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 2 0 obj What are the types of elastomeric impression materials”\? Of these, addition silicone and polyether are … MATERIALS IN DENTISTRY. This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. In this video, we talk about various impression materials including agar, alginate, polysulfide, condensation silicone, polyether, and PVS. The fi gure shows a tear specimen being tested. Have pleasant taste, odor and esthetic color. They reproduce an imprint faithfully, providing details of a high definition despite the presence of undercuts. ! 4 - Elastic Impression Materials-2.pdf - SUMMARY OF WHAT WE NEED TO KNOW(below tis you will find all notes from the lecture What you need to know What. endobj The most significant work in this area since 1966 is reviewed below. o went to copper peroxide gave less problems but no advantage o need to poor it right away polysulfide rubber o don’t leave out too long or else it would mix automatically / accidentally polysulfide rubber mixing o mix with a “metal pen” grasp then flat o had to load a syringe with this tray prolems with poor mxing o mixing was a problem and it was hard to know o became apparent only after you removed the tray o good mixing is a concern with hand mixing systems condenstation silicone setting rxn o next material to come along o cleaner / better to work with o x-­‐link xn of silolyl chains o stannous octoate catalys à multiple x-­‐link point o split off alcohol / alcohol byproduct à dimensional change o a condensation rxn with this byproduct o lose dimensional stability though polyvinyl siloxane (addition silicone) ingredients o change it to an addition reaction à many advantages o vinyl grps along the chains à it’s a free radical rxn à o less shrinkage o no biproduct just x-­‐linked polymer addition silicone (vinyl polysiloxine) setting rxn o catalyzed by platinum salt to give x-­‐link structure o but no biproduct o rapid à nice x-­‐link o good dimensional stability with time o once it set à initial shrinkage and that s it à little after that polyvinyl siloxane – out-­‐gassing (problems) o platinum catylist would split off hydrogen à used to get a lot of bubbles esp when pouring stone o palladium absorbed the hydrogen and that got rid of this problem o we have this well matured system now with PVS – less problems polyether setting rxn o another competitor for crown & bridge products o opening ring structure gives you less shrinkage o same with epoxies (use re-­‐opening procedure) o gives a rapid and complete convient rxn • • • • • • • • elastomeric impression materials o working times – they set rapidly o compared to original polysuflfide – better faster setting with polyether working time characteristics o poly ether = very much a snap set (more so than A-­‐silicone) but both set fast o polysulfide would come way out here and way out here? Hydrocolloid impression materials used in dentistry are based on colloidal suspensions of polysaccharides in water. They reproduce an imprint faithfully, providing details of a high definition despite the presence of undercuts. Find answers and explanations to over 1.2 million textbook exercises. Elastic impression materials are those that remain in an elas- tic or flexible state after they have been removed from the mouth. per minute. After the preparation, they are placed inside impression trays. ELASTIC Material susceptible to being stretched compressed or distorted and then tending to resume the original shape. 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. What is the dimensional stability over time of polysulfide, silicone, 6. • § dimension change is greatest § shrinks the most o ?Heavy body § is almost like a putty o ?Putty setting reaction & dimensional stability o polysulfide rubber & condensation silicone § both have biproducts of rxn (water & alcohol, respectively) § both have dimensional Instability overtime § longest set time o polysulfide (aka PS) § lead peroxide accelerator / catalyst which used to x-­‐link sulfide groups § x-­‐linking sulfide groups à smelly like Hsulfide § lack of elastic properties § restorations may fit die but not patient § used to use lead peroxides which split off water § it’s a condensation rxn or step growth polymerization § implication is that if u leave it for a long time à water biproduct out à shrinkage § accurate but only for a short period of time § longest to set § low elastic modulus à good for undercuts à easy removal o condensation silicone (aka Silicone) § next material to come along § cleaner / better to work with § x-­‐link xn of silolyl chains § stannous octoate catalys à multiple