Impression Materials In Fixed Prosthodontics PDF

10/28/2023 BIBLIOGRAPHY IMPRESSION MATERIALS IN FIXED PROSTHODONTICS Sara R. Jaser (BDS, MDSc, MFDS) Lecturer Dr. Sara R. Jaser MDSc (UK), MFDS RCS Edin(UK), BDS (Jordan) Specialist Prosthodontist Department of Preventive & Restorative Dentistry [email protected] 2 LEARNING OBJECTIVES – PAR...

10/28/2023 BIBLIOGRAPHY IMPRESSION MATERIALS IN FIXED PROSTHODONTICS Sara R. Jaser (BDS, MDSc, MFDS) Lecturer Dr. Sara R. Jaser MDSc (UK), MFDS RCS Edin(UK), BDS (Jordan) Specialist Prosthodontist Department of Preventive & Restorative Dentistry [email protected] 2 LEARNING OBJECTIVES – PART II LEARNING OBJECTIVES – PART I • Classify impression materials, specifically elastomeric impression materials. • Identify the features of ideal and unacceptable impressions. • Compare between the different types of impression trays (i.e., stock vs. custom-made, metal vs. plastic) and their indications. • List methods and materials used in disinfecting impression materials. • Identify the different impression techniques used in Fixed Prosthodontics. • Identify the required properties of ideal impression materials used in Fixed Prosthodontics. • Explain the advantages and disadvantages of each impression technique. • Red - drive notes • Blue -my notes • Green athba notes 1 • Explain the properties, indications, limitations, advantages, and disadvantage of each type of elastomeric impression materials. 4 3 KEY TERMS IMPRESSION MATERIALS • Impression material • Impression tray Key properties Handling behaviour • Dental impression Effective use • Dental cast • Impression technique 6 5 1 Q. What are the speci cation of custom tray for denatate patient? 1. thickness of tray 2-3 mm ( acrylic material 2. Add perforations 2mm in diameter. Why? To help in mechanical retention of impression material 3. Add stopper ( placing acrylic material on tting surface on teeth that are NOT going to be prepared or hard palate) ( not affect our impression) ◦Q. How many stoppers do we need? 3 widely spaced ◦Q. What is the aim of the stopper? Stop the impression material form sinking and having an intimate contact with the teeth ‣ Notice (slide 9) stopper is going to contact the tooth surface what happens we will end up having a space between tray and teeth and this space is going to be preserved and future it will be lled with impression material itself 4. Add wax spacer: this will ll space temporaly during contruction of custom tray the during impression this is going to be lled with material spacer is 1mm in thickness Custom/ special tray: has rigidly, stress distribution, minimize distortion and material waste, high accuracy. ◦Indicated for? Multiple teeth being restored when arch form and size prevent use of stock strays. Stock strays: for average population comes in metal and plastic. Q. What is an impression tray? A container used to carry impression material when making impressions Impression tray must be? Rigid as possible 10/28/2023 • Metal tray: its rigid, block undercuts and prevent locking impressions • Plastic tray: when used with high viscosity material it causes distortion + they ex during impression + rebound on removal from the mouth produces an inaccurate cast and poor restorative t E IMPRESSION TRAYS o o F IMPRESSION TRAYS (STOCK VS. CUSTOM)? (METAL OR PLASTIC)? ptefabricated si weregidsteathidd 8 7 WHAT IS THE IDEAL TRAY? (STOCK OR CUSTOM)? where IE Q. What is the ideal option stock or custom tray? ◦Custom tray the metal: it is supeiror due to its rigidly and can accommodate good o amount of material, See slide 9 • when we add stop this will create a space between tray and teeth, this space is to be preserved and lled later by impression material Inorder to capture the preparation stress is distributed • Case of hard tissue undercut what happens? ◦Impression material is unset when loaded, spacer here is removed ( 1mm mafruuth) we make sure we have the triple space why? Once material is set we will have diffulcty to remove the material from teh pateints mouth without spacer. 10 9141494 9 a Whats DENTAL IMPRESSION STOCK VS. CUSTOM met A negative replica of the oral tissues (soft & hard) É Rigidity Bulk Control Stress Distribution Material Waste Tifica pourmitaay.iqaypsum Custom ga.mp.gmtat gg ii Stock metal ✔ igrin ✔ ✔ ✔ nownshintnemarriae Comfort ✔ Accuracy ✔ nottooiargeortootign Q.wnatanethetypmdtifdi.me diniamiastly replica 12 11 Q. What is the aim of impression? Pour it with gypsum to have a 3D positive replica which is the “dnetal cast” Q. Why is the impression material important? Since its a FPD not done directly in pateints mouth. 