Post and core
Structure, benefits, indications
Author: George Ghidrai, MD
A post and core is a prosthetic device that is utilized when there is inadequate tooth structure remaining to support a traditional restoration or an artificial crown.
Structure
A post and core consists of two parts :
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The post
The post is a small rod, usually metal, that is inserted into the root space of the tooth and protrudes from the root a couple of millimetres. The post is then used to hold the core or a filling in place.
Because the post is inserted into the root canal, a post and core can only be made for a tooth that has had root canal treatment.
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The core
The core replaces missing tooth structure in preparation for making a new dental crown. Normally, a dental core can be directly built up from composite materials without a post to hold it in place.
However, a dental post can be used to help to anchor the core to the tooth. In this case, the core is generally made off metal alloys and the device is called post and core.
The core is then utilized to hold a dental crown in place. The crown can be a single unit crown or a retainer crown for a dental bridge.
Why are post and cores needed ?
A great deal of a dental crown 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.
Basically, the core is rebuilding the tooth so it is closer to its original dimensions. Hence, the crown's stability will greatly increase, and therefore its long-term chances for success are maximized.
before : no stability for the crown
after : post and core will increase crown's stability
Indications
A post and core is indicated when a large part (or all) of a tooth's original crown structure has been lost. The crown structure can be damaged either due to the progression of dental decays or because of a tooth trauma.
tooth trauma
crown destruction caused by advanced dental decay
A post and core can only be manufactured if the tooth has had root canal treatment. After the endodontic procedure has been completed, some of the root canal filling is removed from the canal space to place the post (see post and core procedure).
Is a post always needed ?
A dental post is generally 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.
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 (which basically means a direct build-up with composite materials) will probably suffice.
Drawbacks
Posts do not strengthen teeth
In past decades there was a misconception that metallic dental posts played a role in reinforcing or strengthening the teeth in which they were placed.
Dental research has since shown that posts offer no reinforcement benefit and, in fact, can actually weaken teeth and place them at risk for fracture.
This does not suggest that post placement is a wrong therapeutic approach. However, a dental post should be utilized only when a large part of the crown structure is missing and no other affordable solutions are available.
The main drawback is that, when all of the independent failure rates of the many procedures needed are considered together (endodontic treatment, post and core fabrication and prosthetic crown), the patient is sometimes advised to have the tooth extracted and a dental implant placed.
It must be said though that in the past decades, dental implantology was not at its peak. Post and cores were considered as an alternative to tooth extraction and the subsequent necessity to construct a dental bridge (which requires the preparation of the adjacent teeth).
Secondly, dental implants entail a higher cost, which some patients cannot afford. For these reasons, post and cores are still utilized all over the world.