NBDE Prosthodontics and Operative Dentistry 5 — Questions and Answers
Question 1: Which type of pontic design is most hygienic for a fixed partial denture in the posterior region?
- Sanitary (hygienic) pontic (Correct answer)
- Modified ridge-lap pontic
- Ovate pontic
- Conical pontic
Correct answer: Sanitary (hygienic) pontic
The sanitary (hygienic) pontic does not contact the residual ridge at all, making it the easiest to clean and most tissue-friendly design.
Question 2: During the preparation of an MOD cavity for a Class II amalgam restoration, the proximal box should be extended faciolingually until:
- The width equals one-third of the intercuspal distance
- The margins are in a self-cleansing area just clear of the adjacent tooth (Correct answer)
- The preparation reaches 1 mm beyond the contact area
- The gingival floor is at the level of the cementoenamel junction
Correct answer: The margins are in a self-cleansing area just clear of the adjacent tooth
Proximal margins must extend just beyond the contact area to a self-cleansing zone where instruments can finish margins and caries risk is reduced.
Question 3: The primary advantage of using a facebow transfer when mounting casts for complete denture fabrication is that it:
- Registers the patient's maximum intercuspation position accurately
- Relates the maxillary cast to the hinge axis of the articulator mimicking the patient's TMJ (Correct answer)
- Determines the correct vertical dimension of occlusion
- Records the condylar inclination for the articulator settings
Correct answer: Relates the maxillary cast to the hinge axis of the articulator mimicking the patient's TMJ
A facebow transfer records the spatial relationship of the maxilla to the transverse hinge axis so the casts open and close on the articulator as they would in the patient.
Question 4: Which cavity preparation principle was modified by GV Black's successors to adopt a more conservative 'extension for prevention' approach?
- Resistance form
- Outline form (extension for prevention) (Correct answer)
- Convenience form
- Retention form
Correct answer: Outline form (extension for prevention)
GV Black's 'extension for prevention' placed margins in self-cleansing areas even in caries-free zones; modern adhesive dentistry restricts preparation to only carious or defective structure.
Question 5: A patient with xerostomia and multiple cervical carious lesions is best restored with:
- Composite resin with total-etch technique
- Resin-modified glass ionomer cement (Correct answer)
- Conventional amalgam
- Self-etch resin composite system
Correct answer: Resin-modified glass ionomer cement
Resin-modified glass ionomer releases fluoride, bonds chemically to dentin, and tolerates mild moisture — ideal for xerostomic patients with high caries risk.
Question 6: When designing a maxillary complete denture, the post-dam (posterior palatal seal) is placed:
- At the junction of the hard and soft palate on the vibrating line (Correct answer)
- 2 mm anterior to the hamular notch line
- Along the residual ridge crest posteriorly
- At the distal border of the maxillary tuberosities
Correct answer: At the junction of the hard and soft palate on the vibrating line
The post-dam is placed at or slightly anterior to the vibrating line (junction of movable and immovable soft palate tissue) to create a peripheral seal.
Question 7: A direct composite veneer differs from a porcelain veneer primarily in that:
- Direct composite requires more tooth reduction for adequate esthetics
- Direct composite is more resistant to staining and wear over time
- Direct composite is placed chairside in a single visit without a laboratory step (Correct answer)
- Direct composite provides superior esthetics in the long term
Correct answer: Direct composite is placed chairside in a single visit without a laboratory step
Direct composite veneers are a single-visit, freehand chairside procedure requiring no laboratory fabrication, making them more time- and cost-efficient initially.
NBDE Prosthodontics and Operative Dentistry 5
Which type of pontic design is most hygienic for a fixed partial denture in the posterior region?