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, 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

Final impressions: Anatomical Functional

Types of impressions Single layer Double layer Combined

Types of impressions 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

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 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

Placing of impression tray in oral cavity

Impression of maxillae

Double layer impression

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 registration

Elastomeric Impression Materials Viscoelastic –physical properties vary rate of loading Rapidly remove –decreases permanent deformation chains recoil from a recoverable distance –increases tear strength

Impression Materials Non-elastic Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible) Plaster Compound ZnO - Eugenol Waxes

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 Hydrocolloids Semi-permeable membranes –poor dimensional stability Evaporation Syneresis –fibril cross linking continues contracts with time exudes water Imbibition –water absorption swells

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

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%) agar hydrocolloid (hot) agar hydrocolloid (cold) (sol) (gel) cool to 43ºC heat to 100 º C

Manipulation Gel in tubes –syringe and tray material

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 Dimensionally accurate Hydrophilic –displaces moisture, blood, fluids Inexpensive –after initial equipment No custom tray or adhesives Pleasant flavor No mixing required

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

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

Irreversible Hydrocolloid (Alginate) Most widely used impression material Indications –study models –removable fixed partial dentures framework Examples –Jeltrate (Dentsply/Caulk) –Coe Alginate (GC America)

Composition Sodium alginate –salt of alginic acid mucous extraction of seaweed (algae) Calcium sulfate –reactor Sodium phosphate –retarder Filler Potassium fluoride –improves gypsum surface 2 Na 3 PO CaSO 4 Ca 3 (PO 4 ) Na 2 SO 4 Na alginate + CaSO 4 Ca alginate + Na 2 SO 4 (powder)(gel) H2OH2O

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)

Advantages Inexpensive Easy to use Hydrophilic –displace moisture, blood, fluids Stock trays

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 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

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

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 –water

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

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

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

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

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 alcohol Phillip’s 1996

HO – Si – O – Si - O - H CH 3 n HO – Si – O – Si - O - H CH 3 n C2H5OC2H5OOC 2 H 5 Si C2H5OC2H5OOC 2 H 5 HO – Si – O – Si - O - CH 3 n HO – Si – O – Si - O - CH 3 n OC 2 H 5 Si OC 2 H 5 + 2C 2 H 5 OH Condensation Silicone Reaction metal organic ester ethanol

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

Disadvantages Poor dimensional stability –high shrinkage polymerization evaporation of ethanol –pour immediately within 30 minutes Hydrophobic –poor wettability

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

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 acid Phillip’s 1996

O H - Si – CH 3 O CH 3 - Si - H O ---O – Si – CH = CH 2 CH 3 CH = CH 2 – Si – O --- CH 3 O - Si – CH 3 O CH 3 - Si - O ---O – Si – CH 2 - CH 2 CH 3 CH 2 - CH 2 – Si – O --- CH 3 Chloroplatinic Acid Catalyst Addition Silicone Reaction

Manipulation Adhesive to tray Double mix –custom tray heavy-body –light-body to prep Putty-wash –stock tray

Advantages Highly accurate High dimensional stability –pour up to one week Stock or custom trays Multiple casts Easy to mix Pleasant odor

Disadvantages Expensive Sulfur inhibits set –latex gloves –ferric and Al sulfate retraction solution Pumice teeth before impressing Short working time Lower tear strength Possible hydrogen gas release –bubbles on die –palladium added to absorb

Addition Silicones Surfactants added –reduce contact angle –improved castability –gypsum wettability –still need dry field clinically

Elastic Aqueous Hydrocolloids Non-aqueous Elastomers Polysulfide Silicones Polyether Condensation Addition Agar (reversible) Alginate (irreversible)

Polyether Indications –crown and bridge –bite registration Examples –Impregum F (3M/ESPE) –Permadyne (3M/ESPE) –Pentamix (3M/ESPE) –P2 (Heraeus Kulzer) –Polygel (Dentsply Caulk)

Base –difunctional epimine-terminated prepolymer –fillers –plasticizers Catalyst –aromatic sulfonic acid ester –fillers Cationic polymerization –ring opening and chain extension Composition

SO R + CH 3 – CH – CH 2 – CO 2 – CH – (CH 2 ) n – O – CH – (CH 2 ) n – CO 2 –CH 2 – CH –CH 3 N H2CH2CCH 2 R R m N H2CH2C N H2CH2C R – N – CH 2 – CH 2 – + N H2CH2CCH 2 N H2CH2C R – + + Polyether Reaction catalyst base ring opening

Manipulation Adhesive to tray –stock or custom tray very stiff Paste-paste mix Auto-mixing –hand-held low viscosity –mechanical dispenser high viscosity

Advantages Highly accurate Good dimensional stability Stock or dual-arch trays Good surface detail Pour within one week –kept dry Multiple casts Good wettability

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 Crown & Bridge –vinylpolysiloxane81% –alginate38% –polyether28% Inlays and Onlays –vinylpolysiloxane71% –polyether22% –alginate20%

Impression Material Usage* Civilian General Dentists Complete dentures –alginate58% –vinylpolysiloxane55% –polyether27% Partial dentures –alginate78% –vinylpolysiloxane43% –polyether15%

Handling Properties AgarAlginatePolysulfide Condensation Silicone Addition Silicone Polyether Preparation Boil, temper, store Powder, water 2 pastes 2 pastes or paste/liquid 2 pastes Ease of Use Technique sensitive GoodFair ExcellentGood Patient Reaction Thermal Shock Pleasant, clean Unpleasant, stains Pleasant, clean Pleasant Unpleasant clean Ease of removal Very easy EasyModerate Moderate to difficult DisinfectionPoor Fair ExcellentFair

Handling Properties AgarAlginatePolysulfide Condensation Silicone Addition Silicone Polyether Working Time (min) 7 – – 732 – Setting Time (min) – 126 – 83 – 74.5 Stability 1 hour 100% RH Immediate pour 1 hour Immediate pour 1 week 1 week kept dry Wettability and castability Excellent Fair Fair to good Good CostLowVery lowLowModerate High to very high Very high

Properties AgarAlginatePolysulfide Condensation Silicone Addition Silicone Polyether Elastic Recovery (%) – – – – 99.0 Flexibility (%) – – – – 3.3 Flow (%) – 1.9< 0.10< 0.05 Shrinkage, 24 hours (%) Extreme 0.4 – – – – 0.3 Tear Strength (g/cm) – – – –

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 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 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 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 Alginate88% Polyvinyl Siloxane85% Polyether27% Other6%

Summary Study models –Alginate most widely used inexpensive displaces moisture lower detail reproduction dimensionally unstable

Summary Prosthodontics –Addition silicones most popular accurate dimensionally stable user friendly expensive