Why crowns are recommended on root filled teeth
If bacteria gets into the nerve space inside a tooth, this can lead to irreversible damage of the nerve (causing acute pain and sensitiviy) and eventually to necrosis (death) of the nerve. Root canal treatment is a procedure we perform routinely to treat this condition. After treatment, we often recommend the tooth has a crown placed on it for protection.
If bacteria gets back inside a root filled tooth again, it can become infected again and the root filling can fail. The most common cause for the failure of root canal treatment is a crack in a tooth. A crack or root fracture is a break in a tooth which then allows bacteria to re-enter the inside of a tooth which has been cleaned by the root filling. If a tooth has a root fracture, it is not possible to stick things back together again, so prevention of this developing is important.
Before a root filling is done (or a root filling is repeated) the tooth is thoroughly investigated to check for a crack being present. This tooth (a lower premolar) had an area of extensive infection around it and on the first x-ray which was taken, the root looked normal.
A second x-ray taken of the same tooth shows that the root is split in half. Even if the old root filling was removed, the space in the tooth disinfected and re-sealed with a new root filling, bacteria would re-enter the tooth through this crack in the root and the root filling would fail.
Crowns can protect teeth from fracture.
A crown on a tooth is like a helmet or thimble over the top of the tooth holding everything together. When you bite and chew, there are huge wedging forces which cause a tooth to flex and bend. A crown will stop these wedging forces from causing the tooth to split and fracture giving it a much better long term prognosis.
More information about how crowns can protect teeth can be seen at www.KPteeth.co.uk/crown