Model and die materials

DEPARTMENT
OF
PROSTHODONTICS
DR. FEBEL HUDA, M.D.S,DICOI,FICOI,FAD,DLD.
ORAL MAXILLOFACIAL PROSTHODONTIST AND IMPLANTOLOGIST
 DIPLOMATE FROM THE INTERNATIONAL CONGRESS OF ORAL IMPLANTOLOGY
 FELLOW FROM THE INTERNATIONAL CONGRESS OF ORAL IMPLANTOLOGY
 DIPLOMATE IN LASER DENTISTRY (UNIVERSITY OF GENOVA - ITALY)
 FELLOW IN AESTHETIC DENTISTRY (UNIVERSITY OF GREIFSWALD - GERMANY)

GPT-8
• DIE: the positive reproduction of the form of a
prepared tooth in any suitable substance
(die is used for construction of cast partial
dentures and crowns)
• MODEL : a facsimile used for display purposes; a
miniature representation of something; an example for
imitation or emulation.
(model is used for observation, diagnosis, patient
education)

CLASSIFICATION
MODEL
MATERIALS
TYPE II GYPSUM
HEAT ACTIVATED
ACRYLIC
Other model materials:
Polycarbonate
Lead

TYPE II GYPSUM (MODEL PLASTER)
(ADA;No: 9)
• USED:
For making models and casts.
• REQUIRMENTS:
 It should set rapidly but give adequate time for manipulation.
 It should set to a very hard and strong mass.
After mixing, consistency should be such that it can flow into
all parts of the impression and reproduce all the minute details
Craig’s Restorative dental materials -12th Edition

GYPSUM
HISTORY :
• Gypsum is found in various part of the world and is a
industrial by-product.
• It was used for many centuries for construction
purposes.
• ALABASTER, a form of white gypsum which was used
to construct KING SOLOMON’S temple.
• It was first found in the mines of Paris so called
PLASTER OF PARIS.

CLASSIFICATION (according to ADA)
• TYPE – I → Impression plaster. (ADA;No: 4)
• TYPE – II → Dental plaster. (ADA;No: 9)
• TYPE – III → Dental stone or medium strength
stone. (ADA;No: 20)
• TYPE – IV → Improved stone or high strength
stone (die stone). (ADA;No: 35)
• TYPE – V → High strength, high expansion
dental stone. (ADA;No: 35)

CALCINATION
Calcium Sulfate
Hemihydrate
Calcium Sulfate
Dihydrate
Accelerators
Retarders
[CaSO4-(2)H2O] + [110˚- 130˚]   [CaSO4-(1/2)H2O]

Chemical Name: -calcium sulfate
Formula: CaSO4-(1/2)H2O
Powder Shape: Irregular
Density: Porous
Production Steps: Heat to 110C to 130C in
air in open kittle
Dental Products: Plaster
Calcination: dry
Common Names: Plaster of Paris

MANIPULATION
Transfer to impression

TIME
SETTING STAGES
Mixing
Interval
Working
Interval
Setting
Interval
Mixing
Time
00:00:00 00:01:00
Working
Time
00:07:00
Setting
Time
00:13:00
Final Set
Setting Time = 45 min
Initial Set
Setting Time = 7 – 13min
LOSS OF GLOSS

MEASUREMENT OF SETTING TIME
• LOSS OF GLOSS METHOD: The gloss
disappears from the surface of plaster mix.
• EXOTHERMIC REACTION: The temperature
rise of the mass may also be used for
measurement of setting time ,as the setting
reaction is exothermic.
• PENETRATION TESTS: By using penetrometer

TYPES OF PENETROMETER
 VICAT NEEDLE 300gm, 1mm
 GILLMORE NEEDLE
Large
Gilmore
Needle
Small
Gilmore
Needle
1/4lb wt
diameter½”
1 lb wt
Diameter 1/12”

MODEL PASTER
EFFECT OF WATER/POWDER RATIO ON SETTING TIME
W/P RATIO
ml/g
Spatulation turns Initial setting
time
0.45 ml/g 100 8 min
0.50 ml/g 100 11 min
0.55 ml/g 100 14 min

MODEL PASTER
EFFECT OF SPATULATION ON SETTING TIME
W/P RATIO
ml/g
Spatulation turns Setting time
0.50 ml/g 20 14 min
0.50 ml/g 100 11 min
0.50 ml/g 200 8 min