2 10/28/2023 • Q. What is added to tray to impression material to adhere to it? For an impresson material to adhere to the tray = add tray adhesive • Add a thin layer only, if not it will be thick and turn into a lubricant =causing the impression to slide over the tray • Q. What is the aim of tray adhesive? Chemical retention+ prevent distortion+ prevent delta Ahmet of impression from tray = this lead to inaccurate t • Make sure allow 10-15 mins to dry then load tray with impression tray ◦Remember you choose the tray that’s perforated so you have aWhats chemical and mechanical retention DENTAL CAST TRAY ADHESIVES O.gg 4 A 3-D positive replica of the oral soft and hard tissues • Adhesives used are usually polydimethyl siloxane andtrains ethylsilicate. dentalfast Iesi.awnadoesthe • The adhesive forms a chemical bond to the tray and the impression material. takeanimpress Getransferita accuratty • Recommendation - wait for 10-15 mins after application of the adhesive before making the impression. asposs initiation de rtensmikainmm39 Eiomottnetray 14 13 takygggteontnd.ve Whats Isthe You make an impression ( NOT TAKE) IMPRESSION TECHNIQUE (MAKE OR TAKE)? CLASSIFICATION OF IMPRESSION MATERIALS mn • A method used in making an impression of the oral soft and hard tissues. • Impression materials can be classified according to their: • Impression making is as much an art as it is a science. ofthe ➢ Composition ingredients materialitself ➢ Setting reaction ➢ Properties after the material has set 1 3 16 15 understand Wax Thermal ELASTOMERIC IMPRESSION MATERIALS Non-elastic • A group of flexible chemical polymers that are either chemically or physically cross-linked; generally, they can be easily stretched and rapidly recover their original dimensions when applied stresses are released Wat Reversible hydrocolloids 1925 Polyether 1960s Irreversible hydrocolloids 1941 Chemical Impression materials thing Polysulfide & CS 1953 Hydrocolloids Plaster tenners Zinc-oxide eugenol of casts Agar (reversible) limitedusage Alginate (irreversible) a Addition silicone 1970s Polysulfide Elastic Elastomers The glossary of prosthodontics term Alginate is irreversible how? Once you mix it ( powder and water ) you can NOT undo it! After it sets its unstable must be poured within 30 mins —- Inorder to overcome these disadvangtes tehy have worked one elastomric compound Impression compound 18 anger bmore Silicone material is divided into ( condensation and Addition ) ◦Silicone condensation ◦Silicone addition is teh putty onceimpression setyoucantund Condensation Silicone Polyether p Addition stability elasticity is me 17 ÉÉÉÉ it sets looseswater absorbsmoisture 3 viscosityt whenfillert moredense matnxless 10/28/2023 Q. Viscosity refers to? The amount of llers in the material itself Q. Flowable composite vs packable composite, owable has more or less llers? Less dimens less't.fi itsisiiiiieasgemntase Life Monefillerlessshrinkage Eye • Less llers = more owable = more shrinkage • Heavy llers = less owable = less shrinkage ( dimensionally stable) • Putty has the highest viscosity = high amount of llers sauresittobedimensionally Whatsthe IE VISCOSITIES OF ELASTOMERS INFLUENCE OF FILLER CONTENT2 pIfIEpfty Light Body Filler Content Viscosity shrinkage Setting Contraction Dimensional Stability waging Medium Body Heavy body Increasing Increasing Decreasing Increasing Viscosity Form 3 Low Syringable/wash (light body) 2 Medium Paste (medium body) 1 High 0 Very high ens amqqy.FI Heavy body Putty highest • The viscosity of impression material increases as filler content increases. y packablecomposite Howablecomp • The lower the viscosity, the better the surface details. motefineramenteestable II'esiinage i Type ginefenginkasionaksinsuimpression • Aim 20 19 ◦Having our For bulk impression it’s made from very viscous What arethe REQUIREMENTS OF AN IDEAL IMPRESSION MATERIAL REQUIREMENTS OF AN IDEAL IMPRESSION MATERIAL Elina • Upon removal from mouth ✓ Easy to remove Idimensionally ii iiieiitiiiiiiii na.info ✓ High tear resistance IEEE.inti • Before impression making (extra-oral) ✓ Simple to use and not technique sensitive ✓ Easy to mix ✓ Sufficient working time ✓ Good recovery from deformation (elastic) • During impression making (intra-oral) ✓ Good wettability ✓ Ability to flow around preparation without slumping ✓ Detail-capturing ✓ Fast setting time (snap set) ✓ Dimensionally accurate ✓ Acceptable taste and odour ✓ Safe • After impression making (storage) ✓ Dimensional stability to g • To be able to store and pour it ✓ Easy to read ✓ Disinfected without distortion Aim of impression? • record the prepared tooth with nish line and amount of in prepared teeth lying underneath the sulcus —> so we need to place a retarcation cord = because the technician will the restoration as if it was to emerge from the socket in order to give you teh best aesthetic ( R. Cord push soft tissue away from margin to capture the unprepared part) • record the adjacent teeth that unprepared for countour and contact points and also for occlusion • In order to record occlusion we record teh oppoing dentition • Working time is teh amount of time when you wait to reach teh full