MODELS-AND-DIE-MATERIALS-SEMINAR-PPT.pptx

CONTENTS
INTRODUCTION
MODELS
Gypsum products
Classification of gypsum products
Properties
Manipulation
DIE MATERIALS
Types of die materials
Compatibility with impression materials
CONCLUSION

INTRODUCTION
MODEL:
A fascimile used for display purposes;
A positive likeness of an object.
Glossary of prosthodontic terms
DIE:
The positive reproduction of the form of a
prepared tooth in any suitable substance.

GYPSUM PRODUCTS
 Gypsum is a mineral mined in various parts of the
world.
 It is produced as a by-product of some chemical
processing operations.
 It is obtained from natural rock.
 The dihydrate form of calcium sulfate is called
GYPSUM.
PHILIPS SCIENCE OF DENTAL MATERIALS ELEVENTH EDITION

TYPES OF GYPSUM PRODUCTS
TYPE I - Impression plaster
TYPE II - Model plaster
TYPE III - Dental stone
TYPE IV – Dental stone ,Die , High
strength
TYPE V - Dental stone ,Die , High
strength , High expansion

DENTAL PLASTER AND STONE
 PLASTER is beta form of calcium sulfate hemihydrate.
 STONE is an alpha form of calcium sulfate hemihydrate.
Manufacturing of plaster and stone:
 plaster Produced by calcination process in open
air.
 Dental stone produced by wet calcination.

Beta hemihydrate crystals Alpha hemihydrate crystals

TYPE IV AND TYPE V GYPSUM
 Alpha modified calcium sulfate hemihydrate.
 Also known as Densite.
 Manufactured by boiling gypsum in a 30% aqueous
solution of calcium chloride and magnesium chloride.

SETTING OF GYPSUM PRODUCTS
THEORIES OF SETTING REACTIONS:
• Colloidal theory
• Hydration theory
• Dissolution precipitation theory

WATER –POWDER RATIO
• The amounts of water and hemihydrate should be gauged
accurately by weight.
• The W/P ratio is an important factor in determining the
physical and chemical properties of the final gypsum
product

TEST FOR WORKING AND SETTING
TIMES
 Loss of gloss test
 Initial Gillmore test for initial set
 Vicat test for setting time
 Gillmore test for final set

RETARDERS AND ACCELATORS
 Setting time can be controlled by addition of certain
chemical modifiers.
 Retarders are borax, potassium citrate, and sodium
chloride (20%)(ABC)
 Accelerators are gypsum (<20%),Pottasium sulfate,
sodium chloride (<28%),Terra alba.

SETTING EXPANSION
 An expansion of the mass can be detected
during the change from the hemihydrate to
the dihydrate.
 Depending on the composition of the
gypsum product, this observed linear
expansion may be as low as 0.06% or as high
as 0.5%.

NORMAL SETTING EXPANSION

HYGROSCOPIC SETTING
EXPANSION

STRENGTH
 The strength of gypsum products is generally expressed
in terms of compressive strength.
 The free-water content of the set product definitely
affects its strength.
 Two strength properties of gypsum are reported: the wet
strength (also known as green strength) and the dry
strength

MANIPULATION
 The preferred method of mixing is to add the
measured water first, followed by gradual addition of
the preweighed powder.
 'I'he powder is incorporated during approximately 15
sec of mixing with a hand spatula, followed by 20 to 30
sec of mechanical mixing under vacuum.
 A longer spatulation time reduces the working time
particularly for pouring models.
CRAIGS RESTOATIVE DENTAL MATERIALS

INVESTMENTS
 A ceramic material that is suitable for forming a mold
into which a metal or alloy is cast.
 It is a mixture of three distinct type of materials
Refractory material
Binder material
Other chemicals

TYPES OF INVESTMENTS
Gypsum bonded investments
Phosphate bonded investments
Ethyl Silicate bonded investments

GYPSUM BONDED INVESTMENTS
 Supplied as fine powder.
 Refractory : cristoballite , quartz
 Binder: type III dental stone.
 Modifiers: k, Li,Na chlorides or boric acid
 Reducing agents : copper,graphite
 Small amount of color

PHOSPHATE BONDED INVESTMENTS
 Supplied in sealed sachets weighing 200-500gms
 Used with high fusing alloys
 Refractory : cristoballite or quartz
 Binder : mixture of basic MgO and acidic NH4H2PO4
 Small amounts of carbon
 LIQUID: colloidal silica suspension

ETHYL SILICATE BONDED INVESTMENTS
 Developed to meet the refractory requirements of high
fusing PBM alloys.
 It is supplied as a powder of quartz or crystoballite.
 Setting and bonding mechanisms are more complex.
 Green shrinkage occurs when water and alcohols escape.