SETTING EXPANSION
• Normal setting expansion (0.05 to 0.5%)
linear expansion - outward thrust of growth crystals – nuclei
– intermesh - intercepts .
----- Spherulites
Anusavice Phillips Science Of Dental Materials 10th Edition

Hygroscopic setting expansion
Hydration------- ------ replaced as under water
Intermeshed and
entangled--------------
Prevents further
growth--------- -----------Growth is much free
(0.15%) (0.30%)

 importance of setting expansion
Controlling setting expansion
↑ Spatulation ↑ SE
↓ W/P ↓ SE
• Potassium sulphate (accelerator) — 4% solution ↓ setting
expansion from0.5% to 0.06%
• Sodium chloride 2%(accelerator) and ground gypsum ↑
setting expansion.

PROPERTIES
1 Mixing water 37 – 50 ml/100g of powder
2 Required water 18.6 ml/100g of powder
3 Excess water 18 – 13 ml/100g of powder
4 Setting expansion range ±20%
5 Compressive strength 9.0 Mpa
6 Reproduction of details 75 ± 8 µm
7 Water / Ratio 0.50 ml/g
8 Spatulation 100 turns

Factors Affecting Strength
• Wet strength -Dental Plaster is 9 MPa .
(free water)
• Dry strength -is two or more times greater than
the wet strength.
• Excess water -there is no strength increase until
the last 2% of free water is removed. (This
strength increase on drying is reversible)

• Temperature: Gypsum is stable only below about
40ºC at I00ºC or higher causes shrinkage and a
reduction in strength.
• the strength increases with increased spatulation.
• Addition of accelerators and retarders : Lowers
strength.

MODEL PASTER
EFFECT OF WATER/POWDER RATIO ON COMPRESSIVE
STRENGTH
W/P RATIO
(ml/g) (↑)
COMPRESSIVE STRENGTH
(Mpa) (↓)
0.45 12.5
0.50 11.0
0.55 9.0

(Poly-methyl methacrylate)
(ADA No- 12)
HISTORY:
Introduced to dentistry in
the year 1934
USES:
 Mainly used as denture
base
 Used in construction of
preclinical models

COMPOSITION OF POLYMER
POWDER
• Ingredient Function
• Polymethyle metracrylate - main
• Benzoil peroxide - 0.5 – 1.5 –nitiator
• Dibutyle phthalate - 0.8 – 10% - External plasticizer
• Methacrylate or acrylate
monomer - Internal plasticizer
• Zinc or titanium oxide - opacifier.
• Mercuric sulfide - pigments and dies
• Glass fibres or beads - to increase stiffness

COMPOSITION OF THE MONOMER
LIQUID
Ingredient Function
• Methyl methacrylate - Main chemical which polymerize
• Hydroqyinone 0.003 to 0.1% - Inhibits polymerization while
storage
• Dibutyl phthalate - Plasticizer.
• Glycol dimethacylate 1 – 2% - Cross – linking agent

PHYSICAL PROPERTIES
(methyl methacrylate)
Melting point -48˚c
Boiling point 100.8˚c
Density 0.945 g/ mL at 20˚c
Heat of polymerization 12.9 Kcal/mol
*PHILLIPS science of dental materials,10th edition, pg-231
*PHILLIPS science of dental materials,10th edition, pg-231

POLYMERIZATION
Addition polymerization
• Induction :
The initiator benzoyl peroxide is activated
by heat to produce a free radical
• Free radical – an atom that has unpaired
electrons
• Propagation:
The free radical released combines with
other free radical to form double bond andAnusavice Phillips Science Of Dental Materials 10th Edition

Termination :
• Direct coupling ( exchange of energy)
• Exchange of hydrogen atoms from one
growing chain to another.
Chain transfer :
• The active state is transferred from an
activated radical to an inactive molecule.
• A new nucleus is created for new growth

FEW, WHICH WE MISSED YESTERDAY
• Pfaff, of Germany in 1756 – first to make the
plaster cast (taking the bite)
• Vernon in 1936 – introduced acrylic resin
• Before which-
 Hard coconut shell
 Hippopotamus tusk
Ox femur
Teak wood
Gold, tin, porcelain, gutta-percha, vulcanite ( 1854)
Laney’s, Diagnosis and treatment in prosthodontics, 1st edition

