Elastic impression materials/ dentistry online

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Elastic impression materials/ dentistry online

  1. 1. ELASTIC IMPRESSION MATERIALS INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Contents • Introduction • History • Definition and classifications • Ideal requirements • Impression materials and techniques - Elastomeric materials - Hydrocolloids • Latest advances • Conclusions • Referenceswww.indiandentalacademy.com
  3. 3. “I often say that when you can measure what you are speaking about, and can express it in numbers, you know something about it; but when you cannot measure it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you scarcely in your thoughts advanced to the stage of science, whatever the matter may be.” LORD KELVIN www.indiandentalacademy.com
  4. 4. History: • 18th and 19th century bees wax. • 1782 William Rae – used wax with POP. • 1925-28 Development of Hydrocolloids. • 1930 – A W Ward and E B Kelly introduced ZOE • 1936-40 Alginate by S.William Wilding. • 1950 introduction of elastomers. • 1960 Introduction of polyether in Germany. • 1988 Latest addition and light cured elastomers. • 1990-2000 New auto devices and delivery systems. • Research continues…. www.indiandentalacademy.com
  5. 5. DEFINITIONwww.indiandentalacademy.com
  6. 6. “An impression is essentially a negative or reverse replica of any entity. In dentistry, this replica is of the teeth and its supporting and surrounding structures.” www.indiandentalacademy.com
  7. 7. www.indiandentalacademy.com
  8. 8. 1. By generic chemical name: Silicone material or ZOE or commercial brand names. 2. By the manner in which they harden or set Chemical / irreversible Temp / reversible • Plaster of Paris • ZOE • Alginate • Elastomers Thermoplastic • Impression compound • Wax •Agar www.indiandentalacademy.com
  9. 9. 3. According to the ability of the set material to be withdraw over undercuts :Elastic impression materials Non-elastic or Rigid impression materials  Agar  Alginate  Impression compound  ZOE Hydrocolloid Rubbers  Polysulfide.  Poly silicones.  Polyether. www.indiandentalacademy.com
  10. 10. 4. According to the use of the materials in dentistry A) Materials used for obtaining impression of dentulous mouth  Alginate  Agar  Non-aqueous Elastomers B) Materials used for obtaining Impression of edentulous mouth: • Impression Compound • Impression Plaster • Zinc Oxide eugenol • Wax www.indiandentalacademy.com
  11. 11. MucocompressiveMucostatic 5. According to the viscosity or tissue displacement: - Impression plaster - Impression - Agar Compound - Alginate - Putty elastomers www.indiandentalacademy.com
  12. 12. Ideal Requirements of DentalIdeal Requirements of Dental Impression MaterialsImpression Materials www.indiandentalacademy.com
  13. 13. 1. Fluid enough to adapt to the oral tissues 2. Viscous enough to be contained in the tray 3. In mouth should transform (set) into a rubbery or rigid solid in a reasonable amount of time: setting time less than 7min 4. Set impression should not distort or tear when removed from mouth 5. Impressions made be dimensionally stable until the cast can be poured 6. Impression made should maintain dimensional stability after removal of cast to enable making of a second or third cast from same impression 7. Biocompatible 8. Material, associated processing equipment, and processing time should be cost effective www.indiandentalacademy.com
  14. 14. Elastomers or Rubber base Impression materials www.indiandentalacademy.com
  15. 15. • Soft and rubber-like & are known as elastomers or synthetic rubbers. • As per ADA Sp. No. 19 - non-aqueous elastomeric dental impression materials. • Liquid polymers which are converted into solid rubber at room temperature www.indiandentalacademy.com
