All Free Dental Materials MCQs with Answers

• A. Regulate setting time
• B. To regulate the setting expansion
• C. Acts as retarder
• D. None

Explanation: Potassium sulfate acts as an accelerator in gypsum, so its main role is to regulate or shorten the setting time.

• A. Slower the hygroscopic expansion
• B. Greater the hygroscopic expansion
• C. Normal setting expansion
• D. No setting expansion

Explanation: Finer silica particles provide greater surface area and promote more interaction with the setting material, increasing hygroscopic…

• A. 1
• B. 4
• C. 12
• D. 25

Explanation: Gypsum products are covered under ADA Specification No. 25, which includes dental plaster, stone, and improved stone.

• A. Modify strength
• B. Modify setting expansion
• C. Modify setting time
• D. Decrease the porosity

Explanation: Modifiers are added mainly to control the setting reaction, especially by accelerating or retarding setting time.

• A. H2O interferes with hygroscopic expansion
• B. H2O inhibits polymerization of dental resin
• C. H2O interferes with Crystallization of dihydrate
• D. Gypsum is slightly soluble in water and the surface of the cast will be eroded

Explanation: Gypsum is slightly soluble in water, so running tap water can dissolve and erode the cast surface.

• A. They are more irregular in shape and porous
• B. They are more regular in shape and highly porous
• C. They are more regular in shape and dense
• D. They are more dense and prismatic in shape

Explanation: Beta hemihydrate particles are irregular and porous, giving them a larger surface area and requiring more water to wet and separate them.

• A. Altering P / L Ratio
• B. Addition of accelerators and retarders
• C. Speed and length of hand spatulation
• D. Altering temperature of mixing water

Explanation: The most controlled way to alter plaster setting time is by adding accelerators or retarders.

• A. Stone
• B. Plaster
• C. Investment
• D. All of the above

Explanation: Plaster and stone are gypsum products, while investment is a gypsum product when it is gypsum-bonded and contains gypsum as its binder.

• A. Potassium sulfate
• B. Potassium fluoride
• C. Sodium fluoride
• D. Aluminium sulfate

Explanation: Potassium sulfate is the commonly used accelerator for gypsum and is often added at about 2%.

• A. Hydrocolloids
• B. Investment
• C. Amalgam
• D. Silicate

Explanation: The hygroscopic technique is used with gypsum-bonded investments to increase setting expansion while the material sets in contact with…

• A. Perpendicular to the walls
• B. Parallel to long axis of crown
• C. 45° to the wall
• D. None of the above

Explanation: A malleting force directed at about 45° to the wall helps condense direct filling gold against the wall without driving the material away…

• A. Using contaminated gold foil
• B. Poor finished preparation
• C. Using small condenser point
• D. Improper stepping of condenser point

Explanation: Pitting in an old direct gold restoration commonly results from improper stepping of the condenser, which leaves inadequately condensed…

• A. Electra alloy
• B. Mat gold
• C. Spherical gold
• D. Gold foll

Explanation: Mat gold is a cohesive gold form supplied as a bulk-like mass for building up a direct gold restoration.

• A. 51 to 54 degree F
• B. 70 to 75 degree F
• C. 51 to 54 degree C
• D. 70 to 75 degree C

Explanation: A water bath at about 51 to 54°C softens fluid wax uniformly without overheating or burning it.

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

Explanation: Copper dies are electroplated in an acidic copper sulphate electrolyte, which supplies copper ions for deposition.

• A. Silicate cement
• B. Zinc phosphate
• C. Polycarboxylate
• D. GIC

Explanation: Silicate cement releases fluoride, which gives it a marked anticariogenic effect and historically made recurrent caries less common around…

• A. High strength
• B. It can bond enamel & dentin
• C. Good marginal integrity
• D. It has less occlusal wear

Explanation: GIC chemically bonds to both enamel and dentin, allowing good retention in minimally prepared primary teeth.

• A. Average bonding to tooth
• B. Low bonding to tooth
• C. Excellent bonding to tooth
• D. No bonding to tooth

Explanation: Cavity varnish is a thin resin film that seals dentinal tubules but does not chemically adhere to tooth structure.

• A. Microfilled composite resins
• B. Pure gold
• C. Silver amalgam
• D. Type II Glass ionomer cement

Explanation: Type II glass ionomer cement has a coefficient of thermal expansion relatively close to that of enamel and dentin, reducing thermal…

• A. Compressive stress
• B. Impact stress
• C. Shear stress
• D. Tensile stress

Explanation: Amalgam withstands compressive forces well because its metallic mass resists crushing.