Dental posts and cores.
After your tooth's root canal treatment has been completed, your dentist may recommend the placement of a dental crown.
In some instances, they may also inform you that a dental post and core (or else just a core without a post) must be placed before the crown can be made.
- What are they? / When are they needed?
A) Dental cores.
B) Dental posts and cores.
- How are they placed?
A) Dental cores.
B) Dental posts and cores.
A) What is a "core"?
Teeth sometimes have large portions missing due to decay, fracture, the loss of a filling and, in the case of root canal treatment, the creation of an access cavity.
Core placement refers to a procedure where a dentist replaces missing tooth structure in preparation for making a new dental crown. Replacing these missing portions creates the optimal foundation for the new restoration.
A core can be made out of any type of permanent dental restorative. In most cases it's either dental amalgam (metal filling material) or else dental composite (tooth bonding).
Why are dental cores needed?
Here's the reason why a core is placed. - A great deal of a crown's stability depends on the amount of tooth structure that extends into its interior. If very little tooth structure occupies this space, the crown will be easily dislodged, especially by forces directed at its side.
By "building up" the tooth first with a core (rebuilding the tooth so it is closer to its original dimensions), the dentist can greatly increase the stability of the crown, and therefore maximize its long-term chances for success.
B) What is a "post and core"?
The difference between a dental core and a post and core is that with the latter, a dental post is used to help to anchor the core to the tooth.
While a dental core can be created for any tooth, a post and core can only be made for a tooth that has had root canal treatment.
Is a post always needed?
As a rule of thumb, if more than half of a tooth's original crown portion has been lost, a post is needed to assist in anchoring the core to the tooth. If more than half still remains, a core by itself will probably suffice.
Posts don't strengthen teeth.
Just as a point of information, in decades past there was a misconception that metallic dental posts played a role in reinforcing (strengthening) the teeth in which they were placed.
To the contrary, dental research has since shown that these posts offer no reinforcement benefit and, in fact, can actually weaken teeth and place them at risk for fracture.
As evidence of this, Willershausen (2005) evaluated 775 endodontically treated teeth. It was determined that, as a group, these teeth had a complication rate of 6.6%. In comparison, a subgroup composed of just teeth with metal posts had a complication rate (such as root fracture) of 13.2%.
This is not to suggest that post placement is a "bad thing." However, a dental post should be recognized as just an aid in helping to anchor a dental core to a tooth. If enough natural tooth structure still exists, then no post is needed.
How does a dentist place a dental post and/or core?
a) Placing a dental core.
When placing just a core alone, the dentist will apply dental restorative (meaning filling material, such as dental amalgam or bonding) to the tooth, not unlike when a regular filling is placed. As a part of the process, they may also screw minute "pins" into the tooth. When the restorative is packed around them, they help to anchor the core in place.
The goal is to place enough dental restorative that, once the tooth has been shaped for the crown, the resulting tooth/core combination is the same size and shape that it would have been if no previous tooth structure loss had occurred.
b) Placing a post and core.
When placing a post and core, the dentist will first use their drill to create a "post space." This space will lie in alignment with one of the root canals that was filled during the sealing portion of the tooth's endodontic treatment.
Then, a post, specifically sized (or fabricated) to match the post space, is cemented or bonded into place.
Traditionally, dental posts have been made out of metal (stainless steel, titanium, cast metal). In today's marketplace, a dentist may choose between metal and carbon-fiber posts.
Once the post has been secured, a dental core (see above) is placed over and around the post's exposed end. This way the dental core is anchored both by the post and surrounding tooth structure.
Completing the tooth's reconstruction.
Once the core, or post and core, has been completed, a dental crown can be fabricated and placed. We outline the steps of this process here: How dental crowns are made.