DMD Dental Materials Science 2

Question 1

Which ADA Type of gypsum product has the highest compressive strength and is most suitable for fabricating dental dies?

Accepted Answer

Type IV — Die stone

Answer

Type I — Impression plaster

Answer

Type II — Model plaster

Answer

Type III — Dental stone

Question 2

The elastic modulus (Young's modulus) of a dental material represents:

Accepted Answer

The ratio of stress to strain within the elastic range

Answer

Maximum stress the material sustains before fracture

Answer

The material's resistance to surface abrasion

Answer

Energy absorbed per unit volume before fracture

Question 3

Glass ionomer cement achieves adhesion to tooth structure primarily through which mechanism?

Accepted Answer

Chemical ionic bonding with calcium in hydroxyapatite

Answer

Micromechanical interlocking with etched enamel

Answer

Van der Waals intermolecular forces

Answer

Covalent bonding with collagen fibers

Question 4

What is the primary clinical significance of fluoride release from glass ionomer cements?

Accepted Answer

Provides secondary anticariogenic protection at restoration margins

Answer

Increases compressive strength over time

Answer

Improves translucency and esthetics

Answer

Accelerates final set of the cement

Question 5

In porcelain-fused-to-metal (PFM) restorations, which type of ceramic is layered directly onto the metal coping?

Accepted Answer

Feldspathic porcelain

Answer

Leucite-reinforced pressed ceramic

Answer

Lithium disilicate glass-ceramic

Answer

Monolithic zirconia

Question 6

The setting expansion of dental stone during gypsum product fabrication is clinically important because it:

Accepted Answer

Compensates for the solidification shrinkage of gold casting alloys

Answer

Improves the surface hardness of the die material

Answer

Prevents internal porosity during mixing

Answer

Reduces water evaporation during storage

Question 7

Which elastomeric impression material offers the greatest dimensional accuracy and long-term stability for fixed prosthodontic impressions?

Accepted Answer

Polyvinyl siloxane (addition silicone)

Answer

Alginate (irreversible hydrocolloid)

Answer

Zinc oxide eugenol impression paste

Answer

Polysulfide rubber base