x-­link point § split off alcohol / alcohol byproduct à dimensional Instability § second longest set time o addition silicones (aka PVS, A-­‐Silicone, A-­‐S, VPS) § change it to an addition reaction à many advantages § vinyl grps along the chains à it’s a free radical rxn à § less shrinkage § no biproduct just x-­‐linked polymer § catalyzed by platinum salt to give x-­‐link structure § but no biproduct § rapid à nice x-­‐link § good dimensional stability with time § once it set à initial shrinkage and that s it à little after that § fastest set time § stiff à high elastic moduls à difficult removal for undercuts o poly-­‐ether (aka PE) § another competitor for crown & bridge products § opening ring structure gives you less shrinkage § same with epoxies (use re-­‐opening procedure) § gives a rapid and complete convient rxn § 2nd fastest set time § stiff à high elastic moduls à difficult removal for undercuts dimensional stability and linear dimensonal change with time o A-­‐S > PE > PS > silicone Shrinkage in tray à what happens to die? How does shrinkage toward the tray influence accuracy of the die for Applied Dental Materials Ninth Edition John F. McCabe BSc, PhD, DSc Professor of Dental Materials Science Newcastle University Angus W.G. This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. This textbook covers all aspects of materials science relevant to the practice of dentistry. It is not intended to replace your Dental Visit. In the light of these facts, a study was planned to evaluate the elastic recovery of various elastomeric impression materials on autoclaving and comparing it to the currently practiced method of chemical disinfection. Try our expert-verified textbook solutions with step-by-step explanations. <>/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>> Why is it important to measure impression material creep behavior? %���� 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. § Having long polymer chains helps to à dilute out shrinkage with particle § Diluter particle also dilutes shrinkage o Heavier consistency à less shrinkage o Light body shrinks more / just depends on filler Impression materials / key properties Elastomeric impressions o Can use light body first then fill tray with heavy body o As it sets, still have shrinkage o Shrink toward bonded area (like composite) / shrink toward the tray o There is adhesive on the tray and also mechanical retention – shrinks in that direction § So dies are oversized usually § Short occlusally? Elastic Impression Materials HENKE-PRESS – Application syringe for elastic impression materials . One brand from each chemical group was selected to allow relative ranking of … 19. ELASTIC Material susceptible to being stretched compressed or distorted and then tending to resume the original shape. Different types of impression materials are available, which vary in their properties. of the best impression material from elasticity aspect. Not contain any toxic or irritating ingredients. ! The most significant work in this area since 1966 is reviewed below. Not sure what viscoelastic means? the materials compare? 1. Non-elastic Impression Materials 17.1 Introduction. The greater in the permanent distortion of the impression material if greater the depth of the undercut, for all impression materials. Since addition silicones do not produce a volatile by-product during polymerization, very small dimensional changes occur on setting. They reproduce an imprint faithfully, providing details of a high definition despite the presence of undercuts. • • • • • • o Many components o Take a polymer à cross link it à make it elastic o Problem is that polymerization leads to shrinkage à solution? ���n�:d����>$�>2&�\���IW����2�;��o5Ӻ���4�u��ؚxW���aw�g������b?�`�O �S��zd�Y���ʌ���V�xq��;���j��O�=];EZ5�w0"��{:˹yrc$;Ȏ%|���ؾ�Co9���缿�P�~j���Hs^��A|H��ħ5$��H�v�/l#�ZZ�\�eUפ]st�3{���U�߷�;���i�O߄��ۨ������V@k�eC}�&lϛ ��y����ً�0����4���u��U�}ў�����F_"XC�8�U��� ����04�d""�u%OVY t�\�������RF��МF�bh�8);څ��m����i�r>�v��y�xjZ_�sr_�wj_Q����%�紾�j�%�a�v%��70�,@ Be easy to use with minimum equipments. Many impression materials have an elastic recovery of more than 99%. Only a proper dental Checkup by a professional in person can help diagnose the problem you are suffering from and help give you the required treatment. They could be described as possessing rubbery characteristics. • • • • • • • § 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. The impression should be taken using an elastomeric impression material (poly-vinylsiloxame or polyether rubber) in accordance with the manufacturer’s direc- tions. Elastic impression materials. Elastomeric impression materials are in common use. In hydrocolloid, polysulfide or silicone, the molar crown preparation was the most sensitive to dif- ferences between the materials. View 4 - Elastic Impression Materials-2.pdf from BIOLOGY 205 at University of Windsor. 