Impression Materials PDF

Impression Materials  Definitio ns: Impression:  It is a negative reproduction of the teeth and surrounding oral structures.  Definitio ns: Impression material:  It the material that used for making impression. It is inserted into the mouth in a plastic form then set  Definitio :Cast ns...

Impression Materials  Definitio ns: Impression:  It is a negative reproduction of the teeth and surrounding oral structures.  Definitio ns: Impression material:  It the material that used for making impression. It is inserted into the mouth in a plastic form then set  Definitio :Cast ns(Model):  It is the positive reproduction of the teeth and surrounding oral structure. Definitio ns: Die:  It is the model of single tooth Ideal Requirements Impression Material 1. It should be accurate to produce fine details. 2. It should be biocompatible with oral environment. It should be not toxic or irritant to the oral tissues. 3. It should be easily manipulated without complicated equipment. 4. It should have suitable working time. 5. It should have suitable setting time. Ideal Requirements Impression Material 6. It should have acceptable taste and odor to the patient. 7. It should accept addition and correction. 8. It should be easily disinfected without loss of its accuracy. 9. It should have good shelf life. Factors Affecting Accuracy of Impression Material 1. Flow: The material should have sufficient flow to record all fine details. It should have sufficient viscosity to be contained in the tray. Factors Affecting Accuracy of Impression Material 2. Hydrophilicity: The material should be hydrophilic to wet the oral tissues easily. Factors Affecting Accuracy of Impression Material 3. Dimensional accuracy: The material should not show any dimensional changes during setting (neither expansion nor contraction). Factors Affecting Accuracy of Impression Material 4. Adhesion to the tray: The impression material should adhere to the tray during its removal from the patient’s mouth. Factors Affecting Accuracy of Impression Material 5. Elasticity: The material should be elastic after setting to record the undercuts without distortion or fracture. Factors Affecting Accuracy of Impression Material 6. Dimensional stability: The material should not show any dimensional changes during its storage (the time between making the impression until pouring it at the dental laboratory). Factors Affecting Accuracy of Impression Material 7. Compatibility with model and die materials: The impression material should not react with the model and die material or affects its setting reaction. Tray s: Types:  According to material:  Metallic  Plastic Tray s: Types:  According to perforations:  Perforated Perforations provide mechanical interlocking with the impression for good adhesion to the tray  Non-Perforated: The impression sticks to the tray by itself or after adhesive application Tray s: Types:  According to perforations: Tray s: Types:  According to Use:  Stock tray Used for making primary impression  Special tray Used of making Secondary impression Impressio :ns Primary Secondary Impression Impression Tray used Stock tray Special tray Impression Low accurate High accuracy material accuracy Cast obtained Primary cast Secondary cast Impressio ns: Wash Technique:  It involves using of two impression materials over each other.  The first material has high viscosity to fulfill the bulk of the stock tray, while the second one has high flow to record the fine details Classification of Impression Materials: 1. According to setting mechanism: a) Reversible: They soften by heat and harden by cooling (physical reaction). e.g.: impression compound and agar. Classification of Impression Materials: 1. According to setting mechanism: b) Irreversible: They set by a chemical reaction. e.g.: plaster impression material, zinc oxide-eugenol, alginate and elastomers. Classification of Impression Materials: 2. According to behavior after setting: a) Non elastic (rigid) impression materials: When removed from undercut they fracture or deform. They used for completely edentulous patients. Classification of Impression Materials: 2. According to behavior after setting: b) Elastic impression materials: They recovered after removal from undercut. They used for both dentulous and edentulous patients.  Non-elastic Impression Materials PLASTER IMPRESSION MATERIAL IMPRESSION COMPOUND ZINC OXIDE AND EUGENOL  Non-elastic Impression Materials Plaste Impression Zinc oxide r Compound and Impress Eugenol ion Mode Powder +  Sheets and 2 pastes of of water cakes. different supply  Sticks (green colors stick compound).  