Dental Impression Materials
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Questions and Answers

We shouldn't avoid synersis and imbibition.

False

Immediate casting should be done within how many minutes?

10 minutes

How do we disinfect hydrocolloids?

  • By sprays such as iodophor or glutaraldehyde (correct)
  • By exposure to UV light
  • By heating in an autoclave
  • By soaking in water

    • To solve tear strength problem in hydrocolloids, one should use thick sections of __ mm.

    <p>4-6</p> Signup and view all the answers

    Match the casting solutions with the correct type:

    <p>Poly sulfide = 98 elastic recovery Condensation silicone = 99.5 elastic recovery Addition silicone = 99.5 elastic recovery Poly ether = 98.9 elastic recovery</p> Signup and view all the answers

    What are the components of heat-cured resins in acrylic resin denture base materials?

    <p>Powder, prepolymerized beads of methacrylate, initiator, plasticizers, dyed organic fibers, pigments, and opacifier.</p> Signup and view all the answers

    What is the effect of polymerization shrinkage in spray-disinfected impressions?

    <p>Increase tear strength.</p> Signup and view all the answers

    What type of tray is used for spray-disinfected impressions?

    <p>Special non-perforated tray with adhesive</p> Signup and view all the answers

    Which materials can be electroplated in spray-disinfected impressions?

    <p>Rubber impression materials</p> Signup and view all the answers

    What is the purpose of gypsum products in dentistry?

    <p>To create models or casts.</p> Signup and view all the answers

    What is the chemical composition of gypsum?

    <p>Calcium sulphate dihydrate (CaSO4.2H2O).</p> Signup and view all the answers

    What is a die in dentistry?

    <p>A model of a prepared single tooth.</p> Signup and view all the answers

    What is calcination in the context of gypsum products?

    <p>A high temperature reaction that drives off part of the 'water of crystallization'.</p> Signup and view all the answers

    What is hygroscopic setting expansion in gypsum products?

    <p>The expansion that occurs when gypsum or a gypsum-bonded investment are allowed to set under water during the initial stage of setting.</p> Signup and view all the answers

    What are the desirable mechanical properties of gypsum products?

    <p>High strength to resist breakage and hardness to resist scratching.</p> Signup and view all the answers

    What are the functions of a ring liner?

    <p>Creates a space for investment, allows setting of investment under water, and facilitates removal of investment from the casting ring after casting procedure.</p> Signup and view all the answers

    What is the importance of heating/burnout in wax elimination?

    <p>To vaporize all traces of the wax (200°C for 30 minutes) to avoid incomplete casting and rounded margins, and to allow for thermal expansion of the investment (gradual rise to 650 °C) to avoid undersized restoration.</p> Signup and view all the answers

    What is the purpose of a wetting agent?

    <p>Used to reduce the contact angle and provide better wetting of investment.</p> Signup and view all the answers

    What are the requirements for melting & casting in the casting procedure?

    <p>Heat source: to melt the alloy. Casting force: to drive (force) the alloy into the mould.</p> Signup and view all the answers

    How are yellow colored alloys described?

    <p>By color</p> Signup and view all the answers

    What is the effect of platinum on gold alloy?

    <p>Increases tarnish and corrosion resistance, strength, and hardness of gold alloy</p> Signup and view all the answers

    Silver is stronger and harder than gold.

    <p>True</p> Signup and view all the answers

    What is the function of Trisodium phosphate in Alginate impression material?

    <p>It acts as a reactor to release calcium to react with potassium alginate, forming insoluble calcium alginate gel.</p> Signup and view all the answers

    What are the two types of alginates based on their setting time?

    <p>Fast-setting</p> Signup and view all the answers

    What is the function of diatomaceous earth/silicate powder in impression materials?

    <p>Filler control strength and viscosity.</p> Signup and view all the answers

    What is the purpose of organic glycols in impression materials?

    <p>To reduce dust and prevent inhalation during manipulation.</p> Signup and view all the answers

    What is the role of chlorhexidine in impression materials?

    <p>As a disinfectant.</p> Signup and view all the answers

    What is the setting mechanism for impression materials?

    <p>An irreversible chemical reaction that cross-links the polymer chains into a 3D network structure of calcium alginate gel.</p> Signup and view all the answers

    What is the purpose of the retardation reaction in impression materials?

    <p>To control the rate of the reaction.</p> Signup and view all the answers

    What are the properties that impression materials need to exhibit?

