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Imprints, their classification, method of receipt. Classification of materials of imprint. Clinical, physical and chemical descriptions of materials for imprint. Impression is a negative (reverse) reflection of any organ of the dentomaxillar system: teeth, alveolar sprout or part, palate, nose,

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Types of impressions previous final

Imprints, their classification, method of receipt. Classification of materials of imprint. Clinical, physical and chemical descriptions of materials for imprint


Types of impressions previous final

Impression is a negative (reverse) reflection of any organ of the dentomaxillar system: teeth, alveolar sprout or part, palate, nose,

ear and others like that.

Impression is a negative (reverse) reflection of hard and soft tissues, placed in the area of dental prosthesis and it’s borders which

Is being taken by means of the special impression materials


Types of impressions previous final

Types of impressions:

Previous

Final


Types of impressions previous final

Final impressions:

Anatomical

Functional


Types of impressions

Types ofimpressions

Single layer

Double layer

Combined


Types of impressions1

Types ofimpressions

Anatomical (orientation)– take with standard or individual tray in the state of calmness of tissues of prosthetic bed and tissues, which are placed on a border with them.

Functional - take with individual tray by means of the special functional tests, in the case of making of removable constructions of dentures :

compression - in the case of pressing of buffer areas of prosthetic bed, by masticatory pressure or by the hand of doctor;

decompression - in the case of minimum pressure on the tissues of prosthetic bed


Types of impressions previous final

Double layer – an exact reflection of gingival edge is taken by means of impression materials of the same group (previous layer + correction layer)

Combined– is taken by means of impression materials of different groups (previous layer + correction layer)

Occlusal–for taking impression in position of central occlusion


Impression trays

Impression trays

Standard:made factory

- On maxillae different sizes

- On mandible different sizes

Individual:made in dental laboratory

By material:

plastic

metallic

waxen

Presence of retentin points

perforated

unperforated


Impression trays for taking impression at the same time

Impression trays for taking impression at the same time


Types of impressions previous final

Placing of impression tray in oral cavity


Types of impressions previous final

Impression of maxillae


Types of impressions previous final

Double layer impression


Impression materials

Impression Materials

  • Non-elastic

  • Elastic

    • Aqueous hydrocolloids

      • Agar

      • Alginate

    • Non-aqueous elastomers

      • Polysulfide

      • Silicones

        • Condensation

        • Addition

      • Polyether


Indications

Indications

  • Diagnostic casts

    • preliminary

    • opposing

  • Indirect reconstruction

    • fixed

    • removable

  • Bite registration


Elastomeric impression materials

Elastomeric Impression Materials

  • Viscoelastic

    • physical properties vary

      • rate of loading

  • Rapidly remove

    • decreases permanent deformation

      • chains recoil from a recoverable distance

    • increases tear strength


Types of impressions previous final

Plaster

Compound

Waxes

ZnO - Eugenol

Polysulfide

Silicones

Polyether

Non-elastic

Impression Materials

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Condensation

Non-aqueous Elastomers

Addition


Aqueous hydrocolloids

Aqueous Hydrocolloids

  • Colloidal suspensions

    • chains align to form fibrils

    • traps water in interstices

  • Two forms

    • sol

      • viscous liquid

    • gel

      • elastic solid

  • Placed intra-orally as sol

    • converts to gel

      • thermal or chemical process


Aqueous hydrocolloids1

Aqueous Hydrocolloids

  • Semi-permeable membranes

    • poor dimensional stability

  • Evaporation

  • Syneresis

    • fibril cross linking continues

      • contracts with time

      • exudes water

  • Imbibition

    • water absorption

      • swells


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Reversible hydrocolloid agar

Reversible Hydrocolloid (Agar)

  • Indications

    • crown and bridge

      • high accuracy

  • Example

    • Slate Hydrocolloid (Van R)


Composition

Agar

complex polysaccharide

seaweed

gelling agent

Borax

strength

Potassium sulfate

improves gypsum surface

Water (85%)

cool to 43ºC

agar hydrocolloid (hot) agar hydrocolloid (cold)

