EFDA Provisional Crown Fabrication 2 — Questions and Answers
Question 1: Which impression material is most commonly used to create the matrix for a direct provisional crown?
- Polyvinyl siloxane
- Alginate (Correct answer)
- Zinc oxide eugenol
- Plaster of Paris
Correct answer: Alginate
Alginate is the most common material used to take a preoperative impression for fabricating a provisional crown matrix due to its ease of use and cost-effectiveness.
Question 2: When trimming a provisional crown, the marginal finish line should be:
- Extended 2 mm subgingivally
- Flush with the gingival margin or 0.5 mm subgingival (Correct answer)
- Left at the mid-buccal surface
- Trimmed to the height of the preparation shoulder
Correct answer: Flush with the gingival margin or 0.5 mm subgingival
The provisional margin should be placed flush with or 0.5 mm subgingival to protect the preparation and maintain tissue health.
Question 3: Which property of bis-acryl composite makes it preferable to PMMA for provisional crowns?
- Lower cost
- Less exothermic reaction during setting (Correct answer)
- Longer working time
- Greater flexibility
Correct answer: Less exothermic reaction during setting
Bis-acryl composites produce significantly less heat during polymerization compared to PMMA, reducing the risk of pulpal damage.
Question 4: A provisional crown that lacks occlusal contacts on opposing teeth will most likely result in:
- Supra-eruption of the prepared tooth
- Over-eruption of the opposing tooth (Correct answer)
- Improved patient comfort
- Reduced wear on the provisional
Correct answer: Over-eruption of the opposing tooth
Without proper occlusal contacts, the opposing tooth will over-erupt into the open space, compromising the space for the final restoration.
Question 5: The 'reline' technique for a provisional crown involves:
- Replacing the entire provisional with a new one
- Adding fresh acrylic inside the initial shell after seating on the preparation (Correct answer)
- Polishing the internal surface of the crown
- Adjusting occlusion with a carbide bur
Correct answer: Adding fresh acrylic inside the initial shell after seating on the preparation
The reline technique seats an initial shell over the preparation and adds fresh material inside to create an accurate fit to the actual tooth preparation.
Question 6: Which cement is most appropriate for temporizing a provisional crown on a tooth with a short clinical crown?
- Zinc phosphate cement
- Glass ionomer cement
- Non-eugenol temporary cement (Correct answer)
- Resin-modified glass ionomer
Correct answer: Non-eugenol temporary cement
Non-eugenol temporary cement provides adequate retention while allowing retrievability, and avoids eugenol which can interfere with resin-based final cements.
Question 7: After polishing a PMMA provisional crown, what is the FIRST step before cementing it?
- Apply fluoride varnish
- Check and adjust occlusion on the articulating paper (Correct answer)
- Rinse with chlorhexidine
- Coat with a sealant
Correct answer: Check and adjust occlusion on the articulating paper
Occlusion must be verified and adjusted on the model or in the patient's mouth before final cementation to prevent bite issues.
EFDA Provisional Crown Fabrication 2
Which impression material is most commonly used to create the matrix for a direct provisional crown?