AGD Dental Materials and Biomaterials Questions and Answers

Question 1

A dentist is taking a final impression for a crown on a maxillary molar.
The gingival margins are slightly subgingival, and maintaining a completely dry field is proving difficult despite best efforts.
Which impression material would be the most suitable choice in this situation due to its inherent properties?

Accepted Answer

Polyether

Answer

Addition silicone (PVS)

Answer

Condensation silicone

Answer

Impression compound

Question 2

The primary difference that accounts for the superior strength and abrasion resistance of a Type IV dental stone (die stone) compared to a Type III dental stone (model stone) is the:

Accepted Answer

Shape, size, and porosity of the hemihydrate particles.

Answer

Chemical composition of the calcium sulfate hemihydrate.

Answer

Use of a different accelerator in the powder.

Answer

Higher water-to-powder ratio required for mixing.

Question 3

In the formulation of modern high-copper dental amalgams, what is the primary function of the increased copper content compared to traditional low-copper alloys?

Accepted Answer

To eliminate the weak and corrosion-prone Gamma-2 (Sn-Hg) phase.

Answer

To improve the polishability and luster of the final restoration.

Answer

To increase the setting expansion for a tighter marginal seal.

Answer

To accelerate the setting reaction, reducing clinical chair time.

Question 4

A 55-year-old patient with a history of severe bruxism requires a three-unit fixed partial denture to replace tooth #19. Strength and fracture resistance are the highest priority. Which all-ceramic material would be the most appropriate choice for the framework of this prosthesis?

Accepted Answer

Zirconia

Answer

Feldspathic porcelain

Answer

Leucite-reinforced glass-ceramic

Answer

Lithium disilicate

Question 5

Which of the following dental cements is unique in its ability to form a true chemical bond to tooth structure via an ionic interaction between its polyacid component and calcium in the hydroxyapatite?

Accepted Answer

Glass ionomer cement

Answer

Zinc phosphate cement

Answer

Zinc oxide-eugenol (ZOE) cement

Answer

Self-adhesive resin cement

Question 6

The excellent biocompatibility and long-term clinical success of commercially pure titanium as a dental implant material is primarily attributed to which of the following phenomena?

Accepted Answer

The formation of a stable, inert, and self-passivating oxide layer.

Answer

Its modulus of elasticity being identical to cortical bone.

Answer

Its inherent bacteriostatic properties that inhibit plaque.

Answer

Its low thermal conductivity, preventing thermal irritation.