DIE MATERIALS USED
GYPSUM PRODUCTS: Type IV Dental stone
Type V Dental stone
DIE STONE – INVESTMENT COMBINATION
ELECTROFORMED DIES: Silver plated
Copper plated
EPOXY RESINS
POLYURETHANE DIES
AMALGAM DIES
METAL SPRAYED DIES
 FLEXIBLE DIE MATERIALS
REFRACTORY DIES
SILICOPHOSPHATE DIES
CERAMIC DIES

GYPSUM DIES
Commonly type IV and type V gypsum used.

DIE STONE – INVESTMENT COMBINATION
 Commercially available gypsum bonded materials.
 The divestment is mixed with colloidal silica and
liquid.
 Die is made and wax pattern is constructed on it.
 Then the whole complex is invested in
a mixture of divestment and water.

ELECTROFORMED DIES
 It is done to improve the abrasive resistance of the die
material.
 Metalizing agents like graphite , copper powder or silver
dust - suspension is coated over the impression for
electrical conduction
CONTEMPORARY FIXED PROSTHODONTICS ROSENTIAL.LAND.FUJIMOTO

COPPER PLATING
COPPER PLATED DIES – compound or addition silicone
impression materials.
COMPOSITION:
Copper sulfate
Sulfuric acid
Alcohol or phenol
TORESKOG PHILIPS SV,SCHENELL RJ,PROPERTIES OF DIE MATERIALS : A
COMPARATIVE STUDY JOURNAL OF PROSTHETIC DENTISTRY 1966 Pg 119

SILVER PLATING
For polyether , polysulfide and silicone rubber base impression
materials.
COMPOSITION:
Silver cyanide
potassium cyanide
silver or graphite.

EPOXY RESIN DIES
Highly viscous liquids(sometimes solid) on polymerising
with amines , polysulfides or polyamides hard epoxy resin
die can be obtained.

Epoxy resin exhibits better detail reproduction,
abrasion resistance and transverse
strength than the gypsum products.
The setting shrinkage compared with the expansion
observed with gypsum die materials may require
modifications in technique to obtain castings that will be
well adapted to the tooth preparation .
Philip Duke,B.K.Moore ,Steven Phaug and Carle J Andres .Study of the physical properties
Of type IV gypsum ,resin containing and epoxy die material journal of prosthetic dentistry
2000 ; 83; 466-473

POLYURETHANE DIES
 Most accurate , strongest and cleanest
die material.
Superior mechanical properties.
Water resistant.
DERRIEN G,STURTZ G COMPARISON OF TRANSVERSE STRENGTH AND DIMENSIONAL
VARIATION ODF DIE STONE , EPOXY RESIN AND POLYURETHANE RESIN JOURNAL OF
PROSTHETIC DENTISTRY 1996 569-574

AMALGAM DIES
This is similar to a restorative material.
E.C.COMBE NOTES ON DENTAL MATERIALS

METAL SPRAYED DIES
 A bismuth- tin alloy is used.
ADVANTAGES:
It can be rapidly obtained from impression
materials.
DISADVANTAGES:
Alloy is soft it will tend to abrade.

FLEXIBLE DIE MATERIALS
Similar to heavy bodied silicone or polyether impression
materials

REFRACTORY DIES
•Made for preparation of all ceramic restorations
•Excellent marginal adaptation.

SILICOPHOSPHATE DIES
Similar to the filling and cementing material.

COMPATIBILITY WITH IMPRESSION MATERIALS
 DIE STONE – Impression compound, zinc oxide
eugenol , alginate , impression plaster and rubber base
impression material.
 ELECTROPLATED COPPER – Impression compound
 ELECTROPLATED SILVER - polysulphide , rubber
base material.
 EPOXY RESIN - Rubber base impression material.

CONCLUSION
Good impression and die fabrication with
selection of the die material and its
manipulation paramount to achieve accuracy
in the final restoration.

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