A root canal treatment weakens your tooth for two reasons. Not only does tooth structure have to be removed to accomplish the treatment, but your tooth, which is now a dead tooth, will become dried out and brittle because its blood supply has been cut off.
Molars and premolars should have dental crowns after a root canal treatment to keep them from fracturing. And to help retain the crown, or to strengthen the neck of the tooth, a dental post will often be placed.
In times past, these posts were made of stainless steel. But stainless steel contains nickel, and many people have metal allergies and are allergic to nickel. Since teeth are porous, even if the stainless steel is inside the root, this poses an unnecessary risk. In the 1980s, titanium began to be used for posts because this is a very bio-compatible metal and also is very strong.
In the 1990s, other materials were introduced. Carbon fiber and other fibers were used to make posts. They were found to reduce root fracture because they had a slight amount of flexibility to them. And then white materials began to be used because of the popularity of translucent porcelain crowns. Metal and carbon fiber posts prevented light transmission through the tooth and affected the aesthetics.