Post
and Core Restoration of Endodontically Treated Teeth
The need for immediate and proper coronal restoration
after root canal obturation is paramount for the long-term success
of endodontic treatment. The seal provided by the post, core,
and crown should compliment that of the remaining root canal filling.
The build-up is an extension rather than an invasion of the endodontic
seal.
There
are several important elements of post and core restoration to
consider
Ferrule
Effect: Numerous investigations have determined that the availability
of a substantial ferrule collar of coronal tooth structure for
the marginal finish of the permanent restoration is of greater
importance in crown retention than dowel length and diameter.
The ferrule is a critical element in stabilizing the core from
the ravages of lateral excursive occlusal movements. Occlusal
cycling without an adequate ferrule will break the marginal seal
and allow bacteria to infiltrate the post and eventually, the
remaining root canal obturation.
Post Selection: From a retention stand-point, threaded posts are
the most retentive followed by cemented parallel-sided posts.
Serrations increase post retention. Cemented tapered posts are
the least retentive. Photoelastic stress analysis generally favors
parallel cemented posts. Combined data from multiple clinical
studies report that threaded posts produce the highest root fracture
incidence followed by tapered posts. Parallel posts are the least
likely to fracture posts.
Post
Length and Placement: The perception that post length and
size are strategic variables contributing to root reinforcement
and reduced fracture have been discounted. Posts provide no reinforcement
to an already weakened tooth structure. Length is certainly more
important than width for retention, however, length ultimately
compromises the endodontic obturation. A single post per tooth
should be placed in the largest, straightest, and most circular
canal. Essentially, for posterior teeth, posts are best placed
in the distal root of mandibular molars and the palatal root of
maxillary molars. Posting other posterior molar roots invites
perforation into root concavities. Root canals should never be
shaped to fit posts. Use no instrument in a canal space unless
it is intended to clean and shape the canal for endodontic obturation.
Remaining
Root Obturation Material: The literature often refers to a
minimum remaining length of 5 mm's of gutta-percha that is necessary
to maintain an adequate seal. Actually, anything less than the
entire intact obturation is inferior. The post must function as
an extension of the endodontic seal.
Immediate
Restoration: The timing sequence for post-endodontic rehabilitation
is a seriously under-appreciated variable. Posts must be cemented
as soon as possible after endodontic obturation. Otherwise, a
layer of bonded unfilled resin along the floor of a properly prepared
pulp chamber and canal orifice is an excellent secondary protective
seal after finishing root canal obturation.
Suggestions
for Maintaining Post-Space Sterility Prior to Permanent Post Cementation:
Use Peridex soaked cotton pellets in the chamber or place Calcium
Hydroxide paste (UltraCal or Calasept) into the post space. The
Calcium Hydroxide can be washed out prior to post cementation
using 17% liquid EDTA.
ESCONDIDO
ENDODONTICS 488 EAST VALLEY PARKWAY SUITE 307 ESCONDIDO, CA 92025
(760) 739-1400
FAX (760) 739-1100 www.escoendo.com
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