Abutment Level Impression
Posted on 07/21/2011
The second common implant impression technique is the ABUTMENT LEVEL IMPRESSION. This refers to the technique where the abutment has been secured into the implant fixture (through the use of a screw, or a tap system like Bicon) and has been adjusted based on occlusal and interproximal space constraints. This technique is not as common as the implant fixture level technique due to some serious challenges that the doctor must address before impressioning. Today, we will list some of the more common challenges:
1) Capturing the Margin: Abutment margins are typically subgingival (i.e. beneath the sulcus). Getting impression material to accurately capture subgingival margins is not easy - especially on maxillary molars. As a result, the impression will often miss part of the margin.
2) Occlusal Space: Assessing whether there is sufficient occlusal clearance in the mouth is a challenge. In some cases, a doctor may have not realized that the abutment is too high to allow space for a porcelain occlusal. In that scenario, the only options are to leave a metal occlusal (for PFMs) or to allow the lab to adjust the abutment and provide a reduction coping. However, matching lab adjustments can be frustrating and imprecise.
3) Compromising the Implant: Some doctors are concerned about adjusting the metal abutment in the mouth because of possible effects on the implant fixture. Excessive heat generation or excessive movement of the fixture, they argue, can cause long term instability of the implant - which may not be realized for years.
4) Screw Retained Crown: Many doctors enjoy the retrievability of a screw retained crown. An abutment level impression forces the lab to create a cement retained crown with no option for a screw retained crown.
1) Capturing the Margin: Abutment margins are typically subgingival (i.e. beneath the sulcus). Getting impression material to accurately capture subgingival margins is not easy - especially on maxillary molars. As a result, the impression will often miss part of the margin.
2) Occlusal Space: Assessing whether there is sufficient occlusal clearance in the mouth is a challenge. In some cases, a doctor may have not realized that the abutment is too high to allow space for a porcelain occlusal. In that scenario, the only options are to leave a metal occlusal (for PFMs) or to allow the lab to adjust the abutment and provide a reduction coping. However, matching lab adjustments can be frustrating and imprecise.
3) Compromising the Implant: Some doctors are concerned about adjusting the metal abutment in the mouth because of possible effects on the implant fixture. Excessive heat generation or excessive movement of the fixture, they argue, can cause long term instability of the implant - which may not be realized for years.
4) Screw Retained Crown: Many doctors enjoy the retrievability of a screw retained crown. An abutment level impression forces the lab to create a cement retained crown with no option for a screw retained crown.
