AGD Dental Materials and Biomaterials 4 — Questions and Answers
Question 1: Which property of an ideal implant biomaterial is described as the ability to integrate with surrounding bone without fibrous encapsulation?
- Biocompatibility
- Osseointegration (Correct answer)
- Corrosion resistance
- Bioactivity
Correct answer: Osseointegration
Osseointegration, defined by Brånemark, describes the direct structural and functional connection between living bone and the implant surface without intervening soft tissue.
Question 2: Surface roughness of titanium implants is most commonly increased by which process to enhance osseointegration?
- Electropolishing
- Sandblasting and acid etching (SLA) (Correct answer)
- Anodization only
- Passivation coating
Correct answer: Sandblasting and acid etching (SLA)
Sandblasted, large-grit, acid-etched (SLA) surfaces increase microroughness significantly, improving bone-to-implant contact and osseointegration speed.
Question 3: Which endodontic sealer component is responsible for the antimicrobial activity of zinc oxide eugenol sealers?
- Zinc oxide
- Eugenol (Correct answer)
- Canada balsam resin
- Bismuth subcarbonate
Correct answer: Eugenol
Eugenol is the primary antimicrobial agent in ZOE sealers, inhibiting bacterial growth through disruption of lipid membranes.
Question 4: The fatigue failure of a metal restoration is best described as failure due to:
- A single overload exceeding ultimate tensile strength
- Repeated cyclic stresses below the proportional limit (Correct answer)
- Chemical corrosion under static load
- Thermal expansion mismatch
Correct answer: Repeated cyclic stresses below the proportional limit
Fatigue failure occurs from repeated cyclic loading at stresses well below the material's ultimate strength, eventually causing crack initiation and propagation.
Question 5: Which ion released from glass ionomer cement is primarily responsible for its cariostatic properties?
- Aluminum
- Calcium
- Fluoride (Correct answer)
- Strontium
Correct answer: Fluoride
Fluoride ions released from glass ionomer cement inhibit bacterial metabolism and promote remineralization of adjacent tooth structure.
Question 6: What is the most important clinical reason to use a cavity varnish under amalgam restorations when zinc phosphate cement is not used?
- Increase bond strength between amalgam and dentin
- Reduce microleakage before amalgam seals margins naturally (Correct answer)
- Enhance compressive strength of amalgam
- Prevent amalgam from sticking to matrix band
Correct answer: Reduce microleakage before amalgam seals margins naturally
Cavity varnish seals dentinal tubules and reduces early microleakage while amalgam undergoes corrosion-based marginal sealing over the first weeks.
Question 7: Which agar impression material property makes it necessary to use a water-cooled tray during impression taking?
- It sets by condensation polymerization
- It undergoes sol-gel transition controlled by temperature (Correct answer)
- It absorbs water from oral tissues
- It requires chemical accelerators to set
Correct answer: It undergoes sol-gel transition controlled by temperature
Agar (reversible hydrocolloid) converts from sol (fluid) to gel (solid) via cooling; a water-cooled tray circulates cold water to set the material consistently in the mouth.
AGD Dental Materials and Biomaterials 4
Which property of an ideal implant biomaterial is described as the ability to integrate with surrounding bone without fibrous encapsulation?