    <p>Accuracy and stability.</p> Signup and view all the answers

    What is the function of flow in impression materials?

    <p>To indicate the different stages in manipulation.</p> Signup and view all the answers

    What is the dimensional change of alginate on setting and storage?

    <p>Slight shrinkage on setting, not dimensionally stable on storage due to synersis and imbibition.</p> Signup and view all the answers

    What are the three types of casting machines based on the density of the alloy?

    <p>Air pressure casting machines using compressed air</p> Signup and view all the answers

    What are the consequences of failure to select the proper casting machine?

    <p>Incomplete casting with rounded margins.</p> Signup and view all the answers

    What is the recommended process after casting for the casting ring and contents?

    <p>Left standing until they have lost all traces of redness, then quenching in cold water.</p> Signup and view all the answers

    How can the dark appearance of gold casting due to oxide deposits be resolved?

    <p>Immersion in warm HCI solution until lustrous gold color appears.</p> Signup and view all the answers

    What are the uses of dental casting alloys in the lab?

    <p>To construct indirect metallic restorations like inlays, onlays, crowns, bridges, and removable partial denture frameworks.</p> Signup and view all the answers

    What are the functional requirements of dental casting alloys?

    <p>Stiffness and resilience.</p> Signup and view all the answers

    How is stiffness defined in dental casting alloys?

    <p>As the resistance to elastic deformation, allowing equal distribution of stresses.</p> Signup and view all the answers

    What is the purpose of resilience in ceramo-metallic restorations?

    <p>To support the brittle porcelain veneer by absorbing energy without plastic deformation.</p> Signup and view all the answers

    What are some causes of defective castings in dentistry?

    <p>Distortion, dimensional inaccurate casting, surface roughness, porosity, and incomplete casting with rounded margins.</p> Signup and view all the answers

    What is the purpose of high yield strength in dental casting alloys?

    <p>To resist permanent deformation under masticatory stresses in the mouth.</p> Signup and view all the answers

    Why is high fatigue strength and fatigue limit important in dental casting alloys?

    <p>To resist cyclic loading.</p> Signup and view all the answers

    What is the significance of high tarnish and corrosion resistance in dental casting alloys?

    <p>To prevent dissolution in oral fluids and liberation of toxic corrosion products.</p> Signup and view all the answers

    What compatibility should alloys for ceramo-metallic restorations have with porcelain?

    <p>They should be compatible with porcelain in terms of coefficient of thermal expansion, elastic modulus, and forming of oxides to help bonding.</p> Signup and view all the answers

    What does 'fit' refer to in the context of dental casting alloys?

    <p>The ability of the casting to reproduce accurately the pattern from which it is constructed.</p> Signup and view all the answers

    What are the working requirements for dental casting alloys?

    <p>Ease of casting, ease of soldering, and ease of burnishing.</p> Signup and view all the answers

    Why is high ductility important in dental casting alloys?

    <p>For proper marginal adaptation and adjustment of the restoration.</p> Signup and view all the answers

    What does 'sag resistance' refer to in dental casting alloys?

    <p>The ability of the alloy to resist plastic flow under its own weight at high temperatures.</p> Signup and view all the answers

    What is silica?

    <p>Silicon dioxide</p> Signup and view all the answers

    At what temperature does tridymite undergo displacive transformation?

    <p>870°C</p> Signup and view all the answers

    At what temperature does cristobalite undergo displacive transformation?

    <p>1470°C</p> Signup and view all the answers

    What is the temperature range for fused quartz?

    <p>160°C - 270°C</p> Signup and view all the answers

    What is the expansion percentage of tridymite at 600°C?

    <p>1.4%</p> Signup and view all the answers

    How does the denture isolate the oral soft tissues from temperature sensation?

    <p>Approximately 80 x 10^5/°C</p> Signup and view all the answers

    What may lead to gradual loosening of porcelain teeth attached to a denture base?

    <p>Difference in contraction and expansion</p> Signup and view all the answers

    What is the effect of low thermal conductivity in resin?

    <p>Cracks may appear on the surface of resin</p> Signup and view all the answers

    What are factors controlling setting expansion in gypsum products?

    <p>Water-to-powder ratio and mixing (spatulation) speed and time</p> Signup and view all the answers

    What are 'retarders and accelerators' in the context of gypsum products?

    <p>Chemicals that regulate the setting time of gypsum products</p> Signup and view all the answers

    What factors control hygroscopic expansion in gypsum products?

