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Root canal therapy on a tooth with an existing crown – Dr Sarji explains a common procedure.

Root canal therapy on a tooth with an existing crown – Dr Sarji explains a common procedure.
This is actually a common procedure and we decided to write this article to explain the process to our patients . This often occurs when a tooth has had a previous root canal which has failed. When the first root canal was done a crown was placed over the tooth on the part that was not decayed with a post being inserted into the tooth so that the crown can be attached properly. Now that the root canal has failed and needs to be retreated the dentist is presented with a choice as to how he should progress.

The dentist has two choices

First Option -  Ideally the dentist will remove the crown before he drills the access cavity, however this is not always possible. There may be the possibility that he will damage the existing structure of the tooth.

Second Option – If the dentist determines that the crown will not come off then an  access caity must be drilled. In most cases the crown will be replaced although the tooth structure may have changed so it will not be possible to use it again. If the dentist has had to drill through it then this may weaken the crown.

In most instances a new crown is needed as the structure and integrity of the crown will have been changed or may be compromised.  The root canal could become re-infected very easily if the previous crown is used.  It is almost always advisable to remove the crown therefore protecting the integrity of the crowns and allowing the root canal procedure to take place;
For a dentist to remove  a crown in a manner that  it remains fully intact and unscathed can be very difficult if not impossible. During the attempt it's still possible that the crown will be damaged or worse yet the tooth damaged too and maybe significantly.

 Other reason for a crown failing is because  of tooth decay at the edge of the crown where it meets the gumline. The crown obviously does not decay but the underlying tooth gets decayed.  In a situation like this when it this happens, the decay quickly spreads underneath the crown. 

If the decay is significant there may be very little tooth structure left under the crown before the pulp (nerve) becomes destroyed by the decay. In a case like this a new crown will not fix the tooth and a root canal will be needed along with the new crown assuming we can actually save the existing tooth structure. When a dentist places a new crown on a tooth that already has had a crown it will take more work and will be more difficult to do that the first crown. This is due to the fact that the margins or edges of the crown will need to be deeper in order to cover up the area where the decay was removed after the old crown was taken off. This is often a complicated procedure but we have a lot of experience in dealing with these.

   Crowns are long lasting cosmetic restorations that for the most part will give a cosmetic appearance and perform a function but they will eventually wear out. Decay under the crown causes the crown to eventually fail. It is important that a dentist can detect early signs of decay at the edge of a crown. It takes a high degree of artistic skill to detect early decay on the edges of a crown. It must be replaced quickly in order to prevent a root canal or infection. Ask us when you come to see us about how you can take more care of your crowns. If you need a second opinion about a root canal needed underneath an existing crown then make an appointment to come and see us. 

Jim Sarji, DDS has been performing dentistry for nearly 20 years and divides his time between his children and his practice. He is passionate about dentistry and has upgraded all his equipment at his practice to the highest technology including a 2D and 3D EWOO Panoramic Low Radiation Cone Beam X-ray. This is used to measure bone density when placing a dental implant and to look for infection in the jawbone. If you have a dental emergency then call the practice and ask one of the receptionists to make see if you can get an emergency appointment. If not check ZOCDOC.


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