Clinical Case: Why crowns are recommended for teeth with large fillings.

It can happen at any time – chewing on a hard nut or candy, biting into a carrot, or even sinking your teeth into a soft pizza! At least once a week, I see a patient in my office who has broken a tooth or filling. Those who are lucky are able to have the teeth fixed with a simple filling. However, sometimes broken teeth cannot be saved and the only choice is to extract the tooth.

This patient presented to the clinic as an emergency. She had crunched down on a crouton and felt a “snap” in one of her teeth.  Notice the large size of the fillings.

Fractured Outer Cusp

When I examined the tooth, I found that the outer cusp of the second premolar had been fractured.  The patient was frozen so that I could examine the tooth without causing her discomfort.  As can be seen in the above photo, the cusp could move freely from the tooth itself – it had broken clear off the tooth and was only being held in by the attachments to the gums.

Broken Cusp Removed

The broken cusp was removed to assess the damage and restorability of the tooth.  Unfortunately, this tooth could not be saved for a few reasons:

  1. The cusp has broken below the gumline.  When this occurs, it is nearly impossible to restore the tooth with a filling that is properly sealed.
  2. Gum tissues do not like to be too close fillings – so even if it were possible to place a properly sealed filling on this tooth, the gums would be constantly inflamed, bleeding, and sore due to the proximity of the new restoration.
  3. The fate of this tooth is sealed by the fact that the nerve has been exposed.  In most cases, an exposed nerve could be addressed by performing a root canal.  But this procedure cannot be performed safely in this case because it is impossible to properly isolate the tooth without the missing cusp.

Unfortunately, the only thing left to do with this tooth was to remove it.  Could this have been prevented?  ABSOLUTELY!

How to preventing teeth from breaking

The situation above could have been prevented with the use of a crown, which can be likened to a “thimble” that encapsulates a tooth.  The crown serves the same purpose as the metal rings around a wooden barrel – just as the rings help to hold the barrel’s form and prevent the wooden segments of the barrel from spreading, so too does the crown prevent the cusps of teeth from breaking, chipping or splaying.

Teeth that have large fillings (such as the ones in the pictures above) and teeth that have been root canaled are more susceptible to fracture.  That is why it is usually recommended to place crowns on these teeth, to prevent them from breaking.

It’s impossible to predict whether a tooth will break or not.  However, when they do break, it’s like a lottery – some teeth can be saved, while others cannot (like the case above).  Crowns are simply a preventive measure to help protect teeth that are prone to fracture, and to increase their longevity and function.

– Dr. Michael Banh

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