    <p>Time of immersion in water, amount of water added, and W/P ratio of the original mix</p> Signup and view all the answers

    What is the composition of the final structure of set gypsum products?

    <p>Interlocking crystals between which are pores containing excess water required for mixing</p> Signup and view all the answers

    Is the solubility of the hemihydrate in water higher or lower than the formed dihydrate?

    <p>Higher</p> Signup and view all the answers

    What happens when the solution becomes supersaturated with dihydrate?

    <p>Excess dihydrate starts to precipitate in the form of nuclei of crystallization</p> Signup and view all the answers

    What is the impact strength of conventional acrylic denture base?

    <p>Low</p> Signup and view all the answers

    What is the thermal shrinkage of the resin as the denture cools from the processing temperature to room temperature?

    <p>0.44%</p> Signup and view all the answers

    What is the linear expansion of the resin for each 1% increase in weight due to water sorption?

    <p>0.23%</p> Signup and view all the answers

    Is acrylic resin denture base material soluble in most fluids in the oral cavity?

    <p>No</p> Signup and view all the answers

    What is the significance of low density in denture base materials?

    <p>Better retention of an upper denture</p> Signup and view all the answers

    What are the other considerations and requirements for denture base materials?

    <p>No dimensional changes during denture processing or while in service, easy to process with minimal expenses and equipment, and easy to repair if fractured</p> Signup and view all the answers

    What are the effects of cobalt in dental casting alloys?

    <p>Increases modulus of elasticity, strength, and hardness. Forms solid-solution of cobal and chromium.</p> Signup and view all the answers

    What is the role of chromium in dental casting alloys?

    <p>Responsible for resistance to tarnish and corrosion by formation of passive layer. A minimum of 12% chromium is required to form this passive layer.</p> Signup and view all the answers

    What is the limit of solubility of chromium in cobalt?

    <p>A maximum of 30% chromium.</p> Signup and view all the answers

    What are the effects of nickel in dental casting alloys?

    <p>Increases modulus of elasticity, strength, and hardness. Responsible for the ductility of the alloy.</p> Signup and view all the answers

    What is the role of molybdenum in dental casting alloys?

    <p>Acts as a grain refiner and increases the strength.</p> Signup and view all the answers

    What are the roles of silicon and manganese in dental casting alloys?

    <p>They act as deoxidizers and are responsible for increasing the fluidity of the molten alloy, thus improving its castability.</p> Signup and view all the answers

    What happens when carbon combines with other alloying elements?

    <p>It forms carbides which solidify last during cooling after casting.</p> Signup and view all the answers

    How does the precipitation of carbides at the grain boundaries affect the alloy?

    <p>It increases the strength and hardness of the alloy.</p> Signup and view all the answers

    What change in carbon content affects the properties of the alloy?

    <p>A change of 0.3%.</p> Signup and view all the answers

    What compound is formed by aluminum and nickel in nickel chromium alloy?

    <p>Nickel Aluminide Ni3Al.</p> Signup and view all the answers

    What is the effect of beryllium on the melting range of the alloy?

    <p>It lowers the melting range by 100°C.</p> Signup and view all the answers

    What health risk is associated with beryllium vapor?

    <p>It is carcinogenic and can lead to lung fibrosis.</p> Signup and view all the answers

    What are the grades of commercially pure titanium based on oxygen content?

    <p>0.18-4%.</p> Signup and view all the answers

    How does titanium improve tarnish and corrosion resistance?

    <p>Due to its passivity and the formation of a Titanium Oxide layer.</p> Signup and view all the answers

    What are the two polymorphic forms of titanium?

    <p>Phase and B-phase.</p> Signup and view all the answers

    What is the crystal structure of the alloy described?

    <p>Body centered cubic.</p> Signup and view all the answers

    What are the stabilizers of the alloy?

    <p>Copper, palladium, and vanadium.</p> Signup and view all the answers

    At what temperature does the alloy melt?

    <p>885°C.</p> Signup and view all the answers

    What is the crystal structure of the stabilizer aluminum?

    <p>Closed packed hexagonal.</p> Signup and view all the answers

    What is the process called when metal parts are joined by melting a third metal below 425°C?

    <p>Soldering.</p> Signup and view all the answers

    What is the process called when metal parts are joined by melting a third metal above 425°C?

