1. DIGITAL IMPRESSIONS
BY Dr. SRAVANI
II YR PG

2. CONTENTS
1.Introduction
2.Digital versus conventional impressions
3.Different systems
4.Operating procedure
5.Discussion
6.Conclusion
7.References

3. INTRODUCTION
Dentists have tried to perfect the ultimate way to reproduce the
intraoral condition extraorally since the early days of the profession.
One only needs to study the development of articulators to gain
appreciation for the different theories, and means employed to
reproduce mandibular movement on a laboratory bench.1
Central to recreating the intraoral condition extraorally is to have an
accurate cast of the dentition and corresponding soft tissue (or
strictly the edentulous ridges).

4. Until recently, the only available means to accomplish this
was by taking a physical intraoral impression, which
enabled the dentist or technician to make a stone model of
the teeth, gingival, and/or edentulous areas. Our
predecessors used impression plaster, compound in copper
bands, reversible and irreversible hydrocolloid, and
polysulfide rubber base. At times they even fabricated wax
patterns directly in the tooth preparation. Today, the most
commonly used impression materials in the world are
polyether and vinyl polysiloxane (VPS).

5. Making impressions with polyether and vinyl
polysiloxane impression materials is an everyday
procedure in almost every general dental
practice. Manufacturers have developed and
refined these materials to the level at which it is
nearly impossible to blame the impression
material for restoration misfits. These materials
are accurate and stable.

6. The digital impression concept is emerging
rapidly on the high-tech horizon. Some
optimistic proponents infer that digital
impressions will solve the challenges now
observed with conventional elastomer
impressions.
However, there are several reasons, other
than the properties of conventional
impression material, for the inaccuracies
that arise in conventional impressions for
crowns and fixed prostheses

7. WILL DIGITAL IMPRESSIONS ELIMINATE
THE CURRENT PROBLEMS WITH
CONVENTIONAL IMPRESSIONS?

8. SOFT-TISSUE MANAGEMENT: Perhaps the most significant
reason for the inadequacy of some impressions made with
elastomer impression materials, as observed by dental
laboratory technicians, is the lack of visibility of the
subgingival margins of tooth preparations
This problem is related directly to inadequate soft-tissue
management at the time the impression is made.
Based on observation of conventional impressions in many
dental laboratories, proper isolation of subgingival margins
is one of the most inadequately accomplished procedures in
all of clinical dentistry.

9. Will digital impressions reduce the problems
related to isolation of subgingival margins?
The answer is a definite “No.”
It is obvious to clinical dentists experienced in the
digital impression technique that digital
impressions require even more definitive
preimpression isolation of tooth preparation
margins than do conventional impressions.

10. A digital camera cannot record tooth preparation
margins if they are not visible to the naked human eye,
and the computer cannot “fake” a margin any better
than can a human laboratory technician. To provide an
adequate digital image of tooth preparations, the
dentist must isolate the margins of all of the tooth
preparations and ensure that they are visible to the eye
before making a digital impression

11. IMPROPER IMPRESSION TRAYSELECTION
Most dentists use stock doublearch impression trays for
their elastomer impressions of one or two units and stock
trays for multiple units. Many stock trays are flexible,
requiring rigid impression material to provide the stability
needed. If the stock tray and the impression material inside
it are not adequately rigid, the impression’s accuracy will
be compromised because of the flexibility of the tray and
the material.
The digital impression process does not involve
impression trays, thus eliminating the problems related to
improper tray selection and potentially improving the
quality of impressions.

12. SEPARATION OF IMPRESSION MATERIAL
FROM THE IMPRESSION TRAY
Problems in separating impression material from the
impression tray usually are related to improper use of tray
adhesive materials. Polyether and vinyl polysiloxane
impression materials require adhesive agents to attach the
impression material to the impression tray. Holes in trays
further enhance attachment of the impression material to the
tray. Impression trays are not required for digital
impressions. Therefore, digital impressions can eliminate
this frequently seen problem, thus potentially improving the
quality of impressions.

