Free Impression Materials MCQs with Answers

• 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.

• A. Condensation silicone
• B. Alginate
• C. Polysulfide
• D. Addition silicone

Explanation: Polysulfide has the greatest tear strength among the common elastomeric impression materials, making it more resistant to tearing in thin…

• A. Provides gel strength
• B. Acts as an accelerator
• C. Initiating the setting reaction
• D. increasing the working time of alginate impression material

Explanation: Trisodium phosphate reacts preferentially with calcium ions and delays formation of the alginate gel, thereby increasing working time.

• A. Agar
• B. Alginate impression material
• C. Primary impression
• D. Both of the above

Explanation: Agar syringe material is the low-viscosity component used with agar tray material and can also be combined with alginate in a combination…

• A. Low thermal conductivity
• B. High flow property
• C. Degradation is presence of moisture
• D. Remain distortion free up to 72 hrs. pouring can be safely delayed

Explanation: Impression compound has low thermal conductivity, so it takes time to soften and cool.

• A. Mercaptan
• B. A and B
• C. Reversible hydrocolloid
• D. Silicone

Explanation: Heavy- and light-body consistencies are used in elastomeric systems, including polysulfide, formerly called mercaptan, and silicone…

• A. Increase gel strength
• B. Prevent syneresis
• C. Wash off saliva on impression
• D. Prevent distortion

Explanation: Washing an elastic impression removes saliva, blood and other surface contaminants before the cast is poured.

• A. alginate
• B. Alginic acid
• C. Gelatin
• D. Agar

Explanation: Agar is the principal gel-forming constituent of reversible hydrocolloid impression material.

• A. Hydrocolloids
• B. Impression plaster
• C. Elastomer
• D. Impression compound

Explanation: Hydrocolloids undergo a reversible sol-to-gel transformation: heating converts the gel to sol and cooling converts it back to gel.

• A. Reversible hydrocolloid
• B. Mercaptan impression material
• C. Zinc Phosphate cement
• D. Zinc oxide-eugenol

Explanation: Vulcanization is the cross-linking process used to set mercaptan, or polysulfide, impression material.

• A. Oral mucosal tissues
• B. Dental hard tissues
• C. Oral mucosal tissues and dental hard tissues
• D. None of the above

Explanation: An impression records both the oral soft tissues, such as mucosa, and hard tissues, such as teeth and prepared surfaces.

• A. Gelation
• B. Water absorption
• C. Shrinkage
• D. Seen as water loss

Explanation: Syneresis is the expulsion of liquid from a hydrocolloid gel, so it appears as water loss and causes shrinkage.

• A. Agar-agar
• B. Alginate
• C. Zinc oxide eugenol
• D. Plaster of paris

Explanation: Agar-agar is preferred for duplicating casts because it is a reversible hydrocolloid that can reproduce fine detail and be liquefied for…

• A. Marcaptan group
• B. Silane group
• C. Hydroxyl group
• D. Virryl group

Explanation: The base paste of condensation silicone contains hydroxyl-terminated dimethyl siloxane, which reacts during condensation polymerisation.

• A. Moisture absorption
• B. All of the above
• C. Phenomenon of conversion of gel into sol
• D. Temperature lag between gelation and liquefaction temperature

Explanation: Hysteresis is the temperature difference between liquefaction and gelation of a hydrocolloid, allowing the sol-to-gel and gel-to-sol…

• A. They set by condensation polymerisation
• B. They exhibit a very low setting shrinkage
• C. They have a lower tear resistance than polysulphide rubbers
• D. They evolve hydrogen when cast if they are not fully cured

Explanation: Type II silicone is addition-cured silicone and sets by addition polymerisation, not condensation polymerisation.