PROPERTIES
Polymerization shrinkage (by volume) 6%
Polymerization shrinkage (linear) 0.2% to 0.5%
Coefficient of thermal expansion More than twice of that of composite
(92.8)
Compressive strength 76MPa
Tensile strength 55MPa
Hardness (knoop) 15 – 18 km/mm2
Biocompatibility Good
Thermal conductivity Poor
Wear resistance Fair
Fatique resistance ( to flexing) Good
Impact resistance (to break when
dropped)
Poor

Basic Requirements of Die Materials:
• Should have accuracy and dimensional stability.
• Should have a smooth, hard surface which should not
easily abrade.
• Should be compatible with impression material.
• Should have high strength.
• Should have good color contrast.
• Economical.
• Should be able to manipulate easily and fast.
• Have ability to reproduce fine details & sharp margins
• Resistance to abrasion

Classification:
• Hard die materials:
o Gypsum die materials
 Type IV gypsum
 Type V gypsum
 Die Stone with Disinfectant (Steri-Die-A)
 Die Stone and Die Hardener
 Die Stone and Cyano-acrylate
o Resin based die materials
o Electro plated dies
o Gypsum-resin combination materials
o Refractory die materials
• Flexible die materials:
o Polyether
o Polyvinyl siloxane
• Miscellaneous:
o Silver amalgam
o Silico-phosphate cement
o Plastic steel

Stone, High Strength
(Type IV) (ADA;No: 35)

Formula CaSO4-(1/2)H2O
Powder Shape: Uniform
Density Dense ( compared to type II)
Production Steps Heat to 100C in
30%CaCl2 solution or MgCl2.
( 100 C water or
autoclave 0.5% sodium
succinate)

COMPOSITION
α- hemihydrate Main composition
Potassium sulfate 2-3 % accelerator
Sodium citrate Retarder
Coloring agent 2%

PROPERTIES
Water: powder ratio 0.20 to 0.22 %
Setting time Initial
Final
7min
9 min
Setting expansion
24hr Setting Expansion
0.5 to 0.7%
70%
Compressive strength
Dry
34 Mpa
80 Mpa
Dry hardness 92RHN
Dimensional changes
Occlusal
Cervical
0.06%
0.00%
Tensile strength 8 Mpa

• Advantages:
• Greater abrasion resistance.
• Have higher strength than stone or model
plaster.
• Disinfection:
• This can be achieved by disinfecting the
impression
• By immersing the cast in disinfectant solution
like sodium hypochlorite
• Incorporating disinfectant in the stone itself

Conducted a study to find if gypsum cast as a potential
source of microbial cross contamination
. He sterilized the alginate
impression and dental
stone with ethylene oxide
and used serratia
marcescens to
contaminate the casts
and incubated it in
BHI(brain-heart infusion)
medium for 24hr at 37˚c
and then took pieces of
the cast and incubated in
agar plate for 7 days in
37˚c .
• concluded that
gypsum cast is a
potential source of
cross contamination
hence disinfection is
necessary.
Ralph L. Leung et al (J Prosthet Dent 1983;49:210-211)

Conducted a study on surface detail, compressive
strength, and dimensional accuracy of gypsum casts
after repeated immersion in hypochlorite solution
• He immersed 30 type III
and type IV dental
stone in slurry with
0.525% sodium
hypochlorite solution
and 30casts in slurry
water.
• He concluded that there
is a significant increase
in linear dimension and
significant decrease in
wet compressive
strength but both the
solution produced loss
of surface details.
Mohammed Aleem Abdullah et al (J Prosthet Dent 2006;95:462-468)

Conducted a study to evaluate abrasion and
compressive strength of gypsum casts after repeated
spray disinfectants
. He sprayed iodophor, acid
glutraldehyde, phenol
and water on type III and
type IV dental stone
• . He concluded that there is
a significant increase in
abrasive resistance after
repeated spraying of water
or disinfectant.
• glutraldehyde decrease in
compressive strength of
type III stone by 26%,
• phenol increases the
compressive strength of type
IV stone by 18%,
• Iodophor had no significant
effect on dental stone.
Mitchell A. Stern et al : (J Prosthet Dent 1991;65:713-718)

