Free Properties of Dental Materials MCQs with Answers

• A. Which undergoes rapid expansion
• B. In which amount of water of hydration is controlled
• C. In which accelerators or retarders have been added according to need
• D. In which the crystals are all of uniform size

Explanation: Balanced stone is modified dental stone whose setting behaviour is adjusted by adding accelerators or retarders as required.

• A. Solubility
• B. Shelf life
• C. Particle porosity
• D. Chemical formula

Explanation: Plaster and stone have the same basic calcium sulfate hemihydrate composition, but their particles differ in porosity because of their…

• A. None of the above
• B. Less water
• C. no water
• D. More water

Explanation: Beta hemihydrate particles are irregular and porous, so they require more mixing water to wet their larger internal surface area.

• A. Class I stone or hydrocal
• B. Densite
• C. Class II stone
• D. Model or lab plaster

Explanation: Type III gypsum is the conventional dental stone used for casts and is commonly identified as Class I stone or hydrocal.

• A. Beta - hemihydrates
• B. Alpha - hemihydrates
• C. Calcium sulphate dihydrate
• D. Orthorhombic anhydrate

Explanation: Calcining gypsum under steam pressure or in the presence of sodium succinate produces the denser alpha hemihydrate form.

• A. Tensile strength
• B. Wet strength
• C. Green strength
• D. compressive strength

Explanation: Gypsum products are brittle, so their clinically important strength is conventionally measured by compressive strength.

• A. Setting time
• B. Setting expansion
• C. Hardness of the set product
• D. None of the above

Explanation: Accelerators shorten and retarders lengthen the working and setting periods of gypsum, so they are primarily used to regulate setting…

• A. Calcium phosphate
• B. Calcium sulphate hemihydrate
• C. Calcium anhydrate
• D. Calcium sulphate dihydrate

Explanation: Dental plaster is mainly calcium sulphate hemihydrate, which reacts with water to form calcium sulphate dihydrate.

• A. Impression of single tooth
• B. Impression of whole teeth
• C. Replica of single tooth
• D. Replica of whole teeth

Explanation: A die is a positive replica of a prepared individual tooth, usually used for fabricating an indirect restoration.

• A. Plastic bowl
• B. Metal bowl
• C. Glass bowl
• D. Rubber bowl

Explanation: Plaster is mixed in a flexible rubber bowl because it permits efficient spatulation and can be easily cleaned by flexing the bowl after…

• A. 18.6ml
• B. 22.2ml
• C. 30.4ml
• D. 45.3ml

Explanation: Converting hemihydrate to dihydrate requires 1.5 moles of water for each mole of calcium sulphate hemihydrate.

• A. Dry strength
• B. Compressive strength
• C. The wet strength
• D. Strength of dental stone due to green colour

Explanation: Green strength is the strength of gypsum while it is still moist, before complete drying.

• A. 0.28 and 0.98
• B. 0.6 and 0.28
• C. 0.6 and 3.2
• D. 0.28 and 0.6

Explanation: Dental stone needs much less water than plaster because its particles are denser and more regularly shaped; typical values are about 0.28…

• A. (CaSO4)2-½H2O
• B. CaCO3
• C. CaO
• D. CaSO4-2H2O

Explanation: Before mixing with water, model plaster consists mainly of calcium sulphate hemihydrate, written as CaSO4·½H2O.

• A. Sand
• B. Diamond
• C. Silicon arbide
• D. Aluminum oxide

Explanation: Diamond is classified as a superabrasive because of its exceptional hardness and cutting ability.

• A. Emery
• B. Garnet
• C. Rouge
• D. Pumice

Explanation: Crocus cloth is an abrasive cloth coated with ferric oxide, commonly called rouge.

• A. Mercury sulphide
• B. Mercury vapour
• C. Inorganic mercury forms
• D. Methyl and ethyl mercury

Explanation: Organic mercury compounds, especially methyl mercury and ethyl mercury, are more toxic because they readily enter tissues and the nervous…

• A. Truing
• B. Buffing
• C. Dressing
• D. Blinding

Explanation: Blinding is the clogging of abrasive spaces by metal or other debris, reducing the wheel's cutting action.

• A. QTH
• B. Argon lasers
• C. LED
• D. PAC

Explanation: An argon laser produces energy concentrated at characteristic, very narrow wavelengths, often described as monochromatic.

• A. Compression
• B. Tensile force
• C. Shear
• D. Transverse bending force

Explanation: Torsion twists a material around its axis, producing shear stresses within it.