Why Delivering the Post-and-Core and the Crown Simultaneously Is Not a Precise Decision

In some clinics, to reduce the number of treatment sessions, an impression of the tooth is taken while the cast post and core is being fabricated, so that at the next session the crown can be cemented at the same time the post and core is delivered. Although this approach seems attractive in terms of time, it is not defensible in terms of prosthetic accuracy and biological health.

In the casting process, metal shrinkage, the behavior of the investment, and laboratory variables make the final dimensions of the post and core not fully predictable.

In addition, the seating of the cast post and core in exactly the same position as the resin pattern inside the canal is not guaranteed, and even very minor differences can change the final position of the core.

On the other hand, the location where the sprue is attached and cut off can cause subtle changes in the final form of the core; changes that are not visible to the eye but matter prosthetically.

If the crown is fabricated based on a pattern whose final position changes — even by a few tens of microns — after the post and core seats, the following consequences will be inevitable:

Increased marginal gap
Exposure of the cement to dissolution
Microleakage
Gingival inflammation
Secondary caries

Marginal fit is a vital principle in all prosthetic treatments. The success of treatment is defined on the micron scale; therefore, such uncertainty can lead to biological failure of the treatment.

Reducing the number of treatment sessions should not come at the cost of reduced accuracy. Delivering the post and core separately and then taking the final impression for the crown is a more accurate, more predictable, and more biological approach.

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