Conducted a Study of the physical properties of type IV
gypsum, resin containing, and epoxy die materials
• He compared the properties
of 3 new die materials and 2
conventional type IV
gypsum products for linear
dimensional change, detail
reproduction, surface
hardness, abrasion
resistance, and transverse
strength
• The result showed that
gypsum products
expanded, whereas the
epoxy resin material
contracted during
setting. epoxy resin
exhibited much better
detail reproduction
abrasion resistance, and
transverse strength
than the gypsum
materials.
Philip Duke et al : (J Prosthet Dent 2000;83:466-473)

Die Stone, High Strength, High Expansion
(Type V)
ADA No: 35

PROPERTIES
Setting Expansion Max of 0.10% - 0.30%.
W/P ratio 0.18 – 0.22
Setting time 12±4min
1hr compressive strength 7000psi.
Mixing time 30sec to 1min
Working time 3 min
Temperature alters the
setting time
Above 50˚c retards setting
time
At 100˚c no reaction takes
place

• Advantages:
• Increased strength & greater setting
expansion.
• Compensates for casting shrinkage of base
metal alloys.
• Disadvantage:
• High expansion

Die stone with cyano-acrylate (to
increase surface abrasive resistance)
• Conducted a study to
evaluate the
effectiveness of the
cyano-acrylate on die
stone. They investigated
three products of die
hardeners with regards
to their influence on
surface hardness of
stone, film thickness
and abrasion resistance.
• He concluded that
cyano-acrylate resins
as die hardeners
effectively improve the
surface hardness of the
stone dies and that
surface detail
reproduction can be
achieved by blowing the
excess liquid applied
with compressed air.
Habib H. Ghahremannezhad,et al: (J Prosthet Dent 1983;49:639-646)

Die stone with disinfectant
• Conducted a study to
evaluate the antimicrobial
effect from incorporation
of disinfectant into
gypsum cast.
• He used four
disinfectants and tested
them against five
microorganisms.
• concluded that sodium
hypochlorite and neutral
glutaraldehyde were
effective in eliminating all
growth of bacteria at 1
and 24 hrs.
• Idophore was effective in
eliminating growth at
24hr but not at 1hr.
• Phenol did not have a
profound antimicrobial
effect at 1 or 24hr.
Steven. M. Mansifield et al :(Int. J. Prosthodontics 1991;4:180-185)

Resin based die materials
• Resins are used as die
materials to overcome
the low abrasion
resistance of die stone.
Epoxy resins and
polyurethane are the
resin based die
materials that are
commonly used.

EPOXY RESINS
• Is compatible with most impression materials
• Exhibited better detail reproduction
• Abrasion resistance
• High Transverse strength than gypsum-
materials.

PROPERTIES
Working time 15min
Setting time 1-12hrs
Compressive strength: Initial
After 7
days
9500 psi
16,000psi
Polymerization shrinkage 0.1-0.2%.
Hardness 83RHN
Dimentional changes. Occlusal
Cervical
0 – 0.15%
0.19%
Detail reproduction 25µm
KHN 17.76 – 29.80

Advantages:
• 1. Superior abrasion resistance.
• 2. Less brittle.
Disadvantage:
• 1. Shrinkage on polymerization.
• 2. Less dimensional stability.
• 3. Expensive.
• 4. More viscous than stone, so more prone to
trap air in preparation

Compared three epoxy die material (Pri-Die , unitek
epoxy die and epoxydent) for marginal adaptation, fit
and retention in 60 Complete crown and MOD inlay
• He concluded that there is
no significant difference
between the materials but
pri-die and epoxydent dies
had more clinical acceptance
for MOD and
• unitec die material
acceptable for complete
crown.
P. Yaman, et al: (J Prosthet Dent 1986;55:328-331)

He studied the Dimensional accuracy of an epoxy resin
die material using two setting
Methods
• He retarded setting
reaction and checked the
dimensional accuracy, he
manipulated high-
strength high-expansion
gypsum (Die Keen); and a
resin-filled gypsum (Resin
Rock) as per manufacture
instruction and then
manipulated to retarded
polymerization set.
• He concluded that
Retarding the setting
reaction of an epoxy resin
die material improved its
accuracy.
Jacinthe M. Paquette, et al : (J Prosthet Dent 2000;83:301-305)

He studied three commercially available resin die
systems and evaluated some characteristics that relate
to their clinical performance.
• Characteristics
evaluated include
accuracy of fit, detail
registration, and Knoop
hardness.( epoxydent,
precision, velmix and
die stone).
• Out of the 80 die
evaluated only one did
not fit that is gypsum.
Epoxy group were
harder and had no
significant difference in
accuracy.
Gerald T. Nomura,et al : (J Prosthet Dent 1980;44:45-50)

