Question 1

The inherent roughness limits the ability of gypsum materials to capture the finest details of impressions.Reproduction of detail is sufficient for most applications.

Accepted Answer

Gypsum materials, despite their inherent roughness, can capture sufficient detail for most dental applications, making both statements correct.

Question 2

Proper wetting occurs when gypsum is poured against a _____-based impression material such as _____.

Accepted Answer

Proper wetting occurs when gypsum is poured against a water-based impression material such as alginate. Alginate is a water-based material, which allows for better wetting and adherence of the gypsum product used to create dental models or casts.

Question 3

The final setting time is defined as:

Accepted Answer

The final setting time is the point where the gypsum can be removed without fracture or distortion. The exothermic reaction may continue beyond this point, but it does not affect the setting characteristics of the gypsum. Therefore, choices A and B are correct, but choice C is not necessary for defining the final setting time.

Question 4

Hardness and abrasion resistance is especially important for:

Accepted Answer

Dies require high hardness and abrasion resistance to withstand pressure and wear during the fabrication process. Study models, orthodontic models, and casts do not require the same level of hardness and abrasion resistance.

Question 5

Water-powder ratio is defined as the amount of water in _____ added to the amount of powder in _____.

Accepted Answer

Water-powder ratio is defined as the amount of water in milliliters added to the amount of powder in grams. Milliliters are used to measure liquid while grams are used to measure solids, making D the best choice.

Question 6

When the alginate dries out before it is poured:

Accepted Answer

When alginate dries out, it can cause the gypsum mix to lose water, the edges to harden, and the impression to become distorted.

Question 7

Casts of teeth are used to make:

Accepted Answer

The answer of Casts of teeth are used to make:
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Question 8

Epoxy materials are compatible with most of the elastomeric impression materials.Epoxy materials can be used with alginates.

Accepted Answer

The first statement is correct, as epoxy materials are compatible with most elastomeric impression materials. However, the second statement is incorrect, as epoxy materials cannot be used with alginates. Alginates require water for their setting reaction, while epoxy materials require dry surfaces for bonding. Mixing these materials together can result in incomplete set or distorted impressions.

Question 9

The purpose of the vibrating table is to:

Accepted Answer

The purpose of the vibrating table is to help remove any bubbles that formed during mixing. The vibrations help the bubbles rise to the surface and escape from the mixture, resulting in a more even and stable final product.

Question 10

If a 2% solution of borax is added to the gypsum powder,what will be the result? The setting time will be:

Accepted Answer

Adding borax to gypsum powder significantly extends the setting time because borax acts as a retarder, slowing down the chemical reaction that causes the gypsum to set.

Question 11

The impression should not be removed from the gypsum for _____ minutes.

Accepted Answer

The answer of The impression should not be removed from...

Question 12

If gypsum materials are not adequately spatulated,_____ suffers.

Accepted Answer

Inadequate spatulation of gypsum materials can lead to incomplete mixing, resulting in a weaker final set material, thus affecting its strength.

Question 13

Which of the following statements is(are)correct about making models,casts,and dies?

Accepted Answer

None of the statements are correct. Fine detail is important in making accurate models, gypsums can be dimensionally stable and the material used needs to be strong enough to withstand the casting process.

Question 14

Dies of epoxy for use in fabrication of crowns,bridges,and inlays can be poured into alginate.Epoxy dies are tougher and more abrasion resistant than high-strength stone dies,and they are more accurate and stable dimensionally.

Accepted Answer

The answer of Dies of epoxy for use in fabrication...

Question 15

High-strength stone requires the least amount of excess water,because the crystals are:

Accepted Answer

Large and dense crystals in high-strength stone can bond together tightly, allowing for less space for excess water between them. Therefore, this option requires the least amount of excess water.

Question 16

The initial setting time for gypsum is defined as the time the:

Accepted Answer

The initial setting time for gypsum is defined as the time from when the powder is added to the water until the material reaches a state where it cannot be used for its intended purpose, indicating the beginning of the setting process.

Question 17

Which of the following statements is true regarding disinfection of a gypsum model?

Accepted Answer

Disinfecting the impression rather than the model is preferable because it helps to prevent the potential distortion or damage that could occur to the gypsum model during the disinfection process. Disinfecting the impression can effectively reduce the microbial load before the model is poured, thus indirectly disinfecting the model as well. Autoclaving a gypsum model is not recommended as the high heat and pressure can cause damage or distortion to the model.

Question 18

A hemihydrate will not set if the:

Accepted Answer

A hemihydrate will not set if the mixing water reaches 100° C because the high temperature will prevent the crystallization process necessary for setting.

Question 19

Which of the following statements is true of the handling of an alginate impression?

Accepted Answer

Alginate impressions should be kept moist to prevent distortion, which can be achieved by storing them in a humid environment.

Quiz 9: Model and Die Materials