rigidly of material 22 i 21 Whatarethe OBJECTIVES OF MAKING AN IMPRESSION 1 REQUIREMENTS OF AN IDEAL IMPRESSION MATERIAL ➢ Record the prepared and unprepared tooth surfaces. ✓ Low cost j Capture the unprepared 2➢ tooth cervical to the finish s ✓ Adequate shelf-life line to identify contour of tooth “emergence profile”. I ✓ Compatible with gypsum products needto✓ Easy to use with minimum equipment ➢ Record unprepared teeth so their shape can be used to establish the contour of the restoration and proper occlusion. placearetraction 3 ➢ Record the hard as well as soft tissues. cordtopushthe P 24 agniatieoriteeposingdentition thatwillbepoured toconstructthedental 23 insight.gs ggdIgggfggI Eargheiggetatid 4 • Look at slide 25 • When we look at 2 molars receiving full coverage restoration ( ceramic why? Shoulder all over) • There are two colors, because you used two different material with different viscosities ◦Light green = light body to capture the details ◦Light blue = dark re ect the bulk = more viscous 10/28/2023 Qonatanethe IDEAL IMPRESSION KEY PROPERTIES miterial impression sestIbyk acy.EE green light Optimal impression material characteristics Proper technique artisan tocapturedetails Dimensional Stability Accuracy 2 di diffcolors mater relighting fgstingttirthshar a S I Tear Resistance ate.TL amgiEiEiiae 26 25 Timatithsiin time www.aewidtnitged a eentefjmyetoyig.int I TROUBLESHOOTING im Visible flaws ms o gtfo Invisible flaws Tray and impression recoil Air bubbles in critical places Detachment of impression from tray Voids or drags Permanent deformation I i ofmaterial shrinkage i 11 • Accuracy: ability to flow, capture fine details and replicate the intraoral surface details. any Finish line not visible Unset impression material ofa 9 3keyffmtpytssfgnthemafyf.us Iji • Dimensional stability: ability to retain its absolute dimensional size over time. fij ÉÉ 28 • Tear resistance: ability to resist tearing in thin sections upon removal especially in interproximal, subgingival areas, slots and grooves. stitgteginnaeraforce miameterangaurat 27 draging fear IMPRESSION MATERIAL CHARACTERISTICS dragging 30 notacontinentsmainly inthe finishline lingual 4palatal visibleflaws 29 surfaces 5 10/28/2023 ‣ O • wetability is teh weeting surface ◦E.g drop of water and drop of oil and apply both glass slab do tehy stay in place teh same way? No , ‣ oil contains itself on teh surafce “hydrophobic” material that wets the teh surface it will end up in and angle ( great angle = hydrophilic material ets teh surface properly) the ability of a liquid to spread over a surface. apetota•• Wettability: Wettability can be measured by the contact angle(θ). HYDROPHILIC VS HYDROPHOBIC gaffedbetween the thesurface ontopofit outer surface b b remains as a whenyouhave a largeangle it wetsthesurface droplet 32 31 Casmallangle NOTE: when using hydrophilic materials you stil need to use moisture control protocol whatarethetypesdividendagagtopoerty IMPRESSION MATERIALS • Hydrophilic impression materials still require good moisture control! Hydrophilic • Hydrocolloids • Polyether Elastomeric • No impression should be made in wet environment! TX • Polysulfide • Addition silicone(PVS) • Condensation silicone • Readily wettable by the gypsum. Xbloodall over theplace ssqmbed bmegnsmits.gg • Resistant to wetting (repelled by haemorrhage or tissue fluids). • Not readily wettable by the gypsum. D When we want to capture a detail it must be done with low34 viscosity Once we capture we need to remove ifrom pateints mouth ◦If we we remove it and it distorts this is plastic deformation ◦If we remove it and it rebounds to original shape this is elastic impslide should'hiremiowriscosity impression 33 Before : If its a hydrophiobic material, tehy can’t wet the teeth so they used spray surface of teeth swith surfactant to improve the stability ◦Surfactant: lowers the tension of surface to make it more hydrophilic Now : surfactant itself is embedded sudrong manufacture of impression material witraptangtyingtanetoetails • Detail capturing • To combat the hydrophobic nature of additional silicones, manufacturers have added “surfactants” to lower surface tension creating the so-called hydrophilic silicones. ➢ Elastomeric impression materials are required to record detail down to 20 microns. IfI tagging • Works in “wet” environment! saliva all over the placer using Hydrophobic ftp.T ffd ➢ Die stones are required to reproduce detail down to 50 microns. • Surfactants improves wettability of PVS impression material & reduce voids in recovered cast. ➢ Putty captures details down to 75 microns. ÉÉÉÉhitt o tigqapigsinant ➢ Ability of the material to flow readily into undercuts, set in that position, and be able to “rebound” back to its original shape when removed from the mouth. It ggg • Surfactants used to be sprayed on the set impression before is pouring. the gg.gg • Elastic recovery c