After a root canal, there is an empty hole in the middle of the tooth. Even if the tooth is restored with the canal obturation and the permanent filling on top, it is still fragile and can break under mastication pressure. Under mastication pressure, the filling, not supported, sinks and creates an internal pressure  that leads to the fracture of the tooth.

The tooth can then be compared to an empty eggshell. A full egg can resist to a certain amount of pressure. On the contraty, an empty eggshell will crack and break to any pressure applied on it. All proportions maintained, the same concept applies to a tooth with a recent root canal treatment.

To overcome the situation, a backbone is placed in the middle of the tooth. The backbone structure serves as pillar and transfers a;; vertical force towards the root. The centre of the tooth is now well supported.