Archives for July 2015

What Does a Cavity Under a Crown Look Like?

As this blog approaches nearly 3 years of age and well over 150,000 views, I am able to see what the more popular dental topics are out there. Currently, the fourth most popular post on this site, clocking in with a little more than 19,000 views (as of July 2015), is Dental MythBuster #9: You can’t get a cavity under a crown.

In analyzing what people search for online, many readers – hundreds that is – searched for some variation of: what does a cavity under a dental crown look like?

I had just finished compiling this information when a long time patient of mine – one who I had been telling for several months now about decay under one of her crowns – called to finally schedule her extraction.

Photos and X-rays of Cavities Under a Crown

In this particular case, the decay was so deep that her only option was extraction (see below for why extraction was her only options). Below is a bitewing x-ray:

dental bitewing x-ray showing decay under a crown

The x-ray shows the definite shadow of decay underneath a crown.

I had first diagnosed this nearly a year ago primarily based on the x-ray. In this area of the mouth – the last tooth on the lower left – the cheek drapes up against the tooth – making it very difficult to see – and very difficult to brush!.

I then removed the tooth. And no, I did not put my knee on her chest! The decay was unmistakable. Upon completing the procedure and having the patient go home, the first thing I thought was: “this will make a great photo for my blog!” So here it is:

high quality detailed photo of extracted tooth with decayed cavity under a dental crown

The extracted tooth in all its glory. If you dare, you can click on it to see a larger version!

You can clearly see the decay on this crown when it is out of the mouth. However, when it was in her mouth, it was nearly impossible to see. It could only be “felt” with a dental instrument. But the x-ray showed it.

Why was the tooth extracted?

If you get decay underneath a crown, it doesn’t always mean that the tooth has to be extracted. Before I explain why this was extracted, let’s look at one where the tooth was able to be fixed:

high quality photo of a cavity under an incisor crown

The decay underneath this crown was predictably fixed with a new crown.

The tooth directly above could be saved because the decay was easily accessible and only extended slightly underneath the gum tissue. The tooth had already had a root canal.

For the first tooth, the decay extended deep underneath the gum tissue and went into the furcation (the furcation is where the two roots of two-rooted tooth meet). No amount of modern dental procedures could have saved the tooth. So we extracted it and placed a dental implant.

Please note that I have greatly simplified the criteria for when a tooth can be saved vs. extracted. There are dozens of other factors – all beyond the scope of this post.

So, to summarize:

  • You can get decay or cavities underneath a crown.
  • The extent and location of the decay as well as other factors will dictate the treatment needed to correct the problem.

As always, your dentist should answer all your questions. If he/she doesn’t, it’s time to look for a new one.