Download - Www.rxdentistry.net. Information systems Treatment systems TECHNOLOGICAL TRENDS IN DENTISTRY
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Information systems Treatment
systems
TECHNOLOGICAL TRENDS IN DENTISTRY
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INTRAORAL IMAGING SYSTEM
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COMPUTER IMAGING SYSTEM
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CAD-CAM SYSTEM
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DIGITAL RADIOGRAPHIC SYSTEM
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COMPUTERIZED PERIODONTAL PROBE
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RADIOGRAPHIC IMAGE PROCESSING SYSTEM
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TREATMENT SYSTEMS
Abrasive system Laser system
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CAD-CAM SYSTEM
Acronym for computer
aided designing and
computer aided milling or
machining.
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BRIEF HISTORY
Increasing demand
Restoration at a single
appointment
Development- began in 1970’s
with Duret in France.
French system - in 1983 by
Dr.Francois Duret
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On September 19, 1985, the first ceramic
inlay was produced- at the dental Institute of
the University of Zurich.
Mormann 1985 in Zurich, Switzerland
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FUNDAMENTAL PRINCIPLES OF
CAD/CAM SYSTEM
CSD
CAD CAM
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ADVANTAGES
One visit restoration
Time saving
Improved esthetics
Good morphology
Improved crown fit
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Excellent polish
Less fracture due to single homogenous block
Wear hardness similar to enamel (Craig 1980)
Minimize cross infection
Good patient acceptance
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DISADVANTAGES
Need for costly equipment
Need for extended training
Technique sensitive
Inability to image in a wet
environment
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MACHINABLE CERAMIC MATERIALS
Dicor MGC Vita Mark II Inceram Alumina Inceram Spinell Inceram Zirconia Pro-Cad Procera Allceram
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MACHINABLE CERAMIC FRACTURAL STRENGTH
Dicor MGC 229MPa
Vita Mark II 122MPa
Inceram Alumina 500MPa
Inceram Zirconia 700MPa
Inceram Spinell 350MPa
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CERAMIC BLOCKS
Available in wide range of shades and sizes
More homogenous Less porous Mounted on a metal stub
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Purpose
To determine the fracture strength of
various all ceramic crowns with and without
cyclic loading.
Effects of surface finish and fatigue testing on the fracture strength of CAD-CAM and pressed –
ceramic crown (Hickel - JPD 1999)
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Material & Method
Machinable ceramic material, Vita Mark II
and ProCAD and conventional heat-pressed IPS
– Empress crowns were fabricated, with either
a polished or an oven – glazed surface finish.
Cyclic loading that simulated oral
conditions were performed on half of each
group.
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Conclusion
The Cerec Pro-CAD crowns had significantly
greater strength than the Vita Mark II crowns,
better resistance to cyclic loading and lower
failure probability than laboratory fabricated IPS
empress crowns.
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Cyclic loading significantly reduced the
strength of all-ceramic crowns, but had less
effect on cerec crowns than on the IPS Empress
crowns.
Oven-glazing of ProCAD crowns resulted in
significantly higher strength and higher
resistance to cyclic loading than surface
polishing.
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An upto 5 year Clinical Evaluation of posterior
In-ceram CAD/CAM core crowns (Mormann – Int.
J Prosthodont 2002)
Evaluated the clinical performance of
posterior CAD-CAM generated In-ceram alumina
and In-ceram spinelll core crowns using the
corec 2 CAD-CAM system and after 5 years of
service concluded that the clinical quality of
CAD-CAM generated In-ceram Alumina and In-
ceram Spinell posterior crowns was excellent
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CLINICAL PROCEDURE
Preparation Design
Optical Impression
Computer generated restoration design
Milling
Polishing and cementation
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PREPARATION DESIGN
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OPTICAL IMPRESSION
Lacks reflectivity
Special Powder
Rubber dam
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COMPUTER GENERATED RESTORATION DESIGN
Restoration is designed
Operator moves the
cursor
3-D image
Design phase – 2 – 8 min.