Non-elastic Impression Materials Plaster Impress Zinc oxide Impression ion and Compou Eugenol nd Settin CaSO4. ½ H2O + Heat  ZnO +H2O 🡲 g 1½ H2O Hard Soft ZnOH reacti 🡲 CaSO4. 2 H2O +  ZnOH + Cool on Heat Eugenol 🡲 Zn eugenolate + H2O Chemical Reaction Physical Chemical  Non-elastic Impression Materials Plaste Impression Zinc oxide Compound r and Impress Eugenol ion Flow High flow Low flow Good flow  Non-elastic Impression Materials Plaster Impression Zinc oxide Impression Compound and Eugenol Good Bad Good accuracy It has little expansion The material has high It has very little during setting due to coefficient of thermal shrinkage (0.1%) presence of anti- expansion, so it shows during setting. expansion additives. high contraction during cooling from ensional softening temperature to mouth temperature.  Non-elastic Impression Materials Plaster Impression Zinc oxide Impression Compound and Eugenol Rigid. Rigid. Rigid. Elasticity It fractured if removed It deformed if removed It deformed if from from removed undercu undercu from t. t undercut  Non-elastic Impression Materials Plaster Impression Zinc oxide Impression Compound and Eugenol Adhere to tray Adhere to the tray Adhere to tray Adhere to the tray  Non-elastic Impression Materials Plaste Impression Zinc oxide and r Compound Eugenol Impress ion Good Bad Good stability Small degree  It shrinks due to It should be stored at of contraction cooling from mouth low temperature occurs due to temperature to room due to presence of dryness. temperature. thermoplastic resins  Distortion occurs due that may cause nsional to release of internal distortion at high stresses (developed temperature.  Non-elastic Impression Materials Plaster Impress Zinc oxide and Impression ion Eugenol Compou nd Not compatible Compatible Compatible It requires a After setting of product separating medium cast, it is placed in whichreduces a hotwater path the accuracy of the for easyseparation of final cast the impression psum  Non-elastic Impression Materials Plaster Impression Impress Zinc ion oxide Compou and nd Eugenol  It has an unpleasant consistency Other properties and taste to the patient.  It may dehydrate the tissues due to heat evolution during setting.  Non-elastic Impression Materials Plaste Impression Compound Zinc r oxide Impress and ion Eugenol  It accepts addition and correction Other properties (If the impression is not satisfactory, it can be re- softened and re- inserted in the patient’s mouth).  It can be electroplated with copper  Non-elastic Impression Materials Plaste Impress Zinc oxide and Eugenol r ion Impress Compou ion nd  The eugenol is irritant to some Other properties patients (use eugenol-free formula).  It adheres to the patient’s skin and lips (Coat the extra-oral tissues with Vaseline before impression making).  Non-elastic Impression Materials Plaster Impression Zinc oxide and Impression Compound Eugenol Non-perforated Non-perforated stock Non-perforated acrylic Tray used acrylic tray. resin resin special tray. special tray.  Non-elastic Impression Materials Plaster Impression Compound Zinc oxide Impression and Eugenol Secondary Sheets and cakes: Secondary impression  Primary impression of impression for for completely edentulous completely completely patients. edentulous patients edentulous  Tray material for wash (after border molding Uses patients technique with zinc oxide- with green stick (historically) eugenol. compound) Stick:  Border molding (border Non-elastic Impression Materials  Manipulation: 1. Plaster impression: Like Gypsum products Non-elastic Impression Materials  Manipulation: 2. Impression compound: Sheets and cakes:  Heated in a water path (55 – 60 °C).  Due to its lower thermal conductivity it should be immersed for sufficient time and kneaded.  The material is kneaded outside the water to avoid water incorporation which acts as a plasticizer and increase the flow. Non-elastic Impression Materials  Manipulation: 2. Impression compound: Sheets and cakes: Non-elastic Impression Materials  Manipulation: 2. Impression compound: The sticks:  They heated over a direct flame.  Avoid overheating as it will cause volatilization of some ingredients which will affect its properties. Non-elastic Impression Materials  Manipulation: 3. Zinc oxide and eugenol:  Dispense equal lengths form both tubes on a glass slab or oil resistance pad.  Mix using stainless steel spatula until homogenous color is obtained. Non-elastic Impression Materials  Manipulation: 3. Zinc oxide and eugenol: Non-elastic Impression Materials  Manipulation: 3. Zinc oxide and eugenol:  Reaction is accelerated by: 1. Heat 2. Humidity. 3. Primary alcohols as Ethyl alcohol.  