  16. 16. Types: I. According to chemistry 1) Polysulfides 2) Polysilicones – condensation & addition 3) Polyether II. According to Viscosity 1) Light body or syringe consistency 2) Medium or regular body 3) Heavy body or tray consistency 4) Very heavy body or putty consistency www.indiandentalacademy.com
  17. 17. General Properties:  Excellent reproduction of surface details  Generally hydrophobic (except poly ether)  Good elastic properties (repeated pouring is possible)  Dimensional inaccuracies are lower but exist due to various reasons  Excellent tear strength.  Extended shelf-life  Generally higher cost  Requires tray adhesive or mechanical interlocking www.indiandentalacademy.com
  18. 18. CHARACTERSTICS • Rheological properties- play major role • Viscous pastes- setting reaction- viscoelastic properties • Viscoelasticity describes dependence of an impression materials response to the speed of removal • Maxwell-Voigt viscoelastic model www.indiandentalacademy.com
  19. 19. MAXWELL-VOIGT MODEL www.indiandentalacademy.com
  20. 20. Uses: 1. Impression material for all applications including - Fixed partial dentures - Dentures and edentulous impressions 2. Border moulding of special trays (poly ether) 3. Bite registration 4. As duplicating material for refractory casts • All elastomers - two paste systems (base & catalyst) • Putty consistency – supplied in jars Supplied as: www.indiandentalacademy.com
  21. 21. POLY SULFIDES: Ist elastomer to be introduced mercaptan/Thiokol www.indiandentalacademy.com
  22. 22. Composition: Base Paste: Liquid Polysulfide Polymer - 80 to 85 % Inert fillers (Titanium dioxide, zinc sulfate - 16 to 18 % copper carbonate or silica) Reactor Paste Lead dioxide - 60 to 68 % Dibutyl phthalate - 30 to 35 % Sulfur - 3 % Other substances like Magnesium stearate (retarder) & deodorants - 2 % www.indiandentalacademy.com
  23. 23. Tray adhesive: Butyl rubber or styrene/acrylonitrile dissolved in a volatile solvent such as chloroform or a ketone. www.indiandentalacademy.com
  24. 24. Chemistry and Setting Reactions The lead dioxide reacts with the poly sulfide polymer  Chain lengthening by oxidation of the terminal -SH groups  Cross-linking by oxidation of the pendant -SH groups Exothermic reaction - 3 to 40 C rise in temp. It is accelerated by heat and moisture PbO2 + S HS - R- SH HS - R-S-S-R-SH + H2O Mercaptan + Lead dioxide Poly sulfide + Water T-butyl hydro peroxide – alternative to PbO2www.indiandentalacademy.com
  25. 25. 1. Unpleasant odor and colour - stains linen & messy to work with 2. Extremely viscous and sticky - mixing is difficult 3. Mixing time is 45 seconds 4. Long setting time of 12.5 (at 370 C) - Patient discomfort 5. Excellent reproduction of surface detail 6. Dimensional stability: - Curing shrinkage is high 0.45%. - It has the highest permanent deformation (3 to 5%) among the elastomers 7. It is hydrophobic - so the mouth should be dried thoroughly before making an impression 8. The shelf life is good (2 years) Properties: www.indiandentalacademy.com
  26. 26. www.indiandentalacademy.com
  27. 27. Silicone Rubber Impression Material: Developed to over come some of the disadvantages of poly sulfide www.indiandentalacademy.com
  28. 28. Based on the type of polymerization reaction 1) Condensation silicones 2) Addition silicones Types www.indiandentalacademy.com
  29. 29. • Also known as conventional silicone. • Available in light, medium and putty consistency CONDENSATION SILICONE: Base Accelerators Polydimethyl siloxane (hydroxy-terminated) Orthoethyl silicate – cross linking agent Colloidal silica or microsized metal oxide (filler) 35-75% Stannous octoate - catalyst Color pigments COMPOSITION: www.indiandentalacademy.com
