Dental Materials & Biomechanics Flashcards
6 cards from real ADAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Dental Materials & Biomechanics flashcards as text
What is the primary purpose of a dental die spacer in crown fabrication?
Answer: To create space for luting cement, ensuring accurate seating
Die spacer creates a uniform 20–40 micron space for cement, preventing hydraulic pressure during seating that would prevent full crown seating.
Which mechanical property is most important when selecting an endodontic file material to resist cyclic fatigue in curved canals?
Answer: High flexibility and cyclic fatigue resistance (NiTi alloys)
Nickel-titanium (NiTi) files have superelastic properties and excellent cyclic fatigue resistance, allowing safe negotiation of curved canals without instrument fracture.
What is the role of the 'C-factor' (cavity configuration factor) in composite restoration success?
Answer: Higher C-factor means more bonded surfaces relative to unbonded, increasing polymerization shrinkage stress
The C-factor is the ratio of bonded to unbonded surfaces; high C-factors (like class I cavities) increase polymerization shrinkage stress at margins, risking bond failure.
Which metal alloy is most appropriate for a long-span fixed partial denture (bridge) in the posterior region due to its combination of strength and minimal flexion?
Answer: Base metal alloy (Ni-Cr or Co-Cr)
Base metal alloys (Ni-Cr, Co-Cr) have a high modulus of elasticity (~200 GPa) that minimizes flexion in long-span bridges, reducing the risk of ceramic fracture.
What is the main advantage of fiber-reinforced composite (FRC) posts over metal posts in endodontically treated teeth?
Answer: FRC posts have a modulus of elasticity closer to dentin, reducing stress concentration and root fracture risk
FRC posts have a modulus of elasticity (~40 GPa) closer to dentin (~18 GPa) than metal posts (~200 GPa), distributing stress more evenly and reducing catastrophic root fracture.
Which surface treatment is essential before bonding resin cement to a lithium disilicate (e2.max) ceramic restoration?
Answer: Hydrofluoric acid etching followed by silane coupling agent application
HF acid etches the silica in lithium disilicate creating micro-retentive surface topography, and silane then chemically bonds to the silica for durable resin bonding.