Free Impression Materials MCQs with Answers

• A. Bullock heart
• B. Sea weed
• C. Chemicals
• D. Chick cells

Explanation: Agar is a natural polysaccharide obtained from certain seaweeds, especially red algae.

• A. Impression compound
• B. Zinc oxide-eugenol
• C. Agar-agar
• D. Alginate

Explanation: Perforations retain alginate mechanically as the material passes through the tray openings during removal.

• A. Trisodium phosphate reacts with calcium sulphate
• B. Trisodium phosphate reacts with sodium alginate
• C. Colloidal changes to sol
• D. Material in contact with soft tissues sets last

Explanation: Trisodium phosphate is a retarder that preferentially reacts with calcium sulfate, delaying formation of calcium ions until the retarder…

• A. Accelerating the setting stage of gypsum
• B. Increase strength
• C. Give dimensional stability
• D. None of the above

Explanation: Potassium sulfate in agar impression material counteracts agar's retarding effect on gypsum and accelerates the setting of the gypsum…

• A. Impression plaster
• B. Impression paste
• C. Alginate
• D. Rubber base impression material

Explanation: A corrective or wash impression in a complete denture procedure is commonly made with a thin layer of zinc oxide-eugenol impression paste…

• A. polyether polymer
• B. Colloidal silica
• C. Glycol ether
• D. Di-vinyl poly (dimethyl siloxane)

Explanation: Glycol ether functions as a plasticizer in polyether impression material, improving flexibility and handling.

• A. Concentration of filler and plasticizer
• B. Percentage composition by weight of water
• C. Concentration of potassium sulphate
• D. Temperature

Explanation: Reversible hydrocolloid changes from sol to gel and back according to temperature: cooling produces gelation and heating produces…

• A. Sol
• B. Hydrocolloid
• C. Gel
• D. Colloid

Explanation: Alginate is an irreversible hydrocolloid because its sol changes chemically into an insoluble calcium alginate gel and cannot be returned…

• A. Zinc oxide eugenol
• B. Elastomers
• C. Hydrocolloids
• D. Plaster of paris

Explanation: Syneresis is the loss of liquid from a gel during aging, causing shrinkage and distortion.

• A. Does not require special trays
• B. Does not adhere to tissues
• C. Is easy manipulation
• D. Has dimensional stability

Explanation: Zinc oxide eugenol impression paste sets to a dimensionally stable material, making it useful for accurate edentulous impressions.

• A. Remove saliva
• B. Remove excess impression material
• C. Hydrate the impression
• D. Accelerate the setting

Explanation: Rinsing removes saliva, blood and other oral contaminants from the impression surface before disinfection and cast pouring.

• A. Impression plaster
• B. Irreversible hydrocolloid
• C. Reversible hydroollioid
• D. None of the above

Explanation: Irreversible hydrocolloid, or alginate, is commonly used for preliminary impressions of partially edentulous arches and removable partial…

• A. Aromatic sulfonate esters
• B. Stannous octate
• C. Platinum salt catalyst
• D. Lead dioxide

Explanation: Lead dioxide oxidizes the terminal sulfhydryl groups of polysulfide, producing cross-linking and rubber formation.

• A. Impressions made n the custom trays are easier to remove from the mouth
• B. Custom trays require less impression material
• C. Stock trays may be short in the flange area
• D. Custom trays facilitate uniform contraction of impression material

Explanation: Custom trays provide uniform material thickness, use less material and avoid the inadequate flange extension sometimes seen with stock…

• A. Addition silicone
• B. Condensation silicone
• C. Polyetner
• D. Polysulphide

Explanation: Condensation silicone shows the greatest time-related contraction because its reaction releases volatile ethyl alcohol, which evaporates.

• A. Facilitates fabrication of metal dyes
• B. Solidfies between 50 - 70°C
• C. Liquefies between 71 - 100°C
• D. Cannot register fine surface details

Explanation: Agar is a reversible hydrocolloid that liquefies when heated, usually within about 71 to 100°C, and gels on cooling.

• A. Carbonates
• B. Water
• C. Sulfates
• D. Borax

Explanation: Borax strengthens the agar gel and is used as a modifying ingredient in agar hydrocolloid.

• A. 40 ml of water to 15 gms of powder
• B. 40 ml of water to 40 gms of powder
• C. 100 ml of water to 60 gms of powder
• D. 15 ml of water to 40 gms of powder

Explanation: A common alginate proportion is approximately 40 mL of water for 15 g of powder.

• A. Alginate
• B. Agar
• C. Elastome
• D. Zno paste

Explanation: Elastomeric materials are preferred after crown preparation because they provide accurate reproduction of the finish line and other fine…

• A. 43.5°C
• B. 39°C
• C. 65°C
• D. 100°C

Explanation: Impression compound has a glass transition temperature close to 39°C, which explains its thermoplastic softening and hardening behavior…