2/23/2016 17. • • In contrast, use of addition silicone as an impression material permits easy removal once the impression is set due to its more favorable modulus of elasticity and therefore has also been recommended as a preferred material for implant impressions using direct technique [13, 39, 40]. Elastic materials have a soft consistency but after setting, they become elastic. This textbook covers all aspects of materials science relevant to the practice of dentistry. • § 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. 3 0 obj Does high viscoelasticity mean stiff? Numerically, it is the ratio of stress to strain. A method of measuring the elastic recovery of impression materials after the application of a strain applied at the setting time is described. Abstract This study was conducted to evaluate the methods used for measuring the elastic recovery of various elastomeric impression materials. Compound impression can be added or corrected. Tear Energy (J/m^2): Impressions must resist tearing upon removal from the mouth and when separating the model from the impression. polyvinyl siloxane and polyether? Be economical. Have adequate shelf life for storage and distribution. 1. Y����-��9�t�~��`{9�T%Z���,G��I���`���a*p����+Q���B�#�V`͔}"$�}��Yv6\x�=�����ۃ�/|$ˠdy��(V��e-��`���J. of elastic impression materials. All “elastic impression materials” have the same gener al type of formulation. They are capable of accurately reproducing both the hard and soft structures of the mouth, including the undercuts and interproximal spaces. Cresson3 suggested the revision of the testing procedure for compressive strengths of dental elastic impression materials that would apply the load at the rate of 18,000 Gm. To separate cast from the impression, use warm water. Impression materials o Want to remove the tray very fast o Distortion related to removal rate o Fast removal better (vs. slow) o True of all impression materials o Slow removal à more strain Elastomeric materials o Some materials flow easy à Light body hard to keep in a tray § Polyether/PVS have pseudoplastic behavior (want to hold there shape – need force to move them) o Mixing is also important § Polysulfide à Mix by hand à very sticky § Now we have mixing systems à need force to extrude the material down the tip § That is why you have machines that need to be big § But its great for mixing – 250x mxing Types of impression procedures o Custom tray technique – best accuracy o Can get away with stock tray – bc materials so good now o Putty wash technique o Double impression technique o Or use heavy / light body – combo of things Heavy/light (tray wash) – multiple slides o Extrude a bit to begin with o Get busy à light body in wash o Fill the tray à seat it à leave for “set time” o Can use putty with a spacer o He is just illustrating amore common technique o Light body vs. medium or heavy used (tray/wash) technique o Can even use putty Factors in impression dimensional accuracy o Historically used to use special trays because of all the shrinkage § They used to use wax spacers – still the best way to go but not used that much anymore § Was the best for accuracy and uniform thickness of materials o Because of shrinkage don’t want too much material § 4mm is the max o but don’t want too little material § once material too thin it gets stuck on tooth à stretches à won’t recover elastically as well • • • • independent responses of elastic impression materials under load and provides a better understanding of their mechanical properties. 19.1 Bondoc2 measured the percent per-manent deformation and strain in compres- sion for silicone-based materials according to American Dental Association Specification no. This updated thoroughly revised and revamped edition would serve the students, teachers and professionals associated with clinical dentistry. Current Impression Materials Rei~bick1 stated either high or low viscosity materials produced the same degree of accuracy and stability. • In hydrocolloid, polysulfide or silicone, the molar crown preparation was the most sensitive to dif- ferences between the materials. 