When decay and cavities overrun a tooth so much that a crown becomes necessary, it’s fair to believe that the issues within that tooth are resolved when the crown goes on. After all, by the time a crown is placed, the decay is fully removed and the tooth surface is repaired. And, a dentist cements the crown in place to protect the existing tooth (and its neighbors). Unfortunately, this is not always the case. Even before a crown reaches the end of its viable lifespan, a problem referred to as open margin on crown can cause even more problems than the cavities that led to the crown in the first place.

What is an open margin on crown?

An open margin on crown occurs as a result of improper tooth preparation or improper crown placement. A crown is a dental restoration that can:

  • Protect a cracked or weakened tooth
  • To replace a broken tooth
  • Cosmetically fix a misshapen or discolored tooth
  • Support a weakened tooth that has a large filling in it

In most cases, your dentist will prepare the surface of the natural tooth by filing down an even surface for an attachment. They’ll take an impression of your teeth, and place a temporary crown while customizing the permanent crown. When the permanent crown is ready, they’ll smooth the tooth surface, and fix the permanent crown in place with dental cement.

This works beautifully when the process goes according to plan, but in some cases a gap will appear between the crown and the natural tooth surface. This is what is referred to as an open margin on crown. The margin, or the area where the crown contacts the natural tooth, is not sealed, allowing food and bacteria to enter the space between the crown and the tooth.

What causes an open margin?

An open margin crown is different than a simple space between the crown and the gumline. The crown may stop short of the gumline and still be sealed and properly applied.

The open margin specifically refers to a gap between the natural tooth and crown. This can be due to:

  • A rough surface
  • Uneven application of dental cement
  • Other errors in application or crown manufacturing

In some cases, the crown itself is defective or ill-fitting and will never be able to be effectively sealed. This can be difficult to detect with the naked eye as well. A dentist who does not follow accepted protocols for checking fit or who rushes the process of making a mold of the teeth for the crown is more likely to miss any errors in fabrication, too.

What are symptoms of an open margin crown?

The symptoms of an open margin crown may not be immediately detected and are not necessarily visible to the eye. The symptoms become more apparent as the years progress and can include all of the symptoms of cavity.

  • Sensitive gums and teeth: Decay can cause sensitivity to hot and cold as well as sensitivity to sweet foods.
  • Bleeding gums when brushing and flossing: As with other types of decay, eventually you might experience gingivitis symptoms like bleeding when brushing or flossing teeth. This may or may not go away over time.
  • Pain: As the cement holding the crown in place begins to dissolve in the face of the bacteria that has made its way underneath the dental restoration, the roots of the tooth will begin to be affected. Pain may be mild at first, but as decay continues it can progress.
  • Bad breath: This is a telltale sign of all types of decay, including the decay that occurs as a result of an open margin on crown.

If none of these symptoms occur, an X-ray can also confirm if a crown is properly sealed or not. In some cases, an open margin may be visible to the naked eye, but this is not often the case.

How to fix an open margin crown

Crown margin repair is essential for continued dental health. An ill-fitting or unsealed crown can cause many different problems down the road and may lead to a root canal or eventual tooth extraction.

Fixing an open margin crown is not as simple as just adding some sealant or cement to the tooth and hoping for the best. In the majority of cases, the crown must be removed and examined. A dentist can determine what caused the crown margins to open. If the crown itself does not have any manufacturing defects and fits properly, then they must consider its application.

Before they can replace the crown, the dentist must thoroughly examine your natural tooth. They’ll see if there’s any damage due to the open margin. If the open margin existed for many years, chances are good that there will be some measure of tooth decay underneath the crown.

Any tooth decay will need to be addressed. This might mean drilling out the decay and filling in the open space, or a root canal may be necessary. In some cases, a tooth has decayed so severely or has become necrotic and must be removed.

Once any underlying decay is treated and the natural tooth surface is ready, the crown can be replaced. Properly applied, dental crowns can last anywhere between five and 30 years. Your dentist should make sure to check both the crown fit and natural tooth surface before carefully placing the crown.

Work with a trusted dentist 

Whether getting one crown or several in a row, working with a highly trusted community dentist can make all of the difference. We are a cosmetic dentist with multiple locations in the Phoenix area that specializes in all kinds of dentistry, including repairing open margins on crown. At AZ Dentist, we only work with top dentists and master ceramicists who are experts at their craft. This can help you avoid any more crown issues in the future.

If you are experiencing pain or other symptoms in the teeth with your crowns, or it’s simply time to replace them, give us a call for a complete evaluation of your oral health!

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