(sol)(gel)

heat to 100ºC

Composition


Manipulation

Manipulation

  • Gel in tubes

    • syringe and tray material


Manipulation1

Manipulation

  • 3-chamber conditioning unit

    • (1) liquefy at 100°C for 10 minutes

      • converts gel to sol

    • (2) store at 65°C

    • place in tray

    • (3) temper at 46°C for 3 minutes

    • seat tray

    • cool with water at 13°C for 3 minutes

      • converts sol to gel


Advantages

Advantages

  • Dimensionally accurate

  • Hydrophilic

    • displaces moisture, blood, fluids

  • Inexpensive

    • after initial equipment

  • No custom tray or adhesives

  • Pleasant flavor

  • No mixing required


Disadvantages

Disadvantages

  • Initial expense

    • special equipment

  • Material must be prepared in advanced

  • Tears easily

  • Dimensionally unstable

    • Must be poured immediately

    • Can only be used for a single cast

  • Difficult to disinfect


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Irreversible hydrocolloid alginate

Irreversible Hydrocolloid (Alginate)

  • Most widely used impression material

  • Indications

    • study models

    • removable fixed partial dentures

      • framework

  • Examples

    • Jeltrate (Dentsply/Caulk)

    • Coe Alginate (GC America)


Composition1

Sodium alginate

salt of alginic acid

mucous extraction of seaweed (algae)

Calcium sulfate

reactor

Sodium phosphate

retarder

Filler

Potassium fluoride

improves gypsum surface

2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4

H2O

Na alginate + CaSO4 Ca alginate + Na2SO4

(powder)(gel)

Composition


Manipulation2

Manipulation

  • Weigh powder

  • Powder added to water

    • rubber bowl

    • vacuum mixer

  • Mixed for 45 sec to 1 min

  • Place tray

  • Remove 2 to 3 minutes

    • after gelation (loss of tackiness)


Advantages1

Advantages

  • Inexpensive

  • Easy to use

  • Hydrophilic

    • displace moisture, blood, fluids

  • Stock trays


Disadvantages1

Disadvantages

  • Tears easily

  • Dimensionally unstable

    • immediate pour

    • single cast

  • Lower detail reproduction

    • unacceptable for fixed pros

  • High permanent deformation

  • Difficult to disinfect


Non aqueous elastomers

Non-Aqueous Elastomers

  • Synthetic rubbers

    • mimic natural rubber

      • scarce during World War II

  • Large polymers

    • some chain lengthening

    • primarily cross-linking

  • Viscosity classes

    • low, medium, high, putty

    • monophasic


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Polysulfide

Polysulfide

  • First dental elastomers

  • Indications

    • complete denture

    • removable fixed partial denture

      • tissue

    • crown and bridge

  • Examples

    • Permlastic (Kerr)

    • Omni-Flex (GC America)


Composition2

Composition

  • Base

    • polysulfide polymers

    • fillers

    • plasticizers

  • Catalyst

    • lead dioxide (or copper)

    • fillers

  • By-product

    • water


Polysulfide reaction

O

O

=

=

mercaptan + lead dioxide polysulfide rubber + lead oxide + water

Pb

Pb

=

=

O

O

Polysulfide Reaction

--SH

HS---------------------SH

HS--

-S-S---------------S-S-

S

S

+ 3PbO + H2O

H

S

O = Pb = O

H

S


Manipulation3

Manipulation

  • Adhesive to tray

  • Uniform layer

    • custom tray

  • Equal lengths of pastes

  • Mix thoroughly

    • within one minute

  • Setting time 8 – 12 minutes

  • Pour within 1 hour


Advantages2

Advantages

  • Lower cost

    • compared to silicones and polyethers

  • Long working time

  • High tear strength

  • High flexibility

  • Good detail reproduction


Disadvantages2

Disadvantages

  • Poor dimensional stability

    • water by-product

    • pour within one hour

    • single pour

  • Custom trays

  • Messy

    • paste-paste mix

    • bad odor

    • may stain clothing

  • Long setting time


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Condensation silicone

Condensation Silicone

  • Indications

    • complete dentures

    • crown and bridge

  • Examples

    • Speedex (Coltene/Whaledent)