He compared the pertinent
properties of die materials used for
the indirect materials has been made
• Eight classes of materials
were evaluated and the
result showed that stones
were superior from other
materials in stand point of
dimensional accuracy but it
lacked abrasion resistance.
• The dies made from the
ceramic material,
silicophosphate cement,
one of the resins and by
electrodeposition were
superior in abrasion
resistance
• The surface of the
electroplated dies, the
ceramic material, stones
and silicophosphate cement
provided excellent
duplication of detail.
Svicrker toreskog et al (J Prosthet Dent 1966;16 :119-131)

He studied Accuracy of stone, epoxy
and silver plate-acrylic models for
selected dimensions of stone
• Epoxy resin and silver
plate backed with
acrylic resin models
were compared to each
other and their master
model which simulated
the abutments for a
FPD and
• concluded that Silver
plated models backed
with acrylic resin were
not as accurate as stone
or epoxy resin models,
between which there
was no significant
difference.
Stevens L, Spratley MH et al : (J Dent mater 1987;3:52-55)

Types of electroformed dies
• Silver plated
• Copper plated

SILVER FORMED DIE
• Polysulphide and
silicone impression
materials can be silver
plated (Cathode)

Composition of electroplating bath
solution
• Silver cyamde-36 gm
• Potassium cyanide-60 gm
• Potassium carbonate-45 gm
• Water(distilled)-1000ml
• Electroplated for 10hrs, using 5-10mA/cm2 of
cathode surface

COPPER FORMED DIES
• Composition of electroplating bath solution
• copper sulphate
• alcohol or phenol
• Sulphuric acid
• phenol sulphonic acid
• About 15mA current proceed for 12 to 15 hours

• Advantages :
• Moderately high strength
• Adequate hardness
• Excellent abrasion resistance.
• Disadvantages:
• silver cyanide and acid to the solution
produces hydrogen cyanide,

He compared silver-plated and stone
dies from rubber-base impressions
• Studied The accuracy of
silver-plated dies as
compared with that of
stone dies was
investigated using a
silicone impression
material, Xantopren,
and a polysulfide
material, Permlastic.
• Concluded that Primary stone
dies from Xantopren
impressions are more accurate
than primary or backup silver-
plated dies from Xantopren
impressions.
• There is no significant
difference in accuracy between
primary stone dies and primary
silver-plated dies from
Permlastic impressions.
• Secondary silver-plated dies are
less accurate than primary
stone dies or primary silver-
plated dies from Permlastic
impressions.
Joseph P. Cooney et al :(J Prosthet Dent 1974;32:262-266)

TYPES OF FLEXIBLE DIES
• POLYETHER
• POLYVINYL SILOXANE

POLYETHER
• The polyethers (synonym: epimine) cure
through cross-linking .
• The reaction involves ring opening without
formation of volatile byproducts.
• Polyeter is a stiff material so thinner is used to
reduce the stiffness
J Prosthet Dent 1992;68:372-374

Composition
Base paste
• Polyether polyme
• Colloidal silica as a filler
• Glycoether or phthalate as plasticizer
Accelerator paste
• Alkyl-aromatic sulfonate
• Colloidal silica as a filler
• Glycoether or phthalate as plasticizer

Advantages:
• More rapid setting
• Ease of removal
• Does not adhere to the acrylic resin
Disadvantages:
• Expensive
• Hyper sensitivity to polyether catalyst system
leading to contact dermatitis

Polyvinyl siloxane( Addition silicone)
• It was introduced in 1970s
• It has much greater dimensional stability.
• It’s less rigid than polyether.
• They have excellent dimensional accuracy and
long term stability.

Composition
Accelerator paste
• Divinyl siloxane
• Other siloxane prepolymers
• Platinum salt (chloroplatinic acid) catalyst
• Palladium - hydrogen absorber
• Fillers

Composition
Base paste
• Poly methyl hydrogen siloxane
• Other siloxane polymers
• Fillers

Working time 1-4 min
Setting time 3-5min

Conducted a study to compare the
surface detail reproduction of 7
potential flexible die materials
• Concluded that surface
detail reproduction of
the flexible dies has no
significant difference
from normal stone die
but among the flexible
die IMPREGUM-F die
material reproduce
details better.
• He also said that
polyvinyl siloxane
impression material is
incompatible with
polyvinyl siloxane die
material without die
seperators.
Jack.D.Gerrow et al : (J Prosthet Dent 1998;80:485-489)

Requirements
• Easy manipulation
• Stability at higher temperature
• It should produce mould expansion to
compensate for casting shrinkage of alloy
• It should produce a smooth surface on setting
• It should be porous to allow air from the mould
space to escape.
• It should have adequate strength to withstand
casting pressure.

