PDF: Impression techniques for implant dentistry

The object of making an impression in implant dentistry is to accurately relate an analogue of the implant or implant abutment to the other structures in the dental arch. 

This is affected by use of an impression coping which is attached to the implant or implant abutment. This impression coping is incorporated in an impression much as a metal framework is 'picked up' in a remount impression for fixed prosthodontics.

With implant copings the coping is usually attached to the implant or abutment with screws. 

The impression material used is usually an elastomeric impression material; the two types most widely used and shown to be the most appropriate are polyether and polyvinyl siloxane impression materials.

The impression coping takes two general forms, one type is retained in the mouth when the set impression is removed this type of impression coping is known as the transfer type impression coping. 

The other type is incorporated in the impression and is removed from the mouth together with the set impression and is known as a pick up type impression coping.

Characteristics or the transfer type impression coping are that they remain in the mouth on removal of the set impression, the analogue is attached to the impression coping after removal from the mouth and this assembly is replaced in the indentation left on the set impression. No custom tray is required for this type of impression. 

Characteristics of the pick up type impression coping are that they are removed from the mouth together with the set impression.