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Cast post and core procedure

author icon By Dr. George Ghidrai

A cast post and core is utilized when the post space is not a good match for a prefabricated post and core or when the dentist considers it a more appropriate therapeutic solution.

The cast post and core procedure involves the dental laboratory, so placing it is a 2 session process. There are two ways of manufacturing a cast post and core: direct method and the indirect method.


Indirect method

Lentulo file carriers

Lentulo file carriers

In the indirect method, an impression of the post space and adjacent teeth and gingiva is taken. The impression is then used to construct a suitable post in the dental laboratory.

The impression will have to capture the post space, so a fluid impression material will be inserted into the root canal with a specific file: the Lentulo file carrier.

cast post and core procedure: dental impression

impression for a cast post and core

In most of the cases, a partial impression is taken using the two-step technique.

When the post and core device is designed on a molar or premolar (teeth that can have more than a single root canal), a single unit post and core device can have two or three posts.

impression for a cast post and core with two posts

impression for a cast post and core with two posts

cast post and core with two posts

cast post and core with two posts after fabrication


Direct method

In the direct method, a resin pattern is produced by placing a preformed plastic "burnout" post into the post space and a resin material is used to build up the tooth to the proper dimensions.

When this is completed, the pattern post and core is removed from the tooth structure and sent to the dental lab. The technician will make a duplicate of the post and core using metal alloys or zirconium.


cast post and core procedure direct method phase 1

the plastic "burnout" is placed
into the post space

cast post and core procedure direct method phase 2

the tooth is build up with
the resin material

cast post and core procedure direct method phase 3

the pattern post and core
removed from the tooth


Laboratory stages

The dental technician will fabricate the post and core much in the same way as is done with a dental crown (see laboratory stages). If the indirect method was utilized, the impression is used to obtain the dental (plaster) cast.


post and core impression

dental impression

post and core plaster cast

plaster cast


The technician will then build up a wax pattern of the post and core using a wax-up technique. When this is completed, the wax pattern is removed from the plaster cast and attached to a sprue former.

post and core wax pattern

post and core wax pattern

Regardless of the technique used, the technician has now a post and core pattern: either a wax-pattern (if the indirect technique was used) or a resin pattern (if the direct technique was used).

The pattern is invested with a material that can accurately duplicate its shape and anatomic features. A void space that is an accurate "negative" replica of the post and core pattern is obtained. The molten metal will be cast into this mould through the casting channels (or sprues).

Various metal alloys can be used: gold, titanium, base metals. When casting the metal alloys, the pattern is converted to a replicate in dental alloy.

cast post and core metal

cast post and core

Zirconia post and cores are manufactured using the CAD/CAM systems.


Cementation

After completion, the dental technician sends the post and core to the dental practice for the definitive cementation. Cast post and cores are cemented inside root canals with dental cement or composite resins. The materials are placed inside root canals with Lentulo files.

After the post and core is definitively cemented, an impression can be taken for the fabrication of the prosthetic crown.

Last review and update: May 2019



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