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Optical Impressions and Full-Arch
Implant Restorations:
Go online for
A Case Study
in-depth content
by Guy Rosenstiel, DMD, MAGD and
Michael McCracken, DDS, Ph.D.
Clinicians strive for accurate impressions and well-fitting
implant restorations. An accurate impression reduces
residual stress in the prosthesis by promoting a better
restorative fit. Unfortunately, highly accurate implant impressions
can be difficult to achieve using conventional methods,
due to distortion factors inherent in both the clinical and laboratory
processes. This paradigm may be shifting, however,
as we continue to explore the use of optical techniques in
taking implant impressions, and the superior accuracy of a
model and restoration resulting from a digital scan becomes
more apparent.
Traditional implant impression techniques use a machined
coping to capture the position and orientation of the implant
in the arch using elastomeric impression materials, such as polyvinyl
siloxane (PVS). This impression is then poured in stone to make
the working cast. The impression technique is classified as “open-tray” if the impression
coping is pulled with the impression, and “closed-tray” if the coping remains in
the mouth after the impression is taken.
Proponents of the open-tray technique argue that this impression
method is more accurate because it avoids introducing stress to
the impression when it is removed from divergent implants.
Others counter that the impression is distorted when the
open-tray impression coping is tightened onto the
analog. Whether the open-tray or closed-tray technique
is used, the consensus regarding conventional
impressions is that the opportunity exists
for introducing error into the impression.
Research has shown that splinting the impression
copings together in the mouth
improves accuracy. 1–7 This improvement
in accuracy may be due to the increased
rigidity of the impression complex, which
resists distortion from torque during analog
attachment. Because of this data, many
– Optical Impressions and Full-Arch Implant Restorations: A Case Study – 67