M4 Quiz #3 Chapters 15 & 16: DH104: Dental Materials

Which of the following is an elastic impression material?

Vinyl polyether silicone

Impressions taken with polyvinyl siloxane should be poured within:

1 week.

Increased porosity of the gypsum particles makes it necessary to use _____ water to convert the _____ when mixing gypsum products.

more; hemihydrate particles back to dihydrate particles

When preparing to take an alginate impression, which of the following is not necessary?

Pack the material to mix.

A properly extended maxillary alginate impression tray will extend posteriorly enough to include which oral landmark?

Hamular notch

When mixing alginate, as the water temperature increases, the working time:

decreases.

Which statement is correct regarding alginate hydrocolloid?

Some moisture will be lost from the impression even in 100% humidity.

Which of the following statements is true concerning the mixing of plaster and stone materials?

The measured amount of water is placed into the mixing bowl and the powder is slowly sifted into the water.

Which of the following is true of the double-pour method for fabricating and trimming diagnostic/working casts?

This technique involves two separate mixes.

An increase in spatulation time and rate will _____ the setting time and _____ the rate of setting expansion.

shorten; increase

Which statement is true about impression trays?

Plastic trays are inexpensive and disposable, whereas metal trays are more expensive and must be cleaned and sterilized between uses.

Which of the following statements is true regarding dimensional accuracy of gypsum products?

High-strength stones have the least amount of setting expansion.

Of the items listed, which would not be made from an alginate impression?

Onlay

Which of the following will accelerate the setting of gypsum products?

Set gypsum particles

Impressions taken with polyether should be poured within what time period?

1 week

Why would a dentist choose to use an addition silicone over a condensation silicone?

Addition does not distort as badly.

What could occur if a cast is made from an improperly disinfected impression?

Should be stored for 24 hours first, then sprayed w/ a disinfectant

Which characteristic should be considered when choosing an impression tray?

All of the above are considered.

Mixed alginate should be loaded into the impression tray in _____ increments as _____ as possible.

large; quickly

What does it mean when freshly mixed gypsum loses its gloss?

Initial set

When should impressions be disinfected?

At the chairside upon removal

Which of the following impression materials has the smallest dimensional change on setting of all elastomeric and hydrocolloid impression materials?

Addition silicone (PVS)

As viscosity of the impression materials increases, which one of the following properties decreases?

Accuracy

Which of the following elastomers are the most hydrophilic?

Polyethers

Which of the following dental gypsum products will require the least water for mixing and will have the highest final density?

Dental stone, high strength (Type IV)

How is agar different from alginate impression material?

It is reversible

Which of the following is the most widely used dental impression material?

Irreversible hydrocolloid

The completed impression forms a _____ reproduction of the teeth and tissues, and the replica or model forms a _____ replica of the teeth and tissues.

negative; positive

What is the ideal time frame for pouring an alginate impression?

An hour

The _____ the particles of gypsum powder are, the weaker and less resistant to abrasion is the final product.

larger, more irregular, and more porous

Which material is able to withstand the high heat and stress produced when molten metal is forced into molds to form indirect restorations?

Dental investment

Which of the following gypsum products is ideal for making full or partial denture models, orthodontic models, and casts requiring higher strength and abrasive resistance?

Dental stone (Type III)