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MILLING
Computer selects
Block is inserted
Milling device is
activated
Three axis of rotation
cutting machine
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PROCESSING TIME
Process Step Coping Bridge
framework
Scanning Approx. 10min Approx. 20min
Designing Approx. 2 min Approx. 6 min
Milling Approx. 15min Approx. 50min
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POLISHING
Rough ceramic surfaces are smoothed
with clean white stones
Polished with
- Rubber wheel of fine grit
- Diamond impregnated wheels
& points
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CEMENTATION
Composite resin cement
Zinc phosphate
Glass ionomer
Ceramic restoration that have been
etched internally and bonded with a composite
resin cement are 50% stronger than similar
restoration cemented with zinc phosphate
cement (Ludwig 1994)
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Effects of Preparation and Luting system on All-
ceramic computer generated crowns (Mormann
– Int. J Prosthodont 1998)
Examined the effect of inside crown form
on fracture strength of cemented and bonded
crowns.
Four preparation types were used
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Machined crown were placed on
abutments
a. Without any media as control group
b. Cemented with zinc phosphate
c. Bonded
And were loaded until fracture
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RESULTS
Zinc phosphate cemented crowns showed
significant increase of fracture load values
compared to uncemented control crowns.
Fracture load values of bonded crowns
were significantly higher than those for
cemented crowns.
Bonded crowns with thick occlusal
dimension showed the highest fracture load
values.
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He concluded that bonded all ceramic
CAD-CAM crowns with defect oriented inside
morphology and increased occlusal dimension
showed high fracture load values.
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CEREC CAD/CAM SYSTEM
PROCERA CAD/CAM SYSTEM
TITAN CAD/CAM SYSTEM
CELAY CAD/CAM SYSTEM
CICERO CAD/CAM SYSTEM
LAVA CAD/CAM SYSTEM
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CEREC SYSTEM
Chair side economical reconstruction of
esthetic ceramic.
- Cerec – 1985
- Cerec 2 – 1996
- Cerec 3 – Feb’ 2000
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CEREC CAD-CAM SYSTEM
Limitation
Cannot mill the occlusal
surface
Only inlays and onlays
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CEREC – 2 CAD-CAM SYSTEM
Milling of occlusal surface
possible
Inlays, Onlays, veneers and
crowns
Milling time approx. 10min
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The grinding precision of
the cerec-2 is 2.4 times
higher than cerec system
(Mormann 1997)
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CEREC – 3 CAD-CAM SYSTEM
Advanced version
Technical improvements
Designing and grinding- less
time (27%)
Grinding unit – 2 cutters
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Marginal and Internal Fit of Cerec 3 Cad/CAM All Ceramic Crowns (Kojima –
Int. J Prosthodont 2003)
Examined the effect of the occlusal
convergence angle of the abutment and the
computer luting space setting on the marginal
and internal fit of cerec 3 CAD-CAM all ceramic
crowns.
Mandibular second premolar all ceramic
crowns were fabricated for nine different
conditions using cerec-3 CAD-CAM system
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Occlusal convergence
angle of 4,8 and 12°
Luting space settings of
10, 30 and 50µm.
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Total Oclusal
Convergence
Luting Space
10µm
Luting Space
30µm
Luting Space
50µm
Marginal Gap
4°
8°
12°
108
108
95
66
66
53
61
67
55
Internal Gap
4°
8°
12°
119
135
136
116
132
141
135
162
146
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He concluded that when the luting space
was set to 30µm, crowns with a good fit could
be fabricated with the cerec 3 system,
regardless of the occlusal convergence angle of
the abutment.
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PROCERA CAD-CAM SYSTEM Nobel Biocare
Initially introduced in 1985
Titanium copings
Utilizing the latest scanning, CAD-CAM and manufacturing technologies
Procera Allceram crown in 1991
Procera Allceram bridge in 1999
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TITANIUM CROWN AND FPDS
SUBSTRUCTURE
Reading
Milling
Spark erosion
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READING
The prepared die is
attached
Contact probe registers
the surface
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MILLING
The probe tip of the
reader and the tip of the
milling tool are of same size.