  30. 30. CH3 OC2H5 Sn OH-Si-OH + C2H5O-Si- OC2H5 Silicone + CH3CH2OH octoate CH3 OC2H5 Dimethyl + orthoethyl Silicone + ethyl siloxane silicate rubber alcohol  Ethyl alcohol - byproduct - evaporate - shrinkage & dimensional instability  Tray adhesive – Polydimethyl siloxane & Ethyl silicate SETTING REACTION: www.indiandentalacademy.com
  31. 31. Properties: • Pleasant odor and color. • Mixing time of 45sec & setting time of 8-9mins. • Excellent reproduction of surface details and highly elastic. • Lesser dimensional stability - high curing shrinkage (0.4 - 0.6%) - permanent deformation due to shrinkage caused by the evaporation of ethyl alcohol is also high (1-3%). • Hydrophobic - needs a dry field.. • Biologically inert. • Compatible with all gypsum products. www.indiandentalacademy.com
  32. 32. Addition silicones: Also called as polyvinyl siloxanes Better properties than condensation silicones. www.indiandentalacademy.com
  33. 33. Base: Poly (methyl hydrogen siloxane) Other siloxane prepolymers Fillers Accelerator: Divinyl poly siloxane Other siloxane pre polymers Platinum salt: Catalyst (chloroplatinic acid) Palladium (Hydrogen absorber) Retarders Fillers Composition: www.indiandentalacademy.com
  34. 34. CH3 CH3 CH3 CH3 Pt salt Si-H + CH2=CH-Si Si-CH2-CH2-Si activator CH3 CH3 CH3 CH3 Vinyl + Silane Silicone siloxane siloxane rubber SETTING REACTION: • No by product, but imbalance  hydrogen gas  air bubbles in the stone models • To avoid this palladium is added. www.indiandentalacademy.com
  35. 35. CLINICAL SIGNIFICANCE: Sulfur compounds retard the setting of silicones One source of sulfur contamination is from latex gloves Vinyl gloves should be used •Clair D. Reitz and Nereyda P. Clark 1988 on the setting of vinyl polysiloxanes and condensation silicone putties when mixed with gloved hands. •Winston W. L. Chee, T. E. Donovan and R. L. Kahn in 1991on indirect inhibition of polymerization of polyvinyl siloxane impression material www.indiandentalacademy.com
  36. 36. Properties: • Pleasant odor and color • Excellent reproduction of surface details • Mixing time of 45 secs ,setting time of 5-9 mins. • Best dimensional stability - low curing shrinkage (0.17 %) - lowest permanent deformation (0.05 – 0.3 %) • Stone pouring delayed by 1-2 hours • Extremely hydrophobic, some manufacturers add a surfactant (detergent) to make it more hydrophilic • Good shelf life of 1-2 yrs • Good tear strength (3000gm / cm2 ) www.indiandentalacademy.com
  37. 37. Poly ether Rubber Impression material • Introduced in Germany in late 1960’s • Good mechanical properties and dimensional stability, but short working time, very stiff material and expensive www.indiandentalacademy.com
  38. 38. Composition: Base Paste Poly ether polymer Colloidal silica (filler) Glycol ether or phthalate (plasticizer) Accelerator paste Aromatic sulfonate ester (cross-linking agent) Colloidal silica (filler) Phthalate or glycol ether (plasticizer) Available as 3 viscosities: light, medium & heavy bodied. www.indiandentalacademy.com
  39. 39. CHEMISTRY & SETTING REACTION H O O H CH3– C - CH2– C – O – R – O – C - CH2– C - CH +  Crosslinked rubber N N CH2-CH2 CH2-CH2 Polyether + Sulfonic ester  Crosslinked rubber Exothermic reaction  4-50 C www.indiandentalacademy.com
  40. 40. Properties: 1. Pleasant odor and taste 2. Mixing time is 30 secs, setting time of 8 mins 3. Dimensional stability is very good. Curing shrinkage is low (0.24%) The permanent deformation is also low (1-2%). 4. Very stiff (flexibility of 3%), needs extra space, around 4 mm is given. 5. Hydrophilic (moisture control not critical) 6. Shelf life extends upto 2 years www.indiandentalacademy.com