Elastic Impressio n Materials HYDROCOLLO IDS ELASTOMERS Mixtur es Mixtur es True Colloi suspensio Solutio ns ds ns  Mixtur es True solutions Colloids Suspensions Homogeneous mixture. Heterogeneous solution Heterogeneous mixture. Dispersed phase Dispersed phase Dispersed phase particle size particle size particle size less than 10-7 cm. from 10-7 to 10-5 cm. more than 10-5 cm. Solute particles Solute particles can cannot be seen by be seen by naked naked eye. eye. Solute particles Solute particles cannot be filtered. can be filtered. e.g.: Sugar in water e.g.: Sand in water Mixtur es Mixtur es Colloids Dispersed phase particles are held together .by primary or secondary bonds If the dispersion medium is water, it is called .hydrocolloids They are either sol or gel  Mixtur Colloi es ds  Colloi ds Gel S It is a semi-solid It isola viscous By.liquid state.state agglomeratio The dispersed The dispersed n of the phase form fibrils phase is soluble in dispersed the dispersion or chains in a.medium phase network structure Either by (brush heap The impression.structure) physical or material is inserted into chemical The impression patient’s mouth in reaction is removed from.this state the patient’s General properties of hydrocolloids :Gel strength.1 :It depends on  Concentration of the fibrils: 🡑 fibrils 🡒 🡑 gel.1.strength Concentration of fillers. 🡑 fillers 🡒 🡑 gel.2.strength Temperature (in revisable hydrocolloids): 🡓.3 🡒 temperature gel strength 🡑 General properties of hydrocolloids :Tear strength.2 Hydrocolloids tear strength is relatively lower than .elastomers :To increase tear strength of hydrocolloids  Its thickness should not be less than 4 mm (4-.1.6mm) After setting, the impression should be.2 removed rapidly with sharp snap.movement General properties of hydrocolloids :Elastic recovery.3 Hydrocolloids are viscoelastic material (strain- .rate sensitive) To decrease the permanent deformation  results from impression removing from the undercuts, the impression should be removed rapidly with sharp snap movement  Elastic impression materials are removed from  :patient’s mouth with sharp snap movement to.Increase tear strength.1.Decrease permanent deformation.2 General properties of hydrocolloids :Dimension stability.4 Hydrocolloids are dimensionally  :unstable due to.Synersis and imbibition )a.Thermal changes )b General properties of hydrocolloids 4. Dimension stability: a) Synersis and imbibition:  In the gel state of hydrocolloids, the fibrils entangle to form a network and the water is entrapped within this network.  The gel state can lose or uptake water. General properties of hydrocolloids Dimension.4 :stability Synersis and )a :imbibition General properties of hydrocolloids 4. Dimension stability: a) Synersis and imbibition:  Synersis: It is the loss of the water. This occurs if the impression is left in the air. This results in shrinkage of the impression. General properties of hydrocolloids Dimension.4 :stability Synersis anda) :imbibition :Synersis General properties of hydrocolloids :Dimension stability.4 :Synersis and imbibition )a :Imbibition  It is the uptake of the water. This occurs if the impression is immersed in water. This results in.expansion of the impression General properties of hydrocolloids Dimension.4 :stability Synersis and )a :imbibition :Imbibition  General properties of hydrocolloids :Dimension stability.4 :Synersis and imbibition )a To avoid synersis and  imbibition, the hydrocolloids impression should be stored in 100% relative humidity or stored in 2% potassium sulfate.solution General properties of hydrocolloids Dimension.4 :stability Thermal )b :changes In alginate impression, slight contraction  occurs due to transfer of the impression from the mouth (37 °C) to room temperature (23.°C) In agar impression, slight expansion occurs due  to the difference in temperature of the water cooled tray (15 °C) to room temperature (23 General properties of hydrocolloids:Dimension stability.4 Hydrocolloids should be poured within .short time General properties of hydrocolloids :Disinfection.5 The disinfection process should be rapid  (due to poor dimensional stability) The disinfectant should be sprayed (to avoid  imbibition if the impression is immersed into.disinfection solution) The most commonly used disinfectants are  iodophor, 2% glutaraldehyde and 1% sodium.hypochlorite General properties of hydrocolloids :Compatibility with gypsum.6 Hydrocolloids are not compatible with gypsum.  :The surface of the cast may be soft due to Presence of water at the surface of hydrocolloid )a impression which may affect the setting of.gypsum Constituents of the hydrocolloids (as borax) )b.may retard the setting reaction of the gypsum General properties of hydrocolloids :Compatibility with gypsum.6 :This limitation can be counteracted by  Immersion of the impression into gypsum )a.accelerator (2% potassium sulfate) Addition of gypsum accelerator to the )b.hydrocolloid material during manufacturing General properties of hydrocolloids :Electroplating.7 They cannot be electroplated due to their  tendency for imbibition  General properties of hydrocolloids Hydrocolloids are non-toxic and.8 non-irritant  Hydrocollo ids Reversible hydrocolloid Irreversible hydrocolloid Agar impression material Alginate impression material It is the first elastic It was developed as a substitute impression for agar material introduced in during World War II as agar dentistry. supply decreased during the war. Nature It is a polysaccharides It is a natural material extracted extracted from a from seaweeds marine plant.  Hydrocollo ids Reversible hydrocolloid Irreversible hydrocolloid Agar impression material Alginate impression material Mode of Gel Powder + Water supply suppled in tubes and syringes.  Hydrocollo ids Agar impression material Alginate impression material Compositio  Agar: 12.5%: as dispersed phase. n  Borax: strengthening agent and increase viscosity. It retards setting reaction of gypsum.  Potassium sulfate: accelerate gypsum setting (counteract the inhibitory effect of agar and borax).  Water: 85% as dispersion medium.  Fillers: control strength and viscosity.  Hydrocollo ids Agar Alginate impression material impression material Compositio Soluble salt of alginic acid: (sodium or n potassium alginate) 12%. Calcium sulfate: 12% Tri-sodium phosphate retarder. Fillers: 70%. Fluoride: to improve surface hardness of gypsum cast. Flavoring agent: to give good taste to the patient. Chemical indicators: to indicate  Hydrocollo ids Agar impression material Alginate impression material Setting Physical reaction (reversible reaction) reaction Cooling 43°C Sol Gel Heating 100°C The great difference between liquefaction and gelation temperature is called hysteresis.  Hydrocollo ids Agar Alginate impression material impression material Setting Chemical reaction (irreversible reaction reaction) The alginate is set by formation of the insoluble salts alginic acid (calcium alginate).  Hydrocollo ids Agar Alginate impression material impression material Setting Setting reaction: reaction Potassium alginate + calcium sulfate calcium alginate + potassium sulfate.  Because of the setting reaction is too fast; retarder (tri-sodium phosphate) is added to increase working time.  Hydrocollo ids Agar Alginate impression impressi material Settin on  tri-withreactingpreferssulfateCalcium g material.phosphate more than potassium alginate sodium reacti So, formation of insoluble salts (setting  on tri-sodiumall finishingreaction) untilstartwill not.phosphate molecules :Retardation reaction Tri-sodium phosphate + calcium sulfate Sodium sulfate + calcium phosphate  Hydrocollo ids Agar impression Alginate impression material material Flow Good flow Good flow but less than agar.  Hydrocollo ids Agar impression material Alginate impression material Good dimensional Bad dimensional accuracy. accuracy accuracy.  The setting starts from tissue to  The setting starts from tray tray (as the tissues is hotter than to tissues (as the tray is tray and setting reaction is cooler). chemical reaction accelerated by  So, the impression heat). contacting the tissue stays  So, any changes occur during Dimensional liquid for longest time and setting will affect the accuracy of can flow to compensate any the impression. changes occurs during  The tray should not move during setting. setting to minimize distortion. Hydrocollo ids Ag Algina ar te  Hydrocollo ids Agar impression material Alginate impression material Viscoelastic material. (discussed before) elasticity Elastic recovery 98.8% Elastic recovery 97.3%  Hydrocollo ids Agar impression material Alginate impression material Flexibility High flexibility The most flexible impression material  Hydrocollo ids Agar impression material Alginate impression material Do not adhere to the tray. Adhere to the tray They require perforated trays for mechanical interlocking. Some manufacture provides adhesives.  Hydrocollo ids Agar impression material Alginate impression material Dimensional stability Bad dimensional stability (discussed before)  Hydrocollo ids Agar impression material Alginate impression material ty with gypsum products Not compatible but this problem can be solved (discussed before).  