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Impression Materials

Course Date: 5/05 Reviewed/Updated: 10/10 Expiration Date: 10/13

Objectives Provide general review of types of dental impression materials. Provide general information on the physical and handling properties and indications for use of various types of impression materials.

Official Disclaimer The opinions expressed in this presentation are those of the author and do not necessarily reflect the official position of the US Air Force or the Department of Defense (DoD). Devices or materials appearing in this presentation are used as examples of currently available products/technologies and do not imply an endorsement by the author and/or the USAF/DoD.

Impression Materials Non-elastic Elastic Aqueous hydrocolloids Agar Alginate

Non-aqueous elastomers Polysulfide Silicones Condensation Addition

Polyether

Indications Diagnostic casts preliminary opposing

Indirect reconstruction fixed removable

Bite registrationGiordano, Gen Dent 2000

Elastomeric Impression Materials Viscoelastic physical properties vary rate of loading

Rapidly remove decreases permanent deformation chains recoil from a recoverable distance

increases tear strengthPhillips Science of Dental Materials 1996

Plaster Non-elastic Compound Waxes Impression Materials

ZnO - Eugenol

Aqueous Hydrocolloids Elastic

Agar (reversible) Alginate (irreversible) Polysulfide

Non-aqueous Elastomers

Condensation Addition

Silicones Polyether

OBrien, Dental Materials & their Selection 1997

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 processPhillips Science of Dental Materials 1996

Aqueous Hydrocolloids Semi-permeable membranes poor dimensional stability

Evaporation Syneresis fibril cross linking continues contracts with time exudes water

Imbibition water absorption swellsPhillips Science of Dental Materials 1996

Agar (reversible)

Aqueous HydrocolloidsElastic

Alginate (irreversible)Polysulfide Condensation

Non-aqueous Elastomers

Silicones Addition Polyether

OBrien, Dental Materials & their Selection 1997

Reversible Hydrocolloid (Agar) Indications crown and bridge high accuracy

Example Slate Hydrocolloid (Van R)

Composition Agar complex polysaccharide seaweed

Potassium sulfate improves gypsum surface

gelling agent

Borax strength

Water (85%)

cool to 43C

agar hydrocolloid (hot)(sol)

agar hydrocolloid (cold)(gel)OBrien, Dental Materials & their Selection 1997

heat to 100C

Manipulation Gel in tubes syringe and tray material

Manipulation 3-chamber conditioning unit (1) liquefy at 100C for 10 minutes converts gel to sol

(2) store at 65C place in tray (3) temper at 46C for 3 minutes seat tray cool with water at 13C for 3 minutes converts sol to gelOBrien, Dental Materials & their Selection 1997

Advantages Dimensionally accurate Hydrophilic displaces moisture, blood, fluids

Inexpensive after initial equipment

No custom tray or adhesives Pleasant flavor No mixing requiredPhillips Science of Dental Materials 1996

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 disinfectPhillips Science of Dental Materials 1996

Agar (reversible)

Aqueous HydrocolloidsElastic

Alginate (irreversible)Polysulfide Condensation

Non-aqueous Elastomers

Silicones Addition Polyether

OBrien, Dental Materials & their Selection 1997

Irreversible Hydrocolloid (Alginate) Most widely used impression material Indications study models removable fixed partial dentures framework

Examples Jeltrate (Dentsply/Caulk) Coe Alginate (GC America)Phillips Science of Dental Materials 1996

Composition Sodium alginate salt of alginic acid mucous extraction of seaweed (algae)

Sodium phosphate retarder

Calcium sulfate reactor

Filler Potassium fluoride improves gypsum surface

2 Na3PO4 + 3 CaSO4 Na alginate + CaSO4(powder)H2O

Ca3(PO4)2 + 3 Na2SO4 Ca alginate + Na2SO4(gel)OBrien Dental Materials & their Selection 1997

