When teeth are root treated they are deprived of the living pulp tissue. The lack of the vital essentials of blood and oxygen causes the tooth to become brittle, and after five to seven years, it is usually unable to withstand the pressure of the bite. Just as a wall requires reinforcement with rebar to anchor it to the foundation, so a tooth needs the stress bearing crown strengthened against the force of occluding teeth. This is provided by placing a post into the root to direct the biting force into a part of the tooth structure that is supported by bone.
There are many ways of reinforcing teeth. Frequently prefabricated posts are anchored into the root and then sealed into place with glue or composite resin. These post systems sometimes fail should the bonded resin absorb moisture and separate from the tooth or post.
A better way of reinforcing teeth is with a custom made gold post and core. This is cast to fit the root and pulp chamber in one piece. It provides a solid platform to support a crown and direct the biting force down the long axis of the tooth.