    <p>Brazing.</p> Signup and view all the answers

    In dentistry, at what temperature are the parts joined, and what is the operation commonly called?

    <p>Above 425°C; commonly called soldering.</p> Signup and view all the answers

    Study Notes

    Primary Impression and Uses

    • Uses of primary impression:
      • Primary cast (diagnostic, study)
      • Special tray
    • Types of trays:
      • Stock tray
      • Special tray

    Secondary Impression and Uses

    • Uses of secondary impression:
      • Secondary cast (working, master)
      • Final applications

    Hydrocolloids

    • Forms of hydrocolloids:
      • Reversible (Agar-Agar)
      • Irreversible (Alginate)
    • Synersis and imbibition lead to dimensionally unstable in storage
      • Synersis: shrinkage due to evaporation of water
      • Imbibition: swelling of the gel due to absorption of water

    Casting and Impressions

    • Immediate casting within 10 minutes
    • To solve tear strength problem in hydrocolloids:
      • Thick sections (4-6 mm)
      • Sharp snap removal
    • Disinfection of hydrocolloids:
      • Sprays (Iodophor or glutaraldehyde)
      • Sealed plastic bag with paper towels

    Gypsum Products

    • Calcination reactions for type 1, 2, 3, 4, and 5 gypsum products
    • Particles size and shape:
      • Type 1 and 2: irregular and porous
      • Type 3: regular and less porous
      • Type 4 and 5: most regular and least porous
    • Chemical W/P ratio: 18.61 g for 100 g of caso4.½H20
    • W/P ratio for different types of gypsum products

    Manipulation of Gypsum

    • Armentarium:
      • Rubber bowl
      • Stiff plastic spatula
    • Manipulation steps:
      1. Proportioning
      2. Mixing
      3. Pouring
    • Vigorously advantages:
      • Increase powder wetting
      • Press air bubbles out
    • Visual inspection of final mix: glossy surface, smooth and creamy consistency

    Investment Materials

    • Strength of investment materials:
      • Silicate > Phosphate > Gypsum
    • The type of ring with:
      • Gypsum bonded investment: metallic ring with wet paper
      • Phosphate and silicate bonded investments: rubber ring (removed after setting)

    Casting Technique

    • Steps of casting technique:
      1. Formation of wax pattern
      2. Spruing the pattern
      3. Investing
      4. Wax elimination
      5. Casting
      6. Finishing and polishing
    • Enumerate wax pattern methods:
      1. Direct on a patient mouse (accurate)
      2. Indirect on a die (easy)
      3. Indirect-direct (fabrication on a die and adjust in the mouth)

    Sprueing

    • Enumerate the rules of sprue:
      1. Allow safe handling of wax
      2. Create a channel
      3. Act as a reservoir
    • Enumerate sprue materials:
      1. Wax (the best)
      2. Plastic
      3. Metal filled with sticky wax
    • Sprue attachment:
      • To the thickest portion
      • 45⁰ to the proximal surface

    Elastomers

    • Enumerate the tear strength influences:
      1. Strain rate
      2. Rapid rate of removal
    • Tear strength of elastomers:
      • Poly sulfide > Poly ether > Silicones

    Dental Casting Alloys

    • Classification based on:
      • Joining, working requirements, and sag resistance
      • Mechanical properties
      • Specific use
    • General classifications:
      • ADA specification No. 1 (High type)
      • ADA specification No. 2 (Noble type)
      • ADA specification No. 3 (Predominantly base metal type)

    Gold Alloys

    • General composition:
      • Noble metals and their effect on properties
      • Effect of Gold (Au) on properties:
        • High noble metal resists tarnish and corrosion
        • Low strength, hardness, and high ductility
      • Effect of platinum:
        • Increases tarnish and corrosion resistance, strength, and hardness
      • Effect of palladium:
        • Whitens the color of gold alloy
        • Decreases the greening effect of silver and redness effect of copper
      • Effect of copper:
        • Increases strength and hardness
        • Reduces porosity and rough surface casting development

    Classification of Gold Alloys

    • Classification based on gold content:
      • Carat and Fineness
      • Carat refers to the parts of pure gold in 24 parts of alloy
      • Fineness refers to the parts of pure gold per thousand parts of alloy

    Note: These study notes cover the key points and concepts mentioned in the provided text.### Critical Ratios in Dental Gold Alloys

    • 1% palladium for every 3% silver to balance the tarnish tendency of silver
    • Importance of careful balance: to prevent tarnish of the alloy
    • Consequences of imbalance: tarnish of the alloy