  41. 41. Property Polysulfide Condesn . Addn . Polyether Working time (min) 4-7 2.5-4 2-4 3 Setting time (min) 7-10 6-8 4-6.5 6 Tear strength (N/m) 2500-7000 2300-2600 1500-4300 1800-4800 By product H2O Ethanol - - Custom tray YES NO NO NO Unpleasant odour YES NO NO NO Multiple casts NO NO YES YES % contraction (24hr) 0.40 – 0.45 0.38 – 0.60 0.14 – 0.17 0.19 – 0.24 Stiffness (1= > stiff) 3 2 2 1 Distortion (1= > Dist) 1 2 4 3www.indiandentalacademy.com
  42. 42. RECOMMENDED DISINFECTANTS MATERIAL DISINFECTANTS Polysulfide Glutaraldehyde, Cl compounds, Iodophors & Phenolics Silicones ------ do -------- Polyether Cl compounds or Iodophors Alginate ------ do -------- ZOE Glutaraldehyde or Iodophors Impression compound Cl compounds or Iodophors www.indiandentalacademy.com
  43. 43. AUTOMATIC DISPENSING & MIXING DEVICES ADVANTAGES: - More uniform mix - Less air bubbles - Reduced working time www.indiandentalacademy.com
  44. 44. Different methods of making impressions 1. Single mix or mono-phase technique: - Regular viscosity elastomer is used (addition silicone/polyether) - Paste is mixed, part of it is loaded on to the tray & the remaining onto the syringe - Syringe material is injected onto the prepared area & tray material is seated over it. www.indiandentalacademy.com
  45. 45. Multiple mix technique DISADV: Higher viscosity material may displace more fluid wash material www.indiandentalacademy.com
  46. 46. RELINE OR 2-STAGE PUTTY WASH TECHNIQUE • Preliminary impression is made with a putty consistency using a thin plastic sheet or spacer over it (acts as a spacer) • Light body is injected around the prepared tooth • The plastic sheet is removed & putty impression is seated back www.indiandentalacademy.com
  47. 47. www.indiandentalacademy.com
  48. 48. ELASTOMERIC IMPRESSION MATERIALS: PROPERTIES WORKING AND SETTING TIMES • Working time- begins at the start of mixing and ends just before the elastic properties have developed • Setting time- time elapsing from the beginning of mixing until the curing has advanced sufficiently so that the impression can be removed from the mouth with a minimum of distortion • Increase in temperature- accelerates curing time • Increase in viscosity- decrease in working and setting time www.indiandentalacademy.com
  49. 49. Dimensional stability 1. Polymerization shrinkage 2. Loss of byproduct 3. Thermal contraction from oral to room temperature 4. Imbibition 5. Incomplete recovery of deformation because of viscoelastic behavior www.indiandentalacademy.com
  50. 50. 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, condensation silicone, polyether and polysulfide www.indiandentalacademy.com
  51. 51. Tear strength • Measures the resistance to fracture of elastomeric material subjected to a tensile force acting perpendicular to a surface flaw Biocompatibility Polysulfide- lowest cell death count Polyether- highest cell toxicity www.indiandentalacademy.com
  52. 52. RECENT ADVANCES IN ELASTOMERS www.indiandentalacademy.com
  53. 53. Visible light cured impression material: • Polyether urethane dimethacrylate. • Introduced in early 1988 by GENESIS and L D CAULK. • Two viscosities: Light and heavy. www.indiandentalacademy.com
  54. 54. Composition: - Polyether urethane dimethacrylate - Photo initiators - Photo accelerators - Silicon dioxide (Filler) Chemistry: Similar to light cured composites www.indiandentalacademy.com
  55. 55. Properties: • Long working time and short setting time. • Blue light is used for curing with transparent impression trays. • Tear strength – 6000 to 7500 gm/cm2 (Highest among elastomers) • Other properties are similar to addition silicone. www.indiandentalacademy.com
  56. 56. Manipulation: • Both light body and heavy body are cured with visible light having larger diameter probe. • Curing time approx 3 min. Adv: - Controlled working time - Excellent properties Disadv: - Special transparent trays - Difficult to cure in remote area www.indiandentalacademy.com