    • Primasil (TISS Dental)


Composition3

Composition

  • Base

    • poly(dimethylsiloxane)

    • tetraethylorthosilicate

    • filler

  • Catalyst

    • metal organic ester

  • By-product

    • ethyl alcohol

Phillip’s 1996


Types of impressions previous final

C2H5O

OC2H5

Si

C2H5O

OC2H5

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

HO – Si – O – Si - O - H

HO – Si – O – Si - O -

HO – Si – O – Si - O -

HO – Si – O – Si - O - H

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

n

n

n

n

OC2H5

+ 2C2H5OH

Si

OC2H5

CondensationSilicone Reaction

metal organic ester

ethanol


Manipulation4

Manipulation

  • Mix thoroughly

    • paste - paste

    • paste - liquid

  • Putty-wash technique

    • reduces effect of polymerization shrinkage

    • stock tray

      • putty placed

      • thin plastic sheet spacer

      • preliminary impression

        • intraoral custom tray

      • inject wash material


Advantages3

Advantages

  • Better elastic properties

  • Clean, pleasant

  • Stock tray

    • putty-wash

  • Good working and setting time


Disadvantages3

Disadvantages

  • Poor dimensional stability

    • high shrinkage

      • polymerization

      • evaporation of ethanol

    • pour immediately

      • within 30 minutes

  • Hydrophobic

    • poor wettability


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Addition silicones

Addition Silicones

  • AKA: Vinyl polysiloxane

  • Indications

    • crown and bridge

    • denture

    • bite registration

  • Examples

    • Extrude (Kerr)

    • Express (3M/ESPE)

    • Aquasil (Dentsply Caulk)

    • Genie (Sultan Chemists)

    • Virtual (Ivoclar Vivadent)


Composition4

Composition

  • Improvement over condensation silicones

    • no by-product

  • First paste

    • vinyl poly(dimethylsiloxane)prepolymer

  • Second paste

    • siloxane prepolymer

  • Catalyst

    • chloroplatinic acid

Phillip’s 1996


Types of impressions previous final

O

O

- Si – CH3

H - Si – CH3

CH3

CH3

O

O

CH = CH2 – Si – O ---

CH2 - CH2 – Si – O ---

CH3 - Si - H

CH3 - Si -

CH3

CH3

O

O

CH3

CH3

---O – Si – CH = CH2

---O – Si – CH2 - CH2

CH3

CH3

Addition Silicone Reaction

Chloroplatinic Acid Catalyst


Manipulation5

Manipulation

  • Adhesive to tray

  • Double mix

    • custom tray

      • heavy-body

    • light-body to prep

  • Putty-wash

    • stock tray


Advantages4

Advantages

  • Highly accurate

  • High dimensional stability

    • pour up to one week

  • Stock or custom trays

  • Multiple casts

  • Easy to mix

  • Pleasant odor


Disadvantages4

Disadvantages

  • Expensive

  • Sulfur inhibits set

    • latex gloves

    • ferric and Al sulfateretraction solution

  • Pumice teeth beforeimpressing

  • Short working time

  • Lower tear strength

  • Possible hydrogen gas release

    • bubbles on die

    • palladium added to absorb


Addition silicones1

Addition Silicones

  • Surfactants added

    • reduce contact angle

    • improved

      • castability

        • gypsum

      • wettability

        • still need dry field clinically


Types of impressions previous final

Agar (reversible)

Aqueous Hydrocolloids

Alginate (irreversible)

Elastic

Polysulfide

Condensation

Non-aqueous Elastomers

Silicones

Addition

Polyether


Polyether

Polyether

  • Indications

    • crown and bridge

    • bite registration

  • Examples

    • Impregum F (3M/ESPE)

