced, possibly even 2-3 times. After more time a dentist decided the tooth needed to be crowned. Years later that tooth gave you a toothache, so you had a root canal procedure. This poor tooth has been worked on 9 times over the course of 20-30 years. Even assuming high quality dental work (which unfortunately does not always occur-thus shortening the lifespan of that tooth even further) that tooth is about ready to give up. At this point the root canal can get re-infected, the root can fracture from too much stress, or you can get decay again around the crown. If any of these happen, I unfortunately much be the bearer of bad news-that tooth you thought was supposed to last forever because it had a root canal and a crown needs to be extracted. Sorry!

So please understand that all dentistry has a lifespan and in order to maximize it, you need to take care of all that dental work you invested in years ago!

-Dr. Spillers