13. DISTORTION OF CONVENTIONAL
IMPRESSIONS BEFORE POURING
Polyether and vinyl polysiloxane impression materials
are stable for a reasonable time after the impression is
made, but they can be distorted by inadequate storage or
inadvertent force applied to the tray and impression
during transportation or shipment to the dental
laboratory.
Digital impressions do not involve impression trays,
impression materials or shipment to the dental laboratory
and so eliminate the associated problems.

14. STORAGE OF CONVENTIONAL IMPRESSIONS FOR
POTENTIAL REMAKING OF CASTS AND DIES
Sometimes, an impression is poured improperly. It may contain
bubbles. The stone used for the die material may be too thick or too
thin. The impression or the poured dies may be misplaced or lost. The
result of each of these problems is a need to remake the dies. When this
need arises in the case of an impression made with conventional
impression techniques, the impression must be repoured.
The digital impression concept allows retention of the digital
information in appropriate computer storage as soon as it is received.
Assuming the digital information is backed up adequately, the
problems created by poorly poured, lost or misplaced impressions are
eliminated by the digital impression concept, thus potentially
improving impressions.

15. Many CAD/CAM systems are now available for
design and production of restorations based on
conventional silicone impressions. In these cases, a
plaster cast is made from the silicone impression and is
sent for extraoral scanning, where the plaster cast is
fixed on the extraoral scanner platform. Although the
accuracy of extraoral scanning is adequate, the
intraoral outline depictive process of a conventional
impression is hard to perfectly reproduce due to the
deformation of impression materials and plaster.

16. Therefore, the inadequate precision of plaster casts
is not optimal for completing CAD/CAM
procedures. In contrast, direct intraoral digital
impressions can avoid errors more than a
conventional impression can. Additionally, this
saves time for making conventional impressions
and plaster models and lowers the cost of materials.
Several outstanding intraoral scanning systems
were generated during the past two decades.

17. CAD/CAM systems are composed of three major
parts: (1) a data acquisition unit, which collects the
data from the region of the preparation teeth and
neighboring structures and then converts them to
virtual impressions (an optical impression is created
at this moment directly or indirectly); (2) software
for designing virtual restorations anchored in virtual
impressions and setting up all the milling
parameters; and (3) a computerized milling device
for manufacturing the restoration with solid blocks
of the chosen restorative material. The first two
parts of the system play roles in the CAD phase,
while the third is responsible for the CAM phase.

18. CAD/CAM systems can be divided into two types based on
digital data sharing capacity: open and closed. Closed systems
offer all CAD/CAM procedures, including data acquisition,
virtual design, and restoration manufacturing.
All the steps are integrated in the unique system. There is no
interchangeability between different systems. Open systems
allow the adoption of original digital data by other CAD
software and CAM devices.

19. Obstacles and deficiencies to address in intraoral digital
impressions are Some systems need a layer of powder spray
on the tooth surface, and the inhomogeneous powder thickness
may slightly transfigure the tooth outline.
Another major problem is scanner displacement during the
scanning process, which may affect scanning accuracy.

20. INTRAORAL DIGITAL IMPRESSION
SYSTEMS
The main intraoral digital impression systems currently available on the
market include .
1.CEREC
2. Lava C.O.S. system
3. iTero,
4.E4D, and
5.TRIOS.

21. They vary from each other in terms of
key features such as:
1.working principle
2. light source
3. The necessity of powder coat
spraying
4. Operative process
5. Output file format.

22. CEREC SYSTEM
The first to market in 1987 was the CEREC 1 (Siemens), which
used a 3-dimensional (3-D) scanner and optical powder on the
teeth to create a virtual model.
This system is designed with the concept of “triangulation of light,” in
which the intersection of three linear light beams is focused on a
certain point in 3D space. Surfaces with uneven light dispersion
adversely reduce the accuracy of scans. Therefore, adoption of an
opaque powder coating of titanium dioxide is required for producing
uniform light dispersion and increasing scan accuracy.