Hydrocollo ids Agar impression material Alginate impression material Specially designed water cooled Perforated stock tray Tray required perforated tray  Hydrocollo ids Agar impression material Alginate impression material Requires expensive equipment Cheap Cost  Hydrocollo ids Agar impression material Alginate impression material 1. Duplicating material (for 1. Making primary impressions for duplicating the casts dentulous at the laboratory) and edentulous patients. 2. Making secondary 2. Making impressions for impressions. (This use orthodontic became very limited after appliances. Uses introduction of 3. Making impressions for dental elastomeric impression appliances such as mouth materials). guard, occlusal splints, …. 4. Making impressions for opposing casts in indirect restorations.  Hydrocollo ids Alginate Agar impression material impression material It requires: Manipulation 1. Hydrocolloid conditioner. 2. Water-cooled tray. 3. Running water supply.  Hydrocollo ids Alginate Agar impression material impression material 1. Hydrocolloid conditioner. It has three compartments: a) Liquefaction: at 100°C. The tubes and Manipulation syringes are heated for 10 minutes (gel 🡒 sol). b) Storage: the sol agar can be stored for several hours at 65°C. c) Tempering: The sol agar is loaded at the tray and tempered at 46 °C for 2 minutes just before inserting into patient’s mouth. Hydrocollo ids  Hydrocollo ids Alginate Agar impression material impression material 2. Water-cooled tray. Manipulation It is a specially designed tray. It has channels for circulation of cold water (sol 🡒 gel).  Hydrocollo ids Agar impression material Alginate impression material 3. Running water supply. It supplies the tray with cold water Manipulation (20°C). The water temperature should not be less than 13 °C to avoid developing of thermal stresses.  Hydrocollo idsAgar impression Alginate impression material material  The tray should provide 4mm thickness for alginate.  Shake the alginate powder container before use Manipulation to provide an even distribution of the constituents.  Water-powder ratio (W/P) adjuster as manufacturer instructions. Manufacturer usually provides a measuring tools.  Hydrocollo idsAgar impression Alginate impression material material  Use rubber bowl and wide rigid spatula. Manipulation  The water is added in the bowl then the powder.  Mixing starts with a stirring mixing to wet the powder followed by a rapid and vigorous mixing with squeezing the mix against the sides of the bowl until a creamy mix is obtained. Hydrocollo ids Hydrocollo ids Hydrocollo ids  Hydrocollo idsAgar impression Alginate impression material material  The tray is loaded with alginate mix using the tip of Manipulation the spatula. The mix should be pressed against the tray to release any trapped air. Hydrocollo ids  Hydrocollo idsAgar impression Alginate impression material material  The alginate surface should be smoothed with Manipulation moistened fingertip to prevent formation of air bubbles. Hydrocollo ids  Hydrocollo idsAgar impression Alginate impression material material  The tray is inserted into patient’s mouth. During gelation, it Manipulation should not be moved or subjected to excessive pressure to avoid development of stresses that will released after removal of the tray and cause distortion.  Hydrocollo idsAgar impression Alginate impression material material  The impression is removed from the patient’s mouth Manipulation 2-3 minutes after loss of tackiness to insure that the material reached sufficient strength.  Hydrocollo idsAgar impression Alginate impression material material  The impression should be removed by sharp snap Manipulation motion in direction parallel to long axis of the teeth.  The impression is rinsed and disinfected.  Hydrocollo idsAgar impression Alginate impression material material  The impression should be poured with gypsum as Manipulation soon as possible but if not, it should be stored in 100% relative humidity (wrapped with a moist towel and placed inside a sealed plastic bag.  Hydrocollo idsAgar impression Alginate impression material material  The impression should be removed from the cast Manipulation after 30-60 minutes from pouring as the gypsum may absorb water from the impression leading to a chalky surface.  Hydrocollo idsAgar impression Alginate impression material material The setting time of alginate can be managed by: 1. Water temperature (18 - 24°C). Notes 2. Water/powder ratio 3. Concentration of tri-sodium phosphate (retarder)  Hydrocollo idsAgar impression Alginate impression material material The setting time of alginate can be managed by: 1. Water temperature (18 - 24°C). Notes  Increase water temperature will accelerate the reaction.  