NBDE Prosthodontics and Operative Dentistry 3 — Questions and Answers
Question 1: The major connector for a maxillary removable partial denture should be located at least how far from the free gingival margin?
- 2 mm
- 6 mm (Correct answer)
- 4 mm
- 8 mm
Correct answer: 6 mm
The major connector must be placed at least 6 mm from the free gingival margin to avoid impingement on gingival tissue.
Question 2: Which material demonstrates the highest fracture toughness among current all-ceramic crown systems?
- Feldspathic porcelain
- Leucite-reinforced glass ceramic
- Zirconia (Y-TZP) (Correct answer)
- Lithium disilicate glass ceramic
Correct answer: Zirconia (Y-TZP)
Zirconia (yttria-stabilized tetragonal zirconia polycrystal) has the highest fracture toughness of current all-ceramic materials due to transformation toughening.
Question 3: In operative dentistry, the term 'convenience form' refers to:
- The shape that allows access for instruments and insertion of the restoration (Correct answer)
- The outline form that includes all carious tooth structure
- The depth of preparation to reach sound dentin
- The shape that resists displacement of the restoration
Correct answer: The shape that allows access for instruments and insertion of the restoration
Convenience form involves modifications to the cavity preparation that allow adequate access for instruments and proper placement of the restorative material.
Question 4: The retentive arm of a circumferential clasp for a removable partial denture engages the undercut at what relationship to the height of contour?
- At or above the height of contour
- Exactly at the height of contour
- Below the height of contour (Correct answer)
- At the cervical third regardless of contour
Correct answer: Below the height of contour
The retentive tip of the clasp must be positioned below the height of contour (in the undercut zone) to provide retention through clasp flexion.
Question 5: When evaluating a patient for implant-supported prosthetics, the minimum bone height required above the inferior alveolar canal for a standard implant is:
- 4 mm
- 8 mm
- 6 mm
- 10 mm (Correct answer)
Correct answer: 10 mm
A minimum of 10 mm of bone height above the inferior alveolar canal is generally required for safe placement of a standard-length dental implant.
Question 6: Composite resin polymerization shrinkage is most effectively reduced by:
- Using a higher intensity curing light
- Incremental placement technique (Correct answer)
- Increasing filler particle size
- Extending the curing time
Correct answer: Incremental placement technique
Incremental layering (2 mm or less per increment) limits the volume of composite curing at once and allows each increment to direct stress away from cavity walls.
Question 7: The function of the indirect retainer in a removable partial denture is to:
- Prevent lateral displacement of the denture base
- Resist rotation of the denture away from the tissue on the distal extension side (Correct answer)
- Distribute occlusal forces to the abutment teeth
- Maintain contact between the denture base and the residual ridge
Correct answer: Resist rotation of the denture away from the tissue on the distal extension side
The indirect retainer acts as a fulcrum point anterior to the direct retainers, resisting the rotational (lifting) movement of the distal extension base.
NBDE Prosthodontics and Operative Dentistry 3
The major connector for a maxillary removable partial denture should be located at least how far from the free gingival margin?