  57. 57. D.H. Pratten and M. Novetsky. Study on detailed reproduction of soft tissues: A comparison of impression materials. 1. Low viscosity polysulfide and ZOE produced fewer and smaller impression voids than low or medium viscosity hydrophobic addition silicones 2. Polyether and hydrophilic addition silicone produced casts with more soft tissue detail than low-viscosity polysulfide or ZOE www.indiandentalacademy.com
  58. 58. COMMON FAILURES • Rough or uneven surface on impression 1. Incomplete polymerization- premature removal, improper ratio or mixing, +ce of oil or other organic material 2. Too rapid polymerization- high humidity or temperature 3. Excessively high accelerator/base ratio with condensation silicones www.indiandentalacademy.com
  59. 59. • Bubbles 1. Too rapid polymerization, preventing flow 2. Air incorporated during mixing • Irregularly shaped voids 1. Moisture or debris on the surface of tooth • Rough or chalky stone cast 1. Inadequate cleaning of impression 2. Excess water left on the surface of impression 3. Excess wetting agent 4. Premature removal of cast 5. Failure to pour delay of addition silicone at least 20min www.indiandentalacademy.com
  60. 60. • Distortion 1. Lack of adhesion of rubber to the tray 2. Development of elastic properties in the material before the tray is seated 3. Excessive bulk of material 4. Continued pressure against impression material that has developed elastic properties 5. Movement of tray during polymerization 6. Premature removal from mouth 7. Improper removal from mouth 8. Delayed pouring of the polysulfide or condensation silicone impression www.indiandentalacademy.com
  61. 61. Materials used for maxillofacial prosthetic reconstruction • IDEAL QUALITY 1. Compatibility, biologic and mechanical 2. Flexibility, replicating restored tissue 3. Light weight, replicating bulk tissue 4. Translucency, depth in coloration 5. Ease of processing 6. Nonconductive, minimal heat and cold transfer 7. Durability, resistance to handling, environment 8. Ease of duplication 9. Availability, inexpensive 10. Hygienic, cleanable with disinfectants www.indiandentalacademy.com
  62. 62. RTV-Silicone Elastomers • Room temperature-vulcanizing silicone elastomers • Internal coloring difficult-silica fillers for tensile strength- to mask yellowing • During mixing air entrapment persists • Tear resistance inadequate- once started at an edge void or nick- propagates www.indiandentalacademy.com
  63. 63. HTV-Silicone Elastomers • Heat-vulcanizing silicone elastomers • Designed for higher tear resistance • Requires intense milling • Cured at elevated temperatures in heat transferring metal molds • Improved biocompatibility with human excised donor tissues, biologically and mechanically www.indiandentalacademy.com
  64. 64. Hydrocolloids: • Kola - ‘glue’ and ‘oid’- like, a ‘glue-like’ character. • Colloids are classified as the fourth state of matter , they lie between suspension and solutions. • Characterized by their unique dispersion of particles held together by primary or secondary forces. • The size of the particles larger than solutions & range from 1 to 200nm www.indiandentalacademy.com
  65. 65. • The colloidal materials that are dissolved in water are termed hydrocolloids • If the change of sol to gel is thermal and reversible – reversible hydrocolloid (agar) • If the change of sol to gel is chemical and irreversible - irreversible hydrocolloid (alginate) • An important characteristic of gels is the processes of syneresis and imbibition. • These both alter the original dimensions of the gel www.indiandentalacademy.com
