Dental Materials and Procedures Flashcards

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

Answer: Dimensional change — initial contraction before expansion

Fresh amalgam undergoes slight contraction immediately after setting, before its later characteristic expansion, creating initial marginal gaps that may allow microleakage.

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

Answer: Chemical adhesion through ionic bonding with hydroxyapatite

Glass ionomer cements adhere to tooth structure primarily through ionic bonding between the carboxylate groups of the polyacrylic acid and the calcium in hydroxyapatite.

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

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

The smear layer is a thin film of debris on prepared dentin that plugs tubule openings; acid etching dissolves it and opens dentinal tubules, enabling resin tag formation.

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

Answer: Alginate

Alginate is an irreversible hydrocolloid because its gelation is a chemical reaction that cannot be reversed; it cannot be re-liquefied and reused.

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

Answer: Incremental placement technique with each increment ≤2 mm

Placing composite in increments of 2 mm or less and curing each layer independently reduces the volume contracting at any one time, minimizing stress at the tooth-restoration interface.

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

Answer: Sodium bisulfite (sodium metabisulfite)

Sodium bisulfite (or sodium metabisulfite) is the antioxidant added to local anesthetic cartridges containing vasoconstrictors (epinephrine) to prevent their oxidation and degradation.