Introduction
A post is a rod placed in the prepared root canal of a root-filled tooth to retain a core – the build-up that replaces lost coronal dentin and supports the crown. The topic covers when a post is needed, how it is placed and cemented, and the main types. A badly planned post is a common cause of root fracture and tooth loss.
Purpose and indications
A post only retains the core when too little coronal tooth structure is left; it does not strengthen the root. Preparing the post space removes dentin and weakens the root. Root-filled teeth are fragile mainly because of the tooth structure lost to caries, the access cavity and lost marginal ridges.
- Indicated: a root-filled anterior tooth or premolar that has lost roughly half or more of its crown, so the remaining walls and narrow pulp chamber cannot hold a core.
- Not needed when enough coronal dentin remains – e.g. an incisor with only an access cavity is closed with bonded composite.
- Molars: the pulp chamber usually retains the core (composite or amalgam extending a few millimetres into the canals). If a post is unavoidable, use the largest, straightest canal: palatal in maxillary, distal in mandibular molars.
- Contraindicated: a poor root canal filling or active periapical lesion (retreat first), short, thin or strongly curved roots, and a tooth on which no ferrule can be obtained.