Are dental crowns /posts dangerous and what is the difference?

Not When Done Well: A crown is used to cover all or some of a tooth after it has fractured or has great damage from decay. It has been called a "cap" as it covers and protects the tooth. A post is placed to help build up enough structure for the tooth to be crowned. Neither are dangerous is done well.

Different procedures: A crown is a fabricated covering made outside the mouth and then cemented on a prepared tooth. A post is a reinforcing procedure which is normally done on root canal teeth and consists of placing a metal or acrylic rod inside the canal in order to reinforce the tooth. A post can be part of the procedure needed to build up a tooth for needed stability to place a crown on a tooth. Not dangerous.

Dental crown: A dental crown is put on he top of the tooth structure to replace your missing enamel and dentin of the tooth. A post is placed typically when a tooth has a root canal and has minimal remaining tooth structure to retain a build up material and support the crown of the tooth. Many root canal treated teeth require a post and build up to be able to have a crown placed. They are not dangerous.

Not dangerous: A crown is a dental restoration used to restore a tooth when the tooth is so broken down that a simple filling just won't do. It covers the entire tooth and helps prevent the tooth from further damage. If the tooth had root canal therapy, a post is often placed into the tooth to help redirect chewing forces towards the stronger, inner portion of the tooth. The post is placed under the crown.

Safe and predictable: and very common procedure. The post crown will always need a core in order to be successful, but a core can be used with or without a post to keep a dental crown in place. Hope it helps.