    • Permadyne (3M/ESPE)

    • Pentamix (3M/ESPE)

    • P2 (Heraeus Kulzer)

    • Polygel (Dentsply Caulk)


Composition5

Composition

  • Base

    • difunctional epimine-terminated prepolymer

    • fillers

    • plasticizers

  • Catalyst

    • aromatic sulfonic acid ester

    • fillers

  • Cationic polymerization

    • ring opening and chain extension


Polyether reaction

CH3 – CH – CH2 – CO2 – CH – (CH2)n – O – CH – (CH2)n – CO2 –CH2 – CH –CH3

R

R

m

+ R+

N

N

N

N

N

H2C

H2C

H2C

H2C

H2C

CH2

CH2

CH2

CH2

CH2

SO3-

R – +

R – N – CH2 – CH2 – +

+

Polyether Reaction

base

catalyst

ring opening


Manipulation6

Manipulation

  • Adhesive to tray

    • stock or custom tray

      • very stiff

  • Paste-paste mix

  • Auto-mixing

    • hand-held

      • low viscosity

    • mechanical dispenser

      • high viscosity


Advantages5

Advantages

  • Highly accurate

  • Good dimensional stability

  • Stock or dual-arch trays

  • Good surface detail

  • Pour within one week

    • kept dry

  • Multiple casts

  • Good wettability


Disadvantages5

Disadvantages

  • Expensive

  • Short working time

  • Rigid

    • difficult to remove from undercuts

  • Bitter taste

  • Low tear strength

  • Absorbs water

    • changes dimension


Impression material usage civilian general dentists

Impression Material Usage*Civilian General Dentists

  • Crown & Bridge

    • vinylpolysiloxane81%

    • alginate38%

    • polyether28%

  • Inlays and Onlays

    • vinylpolysiloxane71%

    • polyether22%

    • alginate20%


Impression material usage civilian general dentists1

Impression Material Usage*Civilian General Dentists

  • Complete dentures

    • alginate58%

    • vinylpolysiloxane55%

    • polyether27%

  • Partial dentures

    • alginate78%

    • vinylpolysiloxane43%

    • polyether15%


Handling properties

Handling Properties


Handling properties1

Handling Properties


Properties

Properties


Comparison of properties

Comparison of Properties

  • Working time

    • longest to shortest

      • agar > polysulfide > silicones > alginate = polyether

  • Setting time

    • shortest to longest

      • alginate < polyether < agar < silicones < polysulfide


Comparison of properties1

Comparison of Properties

  • Stiffness

    • most to least

      • polyether > addition silicone > condensation silicone > polysulfide = hydrocolloids

  • Tear strength

    • greatest to least

      • polysulfide > addition silicone > polyether > condensation silicone >> hydrocolloids


Comparison of properties2

Comparison of Properties

  • Cost

    • lowest to highest

      • alginate < agar = polysulfide <condensation silicone < addition silicone < polyether

  • Dimensional stability

    • best to worst

      • addition silicone > polyether > polysulfide > condensation silicone > hydrocolloid

Phillip’s 1996


Comparison of properties3

Comparison of Properties

  • Wettability

    • best to worst

      • hydrocolloids > polyether > hydrophilic addition silicone > polysulfide > hydrophobic addition silicone = condensation silicone

  • Castability

    • best to worst

      • hydrocolloids > hydrophilic addition silicone > polyether > polysulfide > hydrophobic addition silicone = condensation silicone


Regularly used impression materials civilian practitioners

Regularly-Used Impression Materials*Civilian Practitioners

  • Alginate88%

  • Polyvinyl Siloxane85%

  • Polyether27%

  • Other6%


Summary

Summary

  • Study models

    • Alginate most widely used

      • inexpensive

      • displaces moisture

      • lower detail reproduction

      • dimensionally unstable


Summary1

Summary

  • Prosthodontics

    • Addition silicones most popular

      • accurate

      • dimensionally stable

      • user friendly

      • expensive


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