Ig I i.IT Ég.fm giIIghg yjgjigjjjj c PVS impression materials have intrinsically added u• New surfactants. iownosim 36 it hydrophobic cannotwetthe teeth 35 for wettaisiktgt ssurgrfmi.hn theminterfaston surfaceof thetooth 6 10/28/2023 haIeamhfehgfwTysoitt MEEEE.gg • Working time: the time measured from start of mixing. It includes time to manipulate & syringe material around tooth and into sulcus, as well as being placed in tray. MIXING AND DELIVERING • Pastes can be mixed together with: thing demon 1. Mixing pads (manually) • Setting time: the time required to complete the setting reaction (i.e., reach a certain degree of rigidity, hardness or elasticity) 2. Auto-mixing guns (by manually expressing the two pastes through a mixing tip), or • Elastomeric impression materials have a working time of approximately 2 minutes and a setting time 2-6 minutes (i.e., fast vs. regular set). 3. ÉI Mixing equipment (electrically driven pumps for proportioning of materials from larger tubes through a mixing tip) fmenclmpressi typeftp.ggs 38 Ég.gg ÉÉÉÉÉI I Fomin am'in • Working & setting times are affected by several factors. 37 imtqigingygicnwinremain fE.IE ane Elastomeric'impnisstontane 1. POLYSULFIDE • “Thixotropic” materials => Shear-thinning. • Supplied as two pastes: base and catalyst • Advantages of auto-mixing: • Three types of viscosity: low, medium and heavy. - Mix/supply on demand - No mixing instruments to clean or sterilise • Best used in a special tray (4 mm uniform space) - Direct application Q. What is thixotropic property? Means if teh material cartridge one you apply force/pressure on catalyst and base they will go into a thinning property to get extruded “ shear thinning ◦Once its on the tray theres no pressure so impresison contains itself! You can walk from mixing machine to cubicle • So thixotropic property mean it allows the material to be less viscous when pressure is applied and it will be extruded - One mix only • Disadvantages of auto-mixing: - Cost - waste 40 39 condensation 1. POLYSULFIDE 1. POLYSULFIDEadditions • Dimensional stability (0.3% shrinkage within 24hrs). • Mercaptan (Thiol)+ lead dioxide (oxidizing agent) polysulfide rubber +lead dioxide +H2O (condensation reaction) • Elastic recovery is 97% to 98% - it is important to wait 20-30 minutes after tray removal for stress relaxation to occur. lad • Working time (5-7min) relatively good stint.fiEtet • Setting time (8-14min) t Polysgfjdgf.qns2 • Both ST&WT are affected by temperature, moisture & base: catalyst ratio. Reactions 11fi 11 42 tt ssa Q.LY mPgYsg'fdfon7aitn4htIcausesbadodor 41 watererapuzsyggk.gg forms product water by Egging into 7 10/28/2023 limited 2. CONDENSATION SILICONE (TYPE 1) 1. POLYSULFIDE • Not commonly used in clinics but rather used for duplication in the dental laboratory. • Unpleasant odour due to thiol (SH) group • Supplied as a base and catalyst pastes or a paste and liquid. • Dirty • Slow setting • Contains lead • Manufacturers supply condensation silicone in a putty-wash combination. • Hydrophobic • Condensation reaction, water loss results in shrinkage • Dies resulting from polysulphide impressions are generally wider than the tooth preparation. advantage • Good tear resistance (withstand 700% tensile strain before tearing) some Torfof permanentdeforma • Viscoelastic 44 43 highshrinkage • It undergoes condensation reaction causing a byproduct? Ethyl alcohol causes evaporation causing high shrinkage japorate bae 2. CONDENSATION SILICONE byproduct 2. CONDENSATION SILICONE • Condensation setting reaction produces ethyl alcohol as a by-product that gradually evaporates and contributes to the rather high shrinkage during the first 24 hours. • Viscosities: light body, medium body, heavy body, putty. • Cross-linking produces an increase in viscosity and the rapid development of elastic properties. • Setting time (10-12min) • Working time (5min) 20 hey bi contains • Limited shelf-life (tin compound catalyst) • The setting reaction is sensitive to heat and moisture. • Wait 20-30 minutes before pour for stress relaxation to occur. • About 50% of the dimensional change occurs during the first hour after setting, and the remaining 50% occurs throughout the 24 hours. o • Pouring time ranges between 30 minutes to within 6 hours. morefatighnatompared 46 nm 3. ADDITION SILICONE (TYPE 2) • Also known as polyvinylsiloxanes (PVS). of 2. CONDENSATION SILICONE • No odour • Clean ➢ Addition silicones are supplied at different viscosities: Cbfillercontent P • Low viscosity • Medium viscosity Isi b • Non-toxic shrinkage • High viscosity • Very hydrophobic • Condensation reaction – loss of alcohol causes shrinkage is • Limited shelf life (catalyst paste) a • Very high viscosity(putty) shrinkstutperior EI.EEI im • More rapid setting types riscosities 4 Consistencies: iii i 45 intear resistance no by product • Adequate tear resistance (withstand 300% tensile