    Properties of Economy Gold Alloys

    • Comparable to Type III and Type IV gold alloys
    • Replacement for reduced gold: palladium, silver, and other metals

    Casting Ring Selection

    • Factors to consider: investment material strength, expansion, and alloy to be cast (solidification shrinkage)
    • Functions of a ring liner: creates space for investment, allows setting of investment under water, and facilitates removal of investment from the casting ring

    Wax Pattern Handling

    • Importance of immediate investment: to avoid distortion due to release of internal stresses affected by time and temperature

    Investment Mixing Techniques

    • Techniques: regular mix investment technique and double mix investment technique (improves wettability & avoids distortion)
    • Use of wetting agent: to reduce contact angle and provide better wetting of investment

    Investment and Casting Procedures

    • Steps: casting ring and liner, investing, wax elimination, casting, devesting, finishing, and polishing
    • Importance of gradual heating during wax elimination: to vaporize all traces of wax and allow for thermal expansion of the investment
    • Consequences of improper selection of investment type: dimensional inaccurate casting
    • Purpose of heating/burnout: to vaporize all traces of wax and allow for thermal expansion of the investment

    Melting and Casting

    • Requirements: heat source to melt the alloy and casting force to drive the alloy into the mold
    • Importance of melting machine selection: to provide the necessary heat source to melt the alloy
    • Consequences of under-heating: incomplete casting and rounded margin
    • Consequences of overheating: possible volatilization of the alloy and decomposition of the investment

    Casting Machines

    • Types: air pressure casting machines using compressed air, centrifugal casting machine, and a combination of both with an attached vacuum system
    • Consequences of failing to select the proper casting machine: incomplete casting with rounded margins

    Post-Casting Procedures

    • Recommended process: leaving the casting ring and contents standing until they have lost all traces of redness, then quenching in cold water
    • Resolution of dark appearance of gold casting due to oxide deposits: immersion in warm HCl solution until lustrous gold color appears

    Dental Casting Alloys

    • Uses: constructing indirect metallic restorations like inlays, onlays, crowns, bridges, and removable partial denture frameworks
    • Functional requirements: stiffness and resilience
    • Definition of stiffness: resistance to elastic deformation, allowing equal distribution of stresses
    • Importance of resilience: to support the brittle porcelain veneer by absorbing energy without plastic deformation

    Properties of Dental Casting Alloys

    • Importance of high yield strength: to resist permanent deformation under masticatory stresses in the mouth
    • Importance of high fatigue strength and fatigue limit: to resist cyclic loading
    • Importance of high tarnish and corrosion resistance: to prevent dissolution in oral fluids and liberation of toxic corrosion products
    • Compatibility with porcelain: in terms of coefficient of thermal expansion, elastic modulus, and forming of oxides to help bonding

    Fit and Working Requirements

    • Definition of fit: the ability of the casting to reproduce accurately the pattern from which it is constructed
    • Working requirements: ease of casting, ease of soldering, and ease of burnishing
    • Importance of high ductility: for proper marginal adaptation and adjustment of the restoration
    • Definition of sag resistance: the ability of the alloy to resist plastic flow under its own weight at high temperatures### Setting Reaction of Gypsum
    • The temperature rise during the reaction of hemihydrate and water indicates setting, but it is not an accurate way to measure setting time.

    Penetration Test

    • The penetration test is used to determine if the gypsum has reached a measurable strength.

    Vibrate and Gillmore Tests

    • The Vicate test measures the initial setting time of gypsum.
    • The Gillmore test measures the initial and final setting times of gypsum.

    Controlling Setting Rate of Gypsum

    • The setting rate of gypsum can be controlled by altering the solubility of the hemihydrate, changing the number of nuclei of crystallization, and varying the rate of crystal growth.

    Effects of Solubility, Nuclei of Crystallization, and Crystal Growth on Setting Time

    • Increasing the solubility of the hemihydrate achieves supersaturation of the dihydrate faster, accelerating the rate of dihydrate crystal deposition and decreasing the setting time.
    • Increasing the number of nuclei of crystallization leads to faster formation of dihydrate crystals, decreasing the setting time.
    • Faster crystal growth rate decreases the setting time.

    Fineness of Hemihydrate Powder and Setting Time

    • The finer the hemihydrate particles, the faster the rate of dissolution, increasing the number of nuclei of crystallization formed and decreasing the setting time.

