Post-crown Preparations:
Understanding The Ferrule Effect (5)

Here's a representation of the preparation:

1
2
3
4
Dentine prepared to receive ferrule Space prepared for post Post and core fitted Crown provides the ferrule effect. Lateral forces transmitted from the crown to the post result in dentine compression coronally.

 The yellow area is the part of the crown that provides a ferrule (Radiograph No 4)


.
This post-crown prep has a 2mm
ferruled area all the way round.
The ferrule preparation should
incorporate at least 1 to 2 mm of
dentine all round the tooth.


    image     image
    Click these images to see
    the preparation shapes


This post-crown prep only has a
partial ferruled area. This tooth has
a limited life ahead of it. Expect post
decementation, or root fracture.

Once the crown is on, lateral forces
will put the dentine and the post-cement
under tension.

One or the other will give !

If you can not achieve a ferrule effect (as in the picture above), you should consider crown-lengthening (to expose more dentine), an overdenture, or extraction.

What are the options for crown-lengthening?
 

Next Page Next: Indirect Restorations. Post-crown Preparations: Understanding The Ferrule Effect (6)


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