ADAT Dental Materials & Biomechanics 2

Question 1

What is the significance of the critical stress intensity factor (KIC) in dental ceramics?

Accepted Answer

It quantifies the material's resistance to crack propagation

Answer

It measures resistance to thermal shock

Answer

It determines the material's biocompatibility

Answer

It measures flexural strength under loading

Question 2

Which cement is most appropriate for luting a porcelain-fused-to-metal (PFM) crown on a vital tooth with adequate retention form?

Accepted Answer

Resin-modified glass ionomer cement (RMGIC)

Answer

Resin cement (adhesive cementation)

Answer

Zinc phosphate cement

Answer

Zinc oxide eugenol (ZOE) cement

Question 3

What is the ideal water-to-powder ratio for dental stone (Type III gypsum) compared to plaster (Type II)?

Accepted Answer

Stone uses less water than plaster, producing a denser, stronger product

Answer

Stone uses more water than plaster for better flow

Answer

Both use the same water-to-powder ratio

Answer

Stone requires twice the water of plaster for proper setting

Question 4

Which property of wax makes it suitable for occlusal registration but problematic if not handled correctly?

Accepted Answer

Thermal contraction during cooling can cause dimensional inaccuracy

Answer

High melting point prevents distortion

Answer

Chemical bonding to tooth structure provides stability

Answer

Radiopacity allows verification on radiographs

Question 5

Which type of indirect restoration is most appropriate for a large MOD cavity in a mandibular molar with a cracked marginal ridge?

Accepted Answer

Indirect composite or ceramic onlay

Answer

Direct composite resin

Answer

Amalgam restoration with pins

Answer

Full-coverage ceramic crown

Question 6

What causes 'low-temperature degradation' (aging) in zirconia dental restorations?

Accepted Answer

Hydrothermal transformation from tetragonal to monoclinic phase in the presence of water

Answer

UV light causes surface cracking over time

Answer

Thermal cycling causes microcrack propagation at grain boundaries

Answer

Salivary enzymes chemically attack the zirconia surface