    Impurities as Nucleating Agents

    • A small amount of CaSO4.2H2O (Terra alba) can be added as a nucleating agent to accelerate the setting time.

    Effect of Moisture Contamination on Hemihydrate Particles

    • Moisture contamination during storage can change some hemihydrate particles into dihydrate, decreasing the number of nuclei of crystallization and setting time.

    Retarders and Their Action

    • Retarders form an adsorbed layer on the hemihydrate or on the growing dihydrate crystals, inhibiting their growth and increasing the setting time.

    Mechanical Properties of Denture Base Materials

    • High modulus of elasticity, adequate resilience, adequate strength, high impact strength, high fatigue strength, high flexure strength, hardness, and good abrasion resistance are required.

    Importance of Modulus of Elasticity

    • A high modulus of elasticity ensures rigidity and the ability to be made in thin sections while evenly distributing stresses.

    Function of Plasticizers and Dyed Organic Fibers

    • Plasticizers improve polymer resiliency.
    • Dyed organic fibers simulate blood vessels.

    Purpose of Pigments and Opacifier

    • Pigments give a natural tissue-like appearance.
    • The opacifier imparts radioopacity.

    Liquid Monomer and Inhibitor in Acrylic Resin Denture Base Materials

    • Methyl methacrylate (MMA) is the liquid monomer used.
    • The inhibitor prevents the polymerization of the monomer during storage.

    Cross-Linking Agent and Initiator in Acrylic Resin Denture Base Materials

    • The cross-linking agent improves mechanical properties.
    • The initiator is a chemical activator (N,N dihydroxy ethyl para-toluidine).

    Polymerization Reaction for Heat-Cured Resin

    • Polymer Peroxide Initiator and Monomer Inhibitor.

    Components of Self-Cured Resins

    • Powder, Liquid, Polymer Peroxide initiator, Monomer Inhibitor, and chemical activator.

    Nature of Polymerization Process and Shrinkage

    • The polymerization process is exothermic and accompanied by polymerization shrinkage.

    Issues with Self-Cured Resins and Residual Monomer

    • Self-cured resins are not used for construction of denture bases due to the greater amount of residual monomer and limited to denture repair.
    • There is always a residual monomer remaining after polymerization, and its amount depends on the degree of polymerization.

    Effects of Excess Free Monomer in Acrylic Resin

    • Excess free monomer can release from the denture and irritate tissue.
    • It can act as plasticizers and make the resin flexible and weak.
    • It may evaporate leaving porosity which decreases mechanical properties.

    Thermal Shrinkage and Linear Expansion

    • Thermal shrinkage of the resin as the denture cools from the processing temperature to room temperature is 0.44%.
    • Linear expansion of the resin for each 1% increase in weight due to water sorption is 0.23%.

    Solubility and Mechanical Properties of Acrylic Resin Denture Base Materials

    • Acrylic resin denture base material is insoluble in most fluids that may come into contact with it in the oral cavity.
    • It has low mechanical properties due to the presence of weak secondary bonds.

    Impact Strength and Overcoming Brittleness

    • The impact strength of conventional acrylic denture base is low, and the denture will fracture when accidentally dropped.
    • Incorporating butadiene styrene rubber inserts can overcome the low impact strength.

    Gypsum Products in Dentistry

    • Gypsum products are used to create models or casts.
    • The chemical composition of gypsum is calcium sulphate dihydrate (CaSO4.2H2O).

    Characteristics of Gypsum Products

    • High strength to resist breakage and hardness to resist scratching.
    • Ability to reproduce fine details and sharp margins.
    • Little dimensional change on setting and on storage.
    • Compatibility with impression materials (no interaction with the surface of the impression and no need for a separating medium before pouring the impression).
    • Good color contrast with other materials (e.g., impression materials).

    Classification of Gypsum Products

    • Plaster, Impression Plaster (Plaster of Paris), and Model Plaster (Calcined Gypsum) according to ADA specification No. 25.

    Dental Stone and Hydrocal Hemihydrate (ISO Type III)

    • High strength, low expansion, improved stone (ISO Type IV), high expansion (Type V).
    • Characteristics: high strength, low expansion, improved stone (ISO Type IV), high expansion (Type V).

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    Description

    This quiz covers the uses of primary and secondary impressions, types of trays, forms of hydrocolloids, and the effects of synersis and imbibition in dentistry.

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