MFDS Dental Materials 1 — Questions and Answers
Question 1: Which monomer is the principal component of composite resin matrices?
- PMMA
- Bis-GMA (Correct answer)
- UDMA
- TEGDMA
Correct answer: Bis-GMA
Bis-GMA (bisphenol A glycidyl methacrylate) is the foundational dimethacrylate monomer introduced by Bowen that forms the basis of most composite resin matrices.
Question 2: The setting reaction of zinc phosphate cement involves:
- Polymerisation
- Acid-base neutralisation (Correct answer)
- Chelation
- Free radical initiation
Correct answer: Acid-base neutralisation
Zinc phosphate cement sets via an acid-base reaction between zinc oxide powder and orthophosphoric acid liquid, forming zinc phosphate salt.
Question 3: Which alloy system is most commonly used for high-strength dental casting alloys?
- Gold-palladium
- Cobalt-chromium (Correct answer)
- Nickel-titanium
- Silver-tin
Correct answer: Cobalt-chromium
Cobalt-chromium alloys are the most widely used base metal alloys for removable partial denture frameworks due to their high strength, hardness and corrosion resistance.
Question 4: What property of impression materials describes their ability to recover from deformation after removal from the mouth?
- Viscosity
- Elastic recovery (Correct answer)
- Dimensional stability
- Wettability
Correct answer: Elastic recovery
Elastic recovery (or strain recovery) is the ability of an impression material to return to its original dimensions after being deformed during removal from undercuts.
Question 5: Glass ionomer cement bonds to tooth structure primarily through:
- Micromechanical retention
- Ionic bonding to calcium (Correct answer)
- Van der Waals forces
- Covalent bonding to collagen
Correct answer: Ionic bonding to calcium
Glass ionomer cement forms ionic bonds between carboxylate groups of the polyacid and calcium ions in hydroxyapatite, providing true chemical adhesion.
Question 6: Which heat treatment process reduces the brittleness of dental porcelain?
- Sintering
- Glazing
- Tempering (Correct answer)
- Degassing
Correct answer: Tempering
Tempering involves controlled cooling that induces surface compressive stresses in porcelain, increasing its resistance to crack propagation and fracture.
MFDS Dental Materials 1
Which monomer is the principal component of composite resin matrices?