Many people assume a post is a steel rod that makes a weak tooth stronger. It does not strengthen the tooth at all. A post is a small pin cemented into a root canal so that a filling build-up, called the core, has something to hold on to when too little of the natural tooth is left. The core is then shaped so a crown can sit over it.
Why a broken-down tooth needs something to grip
A crown needs a solid stump to sit on. After a root canal, the dentist rebuilds that stump with filling material. If the tooth still has healthy walls, those walls hold the build-up in place and no post is needed. If decay or a fracture has taken away most of the part above the gum, the build-up has nothing to anchor to. That is when a post goes into one of the cleaned canals to retain it.
This often comes up when a tooth has broken off near the gum line but the root is still sound. Front teeth with a single canal and back teeth with larger canals can both take a post. On a molar, the dentist chooses the canal that gives the best support.
The ferrule matters more than the post
How long a rebuilt tooth lasts depends heavily on the ferrule. This is a collar of natural tooth above the gum that the crown wraps around, rather like the metal band that holds a rubber onto a pencil. A 2026 systematic review by Hajeer and colleagues in the Journal of Prosthodontics found that a ferrule around 1.5 to 2 millimetres tall, with walls at least 1 millimetre thick, was linked with better fracture resistance and survival. The authors also noted that no restorative approach matched the support a natural ferrule provides.
When almost nothing is left above the gum, there is no ferrule to work with and the outlook is poorer. Sometimes the gum and bone can be adjusted, or the root brought up orthodontically, to create one. In other cases the more predictable option is to remove the tooth and consider an implant, bridge or denture.
Fibre or metal: the evidence shows little difference
Posts come in two broad types. Fibre posts are made of glass or carbon fibres set in resin and are tooth-coloured. Cast metal posts are made to fit the canal in a lab.
| Fibre post | Cast metal post | |
|---|---|---|
| Made from | Glass or carbon fibre in resin | Custom-cast metal |
| Appearance | Tooth-coloured | Metal, can show through thin ceramic |
| Visits | Usually placed in one visit | Usually needs a lab step |
| Often chosen for | Front teeth and cases with reasonable tooth left | Canals that are wide, oval or need a custom fit |
Fibre posts are often said to protect the root better because they flex more like dentine. The clinical studies do not show a clear advantage either way. A 2024 meta-analysis by Tsintsadze and colleagues in the Journal of Prosthetic Dentistry found no significant difference in survival between teeth restored with glass-fibre posts and those with metal posts. An earlier review by Figueiredo and colleagues in the Journal of Endodontics found no significant difference in root fracture rates. The choice therefore depends on the tooth, the canal shape and how the crown needs to look.
What the appointment is like
Because the nerve has already been removed in the root canal treatment, placing a post is usually comfortable, although local anaesthetic may still be used for the gum. The dentist removes some of the root filling to make space, cements the post, builds the core around it and shapes it. A scan is then taken for the crown, sometimes at the same visit.
How rebuilt teeth fail, and how to lower the risk
In clinical trials, fibre posts most often failed by coming loose, while failures with metal posts more often involved a crack in the root, a broken post or loss of retention. A root fracture usually means the tooth cannot be saved. Keeping as much natural tooth as possible, having a good ferrule, a well-fitting crown, and a night guard if you grind all help. Regular check-ups let your dentist spot a loosening crown or new decay early.
Common questions
Does every root-filled tooth need a post?
No. Only teeth that have lost most of their structure above the gum need one. Many are rebuilt with a core and crown alone.
Will a post make my tooth stronger?
No. It only holds the core in place. Strength comes from the remaining natural tooth and the crown.
Can a post be removed later?
Often, yes, if the tooth needs root canal treatment again, although removal can be difficult and carries some risk to the root.
If you have a heavily broken-down tooth after a root canal, an examination and X-ray will show whether a post, core and crown can save it. See current options on our offers page, or read our guide on whether a root-filled tooth needs a crown.
