ABUTMENT LEVEL IMPESSION SET UP
Distortion
Abutment level impressions fall in to two categories. One subdivision is
just an impression over the already installed abutment in the patients mouth,
without any hardware.
Work up model work in a traditional fashion. This type of impression consistently produces the poorest results in regards to
distortion and unreadable margins.
Impression coping
To ease the tooling and handling requirements for the restoring dentist,
Straumann® pioneered the solid abutment system where the surgeon often installs
the final abutment already and the dentist has to use a plastic coping that snaps over the
abutment for impression purposes. Many manufacturers (Nobel easy abutment and snappy,
Astra direct abutment, Biomet 3i Provide, BioHorizons® simple solution) have followed in pursuit due to
the popularity of this system.
Impression
Record on an inventory list implant brand, platform diameter and abutment
height.
What parts (e.g. transfers, analogs, burn out copings)
and how many of each the dentist sent with the case. Verify
impression copings match information provided on the hopefully included
surgical report. In case there is a mismatch of the impression coping
diameter or color coding and the information from the
surgical report (some transfers are cross compatible with other implant
brands), call the Dr. to verify implant brand, diameter and abutment height.
Analog
Order appropriate analog (clone parts) and burnout coping if the Dr. has not already included
all necessary parts as a set. Snap analog in to the embedded impression coping, lining up the
indexing-antirotational feature of the analog with the plastic transfer. Avoid rotating the
analog when pressing the analog in to the coping.
Reduction coping
Pitfalls of the solid abutment system stem from the use of plastic impression copings
and inadequate positioning features on the abutments and transfers. It is not uncommon
for the dentist to press the plastic coping 180 degrees reverse on to the abutment due
to the inherent plasticity of the impression coping. This is rarely detectable
by the technician and results in a costly remake of the restoration.
Another issue arises if the abutment needs reduction in height or to correct angulation problems.
In case the abutment does need reduction the dentist should take the impression first
and then reduce only what is absolutely necessary. The laboratory technician
can reduce the analog on the finished model to desired specs and provide the dentist with a reduction coping.