All Free Dental Materials MCQs with Answers

• A. Polymerization occurs with repeated elimination of small molecules
• B. Polymerization occurs with elimination of single byproduct
• C. By condensation of repeated molecules of monomers
• D. Condensation does not occur at all

Explanation: Condensation silicone sets by repeated condensation reactions that release a small molecule, chiefly ethyl alcohol, as a by-product.

• A. Using less water powder ratio
• B. Using humidor
• C. Prolonged manipulation
• D. Storing the impression under water

Explanation: Hydrocolloid impressions lose or gain water easily, so a delay before pouring is best managed in a humid environment.

• A. Mineral oil
• B. Water
• C. Surfactant
• D. Plasticizer

Explanation: A surfactant is incorporated into vinyl polysiloxane to lower its contact angle and improve wetting of moist tooth surfaces.

• A. Retarder
• B. Modifier
• C. Plasticier
• D. Accelerator

Explanation: Magnesium chloride accelerates the setting reaction of zinc oxide eugenol impression paste.

• A. Is a thermoset material
• B. Warps at room temperature
• C. Shows increased flow when kneaded with water
• D. Low coefficient of thermal conductivity

Explanation: Impression compound is thermoplastic, meaning it softens on heating and hardens on cooling, rather than undergoing irreversible thermoset…

• A. Reduced dimensional instability
• B. Improved adhesion of the impression to the tray
• C. Minimal permanent deformation
• D. Reduced contamination by saliva

Explanation: A rubber impression should be removed rapidly in one firm motion because prolonged or uneven removal increases viscous deformation.

• A. Alginate
• B. Reversible hydrocolloid
• C. Zinc oxide-eugenol
• D. Polysulphide rubber

Explanation: Zinc oxide-eugenol sets into a relatively rigid, brittle impression material.

• A. Hydrophilic
• B. Potassium alginates
• C. Water loving impression materials
• D. Hydrophobic

Explanation: Most elastomers, including polysulfide and silicone, are hydrophobic, whereas polyether is relatively hydrophilic.

• A. Hydrocolloid
• B. Impression compound
• C. Elastomer
• D. Zinc oxide eugenol

Explanation: Hydrocolloid impressions may require hardening or setting control through cooling or suitable conditioning solutions, unlike impression…

• A. Gelation increase in both on increase in temperature
• B. Mixing time is increased to reduce the setting time
• C. Deformation during removal of impression occurs due to distortion of gel fibers
• D. Both can be re-used for fresh impressions

Explanation: Both alginate and agar are hydrocolloids, so removal can distort their gel network or fibers when the impression is stretched.

• A. 20°C to 25°C
• B. 27°C to 33°C
• C. 37°C to 50°C
• D. 55°C to 60°C

Explanation: Agar generally gels at approximately 37°C to 50°C, allowing it to set in the mouth after being cooled from its liquefaction temperature.

• A. Agar
• B. Zinc oxide impression material
• C. Condensation silicone
• D. Polyether

Explanation: Agar forms a gel with a characteristic brush-heap or fibrillar structure when cooled.

• A. Polysulphide
• B. Impression plaster
• C. Silicone
• D. Zinc oxide eugenol paster

Explanation: Impression plaster is highly mucostatic and records tissues with minimal displacement because it flows readily before setting.

• A. Agar-agar
• B. Alginate
• C. Impression compound
• D. Polyether

Explanation: Impression compound is a rigid, thermoplastic material and therefore cannot undergo elastic recovery during removal.

• A. Close adaptation to soft tissues
• B. Compatibility with gypsum products
• C. Reproduction of surface details
• D. With drawl without permanent distortion

Explanation: The key benefit of elasticity is elastic recovery, allowing an impression to pass around undercuts and be withdrawn without permanent…

• A. Low thermal conductivity
• B. Crystalline structure
• C. Formation of cross linkage with heating
• D. High fusion temperature

Explanation: The base of impression compound has low thermal conductivity, so heat does not spread rapidly through it and uneven softening may occur.

• A. polysulfides
• B. Polyether
• C. addition silicones
• D. Condensation silicones

Explanation: Polyether impression materials can cause hypersensitivity, including contact dermatitis, in susceptible patients, partly because of their…

• A. Accelerator
• B. Reactor
• C. Retarder
• D. Plasticizer

Explanation: Trisodium phosphate consumes the available calcium ions initially and delays alginate gel formation, so it acts as a retarder.

• A. Polyvinyl siloxane
• B. Zinc Oxide eugenol (ZOE) paste
• C. Wax
• D. Impression compound

Explanation: Polyvinyl siloxane is an elastomeric impression material that sets to a flexible rubber-like solid and recovers from undercuts.

• A. 19
• B. 20
• C. 21
• D. 26

Explanation: ADA Specification No. 19 covers non-aqueous elastomeric dental impression materials, including polysulfides, silicones and polyethers.