23. The development of the infrared camera (CEREC 1) was one of
the first steps in providing the profession with a digital practice
experience.
For nearly 20 years, CEREC was the only system capable of direct
intraoral digital impression making. In addition, with the CEREC
system, the practitioner could use CAD/CAM technology to
fabricate one visit inlays, onlays, and crowns.
Over the years, software and hardware improvements, as well as
restorative material improvements have made it easier for the
practitioner to make durable and aesthetic one visit CEREC.

24. Currently, the most prevalent CEREC system is its fourthgeneration
product, known as CEREC AC Bluecam. It captures Images using a
kind of visible blue light emitted from an LED blue diode as its light
source. The CEREC AC Bluecam can capture one quadrant of the
digital impression within 1 minute and the antagonist in a few
seconds.
The newest CEREC system, CEREC AC Omnicam, was brought to
market in 2012.

25. The Omnicam imaging technique is a style of
continuous imaging,where consecutive data acquisition
generates a 3D model, whereas Bluecam imaging is a
single image acquisition.
Omnicam can be used for a single tooth, quadrant, or
full arch, but Bluecam can only be applied for a single
tooth or quadrant.
Powder-free scanning and precise 3D images with
natural color are the most prominent features of
Omnicam. The powder-free feature has particular
benefits for a larger scanning area.

26. The CEREC AC imaging unit. As a
CAD/CAM system, the product includes a
BlueCam camera and a separate, newly
upgraded milling unit, the MC XL.

27. The CEREC AC BlueCam camera captures an image of teeth using
a more precise, shorter wavelength blue light source via active
triangulation sampling.

28. When digitally scanning, the dentist holds the scanner and
aims the camera towards the scanned area. The camera tip
should be a few millimeters away from the tooth surface or
should just slightly touch the surface.The dentist is asked to
slide the camera head over the teeth in a single direction
gently so as to generate the successive data into a 3D
model. This seamless scanning process can express a
notable depth of field. In addition, the scan can be
interrupted and resumed at any time by the operator...

29. A new technology of shake detection system can ensure the
3D images are only captured when the camera is stable and
still, so it can avoid any possible inaccurate data due to
shaking or trembling of the operator’s hand.
When scanning is complete, the preparation can be shown
on the monitor and looked over from any angle. The virtual
die is cut on the effective model, and the finish line is
outlined by the dentist directly on the die image. Then, a
CAD system “biogeneric” proposes an idealized restoration
design to let the dentist makes adjustments using a number
of on-screen tools

30. Once satisfied with the restoration, the dentist can mount a block of
ceramic or composite material with the desired shade in the milling unit
and start to produce the physical restoration. During the design stage,
color-coded tools determine the degree of interproximal contact and
ensure the finished restorations require minimal adjustments, if any,
before cementation. The dentist can either capture the teeth digitally
and fabricate a restoration in a single visit, or can transfer the data to the
dental laboratory by CEREC Connect R , which can in turn select the
restoration design virtually and mill it in the laboratory
CEREC Connect (Sirona) is a Web-based communication platform
designed exclusively for use by CEREC dentists and Sirona inLab
laboratories. This allows CEREC dentists to electronically transmit a
digitally-scanned impression to the inLab laboratory of their choice.

31. This type of intraoral scanner can be used for single
crowns, veneers, inlays, onlays, and implant-supported
FDPs. For crowns over implants, the prepared abutment
can be directly scanned, or a scan body seated on the
implant can be scanned by the dentist. A scan body is a
plastic coping with markers that provide 3D registration of
the implant location.
The CEREC system is a closed system, exporting the digital
impression data as a proprietary format file that works on
Sirona’s supporting CAM devices such as CEREC MC and
CEREC In-Lab.

