All Free Dental Materials MCQs with Answers

• A. Remove oxides from powder particle surface
• B. Achieve a workable mass of amalgam in minimum time
• C. Pulverize pelletes into particles to aid in attack by mercury
• D. Keep the amount of gamma-1 or gamma-2 matrix crystals to maximum

Explanation: Trituration should produce a workable amalgam and expose alloy surfaces for mercury reaction, while reducing undesirable phases such as…

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

Explanation: Gallium and indium are used in mercury-free alloy systems, where they act as liquid metals in place of mercury.

• A. Requires least amount of mercury
• B. Achieves lowest compressive strength at 1 hr.
• C. Has tensile strength both at 15 min & 7 days comparable to high copper unicompositional alloy
• D. Has low creep

Explanation: Traditional lathe-cut silver alloy particles require more mercury and develop strength more slowly than many spherical or high-copper…

• A. Dry Mix
• B. None of the above
• C. Short Mixing Time
• D. Shiny Mix

Explanation: A properly triturated amalgam mix is cohesive and shiny because the alloy particles have been adequately wetted by mercury.

• A. 6%
• B. 12-30%
• C. 29%
• D. 19%

Explanation: Low-copper amalgam contains less than about 6% copper, so 6% is the intended classification value.

• A. Lathe cut
• B. Single composition
• C. Admixed
• D. Spherical

Explanation: Single-composition high-copper alloys generally provide the greatest strength because they eliminate the weak gamma-2 phase throughout the…

• A. Silicate
• B. Composite
• C. Amalgam
• D. Gold

Explanation: Amalgam has traditionally been the most frequently used direct restorative material because it is durable, relatively inexpensive, and…

• A. 24 hours
• B. 1-2 days
• C. 7 days
• D. 3-5 days

Explanation: When zinc-containing amalgam is contaminated with moisture before setting, hydrogen generation causes delayed expansion that becomes…

• A. 13-30%
• B. 0-6%
• C. 10-12%
• D. 20-30%

Explanation: High-copper amalgam contains approximately 12% to 30% copper, with the usual classification threshold being more than 6% copper.

• A. One to two minutes
• B. Three to four minutes
• C. Five to six minutes
• D. Seven to eight minutes

Explanation: Amalgam normally has a working time of about 3 to 4 minutes, during which trituration, insertion, condensation, and carving should be…

• A. Resistance to creep
• B. Dimensional Stability
• C. Better handling property
• D. Toxicity to pulp and dentin

Explanation: Zinc is added mainly to improve the handling and working characteristics of amalgam.

• A. Tarnish
• B. Dry corrosion
• C. Wet corrosion
• D. Tarnish and corrosion

Explanation: Silver-alloy discoloration results from both tarnish, which is surface chemical discoloration, and corrosion, which involves material…

• A. Delayed expansion
• B. Shrinkage
• C. Marginal breakdown
• D. increased stresses

Explanation: Moisture contamination of zinc-containing amalgam produces delayed expansion, commonly through hydrogen gas formation during the setting…

• A. Gamma 1
• B. Gamma 2
• C. Gamma 1 and 2
• D. No phase is eliminated

Explanation: High-copper amalgam uses copper to react with tin and prevent formation of the weak gamma-2 phase.

• A. Both require same condensing force
• B. More condensing force is required
• C. Less condensing force is required
• D. Manipulation is easy

Explanation: Spherical alloy particles have less interparticle friction and flow more readily, so they require less force for condensation than…

• A. Ingestion while removing old amalgam
• B. Skin contact
• C. Mercury vapour
• D. All of the above

Explanation: Chronic mercury toxicity can follow inhalation of mercury vapour, ingestion of mercury-containing material, or absorption through the…

• A. Tarnish and corrosion
• B. Cause fracture of the filling
• C. Increase the strength
• D. Decrease condensation pressure

Explanation: Excess residual mercury leaves more unreacted mercury-rich matrix, which weakens amalgam and increases creep, making fracture more likely.

• A. It has increased tensile and compressive strength
• B. It's edge strength is greater
• C. It has poor tarnish and corrosion resistance
• D. Mercury content in the final restoration is less

Explanation: High-copper amalgams generally have better resistance to tarnish and corrosion because the tin is tied up in copper-tin phases rather than…

• A. Require more mercury
• B. Require heavy compection forces
• C. Have longer setting times
• D. None of the above

Explanation: Spherical alloys usually need less mercury and less condensation force than conventional lathe-cut alloys, and they do not…

• A. Gamma 2
• B. Gamma 1
• C. Epsilon 1
• D. Gamma 3

Explanation: Gamma-2 is the weakest and most corrosion-prone phase of conventional amalgam, which is why high-copper alloys are designed to eliminate…