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)Caswell JADA 1986

Advantages Inexpensive Easy to use Hydrophilic displace moisture, blood, fluids

Stock trays

Phillips Science of Dental Materials 1996

Disadvantages Tears easily Dimensionally unstable immediate pour single cast

Lower detail reproduction unacceptable for fixed pros

High permanent deformation Difficult to disinfectPhillips Science of Dental Materials 1996

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 monophasicPhillips Science of Dental Materials 1996

Agar (reversible)

Aqueous HydrocolloidsElastic

Alginate (irreversible)Polysulfide Condensation

Non-aqueous Elastomers

Silicones Addition Polyether

OBrien Dental Materials & their Selection 1997

Polysulfide First dental elastomers Indications complete denture removable fixed partial denture tissue

crown and bridge

Examples Permlastic (Kerr) Omni-Flex (GC America)

Composition Base polysulfide polymers fillers plasticizers

Catalyst lead dioxide (or copper) fillers

By-product waterPhillips Science of Dental Materials 1996

Polysulfide Reaction--SH O = Pb = O H S mercaptan + lead dioxide polysulfide rubber + lead oxide + water S H O = Pb = O HS---------------------SH O Pb = O = S + 3PbO + H O 2 S HS--S-S---------------S-S-

OBrien Dental Materials & their Selection 1997

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

Advantages Lower cost compared to silicones and polyethers

Long working time High tear strength High flexibility Good detail reproduction

Phillips Science of Dental Materials 1996

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

Phillips Science of Dental Materials 1996

Agar (reversible)

Aqueous HydrocolloidsElastic

Alginate (irreversible)Polysulfide Condensation

Non-aqueous Elastomers

Silicones Addition Polyether

OBrien Dental Materials & their Selection 1997

Condensation Silicone Indications complete dentures crown and bridge

Examples Speedex (Coltene/Whaledent) Primasil (TISS Dental)

Composition Base poly(dimethylsiloxane) tetraethylorthosilicate filler

Catalyst metal organic ester

By-product ethyl alcoholPhillips 1996 Phillips Science of Dental Materials 1996

CH3

CH3 C2H5O OC2H5

Condensation Silicone Reaction

HO Si O Si - O - H CH3 CH3 CH3 CH3 n

Si

HO Si O Si - O - H CH3 CH3 n

C2H5O

OC2H5

metal organic ester CH3 CH3 OC2H5 n

HO Si O Si - O CH3 CH3 CH3 CH3

Si

+ 2C2H5OHethanol

HO Si O Si - O CH3 CH3 n

OC2H5

Phillips Science of Dental Materials 1996

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

Advantages Better elastic properties Clean, pleasant Stock tray putty-wash

Good working and setting time

Phillips Science of Dental Materials 1996

Disadvantages Poor dimensional stability high shrinkage polymerization evaporation of ethanol

pour immediately within 30 minutes

Hydrophobic poor wettability

Phillips Science of Dental Materials 1996

Agar (reversible)

Aqueous HydrocolloidsElastic

Alginate (irreversible)Polysulfide Condensation

Non-aqueous Elastomers

Silicones Addition Polyether

OBrien Dental Materials & their Selection 1997

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)

Composition Improvement over condensation silicones no by-product

First paste vinyl poly(dimethylsiloxane) prepolymer

Second paste siloxane prepolymer

Catalyst chloroplatinic acidPhillips 1996 Phillips Science of Dental Materials 1996

CH3---O Si CH = CH2

OH - Si CH3 O CH3 CH = CH2 Si O ---

Addition Silicone ReactionCH3

CH3

CH3 - Si - HO

CH3

O

Chloroplatinic Acid Catalyst

---O Si CH2 - CH2 - Si CH3 CH3 O CH3

CH3 - Si - CH2 - CH2 Si O --O CH3

Phillips Science of Dental Materials 1996

Manipulation Adhesive to tray Double mix cu