EFDA Provisional Crown Fabrication 4 — Questions and Answers
Question 1: When fabricating a provisional for a patient with known acrylic monomer sensitivity, the BEST alternative material is:
- PMMA with increased powder-to-liquid ratio
- Bis-acryl composite resin (Correct answer)
- Polyether impression material
- Zinc oxide eugenol paste
Correct answer: Bis-acryl composite resin
Bis-acryl composite resins contain less free monomer than PMMA and are preferred when patients have sensitivity to methacrylate monomers.
Question 2: The purpose of applying petroleum jelly (Vaseline) to the tooth and adjacent tissues before injecting provisional material is to:
- Improve the bond between provisional material and tooth
- Act as a separating medium to prevent adhesion to tissues and teeth (Correct answer)
- Disinfect the preparation before temporization
- Reduce sensitivity of the prepared dentin
Correct answer: Act as a separating medium to prevent adhesion to tissues and teeth
Petroleum jelly acts as a separator so the provisional material does not adhere to the tooth structure or soft tissue during fabrication.
Question 3: Which of the following is a sign of inadequate curing of a PMMA provisional crown?
- Excessive hardness and brittleness
- Tacky or soft surface and persistent monomer odor (Correct answer)
- Bright white opaque color
- Excessive shrinkage at the margins
Correct answer: Tacky or soft surface and persistent monomer odor
A tacky or soft surface with persistent monomer smell indicates incomplete polymerization, meaning the material has not fully cured.
Question 4: A provisional crown is fractured at the isthmus connecting two pontics in a three-unit fixed partial denture. The MOST likely cause is:
- Excess temporary cement
- Insufficient bulk of material at the connector area (Correct answer)
- Overly aggressive polishing
- Using too much separating medium
Correct answer: Insufficient bulk of material at the connector area
The connector area must have adequate bulk to withstand occlusal forces; thin connectors are prone to fracture under stress.
Question 5: When seating a provisional crown, the patient should be instructed to bite on a cotton roll to:
- Absorb excess cement
- Help fully seat the crown and verify occlusal fit (Correct answer)
- Prevent the patient from biting the tongue
- Reduce postoperative sensitivity
Correct answer: Help fully seat the crown and verify occlusal fit
Biting on a cotton roll applies even pressure to fully seat the crown and allows the clinician to assess if the occlusion is correct.
Question 6: The color shade of a provisional crown is MOST important for which type of restoration?
- Mandibular second molar
- Maxillary central incisor (Correct answer)
- Mandibular first premolar
- Maxillary third molar
Correct answer: Maxillary central incisor
Maxillary central incisors are highly visible, so shade matching of the provisional is critical to patient satisfaction and proper shade communication to the lab.
Question 7: Which type of bur is BEST suited for adjusting internal fit of a bis-acryl provisional crown?
- Diamond bur at high speed
- Round carbide bur at low speed (Correct answer)
- Sandpaper disc
- 12-fluted finishing bur
Correct answer: Round carbide bur at low speed
A round carbide bur at low speed allows precise removal of internal high spots without cracking the provisional material.
EFDA Provisional Crown Fabrication 4
When fabricating a provisional for a patient with known acrylic monomer sensitivity, the BEST alternative material is: