Dental Materials & Technology Flashcards
7 cards from real AGD 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 Materials & Technology flashcards as text
What is the primary purpose of adding barium sulfate or strontium to composite resins?
Answer: Provide radiopacity for radiographic detection
Heavy metal salts like barium sulfate absorb X-rays, making composite restorations detectable on radiographs and distinguishable from recurrent caries.
Which factor most significantly affects the working time of polyether impression materials compared to vinyl polysiloxane?
Answer: Polyether has a significantly shorter working time due to faster polymerization
Polyether materials typically offer 2–3 minutes of working time compared to the 4–5 minutes available with most VPS materials.
Which type of stress does a cantilever pontic primarily place on the retaining abutment crown?
Answer: Torsional and bending (torque) stress
A cantilever pontic acts as a lever arm, generating rotational torque and bending moments that concentrate at the abutment connector.
The Knoop hardness of enamel (~340 KHN) compared to dentin (~70 KHN) has which clinical implication for composite selection?
Answer: Restorations must withstand occlusal forces against a very hard substrate requiring adequate filler content
Because enamel is very hard, opposing restorations and the composite itself must have sufficient hardness and wear resistance to avoid premature wear.
What is the function of the coupling agent (silane) applied to ceramic restoration surfaces before bonding?
Answer: Creates chemical bonds between the inorganic ceramic and organic resin cement
Silane is a bifunctional molecule with methoxysilyl groups that bond to silica in glass ceramics and methacrylate groups that co-polymerize with resin cement.
Which characteristic differentiates nanofill composites from nanohybrid composites?
Answer: Nanofill contains only nano-sized particles with no larger filler, yielding superior polish retention
Nanofill composites contain only nano-sized particles (5–75 nm), allowing a smoother polished surface with better gloss retention than hybrid systems.
In the lost-wax casting technique for metal restorations, what is the purpose of the sprue?
Answer: Provides a channel for molten metal to flow into the mold
The sprue is a wax rod attached to the pattern that, when burned out, leaves a channel through which molten alloy enters the investment mold.