The graphite electrode is
milled
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SPARK EROSION
Used in dentistry since
1982
Graphite electrode is
fitted
Removes the metal by
electricity in the form
of controlled sparks to
fabricate copings.
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PROCERA ALL CERAM CROWN
Composed of densely
sintered, high purity
aluminium oxide coping that
is combined with low-fusing
Allceram veneering
porcelain.
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Preparation of the tooth
Computer assisted design
Manufacture of the coping
Addition of the veneering porcelain
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PREPARATION OF THE TEETH
Recommendations for the
preparation
Depth orientation grooves
1.5mm
Incisal reduction – 2.0mm
Axial reduction – 1.5mm
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Rounded, smooth contours and lack of line
angles
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Impression is made
Die is fabricated
Articulated
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COMPUTER ASSISTED DESIGN
Die is oriented vertically
Tip of the scanner probe is
brought in contact
As the platform rotates,
one data point is collected at
every degree around the
360° circumference of the die.
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Scanning takes 3min
More than 50,000 data
points are registered
Verified on the computer
screen for completeness
Vertical gap
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The finish line of the preparation is
marked by the operator at every 10° around
the circumference of the die.
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Coping design is
selected
Merged with the die
and its finish line.
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MANUFACTURE OF THE COPING
When the design of the
coping is finalized, it is
saved and transferred
through a modem
communication link to
Procera Stanvik AB in
Stockholm Sweden, where
the coping is fabricated.
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ADDITION OF THE VENEER
PORCELAIN The coping is sent by mail to the dental
laboratory where the ceramist finalizes the
restoration by addition of Allceram veneering
porcelain to create the appropriate anatomic
form and esthetic qualities.
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Titanium copings veneered with Procera Ceramics : A longitudinal clinical study
(Nilson - Int.J Prosthodont 1994)
In 1989, 47 titanium copings veneered
with a low fusing ceramic were fabricated for
24 patients. 44 crowns could be examined
after a period varying between 26 and 30
months.
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CDA ratings for surface and color
changed markedly from the Excellent to the
acceptable level.
For marginal integrity it was recorded as
satisfactory for all crowns and a large
majority were rated excellent.
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A comparison of the Fit of Spark – Eroded Titanium Copings and cast gold alloy copings (Wickens - Int. J. Prosthodont
1994) Compared the fit of spark eroded
titanium and cast gold alloy copings and
showed that the overall fit of titanium
copings was comparable to that of gold
copings. In marginal areas, the space
between die and coping was found to be
larger for spark eroded than cast copings.
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TITAN CAD-CAM SYSTEM
Production of metal
copings for porcelain fused
to metal restorations
Digitizing
Processing
Milling
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Preparation Impression
Die
Preparation Impression
Die
WaxingInvestingCasting
DigitizingProcessing
Milling
Conventional Technique
CAD/CAM system
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DIGITIZING
Die is fabricated
Mounted on the
digitizer
Data are recorded
Short circuited
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Divided into 200µm x
200µm squares
Digitized at least
twice
The finish line and the
adjacent 1mm area are
recorded first
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PROCESSING
The main parameters
for the copings are then
determined – The
gap between the
coping and the die
- The width and
shape of the
coping
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MILLING
Uses titanium alloy dummies of various widths in the form of disks or blocks
Milling device consist of two major units
- A rotatory drilling element with
interchangeable bores
- A mobile platform to which the
dummy is fixed
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Three steps
Rough milling inside the
coping
Fine milling inside the
coping
Rough external milling
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MULTIPLE UNIT RESTORATION
Steps same as for the
single unit restoration
It uses master cast
made from a
multiple unit impression
Master cast allows the
computation of each
individual tooth and of the
corresponding residual
ridge
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Relative parallelism
between the CAD-CAM coping
margin and the tooth margin in
comparison with uneven
appearance of same area of a
coping manufactured with
traditional casting technique
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CELAY CAD-CAM SYSTEM
Introduced in 1992 by
Mikrona Technologies,
Switzerland
Inlays, onlays, crowns and
bridge framework
Not a true CAD-CAM system
Many features in common
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A light cured composite
replica
Either directly or indirectly
Replica is mounted
Scanning tools used to trace
Milling tools removes
ceramic
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Bulk reduction by rough
diamond milling disc
Fine milling disc
Contouring by diamond
point
Milling time 40mins –
three unit bridge
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CICERO CAD-CAM SYSTEM
Computer integrated crown reconstruction
First technical concept- by Denisson et al
in 1999
Crowns with different ceramic layers such
as high alumina core, dentinal and incisal
porcelain for maximal strength and
enhanced esthetic.
