NBDE Restorative Dentistry 5

Question 1

Which type of taper is recommended for full-crown preparations to balance retention and resistance form?

Accepted Answer

6–10 degrees total convergence angle

Answer

A total occlusal convergence of 6–10 degrees provides adequate retention while allowing seating of the crown and appropriate resistance form.

Question 2

A patient has a defective marginal ridge on an existing MOD amalgam. The MOST likely clinical consequence if left untreated is:

Accepted Answer

Loss of contact and food impaction leading to periodontal disease

Answer

A defective marginal ridge can collapse, eliminating the proximal contact and causing food impaction that leads to periodontal bone loss and caries.

Question 3

The ADA Specification No. 1 for dental amalgam specifies maximum allowable dimensional change after setting. Which behavior is ACCEPTABLE?

Accepted Answer

Expansion of 20 μm/cm or less

Answer

ADA Specification No. 1 allows a maximum expansion of 20 μm/cm and a maximum contraction of 0 μm/cm (no net contraction permitted) for amalgam.

Question 4

Bonding to enamel using phosphoric acid etching creates micro-tags by:

Accepted Answer

Selectively removing enamel rod cores or peripheries to create micro-porosities

Answer

Phosphoric acid selectively dissolves enamel rod cores or peripheries depending on the etching pattern, creating micro-porosities into which resin flows and polymerizes.

Question 5

A full gold crown is being cemented with zinc phosphate. To minimize postoperative sensitivity, the dentist should:

Accepted Answer

Mix the cement on a chilled glass slab with prolonged spatulation to slow setting

Answer

Mixing zinc phosphate on a chilled slab and spatulating over a larger area slows the exothermic reaction, lowers the initial pH, and reduces pulpal irritation.

NBDE - National Board Dental Examination Practice Test

NBDE - National Board Dental Examination Practice Test

NBDE Restorative Dentistry 5