This can be recommended way  Hydrocollo idsAgar impression Alginate impression material material The setting time of alginate can be managed by: 2. Water/powder ratio:  Increase water will retard the setting reaction. Notes  This is not recommended as it will adversely affect the properties of the material.  Hydrocollo idsAgar impression Alginate impression material material The setting time of alginate can be managed by: 3. Concentration of tri-sodium phosphate (retarder):  Manufactures can control the setting time by Notes controlling the percentage of tri-sodium phosphate.  They supply alginate in the form of regular set and fast set.  Hydrocollo idsAgar impression Alginate impression material material Notes Alginate powder should be stored under cool and dry conditions  Elastic Impressio n Materials HYDROCOLLO IDS ELASTOMERS Elastomeric impression materials They are a variety of rubber-like impression  :materials that have several names as.Non-aqueous elastomeric impression materials .Rubber base materials .Elastomers  Elastomeric impression materials.They set by a polymerization reaction  They are formed of long, highly coiled chains that  can be highly stretched to produce wide range of.elastic deformation (elastomers) Elastomeric impression materials They supplied in different consistencies; light, .medium, heavy and putty consistencies The consistencies differ in fillers amount and .molecular weight of the polymer Elastomeric impression materials They supplied in two containers; base and .with two different colors catalyst They have higher dimensional accuracy and .stability than hydrocolloids.Elastomers are more expensive than alginate  Elastomeric impression materials Polysulfid Condensati Addition Polyethe e on silic r (Mercapta silicon on n) (PV S) Consistencie Light, Light, medium, heavy and Light, s medium putty medium and heavy and heavy  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Low molecular Low molecular Low molecular Low weight weight weight molecular polysulfide polydimethyl polysiloxa weight Composition (Base) polymer with silozane ne polyether reactive polymer with polymers. polymer with mercaptan terminal (OH) Fillers. ethylene- (SH) group. group. imine group Fillers. Fillers. (-N-(CH2)2) Plasticizers. Fillers. Sulfur (accelerator).  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Lead dioxide (to Tetra-ethyl Low molecular Aromatic Composition (Catalyst) start reaction) orthosilicate weight sulfonic Fillers. (for cross divinylpolysilox acid Plasticizers. linking). ane with vinyl ester. Stearic Tin terminal Fillers. acid octoate group (retarder (catalyst (-CH=CH2). ) ). Chloroplatinic Diluent. acid (catalyst). Fillers.  Elastomeric impression materials Reactor is a more accurate term than.catalyst  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Condensation Condensation Addition Addition Setting reaction polymerization polymerization polymerization polymerization reaction reaction reaction reaction  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Byproducts Water Ethyl alcohol -- -- Manipulati on A special acrylic tray is constructed to allow a  thickness of 2-3 mm for the impression material Increasing thickness of impression material  leads to more polymerization shrinkage and.less dimensional accuracy Manipulati on The tray is painted with adhesive as the .impression material doesn’t adhere to the tray Manipulati on :Mixing techniques :Hand mixing for pastes.1 Use tapered stiff spatula over a disposable oil- .resistant paper Equal lengths of the paste & catalyst are extruded .over the mixing pad Spread the material in a thin layer to release trapped .air.Mix until obtain homogenous color  Manipulati on Mixing :techniques Hand mixing for.1 :pastes Manipulati on Mixing :techniques Hand mixing for.1 :pastes Manipulati on :Mixing techniques Hand mixing for putty consistencies.2 :(kneading).Wear over-gloves in case of addition silicon  The condensation silicon is supplied as a .putty base and catalyst paste The addition silicon is supplied as two .putties Manipulati on :Mixing techniques :Hand mixing for putty consistencies (kneading).2 Recommended ratio for condensation type or  equal scopes for addition type are dispensed and kneaded by using fingertips until homogenous.mixing is achieved Manipulati on :Mixing techniques :Hand mixing for putty consistencies (kneading).2 Kneading is done using fingertips rather than the  palm of the hand because the hand temperature.may accelerate the setting reaction Manipulati on :Mixing techniques Hand mixing for putty consistencies.2 :(kneading) Manipulati on :Mixing techniques Hand mixing for putty consistencies.2 :(kneading) Manipulati on :Mixing