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18 Cards in this Set
- Front
- Back
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What is an accelerator? |
Addition of certain chemicals that decreases the setting time (sets faster). A commonly used one is potassium sulfate. |
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What is an articulator? |
A mechanical device that you attach casts too. |
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What is calcination? |
The process of heating gypsum and driving off part of the water of crystallization. |
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What is a cast? |
A replica on which a restoration or appliance is fabricated. |
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What is a die? |
Is a working replica of a single tooth, typically a removable part of a cast. |
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Define dry strength. |
The strength that is measured when the excess water is not present in the sample. |
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What is final setting time? |
Represents the length of time from the start of the mix until the setting mass becomes rigid and can be separated from the impression. |
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What are gypsum products? |
Are made from gypsum rock, which is a mineral found in various parts of the world. Chemically it is calcium sulfate dihydrate. |
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What is high-strength stone? |
Made from gypsum by calcining the gypsum in a calcium chloride solution. It is the strongest and most expensive product, and is very dense. |
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What is improved stone? |
Made from gypsum by calcining the gypsum in a calcium chloride solution. It is the strongest and most expensive product, and is very dense. |
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What is initial setting time? |
The length of time from the start of the mix until the setting mass reaches a semihard stage. |
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What is plaster? |
It is the weakest and least expensive of the gypsum. Usually white in color and is referred to as beta-hemihydrate or type II. |
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What is a retarder? |
The addition of certain chemicals, a commonly used one is borax. Increases the setting time. |
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What is stone? |
Is made from gypsum by carefully controlled calcination under steam pressure in a closed container. |
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What is a study model? |
It is used to plan treatment and to observe treatment progress. |
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Define the water/powder ratio. |
The proportion of water to powder used to make a workable mix of a particular gypsum product. |
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What is wet strength? |
The strength that is measured when the sample contains some or all of the water in excess of the theoretical amount required for hydration. |
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Define working time. |
The length of time from the start of the mix until the setting mass reaches a semihard stage. |
