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67
However, in the case of passive engagement, there is no macromechanical
bonding and the post relies mainly on cement to hold it in the canal.
The insertion of a post into a prepared root canal presents a challenge for
restorative dentists. During mastication, the stresses developed in the dentine
often reach values that can cause the dislodgement of the post and the fracture of
the tooth. A fractured tooth cannot be restored and has to be extracted. The dental
procedures required to replace the lost tooth are very expensive and produce a less
satisfactory result than the post and core restored tooth they are replacing.
The analysis of stress distribution in endodontically treated teeth with post and
core reinforcements will facilitate the design of post and core configurations that
are less likely to cause tooth fracture.
Evaluation of the stress distribution of the post-core restored endodontically
treated teeth is very complicated. The restored tooth consists of several different
materials: a crown, a core, a post, cement and gutta percha and several types of
tissues such as periodontal ligament, bone and dentin. The respective material
properties are significantly different. The post core system, the root, the canal and
the supporting bone have small dimensions and are structurally complex. The
direction and magnitude of the load are complex. The post design, the thickness of
the remaining dentin and the height of the dentine ferrule affect the stress
distribution in the restoration.
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