EFDA Provisional Crown Fabrication 5 — Questions and Answers
Question 1: A patient returns with a loose provisional crown 3 days after placement. After recementing, which factor should be evaluated FIRST?
- The shade of the provisional
- Occlusal contacts and parafunction habits (Correct answer)
- The brand of temporary cement used
- Surface finish and polish of the provisional
Correct answer: Occlusal contacts and parafunction habits
Repeated loosening of a provisional is most often caused by occlusal forces or parafunctional habits such as bruxism that exceed the retention of temporary cement.
Question 2: During the 'remove and reline' phase of direct provisional fabrication, when should the initial shell be removed from the mouth?
- Immediately after injection of the material
- During the rubbery or doughy stage, before final set (Correct answer)
- After the material is completely hard
- After 10 minutes of curing
Correct answer: During the rubbery or doughy stage, before final set
Removing the shell during the rubbery stage prevents locking into undercuts while preserving the shape needed for the final reline.
Question 3: Which statement about PMMA shrinkage during polymerization is CORRECT?
- PMMA expands by approximately 7% during setting
- PMMA shrinks volumetrically by 6–7% during polymerization (Correct answer)
- PMMA has negligible dimensional change
- PMMA only shrinks when exposed to moisture
Correct answer: PMMA shrinks volumetrically by 6–7% during polymerization
PMMA undergoes approximately 6–7% volumetric shrinkage during polymerization, which can affect marginal fit of the provisional.
Question 4: A provisional crown placed on a tooth with a recent pulp cap should ideally be cemented with:
- Zinc phosphate cement
- Non-eugenol temporary cement
- Resin-modified glass ionomer
- Zinc oxide eugenol (ZOE) temporary cement (Correct answer)
Correct answer: Zinc oxide eugenol (ZOE) temporary cement
ZOE has mild sedative and obtundent effects on the pulp, making it suitable when a recent pulp cap requires pulpal soothing during the provisional phase.
Question 5: The term 'open margin' on a provisional crown refers to:
- A margin that extends past the finish line of the preparation
- A gap between the provisional crown edge and the tooth preparation (Correct answer)
- A margin placed at the gingival crest
- A margin sealed with temporary cement only
Correct answer: A gap between the provisional crown edge and the tooth preparation
An open margin is a gap where the crown edge does not contact the tooth, allowing microleakage, sensitivity, and bacterial ingress.
Question 6: What is the PRIMARY reason for maintaining proper occlusal anatomy on a provisional crown?
- To improve the esthetics of the posterior region
- To prevent over-eruption of opposing teeth and maintain occlusal vertical dimension (Correct answer)
- To reduce the amount of cement needed
- To make the provisional easier to remove
Correct answer: To prevent over-eruption of opposing teeth and maintain occlusal vertical dimension
Proper occlusal anatomy maintains the vertical dimension and prevents supraeruption of opposing teeth, which would compromise space for the final restoration.
Question 7: An EFDA notices that the provisional crown has excess material (flash) extending onto the gingival tissue. The BEST instrument to remove this excess is:
- High-speed handpiece with diamond bur
- Scalpel blade (surgical knife)
- Curved scissors or acrylic bur on a slow-speed handpiece (Correct answer)
- Ultrasonic scaler
Correct answer: Curved scissors or acrylic bur on a slow-speed handpiece
Curved scissors or a slow-speed acrylic bur allow controlled, precise trimming of excess provisional material without damaging the surrounding soft tissue.
EFDA Provisional Crown Fabrication 5
A patient returns with a loose provisional crown 3 days after placement.
After recementing, which factor should be evaluated FIRST?