NBDE Prosthodontics and Operative Dentistry 2 — Questions and Answers
Question 1: Which finish line preparation design provides the best esthetic result for an all-ceramic crown?
- Chamfer
- Shoulder with bevel
- Deep chamfer or shoulder (Correct answer)
- Knife-edge
Correct answer: Deep chamfer or shoulder
A deep chamfer or shoulder finish line provides adequate bulk of ceramic material at the margin for optimal esthetics and strength.
Question 2: The Kennedy Class II modification 1 removable partial denture indicates:
- Bilateral posterior edentulous areas with one anterior modification
- Unilateral posterior edentulous area with one anterior modification space (Correct answer)
- Bilateral posterior edentulous areas with no modifications
- Unilateral posterior edentulous area with no modifications
Correct answer: Unilateral posterior edentulous area with one anterior modification space
Kennedy Class II is a unilateral posterior edentulous area, and modification 1 indicates one additional edentulous area elsewhere in the arch.
Question 3: The resistance form in cavity preparation primarily prevents:
- Microleakage at the margins
- Fracture of the tooth or restoration under occlusal loading (Correct answer)
- Pulpal irritation from the restorative material
- Secondary caries formation
Correct answer: Fracture of the tooth or restoration under occlusal loading
Resistance form consists of features that prevent fracture of both the tooth structure and the restorative material under occlusal forces.
Question 4: When fabricating a complete denture, the vertical dimension of occlusion (VDO) differs from the vertical dimension of rest (VDR) by approximately:
- 1-2 mm (freeway space) (Correct answer)
- 5-7 mm
- 3-4 mm
- 8-10 mm
Correct answer: 1-2 mm (freeway space)
The freeway space (interocclusal rest space) is typically 2-4 mm, so VDO is approximately 2-4 mm less than VDR.
Question 5: A cast metal post and core is contraindicated when:
- The root is longer than 10 mm
- The remaining root structure is less than 1 mm thick at any point (Correct answer)
- The tooth has had a single canal root canal treatment
- Crown-to-root ratio is 1:1
Correct answer: The remaining root structure is less than 1 mm thick at any point
Roots with less than 1 mm of dentin thickness at any point risk perforation or fracture during post preparation or cementation.
Question 6: Which occlusal scheme is most appropriate for a completely edentulous patient with a flat (atrophic) mandibular ridge?
- Canine-protected occlusion
- Group function occlusion
- Lingualized occlusion
- Bilateral balanced occlusion (Correct answer)
Correct answer: Bilateral balanced occlusion
Bilateral balanced occlusion distributes forces evenly across both sides during all excursive movements, improving stability on flat ridges.
Question 7: The smear layer created during cavity preparation should be treated before placing a dentin bonding agent because it:
- Increases microleakage by acting as a diffusion barrier (Correct answer)
- Strengthens the dentin surface for bonding
- Contains viable bacteria that must be eliminated
- Reduces pulpal sensitivity during bonding
Correct answer: Increases microleakage by acting as a diffusion barrier
The smear layer is a weak, loosely adherent layer that acts as a diffusion barrier and reduces bond strength if not removed or modified.
NBDE Prosthodontics and Operative Dentistry 2
Which finish line preparation design provides the best esthetic result for an all-ceramic crown?