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would be designed and milled from the digital scanning
data without the use of stone models.
Treatment
The patient agreed to the placement of two implants in the
areas of tooth #4 and #5 with the aid of a tooth-supported
surgical guide, and the immediate insertion of two provisional
screw-retained abutments and cement-retained crowns. The
treatment was divided into four phases: planning, placement,
provisionalization and final restoration.
Phase I: Planning
Cone beam computed tomography (CBCT) imaging was
performed to produce digital data in the DICOM file format
(Fig. 2). In order to produce an accurate data field of the
surface morphology of the coronal portions of the maxillary
arch, a digital scan was performed with the iTero ® digital
scanning system (Align Technology; San Jose, Calif.) (Fig. 3).
The iTero scan produced STL files, the standard CAD/CAM
file format. These STL files are easily exported directly from
the iTero scanning machine to the user’s computer. Using
file merge software, the DICOM files and STL files were
merged to create an accurate 3-D rendering for the computer-aided
treatment planning and design phase (Fig. 4).
Figure 6: CAD software used to determine optimal crown and implant positions.
Figure 7: Software design of tooth-supported surgical guide.
Digital scanning produces a virtual model with sufficient
accuracy to ensure that the tooth-supported surgical guide
designed with CAD software fits properly on the tooth surfaces
of the mouth. It must fit with a high level of accuracy
or the guided surgery will be inaccurate.
Merging the STL files with the DICOM files creates an
accurate, virtual, volumetric rendering that can be used for
“crown down” planning of implant placement and implant
restoration. Using CAD software, a virtual wax-up was
created to locate the ideal positions of the crown restorations
(Fig. 5). The software was used to select the implant types
and sizes that would fit properly into the available alveolar
bone without violating structures such as the sinus. The
CAD software was then used to position the implants
optimally in the bone and properly coordinate their
locations with the retention screw access holes planned for
the implant crown restorations (Fig. 6).
After all placement parameters were checked, the digital
plan was saved. A guide was designed using the CAD software
and sent to a 3-D printer using the STL file format
(Fig. 7). The 3-D printed guide provided for metal collimators
sized to the planned Nobel Biocare implants (Fig. 8). Two
different diameters and lengths of implants were selected
due to bone volume considerations. At the site of tooth #4,
Figure 8: Guide design for collimator inserts.
Digital scanning produces a virtual
model with sufficient accuracy to
ensure that the tooth-supported
surgical guide designed with
CAD software fits properly on the
tooth surfaces of the mouth.
– iTero Digital Scanning Technology and Tooth-Supported Surgical Guides – 57