Question 1

Depending on ______________, the required temperature of a burnout oven for proper casting will vary.

Accepted Answer

The type of investment and the liquidus of the alloy to be cast are two crucial factors that affect the required temperature of a burnout oven. However, the solidus of the alloy is not directly related to the temperature of the burnout oven. Therefore, only choices A and B are correct.

Question 2

What is the purpose of the sprue?

Accepted Answer

B

Question 3

If molten alloy was cast into a ring at room temperature, what will occur?

Accepted Answer

C

Question 4

Following removal of a ring from the burnout oven, any delay in casting of more than ___________ will severely compromise the fit and quality of the cast restoration.

Accepted Answer

The answer of Following removal of a ring from the...

Question 5

Which of the following is correct about phosphate-bonded investments?

Accepted Answer

Phosphate-bonded investments use a gypsum investment binder and are used for ceramic-alloy restorations. Therefore, option E is the correct choice. Option A is incorrect because silica refractory is used in silica-bonded investments, not phosphate-bonded investments. Option C is partially correct, but it is not the only type of restoration for which phosphate-bonded investments are used.

Question 6

Which of the following sequences describing the steps involved in making a dental casting from start to finish is correct?

Accepted Answer

The correct sequence for making a dental casting is: making the wax pattern, spruing the pattern, investing, burnout, casting, removal of investment, pickling, and finishing. This process starts with the creation of a wax model of the desired shape, attaching it to a sprue to allow for material flow and air escape, then encasing it in a refractory material (investing). The wax is then burned out (burnout) to leave a cavity into which the metal is cast. After the metal has solidified, the investment material is removed, and the casting is cleaned (pickling) and finished to the desired shape and smoothness.

Question 7

What method is used to inject the molten alloy into the casting ring?

Accepted Answer

Centrifugal casting machine is used to inject the molten alloy into the casting ring. This method uses centrifugal force to distribute the molten metal throughout the mold, resulting in a denser and more uniform casting. Slip casting and pressure molding are not used for injecting molten alloy, and linear casting machines are not commonly used in the manufacturing of castings.

Question 8

To prevent premature freezing in the sprue channel, sprues are generally as _____ in diameter and as _____ as possible.

Accepted Answer

To prevent premature freezing in the sprue channel, sprues are generally made as large in diameter and as short as possible. This design helps maintain the flow and temperature of the molten material, ensuring it reaches the mold cavity before solidifying.

Question 9

What regulates the amount of thermal expansion of the investment?

Accepted Answer

The temperature used during burnout and the type of silica refractory used are the main factors that regulate the amount of thermal expansion of the investment. The choice of inlay wax may have some effect, but it is relatively minor compared to the other two factors. Therefore, option D is the best choice.

Question 10

The total expansion of the investment is the sum of the hygroscopic and thermal expansions. Investments rely primarily on hygroscopic expansion to compensate for casting shrinkage of the metal.

Accepted Answer

The answer of The total expansion of the investment is...

Question 11

An invested wax pattern should set for at least ________ before burnout.

Accepted Answer

The invested wax pattern should set for at least 45 minutes before burnout to ensure the investment material has adequately hardened and can withstand the burnout process without distortion.

Question 12

Which of the following statements is(are) true concerning expansion of an investment material?

Accepted Answer

All three statements are true regarding the expansion of investment materials used in casting processes, such as those in dental and jewelry making. Hydroscopic expansion refers to the expansion that occurs when water is added to the investment material. This is a critical factor in the investment's overall expansion. Investments are indeed designed to expand to compensate for the shrinkage of the metal as it cools and solidifies in the mold. Thermal expansion refers to the expansion that occurs as the investment material is heated, which is another critical factor in ensuring the final casting dimensions are accurate.

Question 13

Why is a surfactant used prior to investment?

Accepted Answer

A surfactant is used to aid the flow of the investment material over the wax pattern. It reduces the surface tension, allowing the investment material to flow more easily and uniformly over the pattern. This results in a better reproduction of the pattern and reduces defects in the casting.

Question 14

The accuracy of a cast crown may be as good as ____% in dimensional change from the wax pattern if care is taken to perform each step properly.

Accepted Answer

According to literature, the accuracy of a cast crown may be as good as 0.05% in dimensional change from the wax pattern if care is taken to perform each step properly. Therefore, the best choice is D, 0.05.

Question 15

The temperature in a burnout oven is commonly _____ for high noble alloys.

Accepted Answer

The temperature in a burnout oven for high noble alloys is commonly around 500° C to ensure proper casting and material properties.

Question 16

What is the purpose of a casting ring?

Accepted Answer

A casting ring is used to retain the investment while it sets and hardens. It is commonly lined with either a dry or wet ceramic-paper liner to prevent the investment from sticking to the ring and to provide a smooth surface for the casting to take place. Both options are mentioned as correct choices, so the answer is E.

Question 17

Which of the following statements is(are) true of sprues?

Accepted Answer

The answer of Which of the following statements is(are) true...

Question 18

Which of the following statements is true of investments used for casting?

Accepted Answer

The answer of Which of the following statements is true...

Question 19

A casting alloy is heated in a _________ made of heat-resistant ceramic.

Accepted Answer

A crucible is a heat-resistant container used for melting materials at high temperatures. It is commonly used in casting processes to hold the casting alloy while it is heated and poured into the mold.

Question 20

The investment material is _________; the wax pattern is __________.

Accepted Answer

The investment material is hydrophilic because it needs to absorb water to properly mix and set. The wax pattern is hydrophobic because it repels water, which is necessary to accurately capture the details of the mold without water interfering.

Quiz 12: Casting, Soldering, and Welding