Free Metals and Alloys MCQs with Answers

• A. 18
• B. 20
• C. 22
• D. 24

Explanation: Gold foil used for restorations is 24-carat gold, meaning it is essentially pure gold.

• A. Crystalline
• B. Sponge gold
• C. Mat gold
• D. Granular gold

Explanation: Electrolytically precipitated direct filling gold is also called crystalline, mat, or sponge gold.

• A. High firing temperature
• B. Presence of copper
• C. Disintegration of opaque layer
• D. Formation of excess oxides

Explanation: Copper in the gold alloy can oxidise during porcelain firing and produce a greenish cervical discoloration.

• A. Made by beating pure gold at high temperatures
• B. Made by electrolytic precipitation
• C. Made by a combination of chemical precipitation and atomization
• D. Made by milling pure gold ingots

Explanation: Powdered gold is produced using chemical precipitation together with atomization, which creates fine particles suitable for condensation.

• A. Properly condensed mat gold has no voids
• B. None of the above
• C. Voids can be avoided with manual condensation
• D. Whatever may be the type voids are inherent

Explanation: Voids are inherently associated with direct filling gold, even when condensation is carefully performed, because the material is built…

• A. 1056
• B. 1560
• C. 1668
• D. 1886

Explanation: Titanium melts at approximately 1668°C, a high value related to its strong metallic bonding and refractory nature.

• A. Heating at 700°C for 10 - 15 min and quenching in water
• B. Heating up to 200 - 450°C for 15 - 30 min and quenching in water
• C. Heating at 700°C for 1 hour and quenching in water
• D. Heating above 700°C for 30 min and quenching in water

Explanation: Age hardening commonly involves heating an alloy in the lower-temperature range of about 200–450°C for a controlled period, followed by…

• A. 30-35%
• B. 13-32%
• C. 26-28%
• D. 22-30%

Explanation: Low-copper amalgam alloy typically contains about 26–28% tin, along with approximately 65–70% silver and 2–5% copper.

• A. Hydrogen
• B. Water
• C. Zinc and water
• D. Nascent oxygen

Explanation: Delayed expansion occurs when zinc in the amalgam reacts with moisture and produces hydrogen gas; the gas pressure expands the restoration…

• A. Copper
• B. Tin
• C. Silver
• D. Zinc

Explanation: Tin decreases the setting expansion of amalgam and also contributes to formation of the weaker tin-mercury phase in conventional alloys.

• A. Higher the strength
• B. Lower the creep value
• C. More matrix matrial formed
• D. More gamma 1 phase formed

Explanation: A higher mercury-to-alloy ratio leaves more unreacted mercury available to form the matrix, including mercury-rich reaction products.

• A. The resultant alloy is greater
• B. None of the above
• C. The resultant alloy varies according to the content of Ag of Cu
• D. The resultant alloy is lesser

Explanation: A eutectic composition melts at a lower temperature than either pure component or most non-eutectic mixtures, which is why eutectic alloys…

• A. Low tensile and compressive strength
• B. Low Hg: Alloy ratio
• C. High tensile strength
• D. Low creep

Explanation: High-copper amalgams have higher tensile and compressive strength and lower creep because they eliminate or greatly reduce the weak…

• A. An alloy of two or more metals one of which is mercury
• B. A metallic powder composed of silver, tin, copper and zinc
• C. An alloy of two or more metals that have been dissolved in each other in the molten state
• D. A metallic substances in powder or tablet from that is mixed with mercury

Explanation: An amalgam is an alloy in which mercury is one of the constituent metals, usually combined with silver, tin and copper.

• A. Cu
• B. Zn
• C. Pd
• D. Ag

Explanation: Zinc acts as an oxygen scavenger during alloy manufacture, helping prevent oxidation of the other metals.

• A. Electrochemical Corrosion
• B. Chemical Corrosion
• C. Corrosion does not occur at all
• D. Penetrating Corrosion

Explanation: High-copper amalgam still undergoes electrochemical and chemical corrosion, but it largely prevents the penetrating corrosion associated…

• A. Minimum matrix and maximum alloy phase
• B. Maximum matrix and minimum alloy phase
• C. Maximum matrix phase
• D. Minimum alloy phase

Explanation: Amalgam strength increases when the restoration contains more unreacted alloy particles and less weak matrix phase formed by the mercury…

• A. 5 minutes
• B. 6 minutes
• C. 3 minutes
• D. 15 minutes

Explanation: Amalgam should be condensed immediately after trituration, normally within about 3 minutes, because its working time is short and delayed…

• A. B1
• B. y2
• C. y1
• D. y

Explanation: The silver-mercury solid solution is the gamma-1 phase, written γ1 or Y1.

• A. High strength
• B. Sets quickly
• C. Needs no squeezing of excess mercury
• D. Greater plasticity and adapts well to cavity walls

Explanation: The Eames minimum-mercury technique improves strength, allows rapid setting, and avoids squeezing out excess mercury, but it produces a…