techniques :Static Mixing.3 This system consists of mixing gun, impression .cartridge and mixing tip The cartridge composed of two cylinders .containing base and catalyst separately Manipulati on Mixing :techniques :Static Mixing.3 Manipulati on Mixing :techniques :Static Mixing.3 Manipulati on :Mixing techniques :Static Mixing.3 The cartridge is loaded in mixing gun. Then the .mixing tip is attached to the cartridge The mixing gun compress the impression  material from the cartridge into the mixing tip.to be mixed before its extrusion Manipulati on :Mixing techniques :Dynamic Mixing.4 The impression material is supplied in a .cartridge The cartridge is loaded inside a motor driven  mechanical mixing machine and a mixing tip is.placed on the front of the machine Manipulati on :Mixing techniques :Dynamic Mixing.4 By pressing a button, the material is mixed .and extruded through the mixing tip Manipulati on Mixing :techniques Dynamic.4 :Mixing Manipulati on Impression techniques: 1. One stage single viscosity (monophase): 2. One stage dual viscosity 3. Two stages: Putty-wash 4. One stage: Putty-wash  Manipulati on One stage One stage Two One single dual stages stage viscosity viscosity Putty- Putty- (monoph wash wash ase) Tray Special tray Special Perforated Perforated tray stock tray stock tray Viscosit Medium only Heavy + Putty + Putty + y light light light  Manipulati onOne stage single viscosity One OneTwo stagesstagege sta dual v Putty-washiscosity (monophase) -Putty wash The material is mixed. Part is loaded inside the tray and part is loaded inside a Method syringe. The syringe material is injected around the prepared teeth. The loaded tray is seated inside patient’s mouth.  Manipulati on One stage One stage dual viscosity Two One single stages stage viscosity Putty- Putt (monoph wash y- ase) was h The heavy and light consistencies are mixed at the same time by two operators on separate paper pads. The heavy consistency is loaded inside the tray. thod The light consistency is injected with syringe around the prepared M nipulati a on  Manipulati on One stage One Two stages One single stage stage viscosity dual Putty-wash Putt (monoph viscos y- ase) ity was h The putty is mixed and loaded inside the tray then preliminary impression is taken. The light consistency is mixed then Method injected around the prepared teeth and loaded over the putty impression. Then the tray is repositioned inside patient’s mouth. Manipulati on  Manipulati on One stage One Two One stage single stage stages viscosity dual Putty- Putty-wash (monoph viscos wash ase) ity The putty and light consistencies are mixed at the same time by two operators. The putty is loaded around the tray. The light is injected around the Method prepared teeth. The tray loaded with the putty is inserted inside patient’s mouth over the light injected over prepared Manipulati on Manipulati on Seating trails Manipulati on Syringe loading for intraoral application Manipulati on Syringe loading for intraoral application Manipulati on Syringe loading for intraoral application Manipulati on Syringe loading for intraoral application Manipulati on Syringe loading for intraoral application Manipulati on Syringe loading for intraoral application Manipulati on Intraoral application by static mixer Manipulati on Intraoral application by static mixer Manipulati on Intraoral application by static mixer Manipulati on Intraoral application by static mixer Manipulati on Intraoral application by static mixer Manipulati on Intraoral application by static mixer General properties of elastomers :Flow.1 Their flow depends on the consistency. Light .consistency has high flow The passage of the impression material through  mixing tips or syringe tip increases its flow due.its pseudoplastic nature General properties of elastomers :Dimensional accuracy.2 Their polymerization reaction is accompanied by  polymerization shrinkage which is greater in condensation types (polysulfide and condensation.silicon) General properties of elastomers :Elastic recovery.3 Elastomers are viscoelastic material (strain-rate .sensitive) To decrease the permanent deformation results from  impression removing from the undercuts, the impression should be removed rapidly with sharp snap movement in direction parallel to long axis of.the teeth General properties of elastomers Elastic impression materials are removed from  :patient’s mouth with sharp snap movement to.Increase tear strength.1.Decrease permanent deformation.2 General properties of elastomers :Dimensional stability.4 The evaporation of byproducts in condensation  types (polysulfide and condensation silicon).increases their inaccuracy