NBDE Restorative Dentistry 3

Question 1

A dentist is preparing a tooth for a full-coverage metal-ceramic crown. The facial reduction should be approximately:

Accepted Answer

1.5–2.0 mm

Answer

Facial reduction of 1.5–2.0 mm is required for metal-ceramic crowns to provide adequate space for the metal coping and overlying porcelain without compromising esthetics or strength.

Question 2

Which finish line design provides the best support for an all-ceramic crown margin?

Accepted Answer

Deep chamfer or shoulder

Answer

A deep chamfer or shoulder provides a definitive seat and adequate bulk of ceramic at the margin, reducing the risk of fracture in all-ceramic restorations.

Question 3

The phenomenon where a freshly mixed zinc phosphate cement begins to set rapidly due to excess water is called:

Accepted Answer

Exothermic acceleration

Answer

Excess moisture accelerates the exothermic acid-base reaction of zinc phosphate cement, causing premature setting.

Question 4

A patient requires a posterior composite restoration on tooth #19. To prevent cuspal fracture, the dentist should ensure:

Accepted Answer

Cuspal coverage is included in the restoration design

Answer

When substantial tooth structure is missing, cuspal coverage with composite or an indirect restoration protects weakened cusps from fracture under occlusal stress.

Question 5

Which property of dental amalgam is primarily responsible for its long-term marginal integrity?

Accepted Answer

Corrosion byproducts that seal the margin

Answer

Corrosion products (tin oxides and chlorides) accumulate at the amalgam-tooth interface over time, effectively sealing the margin and reducing microleakage.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

NBDE Restorative Dentistry 3