Term
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Definition
| negative reproduction of teeth and supporting structures |
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Term
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Definition
| positive reproduction used for diagnosis and treatment planning |
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Term
| WHat is a cast? Is it more or less detailed than a study model? |
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Definition
Replica on which a restoration or appliance is fabricated
More accurate than study model |
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Term
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Definition
| A working replica of a single tooth (removeable) |
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Term
| How are impression materials provided? |
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Definition
| powders or paste-paste system |
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Term
| Is this metal or plastic trays: convenient, less expensive, disposable, don’t support as well |
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Definition
| plastic, metal are expensive and need to be disinfected |
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Term
| How do you make a custom tray?(steps) |
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Definition
-Impression taken with alginate
-study model made with gypsum
-Made on model of patient’s arch with acrylic
-Then used to take final impression |
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Term
| What is a bite registration tray? |
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Definition
-Impression to record occlusal surfaces of both arches
-Relate upper and lower casts in the same way they come together in patient’s mouth |
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Term
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Definition
-Dual-arch or closed-mouth technique
-Quadrant tray shaped like a “J” |
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Term
| What does a triple tray take an impression of? |
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Definition
| Impression of prepared tooth, opposing teeth, & bite registration all in one |
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Term
| What does thermoset mean? |
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Definition
| impression material set by a chemical reaction, can't be reversed |
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Term
| What does thermoplastic mean? |
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Definition
| phycial reaction set by cooling (solidification, gelation) |
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Term
| What is an example of solidification? |
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Definition
| melted wax cooling and becoming hard |
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Term
| What is an example of gelation? |
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Definition
| jello changing from liquid to semisolid state when cooled |
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Term
| Are thermoplastic or thermoset materials more stable? |
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Definition
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Term
| What are elastic materials used for? What needs elastic materials? |
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Definition
| impressions of teeth (undercuts need elastic material) |
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Term
| What are inelastic materials used for? What are they like? |
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Definition
| hard /ridged, impressions of edentulous arches |
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Term
| Why is alginate impression material not suitable to use for fabricating crowns, bridges, and inlays? |
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Definition
| because its not accurate enough, just used for study models |
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Term
| What is light-bodied impression material? |
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Definition
| Less (low) viscous (light-bodied) used in syringe to inject around prepared tooth (records margins) |
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Term
| What is heavy bodied impression material? |
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Definition
| High viscous (heavy) makes up bulk of impression (reduces dripping of material out of tray |
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Term
| What is a retraction cord? |
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Definition
| Placed in gingival sulcus to help with crown and bridge preparations |
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Term
| What allows a retraction cord to stop bleeding? |
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Definition
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Term
| How long are retraction cords left in place? |
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Definition
| just a few minutes then taken out |
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Term
| What are some of the common impression materials? |
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Definition
-plaster
-wax/impression compound
-ZOE |
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Term
| How often is plaster used for impressions? Why? |
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Definition
| not much anymore, unpleasant taste |
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Term
| Who is plaster impression used on? |
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Definition
| Only for impression of edentulous ridges for dentures |
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Term
| What works with a thermoplastic reaction and was one of the first impression materials? |
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Definition
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Term
| What is wax still sometimes used to take impressions of? What else is it used for? |
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Definition
-Sometimes used to take impressions for full dentures or to extend borders of stock trays
-Waxes used in dental laboratories for fabrication of crowns/bridges |
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Term
| How does ZOE come? What does it smell/taste like? |
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Definition
| 2 pastes, smell and taste like cloves |
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Term
| Is ZOE used much anymore? What is it like when set? What can it be used for? |
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Definition
-Not used much anymore
-Hard and brittle when set
-can be used for impressions of edentulous ridges |
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Term
| What are irreversible & reversible hydrocolloids both mainly composed of? |
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Definition
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Term
| What is an example of an irreversible hydrycolloid? |
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Definition
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Term
| What does irreversible hydrocolliod mean? |
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Definition
| set via chemical reaction, heating set alginate does not reverse back to sol (fluid state) |
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Term
| What is an example of a reversible hydrocolloids? How is it set? |
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Definition
| agar, set via a physical change (When heated reverse to liquid state, when cooled return to gel state) |
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Term
| What is alginate (irreversible hydrocolloid) made of? (4 parts) |
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Definition
1. Potassium alginate from algae
2. Diatomaceous earth (silica)
3. Calcium sulfate
4. Sodium phosphate |
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Term
| What part of alginate (irreversible hydrocolloid) is the inert filler? |
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Definition
| Diatomaceous earth (silica) |
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Term
| What part of alginate (irreversible hydrocolloid) is the reactor for cross-linking reaction? |
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Definition
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Term
| What part of alginate is the retarder for more working time? |
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Definition
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Term
| Why is alginate easy to use with gypson products? |
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Definition
| because of hydrophilic properties (wetting) |
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Term
| Why do we have to pour up soon after taking a alginate impression? |
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Definition
| because they are mostly water and evaporation makes impression shrink and is no longer accurate |
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Term
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Definition
| Exuding water and thus contracting after setting |
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Term
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Definition
| Absorb water, swell, and distort |
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Term
| Why should impression trays be removed from a patient's mouth quickly? |
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Definition
| Removing slowly can result in distortion and tearing |
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Term
| What is reversible hydrocolloid made of? |