  66. 66. Reversible Hydrocolloid – AGAR  Introduced by “Alphous poller of Vienna” in 1925  Adopted commercially as “Dentacol” in 1928  It was the first successful elastic impression material  Agar is an organic hydrophilic colloid extracted from certain “Seaweed”  It is a sulphuric ester of a linear polymer of galactose  Though highly accurate, it has been largely replaced by alginates and elastomers due to its cumbersome manipulation www.indiandentalacademy.com
  67. 67. ComponentComponent FunctionFunction CompositionComposition (%)(%) AgarAgar Brush Heap structureBrush Heap structure 13 – 1713 – 17 BorateBorate StrengthStrength 0.2 – 0.50.2 – 0.5 Pot. SulfatePot. Sulfate Gypsum hardenerGypsum hardener 1.0 – 2.01.0 – 2.0 Wax, ZO, Silica, DM,Wax, ZO, Silica, DM, etc.etc. FillerFiller 0.5 – 1.00.5 – 1.0 Thixotropic materialsThixotropic materials ThickenerThickener 0.3 – 0.50.3 – 0.5 WaterWater Reaction mediumReaction medium Balance 84%Balance 84% AlkylbenzoatesAlkylbenzoates PerservativePerservative 0.10.1 Composition: www.indiandentalacademy.com
  68. 68. The Material is supplied as:  Gel in collapsible tubes (for impressions)  A number of cylinders in a glass jar (syringe material)  In bulk containers (for duplication) Manipulation: Agar hydrocolloid requires special equipments - Hydro colloid conditioner - Water cooled rim lock trays www.indiandentalacademy.com
  69. 69. Conditioner Consists of:Conditioner Consists of: a. Boiling or liquefaction section: 10 mins in boiling water (1000 C). b. Storage section: 65-680 C is ideal it can be stored till needed c. Tempering section: 460 C for about 2mins www.indiandentalacademy.com
  70. 70. WATER COOLED RIM LOCK TRAYS www.indiandentalacademy.com
  71. 71. FINAL IMPRESSION WITH AGAR www.indiandentalacademy.com
  72. 72. Advantages: 1. Hydrophilic Impression material 2. Good elastic properties, Good recovery from distortion 3. Can be re-used as a duplicating material 4. Long working time and low material cost 5. No mixing technique 6. High accuracy and fine detail recording Disadvantages: 1. Only one model can be used 2. Extensive and expensive equipment required 3. Impossible to sterilize for reuse 4. Low dimensional stability & tear resistance www.indiandentalacademy.com
  73. 73. Uses of Agar: 1. Widely used at present for cast duplication 2. For full mouth impression without deep undercuts 3. As tissue conditioner 4. Was used for crown & bridge before the advent of elastomers www.indiandentalacademy.com
  74. 74. Laminate technique or agar-alginate combination technique • Injecting syringe agar material onto the prepared tooth • Placing an impression tray with alginate over the injected syringe agar Wet field technique • Area to be recorded is flooded with warm water • Syringe agar material – quickly & liberally over prepared tooth • Immediately, tray agar placed over the syringe agar www.indiandentalacademy.com
  75. 75. Irreversible HydrocolloidIrreversible Hydrocolloid oror AlginateAlginate www.indiandentalacademy.com
  76. 76. • ‘Algin’ - a peculiar mucous extract yielded by Algae (brown seaweed). • In England, 40 yrs later, “S. William Wilding” received the patent for alginate as impression material. • Alginate was developed as a substitute for agar when it became scarce due to II world war. • Currently, alginate is more popular than agar because,  It is easy to manipulate  It is comfortable for the Patient  It is relatively inexpensive and does not require elaborate equipmentwww.indiandentalacademy.com
  77. 77. Component Function Wt% Potassium alginate Soluble alginate 15 Calcium sulfate Reactor 16 Zinc oxide Filler particles 4 Potassium Titanium fluoride Accelerator 3 Diatomaceous earth Filler Particles 60 Sodium phosphate Retarder 2 COMPOSITION OF ALGINATE www.indiandentalacademy.com
