Dental Materials Flashcards

The coefficient of thermal expansion of an ideal restorative material should be:

Answer: Similar to natural tooth structure to minimize marginal stress

A restorative material with a coefficient of thermal expansion close to tooth structure expands and contracts similarly, reducing marginal gaps and microleakage.

When pouring a gypsum model, the vibrator is used primarily to:

Answer: Eliminate air bubbles from the mix

Vibration causes air bubbles incorporated during mixing to rise to the surface, preventing voids in the finished model.

Which type of porcelain firing produces the strongest ceramic restoration?

Answer: Vacuum-fired porcelain

Vacuum firing removes air from the ceramic mass during sintering, producing a denser, stronger, and more translucent porcelain.

A study model poured from an alginate impression should ideally be poured within:

Answer: 30 minutes

Alginate impressions must be poured within 30 minutes to prevent dimensional changes from syneresis and imbibition.

What is the primary advantage of polyether impression material over addition silicone?

Answer: Superior hydrophilicity for accurate impressions in moist fields

Polyether is inherently more hydrophilic than addition silicone, allowing it to produce more accurate impressions in the presence of moisture.

Hybrid composite resin was developed to improve upon microfill composite's weakness in:

Answer: Strength and resistance to fracture in posterior areas

Hybrid composites incorporate larger filler particles to achieve the strength needed for posterior load-bearing restorations that microfills lacked.

The film thickness of a luting cement is critical because an excessively thick film will:

Answer: Prevent complete seating of the casting and affect the occlusion

Thick cement film prevents a casting from seating to its intended depth, raising the restoration and causing high occlusal contacts.