32. The CEREC MC is a chairside milling unit that can
provide single-appointment treatments. Earlier, the
CEREC chairsidemilling unit was not capable of
milling FPDs and some high-strength ceramic
materials.Therefore, these types of cases had to be
milled through CEREC In-Lab.
With recent developments in CEREC devices, the
CEREC MC X and CEREC MC XL combined with
CEREC AC Omnicam can be used for a majority of
indications and materials, including FPDs and
zirconium oxide.

33. LAVA C.O.S SYSTEM
LavaTM C.O.S. (Lava Chairside Oral Scanner; 3M ESPE,
Seefeld, Germany) is an intraoral digital impression
device invented in 2006 and brought to market in 2008.
It works under the principle of active wave front
sampling.
This principle refers to obtaining 3D data from a single-
lens imaging system. Three sensors can capture clinical
images from diverse angles simultaneously

34. The Lava Chairside Oral Scanner
(C.O.S.). Note the absence of a
keyboard because data entry and
laboratory prescriptions are done
onscreen.

35. The Lava C.O.S. has the smallest scanner tip—only 13.2- mm
wide. The scanner sends out pulsating visible blue light as
light source and works with a mobile host computer and a
touch-screen display.
Similar to CEREC AC Bluecam, the Lava C.O.S. also requires
a powder coating spray on the tooth surface before scanning.
After the mouth is rinsed and air dried, the particular powder
(LavaTM powder for chairside oral scanner; 3M ESPE) is
sprayed on the tooth surface to form a homogeneous layer.
.

36. The Lava C.O.S. camera has the smallest wand of
any of the reviewed systems, making access to all
parts of the oral cavity easier to achieve.

37. In the progress of scanning, the dentist should start with the posterior
tooth area and move the camera forward, ensuring both buccal and
lingual sides are captured. The Lava C.O.S. can display the images
seized in the mouth on the touch screen at the same time.
With real-time visibility, dentists can immediately see if they are
receiving enough information from the preparation. Once it is
confirmed that all necessary details were captured on the preparation
scan, a quick scan of the rest of the arch is required.
If the display shows a critical missing or blurry area in the scan, the
dentist simply needs to rescan this specific area, and the software will
be amended automatically. The dentist then scans the opposite arch in
the same manner.

38. Finally, a scan from the buccal side with the patient in
occlusion is taken, and the system will articulate the
maxillary and mandibular teeth automatically to create a bite
record. After reviewing all the scans, the dentist can fill out
an onscreen laboratory prescription. The data are wirelessly
transferred to the laboratory, where a technician cuts the die
accordingly and digitally marks the margin with customized
software.
The compatibility with only few softwares makes Lava
C.O.S. a semi-open system.

39. iTERO SYSTEM
The optical impression iTero System (Cadent,
Carlstadt, NJ) was introduced in 2007, after 5 years
of intensive research. iTero system uses parallel
confocal imaging to capture the digital impression.
Parallel confocal imaging uses laser and optical
scanning to digitally capture the surface and contours
of the tooth and gum structure.

40. Parallel confocal scanning with the iTero system
captures all structures and materials found in the
mouth without the need for scanning powders that
coat the teeth. This system includes a computer,
monitor, mouse, integrated keyboard, pedal, and
scanner device . It is easily disinfected by replacing the
scanner disposable cover.

41. The iTero 3D digital impression system. Scan
data of preparations are e-mailed wirelessly to
Cadent for creation of the model, which then is
sent to the laboratory for the restoration .

42. When the prepared tooth is finished by rinsing, retraction,
hemostasis, and air drying, the dentist puts the scanner over
the tooth and starts the scan process. Scans over prepared
teeth should involve the following areas: occlusal, lingual,
buccal, and interproximal contacts of the adjacent teeth.
If any shake is detected, the system requires a rescan. After
completion, a 45° angle view from buccal and lingual
directions of the remaining teeth in the arch and opposite
arch are achieved. Eventually, a buccal scan of the patient’s
centric occlusion is obtained

43. Once the digital impression has been completed, the
clinician can select from a series of diagnostic tools to
evaluate the preparation and complete the impression. The
occlusal reduction tool shows in vivid color how much
clearance has been created in the preparation for the
restoration selected by the clinician.
A margin line tool is available to assist in viewing the
clearly defined margin. Once the clinician has completely
evaluated all aspects of the digital impression, adjustments,
if any, are made at that time and a few additional scans will
register the changes that were made to the prepared tooth.