  78. 78. SETTING REACTION: Alginic acid is a linear polymer of Anhydro- B-D mannuronic acid of high molecular weight Two main reactions occurs during setting: i) 2 Na3 PO4 + 3 Ca SO4 Ca3 (PO4)2 + 3 Na2 SO4 (Sodium phosphate) (Calcium sulphate) (Retarder) (Reactor) ii) Sodium Alginate + Ca SO4 + H2O Ca Alginate + Na2 SO4 (Powder) (Reactor) (Gel) www.indiandentalacademy.com
  79. 79. Types: Type I - Fast Setting Type II - Normal Setting Latest advances - Modified Alginates: 1. In the form of a sol, containing the water. A reactor of plaster of Paris is supplied separately. 2. 2 paste system, one containing the alginate sol, the second the calcium reactor. These materials are said to contain silicone and have superior tear resistance.www.indiandentalacademy.com
  80. 80. 3. Chromatic alginates: contain acid/base indicator that change colour at different critical points, indicating mixing time, loading into mouths & setting. 4. Dustless Alginate: To avoid dust inhalation - coating the material with a glycol. 5. Siliconised Alginates: Alginates modified by the incorporation of silicone polymers which improve the physical properties.www.indiandentalacademy.com
  81. 81. Manipulation: - 15 gm. Powder : 40 ml of water - figure-of-eight motion, swipe & strop Control of gelation time: 1. By manufacturers : by adding retarders 2. By Dentist - Cold water : Longer is the geln . time - Warm water : Shorter is the geln . time Types Mixing time Working time Setting time I- Fast set 45 sec 1.25 mins 1-2 mins II- Normal set 60 sec 2 mins 2 - 4.5 mins www.indiandentalacademy.com
  82. 82. Advantages: 1. Easy to mix and manipulate. 2. Minimum requirement of equipment. 3. Accuracy (if properly handled) 4. Low cost 5. Comfortable to the patient 6. Hygienic (as fresh material is used for each impression) Disadvantages: 1. Distortion occurs easily 2. Poor dimensional stability (poured within 15 min.) 3. Poor tear strength www.indiandentalacademy.com
  83. 83. Uses: 1. Complete denture prosthesis & orthodontics 2. Mouth protectors 3. Study models and working casts 4. Duplicating models www.indiandentalacademy.com
  84. 84. COMPARISON BETWEEN HYDROCOLLOIDS Properties Agar Alginate Flexibility 20 % 14 % Elasticity & elastic recovery 98.8 % 97.3 % Reprodn . of details 25 um < agar Tear strength 715 gm/cm2 350-700 gm/cm2 Comp. strength 8000 gm/cm2 500-8000 gm/cm2 Diml . Stability Better Poor Reuse Possible Not possible Manipulation Conditioner & rim lock trays Normal trays www.indiandentalacademy.com
  85. 85. CONCLUSION www.indiandentalacademy.com
  86. 86. References: • Kenneth J. Anusavice: Philips’ Science of Dental Materials Eleventh Edition • William J. O’Brien: Dental Materials Properties and Selection • E. C. Combe: Notes on Dental Materials Fifth Edition • John F. McCabe: Applied Dental Materials Seventh Edition • V. K. Subbarao: Notes on Dental Materials Fourth Edition • Clair D. Reitz, DDS and Nereyda P. Clark, DMD The setting of vinyl polysiloxane and condensation silicone putties when mixed with gloved hands. JADA Vol. 116:371-5, 1988 • Winston W.L. Chee, T.E. Donovan, R.L. Kahn. Indirect inhibition of polymerization of a polyvinyl siloxane impression material: a case report, Quint. Int. Vol. 22:133-5, 1991 • D. H. Pratten, M. Novetsky. Detail reproduction of soft tissues: A comparison of impression materials. JPD Vol. 65:188-191, 1991 • John F. Lontz: State-of-the-Art Materials Used for Maxillofacial Prosthetic Reconstruction DCNA- Vol. 34, No. 2, April 1990 • Terry E. Donovan, Winston W. L. Chee:A review of contemporary impression materials and techniques DCNA- Vol. 48, No. 2, April 2004 www.indiandentalacademy.com
  87. 87. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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