Post and core.
A post retains a core; it does not reinforce a tooth. What actually resists the forces that fracture endodontically treated teeth is the ferrule, and that governs whether the tooth should be restored at all.
The ferrule matters more than the post
A circumferential band of sound tooth structure coronal to the finish line — commonly cited as one and a half to two millimetres of vertical height with adequate wall thickness — is what resists the wedging forces that split post-restored teeth.
A post placed in a tooth with no ferrule does not compensate for its absence. It provides retention for the core and transmits load into the root, which is where the fracture then occurs.
If the ferrule is inadequate, the options are crown lengthening, orthodontic extrusion, or reconsidering whether the tooth should be restored. Building over an unsupported core is a decision to take knowingly and to note on the prescription.
Cast or prefabricated
A prefabricated post with a directly built core is quicker, requires no laboratory stage, and works well where the canal is reasonably circular and sufficient coronal structure remains to retain the core material.
A cast post and core suits the situations where that is not true: a canal that is markedly oval or flared, very little remaining coronal structure, or an abutment where the core's form and angulation need controlling precisely — for a bridge abutment or a tooth requiring path correction.
The cast option adapts to the canal's actual shape rather than requiring the canal to be shaped to the post, which is more conservative of root dentine in a flared canal.
Canal preparation
Retain apical gutta-percha — commonly four to five millimetres — to preserve the seal. Post length is a balance: enough for retention, not so much that the apical seal or the root's structural integrity is compromised.
Preserve root dentine. The commonest error is over-preparing the canal to accommodate a larger post, which weakens exactly the structure the restoration depends on.
For a cast post, an accurate impression or scan of the prepared canal is required, along with the coronal preparation and the opposing arch.
Material
The Rx form lists post and core under full metal work, and the alloy applies as it does to any casting. A non-precious alloy gives rigidity; a noble alloy gives better handling and tissue response.
Where the tooth will carry a translucent all-ceramic crown, a metal post and core creates a dark substrate that will show through. Record the core shade on the prescription so the crown's opacity can be selected accordingly, or discuss an alternative approach before proceeding.
Multi-rooted teeth
In a molar, a single post in the largest and straightest canal is generally preferable to posts in several. Multiple posts in divergent canals create a restoration with no common path of insertion and remove more dentine than the retention gained justifies.
Where a cast post and core is used in a molar, the design usually engages one canal for retention with the core built over the remaining coronal structure and pulp chamber.
Say which canal you have prepared and how far, and send the opposing arch along with the coronal preparation.
What to put on the prescription
State post and core, name the alloy, and mark the tooth on the design chart. Say what restoration will sit over it and in which material.
Note the ferrule available. If it is minimal or absent, say so — it changes the design and it is information the laboratory should have rather than infer from the die.
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