44. The completed digital impression is conveyed to
the Cadent facility and the dental laboratory
through a HIPAA-compliant wireless system.
Upon laboratory review, the digital files are output
to a model by Cadent
Cadent models have a unique feature. Among
them, one model can be used as either a working
model or soft-tissue model.

45. The iTero model is made of a stable polyurethane
material which presents numerous advantages . There is
exceptional resistance to wear when used in the dental
laboratory.
It will not break or chip if accidently dropped, and
because the models are milled from the polyurethane,
there is no polymerization shrinkage. Additionally, the
plaster-like color is similar to conventionally poured
models

46. iTero scanner in place recording images
on the patient’s lower right side

47. The enhanced quadrant image.

48. The enhanced image of the arches in occlusion.
Color mapping gives the operator an idea of how
much occlusal reduction has been achieved.

49. E4D SYSTEM
The E4D system was developed by D4D Technologies, LLC
(Richardson, TX) under the principle of optical coherence
tomography and confocal microscopy.
It uses red laser as a light source and micromirrors to vibrate
20,000 cycles per second obtaining a sequence of images and
generating a 3D model

50. The E4D imaging unit. The CAD/CAM
system also includes a separate milling
unit for fabricating restorations.

51. During the image acquisition, the operator can choose
between the manual option by holding down the foot
pedal while centering the image and an automatic option
with images captured automatically when in focus. This
system can be used to scan conventional impressions and
casts.
Similar to CEREC AC Bluecam and Omnicam, this
system offers a char side milling unit, eliminating the
laboratory step and allowing a single-appointment
restoration. With this system, the patient can have the
final restoration in a much shorter time.

52. When the structure has to be processed in a milling
center, the optical impression data is sent to
DentaLogic software to create a virtual cast where
the restoration will be designed.
The E4D system can be considered as a semi-open
device as the digital impression data can be used by
other CAD/CAM systems,

53. The E4D system can scan the traditional impression made
of elastic materials and invert the image to create a virtual
model. This procedure is based on the virtue of traditional
impression materials yielding less reflective properties
compared to those by the tooth surface. Therefore,
traditional materials may help to improve the accuracy of
digital scanning

54. TRIOS SYSYTEM
In 2010, 3Shape (Copenhagen, Denmark) launched a new type of
intraoral digital impression system, TRIOS, which was presented
to market in 2011. This system works under the principle of
ultrafast optical sectioning and confocal microscopy. The system
recognizes variations in the focus plane of the pattern over a
range of focus plane positions while maintaining a fixed spatial
relation of the scanner and the object being scanned.
Furthermore, a quick scanning speed of up to 3000 images per
second reduces the influence of relative movement between
scanner probe and teeth.

55. By analyzing a large number of pictures obtained, the
system can create a final digital 3D model instantly to
reflect the real configuration of teeth and gingival color.
Similar to the iTero and E4D systems, the TRIOS intraoral
scanner is a powder-free device in the scanning process
The main essential trait of this system is, “the variation of
the focal plane without moving the scanner in relation to
the object being scanned.”