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Preparation of Scan Model
Optical Scanning
Design
Occlusion
Design of crown layer build-up
Production process
STEPS
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PREPARATION OF THE SCAN MODEL
Model is marked with
black/white contrast
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OPTICAL SCANNING
Obtained by laser
scanning of the cast
Upto 1,00,000 surface
points are recorded
per minute
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DESIGN
Appropriate tooth
selected
Mesial and distal
contact are outlined
The margin line of new
crown is adjusted
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OCCLUSION
The new crown is
superimposed on the
opposing teeth to check
for occlusion
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DESIGN OF CROWN LAYER BUILD-UP
The interior and exterior tooth surfaces
are designed and interface surfaces between
cement and ceramic core and between dentin
and incisal porcelain are defined.
Thickness of the ceramic core of 0.7mm
Ceramic core – die cement thickness of
0.02mm is adjusted.
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PRODUCTION PROCESS
Refractory block is
fitted
Negative of the
inside surface of the
crown is milled
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Cutting tools used
- Diamond cylinder of 5.3mm dia
- Diamond rounded disk of 09.3mm
dia
- Diamond pointed tool of 0.9mm
dia
Automatically exchanged
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High strength
aluminium oxide based
ceramic is applied and
sintered
Ceramic is grounded
to calculated oversize to
compensate the shrinkage
that will occur during the
final sintering
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Dental porcelain
applied and fired
After firing block is
placed on milling machine
and interface between
dentinal and incisal
porcelain is milled
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Translucent incisal porcelain is applied,
fired and milled
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LAVA CAD-CAM SYSTEM
Produce high strength all ceramic crowns and FPD’s
Uses yttrium tetragonal zirconia polycrystals (Y-TZP) based material
Introduced as a hip replacement material in early 1990’s
High fractured strength 900 – 1200MPa and biocompatibility
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Special scanner (Lava Scan)
Computerized milling machine
(Lava Form)
A sintering Oven (Lava Therm)
CAD-CAM software technology
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STEPS IN FABRICATION
Saw cut working cast is mounted on the
scanner
The configuration of the tooth
preparation are scanned
Scanning process takes
- Crown – Approx.5min
- 3 unit FPD – Approx.12min
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Produces an enlarged framework to
compensate shrinkage during sintering
process.
Average milling time
- Crown coping – Approx.35min
- 3 Unit FPD – Approx.75min
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The framework is sintered in the Lava
Therm
Pre programmed to run for 8hrs,
including the heating and cooling phases.
The sintered framework is then veneered
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To conclude,
Computer graphics and CAD-
CAM have revolutionized dentistry.
It is now possible to provide
equivalent of a cast restoration in
a single appointment
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BIBLIOGRAPHY
Philips Science of Dental Material, - ANUSAVICE
Art & Sciences of Operative Dentistry- STURDEVANT’S
Dental Clinics of North America – Fixed prosthodontics
Fundamentals of Fixed prosthodontics – SHILLINGBURG
Contemporary fixed prosthodontics – ROSENSTEIL
Restorative dental material – CRAIG
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