Usually, no. The post is made to fit snugly into the root canal of the tooth after root canal treatment is completed. It may be held in by cement, or it can be screwed into the canal. The top part of the post supports the crown.
Posts fail for many reasons. They may be made too short and cannot support the crown. Chewing forces can loosen the post.
After a post falls out, a new, longer post can replace it. Sometimes there also is decay around the crown. This decay may continue down the root of the tooth into the canal space. If there is decay, it will need to be removed, and a new post made to fit the enlarged canal space.