56. The operation of TRIOS is relatively simple. The dentist can
hold the scanner at a range of distances to the tooth. Either
closely over the tooth or 2 to 3 cm away will not affect the
focus and the capturing of images.
The 3D profiles of teeth and gingiva are generated
simultaneously, while the dentist moves the scanner gradually
above them. After scanning the upper and lower teeth, a
buccal scan can be taken when the patient closes into an
intercuspal position. The system of the host computer will
implement a digital registration to create a 3D occlusion
relationship

57. The TRIOS system is an open system that can
export 3D data as an STL file or a proprietary file.
The STL file can work together with other
CAD/CAM systems
TRIOS is a professional digital impression
acquisition and CAD system, and does not
include a CAM milling device
TRIOS and iTero contain diagnostic tools to
evaluate the preparation, which can be used to
instruct dental students in proper tooth
preparation and to grade tooth preparation at
dental schools

58. OPERATIONAL PROCESS
The patient received a standard preparation of the abutment
tooth under clinical criteria. To expose the margin of preparation,
two retraction cords of selective sizes were placed in the gingival
sulcus (Fig 1).
After waiting approximately 5 minutes when the sulcus was
expanded adequately, the area around the abutment tooth was
rinsed and air dried thoroughly for the scanning. If powder
spraying were required in accordance with manufacturer’s
instruction, a special sprayer would be used to perform an opaque
powder coating on the surface of prepared tooth (Fig2

59. STEPS IN DIGITAL IMPRESSION
1 Gingival retraction of prepared tooth

60. 2 Powder spraying tooth

61. Afterwards, the coronal cord was removed, and secondary
spraying was conducted to lay the powder over the area of
the removed cord. Then the digital scanning started. The
operator grasped the scanner control to let the scanner tip
slide towards the tooth from different directions for
capturing images.
Adequate pieces of 2D pictures taken by the scanner from
several angles were critical to generate precise 3D data of
the prepared tooth (Fig 3

62. 3 Intraoral digital
scanning.

63. A 3D stereopicture was displayed on the screen after the
missing and incorrect scanning areas were analyzed by the
operating system (Fig 4). The system could figure out if this
scan was eligible for use or required a rescan. After the scan
of the prepared tooth was completed, spraying and scanning
on the antagonists could begin in the same manner (Fig 5).
Eventually, a patient’s buccal side scan at oral occlusion was
taken to acquire a bite record (Fig 6). The final digital file
output from the scan system was transmitted to the technician
for further CAD/CAM process or applied for chairside
design and manufacturing.

64. 4. 3D image of
prepared tooth

65. 5. 3D image of
antagonists

66. 6. 3D image of
occlusion.

67. DISCUSSION
The impression of teeth, implants, and surrounding areas
is one of the most critical steps for making an indirect
restoration. As mentioned before, the more accurate the
preparation reading, the more precise the final restoration.
The correct reproduction of finish line and emergence
profile are essential for a satisfactory final impression

68. There are few studies about optical impressions in the
literature. Ender and Mehl1 compared in vitro the accuracy
of data obtained by CEREC Bluecam, Lava C.O.S., and
the conventional method. The authors obtained similar
results for the 3 methods, concluding that the digital
impression is as accurate as the conventional one.

69. The digital impression is reported to be less uncomfortable to
the patient, particularly the ones with previous experiences
with the conventional technique, with no discomfort or
gagging
Although there is no study showing a relation with the size
of the camera and the comfort level of the patient, this
aspect can be considered. Comparing the 4 systems
presented in this review, the Lava C.O.S. has the smallest
intraoral camera.
However, this system and the CEREC Bluecam require
powdering. This product has to be carefully used to provide
a thin and homogeneous layer avoiding distortions in the
final data.

70. Another limitation of these and any other system
is the necessity of gingival tissue displacement to
correctly visualize the finish line. This can be
done as in the conventional technique using
cotton Cords.
It is known that D4D Technologies are
developing an ‘‘optical coherence tomography’’
that allows the intraoral data acquisition without
the necessity of tissue displacement, as this
technique is able to distinguish between tooth
structure, bone, and soft tissue

71. CONCLUSION
The learning curve for any of the systems
presented in this study requires the development
of new abilities that request time and patience
The possibility of application and fast spreading
of the automatized systems in dentistry forecast a
future with less individualized procedures and
always moving toward the regulation of the
quality of the oral rehabilitation

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74. THANK YOU