strain before tearing). elasticity 48 47 8 10/28/2023 • We need to mix it with latex free gloves, why? It will get contaminated and you will have unset material ◦Use latex free gloves or wash hand v well 3. ADDITION SILICONE 3. ADDITION SILICONE Composition and setting reaction: Composition and setting reaction: • No volatile by-product is formed, minimal changes occur during polymerization. Mg www.t.t composition • The material is supplied as a two-paste or two-putty system: • Nowadays, it is modified by adding Palladium to absorb H2. estradaopnYtin't sittin Newly all addition silicones contains surfactants and are “hydrophilic”. ➢ Other contains a low-molecular-weight silicone with silane hydrogens and reinforcing filler. • PVS are hydrophobic in nature. • • Hydrophilic silicones wet the oral tissues better than earlier hydrophobic materials and permit gypsum models and dies to be prepared with fewer air bubbles. To improve wetting of addition silicone material they used to spray “surfactant” turn hydrophobic material into hydrophilic material 3. ADDITION SILICONE nine similis • iÉ to material elastic back goes 50 asana gsiYii it i 49 aged 3. ADDITION SILICONE advantagescomparedto major Properties: • Surfactant: a surface tension agent that improves wettability of set PVS impression material and thus reduces voids formation in the recovered cast. • Less dimensional change and higher elastic recovery are improvements over condensation silicones. • Earlier! Spray the impression with the surfactant and then gently air dry! Improves the compatibility with the waterbased gypsum model materials. • The dimensional change in 24 hours is very low, about 0.1%. • The elastic recovery at the time of removal from the mouth is about 99.8%. Superior accuracy! • Coat the surface of the hard and/or soft tissues prior to recording an impression. • Instantaneous elastic recover – can be poured immediately. • New “hydrophilic polyvinyl siloxane” materials contain intrinsic surfactants that improve their wettability and facilitate the pouring process with gypsum materials. • Removal of addition silicones from undercut areas may present difficulties because of stiffness. 52 • Addition silicone will have elastic recovery ( rebound back to its original shape) BUT if you exceed the limit it causes plastic deformation ( permanent deformation) • Something that lie sin betweennpart of teh material return elastic and plastic is51 the vascoelastic ◦Meaning part of the material deformed permanently and part is return to original shape 3. ADDITION SILICONE 3. ADDITION SILICONE WARNING!! • • • • • • • • • • When mixing PVS putties, latex gloves should not be worn!! • Sulphur in the latex rubber reacts with chloroplatinic acid catalyst in PVS materials that inhibits polymerization. • Also consider: ➢ Rubber dam ➢ Haemostatic agents (Ferric salts) Addition reaction occurs between the vinyl and hydrogen groups with no by-product formation. • Hydrogen-containing siloxane + Vinyl-terminal siloxane + chloroplatinic acid => Silicone rubber. theprevious stable evenif stored canrepour it morethanonce IgIggfggfynginatd ➢ One contains a low-molecular-weight silicone with terminal vinyl groups, reinforcing filler, and a chloroplatinic acid catalyst. • Earlier! Best to wait for at least 60 minutes before pouring PVS impression – H2 production. f disadvantages ➢ Freshly-placed composites 54 No odour Rapid setting Clean Recently modified to be hydrophilic surface Addition reaction, dimensionally stable Longer shelf-life Adequate tear resistance High elastic recovery Can be poured multiple times incident amins ❖ Hydrophobic material ❖ Catalyst may be contaminated 53 9 10/28/2023 Q. What is teh polyetehr used for? Implants + bridges. Why? It’s rigid and elastic ◦It’s rigidity is more supeiror to addition silicone why? A more owable material might tear upon removal or when poured with gypsum product and seperate gypsum from impression since its rigid it might fracture Q. What is teh main advantage of polyetehr when compared to addition silicone (both are hydrophobic)? Polyetehr is more hydrophilic 4. POLYETHER 4. POLYETHER Composition and setting reaction: • The material is supplied as two pastes; base and catalyst. I • Polyether impression materials have properties similar to addition silicones. Puss us • They are more hydrophilic and exhibit good wetting properties even in a moist field. • The setting reaction is via cationic polymerization by opening of the reactive ethylene imine terminal rings to unite molecules with no by-product. • Older polyethers are rigid – caution if undercuts or long teeth are present. Perfectly used with dental implants. i injected throughane • automixing mine • Problems: a) fracture of delicate gypsum materials b) tear in thin areas (gingival sulcus). Available in low, medium and high viscosities. - Working time (2-3 min) - Setting time (5-6 min) grooves Ja's.IEgqatton rigiditymoresuperiorto aditionfilicone 56 adisadvantage additionvan 55 mightteartn.tnnggYtEue nobyproduct stable 4. POLYETHER 4. POLYETHER Manipulation: • A stock or a custom tray can be used, but in both cases a tray adhesive is needed. Properties: • The consistency is listed as medium viscosity but is high compared to medium-viscosity elastomeric impression materials. • The impression should be pulled slowly to break the seal and removed in a single stroke. r beit'sveryhydrophilic • The impression should not be stored in water. otani • Best poured within one hour after removal. Can extend to 48 hours. • Elastic recovery is slightly less than that for addition silicones. titis • Dimensional changes is higher than that for addition silicones. Polyether absorbs water and undergoes dimensional changes if stored in contact with water. ◦We have to be v careful when stored and disinfect since58 its hydrophilic we can’t reverse it VINYL SILOXANETHER (VINYL POLYETHER SILOXANE) 57 4. POLYETHER • Disadvantages • May cause allergic reaction due to the sulphonic acid ester • A new impression material that combines the properties of polyether and PVS. r additionsilicon • Low tear strength • Combines the ease of removal of PVS with the hydrophilicity of polyether. • Rapid setting time mighttearuponremoval adisadvantageforyoubutan advant • Stiff set material (sometimes hard to remove from mouth) 60 forthept 59 10 NOW we need to record the pateints occlusion Traditionally wax is not used, elastomric material is made to record occlusion never used for impression ◦Doenst record details like nish line ◦Has very short working and setting time 10/28/2023 DISINFECTION OF ELASTOMERS • First, rinse the impression with tap water immediately after removal from the patient’s mouth. notaccurate stable not crushed easily betweenyour • Second, spraying or immersion in an appropriate disinfecting agent. Follow the manufacturer’s instruction! fingers ifyouplace • A variety of disinfectants are available, such as: 1. Neutral glutaraldehyde 2. Acidified glutaraldehyde 3. Neutral phenolated glutaraldehyde 4. Neutral phenol 5. Iodophor 6. Chlorine dioxide ELASTOMERS FOR BITE REGISTRATION • Addition silicone and polyether materials are now commonly used to take bite registration. of anythingon top Q. Must be removed in a quick SNAP way, why? specific m record • Polyethers have similar properties except for higher dimensional changes and less elastic recovery. occluss details 61 settingtime s procedures may result in the loss of sothatthetechnician• Disinfection surfactant and can subsequently compromise the canfabricateit impression surface and cast quality. accurately • Chlorine-based disinfecting agents are less effective in removing the non-ionic surfactants from PVS compared with quaternary ammonium-based agents. • Standard disinfection regime of a 10-minute immersion in 1% sodium hypochlorite will have no effect on the dimensional stability of these materials. Rapid removal of an elastomeric impression material insures the lowest probability for plastic deformation. Remove the impression with a SNAP! most mn • Immersion in 2 % glutaraldehyde solution can be taken without a marked effect on their accuracy. tokeeptheelastomerFproperty ifyoukeepbending strugglingtoremove snapway 64 theimpr allstresses elastic recovery onceremoved bebuiltupwithinthe will rebound 63 impression itself back Shrinkage Impression itself is held over teh tray with peeformation tha shrinkage will be toward teh tray If the impression is not adhered to the try , it will shrink away from tray • Shrinkage occurs as the molecules move together to form polymer chains, and form cross-linkage. • All setting reactions generate polymerization shrinkage that is approximately 1-4 %. Addition of extensive fillers (50-70 % by weight) decreases this to tolerable levels of about 0.2 to 0.4 %. trayFimpression hasa veryshortwo it be stableposition requires a ✓ Provision of a uniform bulk of material ✓ Impression material adequately adheres to the impression tray ✓ Pouring the impression at the appropriate time ✓ Using optimum viscosity materials ✓ Adequate mixing ✓ Proper disinfection procedures SHRINKAGE b www.mia fine doesn'trecord absorbing water • To obtain maximum accuracy: material • Addition silicones are noted for their short working time, high stiffness, no measurable flow, and low dimensional changes. polyethert youcannotimmerse it for more 62 thantomins be it willstart We will use tray perforated to allow mesh nia Al retention and reinforce with chemical reaction by adding a thin layer of ….. impre nothing d if shrinkage towardsthe 66 itnot adheredtothetray tray itwillshrink awayfrom the QUALITATIVE RATING OF PHYSICAL AND MECHANICAL PROPERTIES OF ELASTOMERIC IMPRESSION MATERIALS Property Polysulphide Condensation Silicon Addition Silicon Polyether Working time Moderately long (5-7 mins) Short (3 mins) Short- moderate (2-4.5 mins) Short (2.5 mins) Setting time Moderately long (8-12 mins) Moderate (4-6 mins) Short moderate (4-6 mins) Short (4.5 mis) Shrinkage on setting Moderately high Moderately high Very low Low Permanent deformation in compression Moderately high Moderately high Very low Moderately high Flexibility during removal High Moderate Low moderate Low Tear strength (g/cm) Moderate high (2240 – 7410) Low moderate (2280 – 4370) Moderate (1640 – 5260) Low (1700 – 4800) Flow setting under small forces Moderately high Low Very low Very low Wettability by gypsum mixes Moderate Fair Good Good Gas evolution after setting Yes No No No Detail reproduction Excellent Excellent Excellent Excellent knowcomparisonbetween them stabilityofadditionsiliconis 99.81 65 0.2 11 shrinkage ay my 10/28/2023 How to minimize sinkage? ◦Do we prefer impression record in viscous or low viscosity? Viscous more ller ◦So majority of bulk of teh impression should be by viscous material ‣ Which is either putty or heavy body BUT we need to record the details by light body • = so a combo of heavy body for bulk and light body to record details Illia'sb • To minimize any effects of shrinkage, almost all impression materials are supplied as a combination of: 1. High viscosity and low viscosity pastes 2. Putty-wash option • Shrinking of most impression materials tends to be distorted ftp.iggrautlibitofneg.argaemed toward the impression tray. • This ultimately results in an impression that is slightly oversized. it works? plowbodytorecordfidelais Effybody•➢ How Low viscosity material (more shrinkage Fatty shrinkstowardsthetray SHRINKAGE SHRINKAGE MANAGEMENT due to less filler) is used to wet surfaces of preparation (better detail reproduction) and then a bulk fill of high viscosity material (low shrinkage but poor flow) is used. • Shrinkage is counteracted by slight expansion of the gypsum casting material. 67 G whats the IMPESSION TECHNIQUES 1. Putty/wash (I or II step-impression) 2. Dual-phase (heavy and light) infuriate Look at pic See teh adhesion of tray and impression, this causes shrinkage toward the tray you will end up having enlargement in size and this is compensated by the expansion of the gypsum 68 G WhatAre Inhtfghemed setting expansion CLASSIFICATION OF IMPRESSION TECHNIQUES mostviscous 3. Monophase (single-phase) Based on the position of the mouth ➢ Open mouth technique ➢ Closed mouth technique Based on the pressure applied ➢ Positive pressure ➢ Negative pressure ➢ Selective pressure 4. Dual-arch Tdontincompletedenture Based on the tray used ➢ Custom tray impressions ➢ Stock tray impressions patistfiritimattring y technique 70 tight costumtray I eschitkaynotcostenmpbatientlheuta ONE-STAGE PUTTY/WASH Iigtaffgy Tagging logit pplaudnigyytpbg.ly 69 • One step: tray is loaded with putty and pateint mouth is ready to receive and place light body and seat loaded tray on patients mouth • Q. What tray do we use? Stock metal tray? Because putty is most vicious not used with custom tray it will lock teh material ( very tight and viscous) 1. PUTTY/WASH TECHNIQUE 1. One-stage impression “twin-mix” or “squash” or “laminate” technique ➢ Putty & wash are recorded simultaneously ➢ Use a metal stock tray => the highly-filled putty is used to convert the stock tray into a closely fitting custom one b seatmittipt Inuset demon flight bftfeIIpthyseatinpt.mn 71 onestepopinupuityon tray 72 done 2 waynettyoset impression 12 • Q.do you expect teh prepared tooth and tray will yup have space of right bidy? No ◦Solved by creating space ‣ Space can be by adding sheet as a spacer for light bidy ‣ No spacer = no space for light body • • • • • Q. How to create spacer? TWO-STAGE PUTTY/WASH catalyst 1. PUTTY/WASH TECHNIQUE FEEL 2. Two-stage impression base a. Putty is recorded first (ensure to preserve the space for the light body!) b. Add a thin layer of light body over the set putty c. Use metal stock trays sheet mixth Spaces t ➢ Space is created for wash by: a. b. c. d. g EEE qq.gg 10/28/2023 2 stage means its done in two steps 1. Load putty on tray 2. Place in pateint mouth without light body 3. Removed from pateint s mouth and apply light body 4. Replace it in pateints mouth q Polyethylene spacer 2 mm wax spacer Record putty before teeth preparation Providing escape channels for wash 74 spacercanbe 73 Piggysheast TWO-STAGE PUTTY/WASH remorespaar Igisteryntil M app alloverb b removed with 76 Two-step ✓ Seating difficulties are overcome. ✓ Putty taken before tooth preparation can be used for temporization. • Light body gets displaced by the viscous putty. • Difficulty in re-seating the tray – uneven thickness of wash & shrinkage! • Multiple steps. • Outward flexion & rebound when using unrigid trays – undersized dies buccolingually! • Build-up of hydraulic pressure. • Contamination of the platinumcontaining catalyst impedes the setting of the light body. Indstopush Lightbodyaway 75 ONE VS. TWO-STAGE TECHNIQUE y Intimetinmatteridwiitiatx 78 If you have one step with no spacer usually teh light bdoy is squeezed from teh preepration itself ( seating pressure pushes the putty away) over baidu.tn ytsd dy • Outward flexion & rebound when using non rigid trays – under-sized dies buccolingually! spacerwa applieda right yegg Fight printing flight body Reggie stars One-step lightbody b morecomfortable difficulttoreinsert corrupt After its sets 77 more accurate compared tothe 2step 13 Dual phase is • one step • Major difference is we replace teh body with teh medium viscous ( forms bulk with minimum shrinkage) • Material of medium body comes in cartridge and injecting type of mixing so no need to load it in after mixing machine • Best tray option is custom tray or wont rock in pateints mouth 10/28/2023 1 step • Putty/wash technique should not be made with custom tray because: 1. The purpose of the putty is to fill the large space of a stock tray and minimize the volume of the wash material. 2. A close-fitting custom tray containing putty will be very difficult to seat without setting enormous stresses in the putty. 3. Bulky constructed custom tray!?? disadvantage beoftheshrinkage bi it doesn'trecord p thedetails the body heavy of only in cartridge injecting notusedforcrown bridgebutfor material 80comes cobalt chromium light bodypushedaway fromthemargin 79 Gsfnenitorieniginumannmining highestviscosity Imaterial II viscosity 3. MONOPHASE – (MEDIUM BODY) • Similar to dual-phase but using the same material to bulk fill the tray and being syringed over the preparation. putty replaced with step but morebflowable thanheavy 2. DUAL-PHASE TECHNIQUE withminimum formsbulk shrinkage so more • Addition silicone and polyether are well suited for this technique. ityb as • The most accurate impression is usually achieved using heavy body and light body addition silicone in conjunction with a rigid custom tray and a meticulous clinical technique. ftp.ggghy Shrinkage • Best to be used in a special tray to reduce shrinkage. + Minty => • Problems of combining materials is overcome! But detail reproduction is inferior to light body materials. taste 82 f putty weuse I loadthetraywithheavybody heavybody Titian's its arigidmaterial 41 metaltray is an option but Best81 mo optioncustomtray no locking lightbodyinptsmonth YÉiIman b intoptsmonth tepffggggy recordinfifpionsintergo 4. DUAL-ARCH TECHNIQUE I 4. DUAL-ARCH TECHNIQUE • Closed-mouth technique, double-bite technique!• All others are open mouth • PVS or polyether impression materials can be used. a • Captures an impression of the prepared tooth, the adjacent and opposing teeth, and records the relationship between them in maximal intercuspation without the need for an inter-occlusal record, all in a singlestep procedure! • Die-stone is poured firstly on prepared teeth side then to opposite arch. • Trays: full or partial arch, metal or plastic, possessing side walls or sideless. Iostly innerpart finishline 84 fullmouthorbridges not very specific gyrating.ge SstadetmPgyringntWaiintshYne closed only 1crownprep Eisen it imiyat.ggiytkur3deda 83 month techm f 14 behindit 10/28/2023 can'tuseif there's a prep lgrgeeitybgysi.bg integer'ebowith theseating Indications: 4. DUAL-ARCH TECHNIQUE Single-unit or short span FPD bounded by intact and opposed teeth. Stable, reproducible and clear ICP. Advantages ✓Less impression material is needed ✓Accurate recording of ICP ✓Less time! ✓Less gagging Disadvantages 4. DUALARCH TECHNIQUE ✓Tray is not rigid ✓Shallow impressions difficult to pour & mount ✓Limited to one casting per quadrant Co-operative patient able to close directly into ICP. Tray does not contact axial tooth surfaces, or the adjacent tissues on closure. Enough space for the connector bar behind the last molar. Technician familiar with the specific pouring and mounting procedures. ✓The distribution of impression material is not uniform Canine guidance or posterior disocclusion, angle class I occlusion. Canine should be registered in the impression to avoid the potential of occlusal interferences. 86 DIGITAL IMPRESSIONS 85 DIGITAL IMPRESSIONS 88 87 asaccurateas convent forpls fu'Erynvenient ELIMINATING STEPS AT THE OFFICE dig F1 DIGITAL IMPRESSIONS I thigh tied impression Tray Selection Dispensing Material Disinfection Setting of Material Shipping 90 89 15 10/28/2023 REFERENCES • Applied Dental Materials – John F. McCabe and Angus Walls (Ninth Edition), chapters 16 and 19. • Contemporary Fixed Prosthodontics – Rosenstiel, Land, Fujimoto (Fifth Edition), chapter 14. • A review of contemporary impression materials and techniques – Terry E. Donovan, Winston W.L. Chee. The Dental Clinics of North America. • Crowns and other extra-coronal restorations: Impression materials and technique - R. W. Wassell1 D. Barker and A. W. G. Walls. British Dental Journal. 91 16