NBDHE Dental Materials and Procedures 2

Question 1

Which property of amalgam restorations is responsible for the initial poor marginal seal shortly after placement?

Accepted Answer

Dimensional change — initial contraction before expansion

Answer

Immediate galvanic corrosion

Answer

Excessive plasticity

Answer

High coefficient of thermal expansion

Question 2

Which bonding mechanism primarily explains the adhesion of glass ionomer cement to tooth structure?

Accepted Answer

Chemical adhesion through ionic bonding with hydroxyapatite

Answer

Micromechanical interlocking only

Answer

Van der Waals forces

Answer

Hydrophobic bonding

Question 3

What is the purpose of the smear layer in restorative dentistry, and how does acid etching affect it?

Accepted Answer

It plugs dentinal tubules; acid etching removes it and opens tubules

Answer

It strengthens dentin; acid etching hardens it further

Answer

It prevents bacterial invasion; acid etching reinforces it

Answer

It has no clinical significance; acid etching has no effect

Question 4

Which type of impression material is classified as an irreversible hydrocolloid?

Accepted Answer

Alginate

Answer

Agar

Answer

Polyvinyl siloxane

Answer

Zinc oxide eugenol

Question 5

Composite resin restorations undergo polymerization shrinkage. Which technique BEST reduces the clinical consequences of this shrinkage?

Accepted Answer

Incremental placement technique with each increment ≤2 mm

Answer

Bulk placement in a single increment

Answer

Placing composite without bonding agent

Answer

Using a high-intensity curing light for the full bulk at once

Question 6

Which component of local anesthetic solution is primarily responsible for preventing oxidation of the vasoconstrictor?

Accepted Answer

Sodium bisulfite (sodium metabisulfite)

Answer

Sodium chloride

Answer

Methylparaben

Answer

Hydrochloric acid