NBDE Restorative Dentistry 4 — Questions and Answers
Question 1: A dentist discovers a previously placed composite restoration has secondary caries confined to the margin. The MOST conservative management is:
- Complete removal and replacement of the entire restoration
- Repair by selectively removing only the carious margin and rebonding (Correct answer)
- Placing a full-coverage crown
- Monitoring without treatment for 6 months
Correct answer: Repair by selectively removing only the carious margin and rebonding
Selective repair of a marginal defect with secondary caries is the most conservative option, preserving sound tooth structure and the remaining sound restoration.
Question 2: Glass ionomer cement releases fluoride primarily through which mechanism?
- Ion exchange with saliva
- Dissolution of the cement matrix
- Sustained diffusion from the set material (Correct answer)
- Reaction with enamel hydroxyapatite
Correct answer: Sustained diffusion from the set material
Fluoride ions are entrapped within the set glass ionomer matrix and are released by sustained diffusion over time, providing a caries-inhibiting effect.
Question 3: Which of the following best describes the 'C-factor' in composite resin placement?
- Coefficient of thermal expansion relative to enamel
- Ratio of bonded to unbonded surfaces in a cavity (Correct answer)
- Concentration of filler particles
- Cure depth in millimeters
Correct answer: Ratio of bonded to unbonded surfaces in a cavity
The C-factor (configuration factor) is the ratio of bonded cavity walls to unbonded free surfaces; a higher C-factor increases polymerization shrinkage stress at the bond interface.
Question 4: A patient presents with a fractured maxillary central incisor involving enamel and dentin without pulp exposure. The FIRST step in treatment is:
- Place a direct composite restoration immediately
- Perform pulp capping with calcium hydroxide
- Cover exposed dentin with a sedative dressing and reassess pulp vitality (Correct answer)
- Extract the tooth and place an implant
Correct answer: Cover exposed dentin with a sedative dressing and reassess pulp vitality
Exposed dentin should be protected and pulp vitality assessed before definitive restoration, as pulpal response can change in the weeks following trauma.
Question 5: In pin-retained amalgam restorations, the most common complication associated with threaded pins is:
- Pulp perforation
- Dentinal crazing and cracking (Correct answer)
- Pin corrosion
- Inadequate retention
Correct answer: Dentinal crazing and cracking
Threaded pins create stress concentrations that cause dentinal crazing and microcracks as the pin is driven into dentin, potentially weakening the tooth.
Question 6: Which of the following composite resin filler particle sizes provides the best combination of esthetics and wear resistance for posterior restorations?
- Macrofill
- Microfill
- Hybrid (microhybrid) (Correct answer)
- Nanofill
Correct answer: Hybrid (microhybrid)
Hybrid composites combine multiple filler sizes to achieve both adequate wear resistance for posterior use and a smooth, esthetic surface finish.
Question 7: When preparing a tooth for a ceramic veneer, the preparation depth on the facial surface should remain primarily within:
- Enamel only (Correct answer)
- The outer third of dentin
- The middle third of dentin
- The inner third of dentin near the pulp
Correct answer: Enamel only
Veneer preparations should remain within enamel whenever possible because enamel provides better bonding for ceramic veneers and preserves the vitality of the tooth.
NBDE Restorative Dentistry 4
A dentist discovers a previously placed composite restoration has secondary caries confined to the margin.
The MOST conservative management is: