Tear Energy (J/m^2): Impressions must resist tearing upon removal from the mouth and when separating the model from the impression. There are four kinds of Elastomers used as impression materials viz., polysulfide, condensation silicone, addition silicone and polyether. The impression should be taken using an elastomeric impression material (poly-vinylsiloxame or polyether rubber) in accordance with the manufacturer’s direc- tions. ! They could be described as possessing rubbery characteristics. The most significant work in this area since 1966 is reviewed below. Oui, effectivement j'avais vu ce lien et je ne me souviens pas avoir vu ce que je cherchais pour 400°C (j'ai interpolé pour le 316L et en supposant que la diminution de limite d'élasticité était linéaire avec la température mais je ne peux en être sûr, j'obtiens 89MPa par cette méthode). This updated thoroughly revised and revamped edition would serve the students, teachers and professionals associated with clinical dentistry. This textbook covers all aspects of materials science relevant to the practice of dentistry. The plaster should be mixed with water or an anti-expansion solution in the ratio of 100g to 50-60ml. of the best impression material from elasticity aspect. They are capable of accurately reproducing both the hard and soft structures of the mouth, including the undercuts and interproximal spaces. After the preparation, they are placed inside impression trays. ! • • • • What does 0.1% shrinkage mean clinically? Reproduction of oral detail The rubber impression materials are capable of reproducing detail more accurately than can be transferred to the stone die or cast ELASTICITY Elastic properties of elastomeric impression materials improve with an increase in curing time in the mouth Permanent deformation following strain in compression increases in following order- addition silicone, … ! • • o Don’t want bubbles in the dies § And also when you put matterial on stone § so die stone will wet into it and you won’t have bubbles in dies o Want good wettability with tissue and with water o Need modifications to achieve this Relative wettability of polymeric impression materials o Polyvinyl siloxane: High contact angle with water à need to modify à lower contact angle so it can compete with polyether o PE better > than PVS (AS) o AS used to be hydrophobic (high contact angle) o PE > hydrophilic AS (modified) > PS > hydrophobic AS > CS (condensation silicone) Contact angles on moiste dentin… o Want to lower Preparation pretreatments o Want to we the tooth structure o Can add a surfactant to wet the tooth structure Change with surfacting applicatoin o Light body material on the tooth o B4 materal helps it slide down the tooth surface o Get more detail by using this B4 stuff – more wetability – lower contact angle Recommending disinfection techniques o Don’t want to swell the impression material o Don’t apply more than 10-­‐ minutes or else get swelling o Polyether à use chorline type compounds / iodifores o Gluteraldehydes can’t be used with polyether Web based impression update o Can find this overview Digital impression – multiple slides o Lab builds the dye to replicate what you’ve captured o Lava system is good – oral system from MIT § 20 scans perminute à comes up with a dye § then can get the CAD CAM o cadent itero § lets you know if you have clearance o used to have to put powder on teeth to give computer an opque surface but now u don’t need that § ciraq used to need that and some still do mouthguard elastomers o ethyl vinyl acetate o need 3mm thick for sports o heat process – drape over a die o 4mm à heat à become 3mm o impact force à energy to distort material à tooth protected bc displacement is limited o can use impact tester with a weight that drops down o 2010 study comparing the air / water / artificial saliva systems § polyshock sets the standard for these materials § it’s a combo of the eva and proform ...View US2359512A US479446A US47944643A US2359512A US 2359512 A US2359512 A US 2359512A US 479446 A US479446 A US 479446A US 47944643 A US47944643 A US 47944643A US 2359512 A US2359512 A US 2359512A Authority US United States Prior art keywords alginate impression water soluble insoluble … • Once the material has set, the Positioning Screws are loosened, and the impression is removed. § It wants to engage burr marks and undercuts Elastomeric impression materials o Dimensional stability in 24 hrs (longterm) § Advantage to the A-­‐S and PE § Nice degree of accuracy o Linear dimensional change with time § Same à advantage to A-­‐S and PE § A-­‐S > PE > PS > silicone § Points out that some of it is time in hours § So really just need to poor the impression quickly o Impression à temporary à poor (best way) – just do it quick o Now we can just take the impressiona and ship it to the lab bc of PE and A-­‐S (PVS) Impression material shrinkage – multiple slides o Shrink toward tray à BL/MD direction shrinkage à die is wider o But also have to consider the material dimension and shrinkage § Along certain directions u get more shrinkage § May end up with a short die vs. what was inteded § à OG die will be shorter o Gets worse when you are doing abutments § In areas of these changes, molar tooth buccal margin is usually open (a common area of error) o Polysulfide low elastic modulus à Patient with a lot of undercuts à polysulfide is a great material • This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. 2 0 obj F i n g e r 1, M. K o m a t s u 2 1Department of Prosthetic Dentistry and Dental Technology, Dental School of the RWTH, Aachen, W, Germany and 2Department of of elastic dental Operative Dentistry, Dental School, Tohuku University, Sendal, Japan impression materials Finger W, Komatsu M. Elastic and plastic properties of elastic dental impression materials. Walls BDS, PhD, FDSRCS Elastic impression materials are those that remain in an elas- tic or flexible state after they have been removed from the mouth. Dentistry and Dental Materials, 2. Tear Energy (J/m^2): Impressions must resist tearing upon removal from the mouth and when separating the model from the impression. Compatible with cast & die materials & does not need separating medium. SUMMARY OF WHAT WE NEED TO KNOW (below tis you will find all notes from the lecture) What Why is it important to measure impression material creep behavior? 6 CONTRAINTES ET DÉFORMATIONS 6.1 CHARGEMENT UNIAXIAL 6.1.1 Introduction Lorsqu'un corps est soumis à des forces extérieures, il y a un changement de sa forme ou de ses In this video, we talk about various impression materials including agar, alginate, polysulfide, condensation silicone, polyether, and PVS. Different types of impression materials are available, which vary in their properties. (Table I lists brand names and manufacturers). Basic Dental Materials by Manappallil PDF, ePub eBook D0wnl0ad Serves as a keystone to the understanding of Basic Dental Materials in general and their application to clinical dentistry in particular. • EASY TO DELIVER Thermo Clone impression material is available in 50 ml cartridges or 380 ml jumbo cartridges for automatic mixing. Compound impression can be added or corrected. The creep compliance is the time-dependent relationship of the strain to stress ratio of a material under load. <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/Annots[ 15 0 R] /MediaBox[ 0 0 595.32 841.92] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> View 4 - Elastic Impression Materials-2.pdf from BIOLOGY 205 at University of Windsor. <> The creep compliance is the time-dependent relationship of the strain to stress ratio of a material under load. Applied Dental Materials Ninth Edition John F. McCabe BSc, PhD, DSc Professor of Dental Materials Science Newcastle University Angus W.G. of elastic impression materials. • • • • Creep behavior o With viscoelastic elements, the longer the tray stays in the mouth à viscoelastic element works for a long time à more permanent deformation and less rebound à thus want to remove impression quickly Tear strength of the different types o Don’t want tear in sulcus o PS Rubber (best) >>> CS > AS (PVS) > PE (worst, tears easily) Elastic modulus o PE, AS – high elastic modulus – bounce back -­‐ bad for undercuts, hard to remove impression o Its important for undercuts and ease of removal o PS rubber low modulus and easier to remove Viscoelastic o Stiff: AS and PE have little changes à will come back to normal à gives you good dies o Silicone (condensation) and PS (the worst) have deformation with a load o ????? • • • • • • • § permanent deformation o need to balance shrinkage vs. absorbing deformation à which is why custom tray is the ideal polysulfide rubber o this is an original material o lead peroxide accelerator / catalyst which used to x-­‐link sulfide groups o x-­‐linking sulfide groups à smelly like Hsulfide polysulfde rubber setting rxn o used to use lead peroxides which split off water o it’s a condensation rxn or step growth polymerization o implication is that if u leave it for a long time à water comes out à shrinkage o accurate but only for a short period of time polysulfide rubber stting rxn o led peroxide used to stane clothing à problems with patient etc. ! 4 (December 2015) 768 Modified procedure of indirect pattern for fabricating cast post and core Conflict of Interest Statement: The 3M - ESPE - US impression material was used. The operating principle involves the application of a fixed compressive strain and the resulting stress is measured. Elastic impression materials are capable of accurately reproducing both the hard and the soft structures of the mouth including the undercut areas and interproximal spaces 4. They are essential in daily clinical practice in all dental specialisations: conservative, cosmetic, aesthetic, prostheses, orthodontics, implantology and pediatric dentistry. Impression Plaster 3. • Be easy to use with minimum equipments. Skinner et al.4 and Phillips5 point out the importance of the rate of deformation on the technic of handling alginate hydrocolloids. § May have to cut out the impression with polyvinyl siloxane § PE and PVS (A-­‐S) is very stif o Lowe elastic modulus and high tear strength good sometimes with polysulfide Complex stressed during impression o Material sticks to tooth à dimensional changes possible Modeling viscoelastic behavior o Can model this with springs and dash pots o Measure stretch and recovery Viscoelastic behavior medles o Can only pull the shock absorber at a certain rate Parallel elements o Dsashpot = a shock absorber o In parallel spring pulls on dashpot but it takes longer Model combinations in compression ~ real world o Once it changes dimension doesn’t want to come back o Everything else recovered elastically o There is an amount of permanent deformation Creep = visoelastic flow eprmanent set o Viscoelastic à you ckeep the load on à get deformation and won’t recover o Don’t want the viscous element to act very long à that’s why you remove it very quickly o Oly come a little bit up the curve on the graph Creep compliance o Spring element with a polyether à if u remove it will ome back o Polysulfide gets the most change o These materials much better with elastic behavior Comparitive physical prperieis o Very low values are good o Measure by putting the weight on à does it recover à how much Tear strenth improtant o Don’t want a tear down in the sulcus that you don’t see and don’t remove o Repsonse to these materials over a few days is equisite o Check in the mouth and check impression Cell response o Look at cell viability o Polyether is the worst – nice properties but don’t leave it in the sulcus o Tremendous inflamation and bone loss may result o PS rubber not bad at all < alginate < ZOE paste < PE (worst) Tear strength testing Tear strength test o Monitor how much force it takes etc. ELASTIC Material susceptible to being stretched compressed or distorted and then tending to resume the original shape. They are easy to handle and their accuracy is pretty good. ELASTIC Impression MATERIALS ABHISHEK KAVLEKAR 3. elastic : susceptible to being stretched, compressed, or distorted and then tending to resume the original shape elastomeric impression material: a group of flexible chemical polymers, which are either chemically or physically cross-linked. Non-elastic Impression Materials 17.1 Introduction. Why is the elastic modulus of the set impression material important 0.1% shrinkage o 0.1% x 8000 microns for 1 tooth à 8 microns à 4 microns on mesial or distal o There is adhesive on the tray and also mechanical retention – shrinks in that direction o So dies are oversized usually o Short on occlusal ? Elastic impression materials are capable of accurately reproducing both the hard and the soft structures of the mouth including the undercut areas and interproximal 2/23/2016 17. 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