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)

MODEL AND DIE MATERIAL

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)

MODELS

CLASSIFICATION

MODEL MATERIALS

TYPE II GYPSUM

HEAT ACTIVATED

ACRYLIC

Other model materials:PolycarbonateLead

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

GYPSUMHISTORY :

• 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)Craig’s Restorative dental materials -12th Edition

CALCINATION

Calcium SulfateHemihydrate

Calcium SulfateDihydrate

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 110C to 130C in air in open kittle

Dental Products: Plaster

Calcination: dry

Common Names: Plaster of Paris

MANIPULATION

Transfer to impression


TIME

SETTING STAGES

MixingInterval

WorkingInterval

SettingInterval

MixingTime

00:00:00 00:01:00Working

Time00:07:00

SettingTime

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

LargeGilmoreNeedle

SmallGilmoreNeedle

1/4lb wtdiameter½”

1 lb wtDiameter 1/12”


MODEL PASTEREFFECT OF WATER/POWDER RATIO ON SETTING TIME

W/P RATIOml/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 PASTEREFFECT OF SPATULATION ON SETTING TIME

W/P RATIOml/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 PASTEREFFECT 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

HEAT ACTIVATED RESIN MODELS

(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 POLYMERPOWDER

• 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

POLYMERIZATIONAddition 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 and release another free radical.Anusavice 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 growthAnusavice Phillips Science Of Dental Materials 10th Edition

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 tuskOx femurTeak wood Gold, tin, porcelain, gutta-percha, vulcanite ( 1854)

Laney’s, Diagnosis and treatment in prosthodontics, 1st edition

PROPERTIESPolymerization 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 materialsType IV gypsumType V gypsumDie Stone with Disinfectant (Steri-Die-A)Die Stone and Die Hardener Die Stone and Cyano-acrylate

o Resin based die materialso Electro plated dieso Gypsum-resin combination materialso Refractory die materials

• Flexible die materials:o Polyethero Polyvinyl siloxane

• Miscellaneous:o Silver amalgamo Silico-phosphate cemento 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 100C in 30%CaCl2 solution or MgCl2. ( 100 C water or autoclave 0.5% sodium succinate)

COMPOSITIONα- hemihydrate Main composition

Potassium sulfate 2-3 % accelerator

Sodium citrate Retarder

Coloring agent 2%

PROPERTIESWater: powder ratio 0.20 to 0.22 %Setting time Initial Final

7min9 min

Setting expansion24hr Setting Expansion

0.5 to 0.7%70%

Compressive strengthDry

34 Mpa80 Mpa

Dry hardness 92RHNDimensional changes

OcclusalCervical

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 – 0.22Setting time 12±4min1hr compressive strength 7000psi.Mixing time 30sec to 1minWorking time 3 minTemperature alters the setting time

Above 50˚c retards setting timeAt 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 15minSetting time 1-12hrsCompressive strength: Initial After 7 days

9500 psi16,000psi

Polymerization shrinkage 0.1-0.2%.Hardness 83RHNDimentional changes. Occlusal Cervical

0 – 0.15%

0.19%

Detail reproduction 25µmKHN 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)

ELECTROFORMED DIES

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)

FLEXIBLE DIES

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.


http://1970s.it/

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 minSetting 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)

REFRACTORY DIES

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.

PROPERTIESUltimate 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 IZODRockwell hardness F- 93Resistance to heat 300˚F.Dielectric constant 2.9Machining qualities PoorSpecific volume 15-16 cubic inches per poundShrinkage 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 MATERIALSMATERIAL RECOMMENDED

USEPRECAUTION

Type IV & V dental stone

Most situations •Proportionate mix•Vacuum mix•Surface Hardeners

Epoxy resin All ceramics •Incompatible with poly sulfides & hydrocolloids•Spacer (shrinkage)

Electro plated 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 materialElectro plated ( silver) •Polysulphide

•Polyether•Addition silicone

Polymer epoxy •Rubber base materialResin •Polyether

•Addition silicone•Polysulphide

FUTURE MODEL AND DIES

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

Health & Medicine

Transcript of Model and die materials