Types of refractory dies
• Gypsum bonded die-vestment
• Phosphate bonded die-vestment ( for all
ceramic)
• Ethyl silicate-bonded

Gypsum bonded die-vestment
• Brodsky in 1933
• Composition
• 70% mullite
• 30% plaster of Paris
• Phillips, suggesting that gypsum-bonded
investments should not be heated above 700 ̊C
as decomposition of the gypsum occurs,
producing sulfur trioxide.
• Modifiers, such as boric acid, added to reduce
the contraction

Setting expansion of
divestment
0.9%
Thermal Expansion 0.6%

Phosphate bonded die-vestment
• Moore and Watts in 1949 developed
phosphate- bonded material

Gypsum – resin combination
materials
• Resin rock die material :
epoxy resin + high expansion stone
• Advantages of both.
• Dimensional shrinkage is compensated with
the expansion of the gypsum stone.

Plastic steel: (Victor.E.Wasser)
• A material used in industry for making molds,
models, and dies has been found to be useful
for making dies and casts for splints and other
restorations.

PROPERTIES
Ultimate compressive strength 16,000 p.s.i.
Tensile strength 8,000 p.s.i.
Flexure strength 11,000 p.s.i.
Relative impact strength O.8 Foot-pounds per inch of
Notch IZOD
Rockwell hardness F- 93
Resistance to heat 300˚F.
Dielectric constant 2.9
Machining qualities Poor
Specific volume 15-16 cubic inches per pound
Shrinkage on 4 by 3 by 1
casting
0.00016 inch per inch

DISADVANTAGES
• Its color is black.
• The material is more difficult to mix than die
stone.
• It is necessary to use a separating medium
before the master cast is poured.
• A separating medium is necessary if the wax
patterns are to be formed.

Other die materials
• Silver amalgam
• Silico-Phosphate cement
• Silica modified epoxy resin
• Bismuth alloy

SELECTION OF DIE MATERIALS
MATERIAL RECOMMENDED
USE
PRECAUTION
Type IV & V dental
stone
Most situations •Proportionate mix
•Vacuum mix
•Surface Hardeners
Epoxy resin All ceramics •Incompatible with poly
sulfides & hydrocolloids
•Spacer (shrinkage)
Electroplated dies
All ceramic crowns •Cyanide usage(toxic)
•Incompatible with
hydrocolloids, polyether &
polysulfides(Ag plating)
Flexible die materials
Provisional compatibility
indirect compsite
material inlay/ onlay
material
•Check for between die and
impression especially
elastomers)

Compatibility with impression
materials
Dental stone •Impression compound
•Alginate
•Zinc oxide euginol
•Agar-agar
•Rubber base material
Electro plated (copper) •Rubber base material
Electro plated ( silver) •Polysulphide
•Polyether
•Addition silicone
Polymer epoxy •Rubber base material
Resin •Polyether
•Addition silicone
•Polysulphide

Types of optical impression and
model technology
• CEREC
• The E4D (D4D TECH)
• DCS PRECIDENT SYSTEM
• iTero
• LAVA
• Haptic technology

Potential benefits
• Saves time and one visit for in-office systems
• Opportunity to view occlusion
• Accurate restorations created on digital models
• Potential for cost-sharing of machines.
• Accurate, wear- and chip-resistant physical
CAD/CAM derived models.
• No layering/baking errors.
• No casting/soldering errors.
• Cost-effective.
• Cross-infection control.

CEREC
• The first system
introduced was the
CEREC 1 in 1986.
• The CEREC 1, 2 (1994)
and 3 (2000) systems
(Sirona Dental) have all
used a still camera to
take multiple pictures
that are stitched
together with software.