Thermal shrinkage occurs due to change .between mouth and room temperatures General properties of elastomers :Dimensional stability.4 The condensation types should be poured within  30:60 minutes. While addition types can be poured.up to 24 hours Polyether impression should be stored in dry .conditions due to its hydrophilic nature Limitations of elastomers :Polysulfide.1 It has an unpleasant smell and taste due to .sulfur content.It has long setting time .N.B: The use of polysulfide is limited nowadays Limitations of elastomers :Addition silicon.2 Hydrophobicity results in poor wetting to  tissues during impression making and poor wetting with gypsum during cast making. This.results in a cast with poor details The manufacturers added surfactant to the .composition to decrease this hydrophobicity Limitations of elastomers :Addition silicon.2 Sulfur contamination from natural latex and some  vinyl gloves inhibits polymerization reaction. So avoid touching the impression material or prepared.teeth with gloves Wearing latex-free glover or over-gloves during .kneading the putty can solve this problem Limitations of elastomers :Addition silicon.2 Hydrogen gas release during setting reaction. It  may occur if the proportions of the material are unbalanced. The hydrogen gas causes poor surface.details of the cast To avoid this effect, the manufacturers added  palladium to absorb the gas and recommend pouring the impression after 30 minutes to ensure.evolution of the hydrogen gas Limitations of elastomers Addition.2 :silicon Hydrogen gas  release Limitations of elastomers :Addition silicon.2 N.B: The hydrogen gas is not a byproduct of .polymerization reaction Limitations of elastomers :Addition silicon.2 Interaction with resin based provisional crown  :material If the putty impression is used for construction of  the provisional resinous crown, the surface layer of the crown will not be polymerized (air inhibited.layer) Limitations of elastomers :Addition silicon.2 If this oily surface layer is left at the impression, it  will prevent the bond between the putty and light.wash leading to failure of the secondary impression Limitations of elastomers Addition.2 :silicon Limitations of elastomers :Polyether.3 The higher stiffness of the polyether (flexibility 3%)  makes its difficult during removing from undercuts and may break the cast during separate the cast.from the impression The impression thickness is recommended to be .4mm to facilitate its removing from undercuts Polyvinyl Ether Silicone :(PVES) It is a combination between polyvinyl siloxane and .polyether The material combines the benefits of both polyvinyl  siloxane and polyether impression materials such as higher flowability, hydrophilicity, dimensionally accuracy, elastic recovery and easy removal from.the mouth  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Flow Discussed before  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) 0.25% 0.6% 0.05% 0.3% Dimensional accuracy polymerization polymerization polymerization polymerization shrinkage (in shrinkage (in shrinkage (in shrinkage (in 24 hours) 24 hours) 24 hours) 24 hours)  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) 98% 99.5% 98.9% Elastic recovery  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Most flexible Less flexible Least flexible Its thickness Flexibility should be 4 mm for easily removal from the mouth.  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Needs Needs adhesive Needs adhesive Adhesion to the tray adhesive Perforated stock tray (with putty only)  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Dimensional stability Discussed before  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan silicon (PVS) ) Incompatible due to their hydrophobicity. Compatible Surfactant should be used to improve their wetting. due to ith gypsum products its hydrophilicity  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Tear strength Highest Least lower  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan) silicon (PVS) Tear strength Highest Least lower  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan silicon (PVS) ) Electroplating Cannot Can be electroplated with silver be electroplating due to its hydrophilicity  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan silicon (PVS) ) Disinfection Spray Can be disinfected by immersion in 10% sodium disinfectant is hypochlorite recommended not more than 30 minutes. due to its hydrophilicity.  Elastomeric impression materials Polysulfide Condensation Addition silicon Polyether (Mercaptan silicon (PVS) ) Uses Making secondary impression for dentulous and edentulous patients. Than k You