Free Metals and Alloys MCQs with Answers

• A. 0%
• B. 2 to 3%
• C. 5 to 10%
• D. <1%

Explanation: The intended classification describes a highly corrosion-resistant cast alloy, for which tarnish and corrosion are considered negligible…

• A. To felicitate wetting of ring liner
• B. To felicitate mixing investment
• C. To reduce contact angle of liquid with max surface
• D. For better wax elimination

Explanation: A wetting agent lowers the contact angle between the liquid and the wax pattern or investment surface, allowing the liquid to spread more…

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

Explanation: Zinc acts as a deoxidizing or scavenging agent in dental alloys by preferentially reacting with oxygen during melting.

• A. It prevents the formation of chromium oxide or dissolves chromic oxide layer
• B. It prevents the formation of copper oxide
• C. It prevents the flow of material in undesirable area
• D. Increase the strength of solder

Explanation: Fluoride flux is especially important with chromium-containing alloys because it dissolves or disrupts the tenacious chromium oxide layer…

• A. N 25%
• B. >40%
• C. 25%
• D. 0%

Explanation: A high-noble alloy must contain at least 40% gold by weight, with the total noble-metal content meeting the higher high-noble requirement.

• A. Suckback porosity
• B. Gas inclusion porosity
• C. Localized shrinkage porosity
• D. Microporosity

Explanation: Gas dissolved in molten metal becomes less soluble as the metal cools and is released as bubbles, producing gas-inclusion or gas porosity.

• A. Rapid solidification of metal
• B. No place for reservoirs
• C. Incomplete evacuation of gases
• D. Difficulty in removing casting from investment

Explanation: A short sprue may not provide adequate length for gases to escape from the mold, causing gas entrapment and incomplete casting.

• A. 18% Nickel 8% Chrominum
• B. 18% Carbon 8% Iron
• C. 18% Chromium 8% Cobalt
• D. 18% Chromium 8% Nickel

Explanation: The familiar 18-8 stainless-steel designation means approximately 18% chromium and 8% nickel.

• A. At right angle
• B. At 45°C angle
• C. At obtuse angle
• D. It depend upon type of wax pattern

Explanation: A sprue is generally attached at about 45 degrees to promote smooth metal flow and reduce turbulence at the pattern junction.

• A. 25%
• B. 50%
• C. 75%
• D. 100%

Explanation: An 18-carat alloy contains 18 parts gold out of 24, so its gold content is 18/24 × 100 = 75%.

• A. Using CAD-CAM technique
• B. Under air pressure in nitrogen atmosphere
• C. In specially fabricated aluminium vanadium
• D. Under vacuum in argon atmosphere

Explanation: Titanium reacts readily with oxygen and nitrogen at casting temperatures, so it is melted and cast under vacuum or an inert argon…

• A. Heating upto 250°C for 15 to 30 min
• B. Heating quickly upto 450°C followed by sudden quenching
• C. Heating 750°C and slowly cooling to zero degree
• D. Heating at 750°C and then quenching to room temperature

Explanation: Heat or age hardening involves holding the alloy at a moderate temperature for a period, allowing strengthening phases to precipitate and…

• A. Carbon crucible
• B. Quartz crucible
• C. Clay crucible
• D. High melting plastic crucible

Explanation: Quartz or fused-silica crucibles withstand the high temperatures and chemical conditions used for base-metal alloy casting.

• A. Cr, Gold, Ti
• B. Cr, Mo, Ti
• C. Cr, Al, Ti
• D. Cr, Fe, Ti

Explanation: Chromium, aluminium, and titanium readily form thin, adherent oxide films that protect the underlying alloy from further corrosion…

• A. Acidic copper sulfate
• B. Ionic copper
• C. Copper cynide
• D. Silver cyanide

Explanation: Acidic copper sulfate provides copper ions that are deposited electrolytically onto the die during copper plating.

• A. To strength amalgam
• B. In orthodontic wires
• C. To construct clasps for partial dentures
• D. To replace internal gold restorations

Explanation: Stainless steel is used extensively for orthodontic wires because it combines high strength, springiness, corrosion resistance, and…

• A. Pinhole porosity
• B. Gas inclusion porosity
• C. Subsurface porosity
• D. Micro porosity

Explanation: Subsurface porosity forms just beneath the casting surface when gas bubbles nucleate at the advancing solidification front as metal first…

• A. Platinum
• B. Gold
• C. Silver
• D. Copper

Explanation: Copper forms lower-melting phases with gold, thereby reducing the alloy’s fusion temperature while also increasing hardness.

• A. Ductility
• B. Proportional limit
• C. Tensile strength
• D. Hardness

Explanation: Softening heat treatment relieves internal stresses and produces a softer, more ductile alloy.

• A. Help polish cast restorations
• B. Form an opening of molten metal to enter the mold
• C. Eliminate air bubbles on the wax pattern
• D. Reproduce fine detail

Explanation: The sprue is the channel through which molten alloy flows into and fills the mold cavity.