• Parsell DE et al(2000)
• study found that the average camera
angulation error by clinicians was just under
two degrees, insufficient to introduce error as
the camera was tolerant of errors up to five
degrees in buccolingual and mesiodistal
planes
Parsell DE et al:(J Prosthet Dent 2000;83:301-305)

E4D (D4D TECH)
• Takes several images, using a red light laser to
reflect off of the tooth structure
• Requires the use of powder in some limited
circumstances.

DCS PRECIDENT SYSTEM
• Designed for metal
copings for PFM & FPDs.
• Conventional wax up
required.
• Touch probe
• 7 –unit bridge on one
side.
• Acceptable marginal
accuracy.

Compare the marginal accuracy and refinement time of
titanium copings fabricated by 3 different CAD/CAM
systems relative to standard casting techniques
• Concludes that manual
adjustment significantly
improves the marginal
accuracy of CAD/CAM
system-fabricated
titanium copings.
• The highest marginal
accuracy was achieved
with the DCS system,
using a longer
refinement time.
Siegbert Witkowski et al :(J Prosthet Dent 2006;96:47-52.)

iTero
• The iTero system uses a
camera that takes
several views (stills),
and uses a strobe effect
as well as a small probe
that touches the tooth
to give an optimal focal
length.
• NO use of powder

LAVA
• Chairside Oral Scanner (LAVA COS, 3M ESPE)
takes acompletely different approach using a
continuous video stream of the teeth.

Compare the fit of all-ceramic crowns fabricated from
LAVA intraoral digital impressions with the fit of all-
ceramic crowns fabricated from silicone impressions
• 1. Crowns from intraoral
scans revealed
significantly better
marginal fit than crowns
from silicone
impressions.
• 2. Marginal
discrepancies in both
groups were within the
limits of clinical
acceptability.
• 3. Crowns from intraoral
scans tended to show
better interproximal
contact area quality.
• 4. Crowns from both
groups performed
equally well with regard
to occlusion
Andreas Syrek et al :( J prosthet dent 2010;38;553-559)

Haptic technology
This is a virtual waxup system whereby the
technician can sit in front of a computer screen looking
at a 3D model, and holding a computerized wax spatula
(actually an elaborate computer mouse)

INITIAL SCANNING
ANGULATION
DIGITAL MODEL

REFERENCES
• Craig’s Restorative dental materials -12th Edition
• Anusavice Phillips Science Of Dental Materials
10th Edition
• Rosenstiel, Contemporary Fixed Prosthodontics –
4th Edition
• William J. O’ Brien: Dental materials and their
selection, 2nd edition.
• Properties of die materials: A comparative study
(J Prosthet Dent 1966;16 :119-131)

• A comparison of silver-plated and stone dies
from rubber-base impression
(J Prosthet Dent 1974;32:262-266)
• An investigation of epoxy resin dies
(J Prosthet Dent 1980;44:45-50)
• Effect of cyano-acrylate on die stone
(J Prosthet Dent 1983;49:639-646)
• Gypsum cast as a potential source of microbial
cross-contamination
(J Prosthet Dent 1983;49:210-211)

• Comparison of three epoxy die materials
(J Prosthet Dent 1986;55:328-331)
• Accuracy of stone, epoxy and silver plate-
acrylic models (J Dent mater 1987;3:52-55)
• An evaluation of dental stones after repeated
exposure to spray disinfectants. Part I:
abrasion and compressive strength
(J Prosthet Dent 1991;65:713-718)
• Antimicrobial effect from incorporation of
disinfectants into gypsum casts
(Int. J. Prosthodontics 1991;4:180-185)

• Flexible casts used in making indirect interim
restoration (J Prosthet Dent 1992;68:372-374)
• Comparison of the surface details
reproduction of flexible die material system
(J Prosthet Dent 1998;80:485-489)
• Study of the physical properties of type IV
gypsum, resin-containing, and epoxy die
material (J Prosthet Dent 2000;83:466-473)
• Dimentional accuracy of an epoxy resin die
material using two setting methods
(J Prosthet Dent 2000;83:301-305)

• Surface detail, compressive strength, and
dimen sional accuracy of gypsum cast after
repeated immersion in hypochlorite solution
(J Prosthet Dent 2006;95:462-468)
• Marginal accuracy of titanium copings
fabricated by casting and CAD/CAM
techniques (J Prosthet Dent 2006;96:47-52.)
• Clinical evaluation of all-ceramic crowns
fabricated from intraoral digital impressions
based on the principle of active wave front
sampling ( J prosthet dent 2010;38;553-559)

Model and die materials

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