4 0 obj Skinner et al.4 and Phillips5 point out the importance of the rate of deformation on the technic of handling alginate hydrocolloids. stream (Table I lists brand names and manufacturers). Impression Plaster 3. Elastic impression materials are used more extensively than rigid materials, because elastic materials flex from tissue undercuts when removed from the mouth, whereas rigid materials cannot. of "elastic" impression materials are ob-tained from tests similar to those described in American Dental Association Specification no. MATERIAL AND METHODS Parti A total of five elastomeric impression materials were evaluated: two polysufides (one lead catalyzed and one copper catalyzed), two silicones (one con- densation polymerization and one addition polymer- ization), and one polyether. The higher this value, the more tear resistant is the material. ! Comparative elasticity tests for elastomeric (non putty) impression materials Blomberg, P. A. H.; Mahmood, S.; Smales, R. J.; Makinson, O. F. 1992-10-01 00:00:00 materials. 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 … The impression taken should be highly precise, thus, requiring specific care when manipulatingthese materials. Elastomers refer to a group of rubbery polymers, which are either chemically or physically cross-linked. They are easy to handle and their accuracy is pretty good. independent responses of elastic impression materials under load and provides a better understanding of their mechanical properties. Current Impression Materials Rei~bick1 stated either high or low viscosity materials produced the same degree of accuracy and stability. They all have a flexible matrix (the continuous phase) that is filled with extender or filler (the dispersed phase) to minimize the effects of polymerization shrinkage during setting on the overall accuracy and dimensional stability of the system. After the preparation, they are placed inside impression trays. • • Course Hero is not sponsored or endorsed by any college or university. Material susceptible to being stretched compressed or distorted and then tending to resume the original shape. Elastic impression materials include reversible (agar-agar), irreversible (alginate) hydrocolloids and synthetic elastomers (polysulfides, polyethers, silicones). Elastic impression compositions Download PDF Info Publication number US2359512A. Dr Mohd Haidil Akmal Mahdan DDS (USM),Ph.D (TMDU,Tokyo) 25th June 2015 Contents… • Definitions • Classification • Impression plaster • Impression compound • Zinc oxide eugenol • Impression waxes Definitions.. The higher this value, the more tear resistant is the material. All NOTES We will discuss differences in elast materials References What we need to know for test Problem anaylisis o Need to capture the detail and have acurcy for casting / implants o Many areas of errors o Investing and casting are major changes o Prepared tooth with 8mm diameter for lets say a molar § Impression has 0.5 % accuracy realative to 8000 microsn à 40 microns à 20 microns on mesial vs. distal or buccal vs. lingual on the crown prep à so you are fine but not that good § But if you have implants on oppositie sides of the arch à 80,000 microns (not just 8,000) § So need even more accuracy § But for a single tooth or 3 unit bridge not a big problem classification – we will talk about types that polymerize Slide 6 -­‐ classification o Elastic à § Hydrocolilds à • Agar – need heating apparatus • Alginate – o He said something about ones that had enough accuracy for crown and bridge but there’s no pointer so don’t know what he’s talking about Impression objective o We want to take prepared teeth à impression à nice replica with tissue below finish line o So you know the right contour of the die relative to ceramic and metal Dies from impression o Making dies o Stone or epoxy dies o If stone die à need to factor in investment expansion of die stone o Epoxy à need to allow for more expansion (epoxy shrinks so need to consider) o Appplying the die spacer to make room for cement General forumlation • = visco-­‐elastic deformation? Alginates are the most used impression materials in all dental practices. %PDF-1.5 Elastic Impression Materials - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. Compatible with cast & die materials & does not need separating medium. 4. 1 0 obj Unformatted text preview: SUMMARY OF WHAT WE NEED TO KNOW (below tis you will find all notes from the lecture) What you need to know This instrument has been called a Comprheometer. Generally, they can be easily stretched and rapidly recover their original dimensions when … This updated thoroughly revised and revamped edition would serve the students, teachers and professionals associated with clinical dentistry. Full Document, University of the East, Manila • ENGLISH 20. This instrument has been called a Comprheometer. 2. 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