Dental Biomaterials Flashcards
7 cards from real ADEX practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Dental Biomaterials flashcards as text
Which impression material is considered the most dimensionally accurate and is preferred for fixed prosthodontic impressions?
Answer: Polyvinyl siloxane (addition silicone)
Polyvinyl siloxane (addition silicone) is considered the gold standard for fixed prosthodontic impressions due to its exceptional dimensional accuracy and stability.
In ceramics used for dental restorations, leucite crystals are added primarily to:
Answer: Increase fracture toughness and adjust thermal expansion coefficient
Leucite reinforcement increases the fracture toughness of porcelain and raises its coefficient of thermal expansion to match metal substructures in PFM restorations.
When mixing alginate impression material, using cold water will:
Answer: Prolong the working and setting time
Cold water slows the chemical reaction in alginate, extending both working and setting times, which is useful when more manipulation time is needed.
What is the primary cause of polymerization shrinkage in composite resins?
Answer: Van der Waals distances converting to shorter covalent bonds during crosslinking
During polymerization, monomers linked by van der Waals forces form shorter covalent bonds, reducing intermolecular distance and causing volumetric shrinkage.
Agar (reversible hydrocolloid) impression material converts from gel to sol by:
Answer: Heating to approximately 100°C
Agar is a thermoreversible material that liquefies (sol) upon heating to ~100°C and gels upon cooling, allowing it to be reused multiple times.
Which property is most critical when selecting a luting cement for cementing a porcelain-fused-to-metal crown?
Answer: Low film thickness to ensure accurate seating
Film thickness of a luting cement must be minimal (ideally ≤25 µm per ADA specification) to allow complete seating of the casting without distorting the occlusion.
Which statement about zirconia (zirconium oxide) dental ceramic is correct?
Answer: It is opaque and relies on transformation toughening for high strength
Zirconia is a polycrystalline ceramic that undergoes transformation toughening (tetragonal to monoclinic phase transformation) under stress, giving it exceptional fracture resistance.