Understanding The Ferrule Effect (5)
Here's a representation of the preparation:
|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.
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?