PRIMARY RETENTION FORM

Definition – Prevention of dislodgement of the restoration.
Prepare wall configurations- shape, height & form

● Class I
- buccal and lingual wallsー converge occlusallyー or parallel
- mesial and distal walls has to be divergent because dentine will be removed otherwise as dentine is the major supporter / retentive component.
● Onlay ー entire cavity prep will be divergent
● Class II ー create dovetail.

● Q. If a caries at the Marginal ridge? How would you manage?

• Prepare a conservative cavity where wall closer to the marginal ridge is divergent in order to include the caries & Other side parallel.
• No need to make it as a class II preparation.
• Because we always follow preservation method.

Please go to Lecture 21.CONVENIENCE FORM.