The use of a post-retained core and subsequent crown to restore a badly broken down
tooth has been a recognized treatment modality for over 150 years
The use of the technique has responded to various fashions within Operative
Dentistry and has undergone various incarnations as a reinforcement for root filled teeth
, a desirable method of realigning misplaced anterior teeth
or more recently simply as a method to gain retention for a
core in the absence of sufficient coronal tissue. The use of
bonding techniques and resin-based post systems are again being hypothesized as a
means of gaining root reinforcement, however, the
majority of post and core restorations currently in place within the population are still the
‘traditional’ metallic post systems retained with a conventional (rather than composite
resin-based) cement.
Most of the metallic-based post and core systems can be categorized by the fabrication
method (i.e. prefabricated wrought or cast metal alloy), by the post morphology (tapered
or parallel) or by the post design (e.g. threaded, serrated, smooth, vented or unvented)
. The ‘gold standard’ has traditionally been accepted as the indirect fabrication of a cast post and core using a custom direct intra-oral pattern build-up an impression of
the post channel preparation or a matched post reamer and impression post system. The
relative performance of these various systems are usually assessed in vitro where a single
mechanical parameter such as retention,
tensile or fracture strength of a post can be investigated. Conversely, clinical studies on failure of post and core restorations often report the incidence of root fracture or biological
consequences of post and core placement.There have been relatively few studies that have systematically examined the factors leading to the fracture of metallic post and core restorations in vivo. This is important as the consequences of fracture can leave both the patient and clinician in a difficult situation.
If it can be assumed that the dowel length originally chosen was the best obtainable, the
fractured portion has almost always to be removed to ensure that a subsequent
suboptimal restoration is avoided. The methods to remove fractured posts have been
reviewed but none of these are without clinical risks either through dentinal
microcracking with ultrasonics, root perforation with trepans or root
fracture with ‘post-pulling’ instruments.
As identification of clinical risk factors may suggest situations where metallic postretained
crowns are contraindicated, an attempt to recognize these factors was
considered appropriate to reduce the incidence of post fracture.
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