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Definition
| Water and agar (carbohydrate polymer) |
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Term
| What is agar use for in microbiology? |
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Definition
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Term
| Why aren't agar impressions as common? |
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Definition
| becase it requires special equipment- Hydrocolloid conditioner |
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Term
| How many compartments does a Hydrocolloid conditioner have? What happens to change it to a liquid in the container? |
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Definition
-3 compartments
-boils to change to a liquid |
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Term
| What is the temperature in the water bath to store the material? |
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Definition
| Water bath (150 degrees) to store material |
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Term
| What is the temperature of the water bath to temper material? |
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Definition
| Water bath (110 degrees) to temper material (lower temperature so that it can be tolerated in mouth) |
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Term
| What cools the hydrocolloid container? |
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Definition
| Circulating cold water through tubing and a special tray facilitates cooling |
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Term
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Definition
| Melting and gelling at different temperatures (Melts at a higher temperature than boiling water and gels at mouth temperature) |
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Term
| Is agar popular? What enviorments is it good in? |
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Definition
-no, requires special equipment
-Good in wet environments when crown margins are submarginal |
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Term
| What is a downside to polysulfide (aka rubber base) impression material? |
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Definition
| not as accurate as other impression materials |
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Term
| What is bad about polysulfide impression materials? |
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Definition
| Stain clothing, smell and taste bad |
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Term
| What is the working and set time like with polysulfide impression materials? |
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Definition
Long working time – good for multiple preparations
Bad – long setting time (15 minutes) |
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Term
| What are condensation silicones based on? |
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Definition
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Term
| Why are condensation silicones not popular? |
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Definition
| difficult to pour models without voids, distortion due to evaporation (pour quickly) |
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Term
| What are poly ethers like? What are they accurate/easy to pour with? |
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Definition
-Stiff and set quickly
-Accurate and easy to pour with gypsum |
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Term
| What are polyethers good for? |
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Definition
| the triple tray technique |
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Term
| What is a brand name of a poly-ether? |
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Definition
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Term
| What is the most popular material? |
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Definition
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Term
| What are some advantages to using addition silicone? |
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Definition
-clean
-no unpleasant taste or smell
-Most accurate, stable |
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Term
| What is the most expensive material? What is it? |
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Definition
| addition silicone, elastomeric impression material (good for crown and bridge impressions) |
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Term
| What is the process of addition silicones? What are they mixed with? |
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Definition
-Automix gun allowing pastes to swirl together
-Putty is used with low-viscosity material
-Mix with fingers so not heat with hands
No latex gloves interferes with polymerization |
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Term
| What are 2 additives in addition silicone? |
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Definition
-Hydrogen absorbers
-surfactants |
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Term
| What do the surfactants in addition silicone do? |
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Definition
| increase wetting of impression, reduction of voids in gypsum |
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Term
| What do the hydrogen absorbers in addition silicone do? |
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Definition
| reduce hydrogen bubbles on surface of gypsum cast |
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Term
| What is a CAD/CAM machine? |
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Definition
| makes crowns and bridges in office without sending to lab |
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Term
| What are gypsum products made of? |
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Definition
Gypsum rock mined and ground into powder
Calcium sulfate dihydrate |
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Term
| What is the calcination process? How is it made? |
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Definition
-Calcium sulfate hemihydrate (plaster, stone, improved stone)
-Produced by heating gypsum and driving off part of the water of crystallization |
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Term
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Definition
| fine powders that are mixed with water to form a fluid mass that can be poured and shaped and hardens into a rigid/stable mass |
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Term
| What are 3 gypsum materials? |
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Definition
-plaster
-stone
-improved stone |
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Term
| What is plaster like? What is it used for? |
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Definition
-weakest and least expensive
-Preliminary casts for complete dentures |
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Term
| What is stone like? What is it used for? |
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Definition
-stronger and more expensive than plaster
-Diagnostic casts |
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Term
| What is improved stone like? What is it used for? |
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Definition
-strongest, most expensive
-Making casts for fabrication of crown & bridge |
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Term
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Definition
| Mechanical device to attach casts |
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Term
| What is the setting reaction of gypsum products? |
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Definition
-When mixed with water hemihydrate changed back to dehydrate by the process of hydration
-Heat is liberated
-The calcium sulfate dehydrate precipitates out of solution as interlocking crystals, which form a hard mass |
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Term
| What is the initial setting time? |
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Definition
-length of time to start of mix until mass reaches a semi-hard stage
-Available time for manipulating the product |
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Term
| What is the final setting time? What is this a completion of? |
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Definition
-when mass becomes ridged and can be separated from impression
-Major completion of the hydration reaction |
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Term
| What are some materials that can increase setting time is gypsum products? |
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Definition
| decreased mixing, more water (thinner mix), retarder added |
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Term
| What is a retarder added to gypsum products to increase the setting time? |
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Definition
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Term
| What are some variables that decrease the setting time of gypsum products? |
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Definition
| more mixing, thicker mix, accelerator |
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Term
| What is an accelerator added to gypsum products to decrease setting time? |
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Definition
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Term
| What will increase setting expansion of gypsum? |
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Definition
-Thicker mix and increased spatulation
-Immersed in water while setting |
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Term
| ***********See page 114 in book for all materials listed************* |
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Definition
| ***********See page 114 in book for all materials listed************* |
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