INTRAORAL SCANS FOR CAD/CAM APPLICATION
data set is created by intraoral scanning. Intraoral
scanners are intraoral devices for capturing direct
optical impressions [6] (Fig. 4). Intraoral scanners are
based on different data capture principles: confocal
laser technology, confocal microscopy, triangulation,
wavefront sampling, multiscan imaging, stereopho-
togrammetic video, accordion fringe interferometry
[7,8].
It is important that the user takes digital impressions
according to the manufacturer’s instructions. This
method can eliminate many inaccuracies derived
from indirect CAD/CAM impression process. However,
the traditional principles of the impression-taking
procedure are still alive, soft tissue control and isolation
remain basic principles. The scanning process ends
with biterecord. There are intraoral scanners which can
also determine the tooth-color.
The next step following the digital impression-taking
procedure is to evaluate the quality of the virtual cast
(Fig. 5). Inaccuracies can be eliminated by the dentist
directly chairside within this step. The occlusal and axial
reduction, the insertion direction can be observed on
the computer screen with built in tools of software.
The margin line can also be checked enlarged by the
software.
Any imperfections of the virtual cast can be corrected
without the need to retake the whole impression.
Additional images of the areas of interest can be added
to previous scan. When satisfied with the impression
and resulting virtual cast, it is sent to laboratory with
the digital worksheet via e-mail.
There are open and closed dental CAD/CAM systems.
Closed systems’ files can be opened by the manufacturer’s
CAD software only. Closed systems are CEREC AC and
E4D systems. Most intraoral scanners work with an open
system and they are compatible with several types
of CAD softwers and milling machines (for example
3Shape TRIOS, Planmeca PlanScan, CEREC Omnicam,
iTero Element, Carestream CS 3500, 3M True Definition,
GC Aadva, DWIO Dental Wings, KaVo Lythos, Dentium
Rainbow, Zfx IntraScan, MFI Condor IOS, etc) (7).
3.2. Direct CAD/CAM workflow
3.2.1. Labside system
The labside workflow of CAD/CAM technology means
The labside workflow of CAD/CAM technology means
that the dental technician processes data coming
from the dental office. The technician performs the
preparatory work on the virtual cast, model occlusion
with CAD software and design restoration on the
computer screen (Fig. 6).
The technician sets the margin line and the space for
the cement. After that the framework or the full-contour
restoration is designed. The anatomical occlusion surface
and contour of the teeth can be made individually. The
software contains the color of the restoration, so the
suitable block is chosen for the milling. Digital planning
does not exclude model making. From the digital data
a polimer model can be made by milling, 3D printing or
with stereolithography (SLA) [9]. The final restoration can
be checked on this model (Figs. 7, 8).
Another option of the computer-assisted production
is centralised production in a milling centre. In this
variation, it is possible for the local laboratory to design
112
Figure 4. Trios intraoral captures optical impressions of the prepared
teeth for the direct CAD/CAM method.
Figure 5. Full arch virtual casts in ICP position on computer screen after
scanning.
Figure 6. Dental technician designs restoration on computer screen with
CAD software.
the restoration, then data sets are sent for milling to the
centre. Procera is a well-known example for milling centre.
It is specialised for milling technically sensitive materials
like high strength ceramics and titanium (Figs. 9, 10).
3.2.2. Chairside systems
We must not forget that initially intraoral scanners were
developed for chairside solutions (CEREC). The main
Stoma Edu J. 2018;5(2): 110-117
http://www.stomaeduj.com