All Free Dental Materials MCQs with Answers

• A. 80 Mpa
• B. 140 Mpa
• C. 260 Mpa
• D. 510 Mpa

Explanation: ADA Specification No. 1 requires silver amalgam to develop a minimum compressive strength of about 80 MPa after one hour.

• A. 9-30% copper
• B. 13-20% copper
• C. 9-20% copper
• D. 13-30% copper

Explanation: Admixed high-copper amalgam powders contain approximately 9 to 20% copper, usually supplied as conventional silver-tin particles mixed…

• A. Increased compressive strength
• B. Increase the marginal strength
• C. Decrease the tarnish and corrosion resistance
• D. Increase in tarnish and corrosion resistance

Explanation: Finishing and polishing smooth the amalgam surface, removing rough areas that retain plaque and promote electrochemical attack.

• A. Using spherical particles
• B. Trituration time
• C. Altering Hg-Alloy ratio
• D. Lathe cut alloy

Explanation: Trituration is the main clinical method for controlling amalgam’s setting time because it changes the extent and rate of mercury-alloy…

• A. Less than 0.02%
• B. Less than 0.1%
• C. Less than 0.01%
• D. None of the above

Explanation: A zinc-free amalgam alloy may contain only a trace amount of zinc, defined as less than 0.01%.

• A. Have less resistance to tarnish and corrosion
• B. Are workable at lower Hg-alloy ratio
• C. Have a higher ratio of tensile to compressive strength
• D. Have less marginal breakdown

Explanation: High-copper amalgams eliminate or greatly reduce the weak gamma-2 phase, so they show less corrosion-related marginal breakdown.

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

Explanation: Silver is the largest component of conventional amalgam alloy powder by weight and contributes strength, resistance to corrosion and…

• A. Dissolve the alloy in mercury
• B. Coat the alloy particle with mercury
• C. Remove excess mercury from the amalgam
• D. Dissolve Hg in alloy

Explanation: During trituration, mercury wets and coats the alloy particles, allowing the surface elements to react and form the amalgam matrix.

• A. 38-42%
• B. 58-62%
• C. 48-52%
• D. 68-72%

Explanation: Amalgam generally provides the best clinical service when the residual mercury content is approximately 48 to 52%.

• A. 35 pounds
• B. 3 pounds
• C. 15 lb
• D. 25 lb

Explanation: Amalgam is commonly condensed with approximately 3–5 pounds of pressure, enough to adapt the material and express excess mercury without…

• A. Ag
• B. Cu
• C. Zn
• D. Hg

Explanation: Copper strengthens the amalgam matrix and reduces the weak tin-mercury phase, so increasing copper raises strength and hardness.

• A. Requires least amount of mercury
• B. Achieves high compressive strength at 1 hr.
• C. Has tensile strength both at 15 minutes and 7 days is comparable to high copper, unicompositional alloys
• D. Has lower cree value

Explanation: Lathe-cut low-copper alloys generally require more mercury and develop lower early compressive strength than high-copper alloys, but their…

• A. Creep value of all the above mentioned alloys is same
• B. Admix alloy
• C. Single composition alloys
• D. Low copper amalgam alloy

Explanation: Low-copper amalgams have the highest creep because they retain more of the weak gamma-2 tin-mercury phase.

• A. 8 hours
• B. 4 hours
• C. hours
• D. 16 hours

Explanation: Amalgam gains strength gradually after placement and reaches about 70% of its ultimate strength at approximately 8 hours.

• A. All of the above
• B. Trituration time
• C. Speed of amalgamator
• D. Amalgam alloy

Explanation: The effect of trituration on amalgam strength depends on the alloy formulation, trituration time and mixing speed.

• A. Decreased compressive, increased strength
• B. It increases compresssive and tensile strengths
• C. Decreased compressive, decrease tensile strength
• D. Increased compressive, increased tensile strength

Explanation: Amalgam margins should have a 90-degree butt-joint cavosurface angle so the material has adequate bulk and is supported by tooth…

• A. Low compressive strength
• B. High marginal breakdown
• C. High creep
• D. Less marginal #

Explanation: High-copper amalgams eliminate or greatly reduce the weak gamma-2 phase, producing lower creep and much less marginal breakdown.

• A. Galvanism
• B. Pulp exposure
• C. Improper amalgam filling
• D. None of the above

Explanation: Contact between dissimilar metals such as amalgam and gold in the presence of saliva can produce a galvanic cell, causing an electric…

• A. Tensile strength
• B. Compressive strength
• C. Corrosion
• D. Creep

Explanation: Amalgam performs well clinically mainly because it tolerates heavy occlusal forces through its high compressive strength.

• A. From smooth atomized particles
• B. From lathe cut particles
• C. From irregular and spherical particles
• D. From traditional alloy particles

Explanation: High-copper amalgam can be made by admixing irregular or lathe-cut silver alloy particles with spherical silver-copper eutectic particles.