EFDA Amalgam and Composite Restorations 4 — Questions and Answers
Question 1: Zinc-containing amalgam alloys should NOT be contaminated with moisture during condensation because this causes:
- Color change to gray
- Delayed expansion and post-operative pain (Correct answer)
- Faster setting time
- Reduced compressive strength
Correct answer: Delayed expansion and post-operative pain
Moisture contamination of zinc-containing amalgam causes a secondary (delayed) expansion due to hydrogen gas production, which can cause pain and restoration failure.
Question 2: When finishing a composite restoration, the sequence of instruments should generally proceed from:
- Coarser to finer abrasives (Correct answer)
- Finer to coarser abrasives
- Polishing paste directly on uncured resin
- High-speed handpiece to pumice
Correct answer: Coarser to finer abrasives
Finishing proceeds from coarser instruments (carbide finishing burs, coarse discs) to progressively finer polishing instruments to achieve a smooth surface.
Question 3: Which finding after amalgam placement indicates the presence of an amalgam overhang?
- Smooth floss passage interproximally
- Floss tears or catches on the gingival margin (Correct answer)
- Patient reports cold sensitivity
- The restoration is slightly high in occlusion
Correct answer: Floss tears or catches on the gingival margin
Floss that tears or catches at the gingival margin indicates an amalgam overhang that must be removed to prevent periodontal disease.
Question 4: A Class V composite restoration on the facial surface of tooth #9 requires etching of:
- Dentin only
- Enamel only
- Both enamel and dentin (total-etch technique) (Correct answer)
- Neither surface — self-etch primer is always required
Correct answer: Both enamel and dentin (total-etch technique)
Total-etch technique involves etching both enamel and dentin to maximize bond strength, especially at cervical margins where enamel may be minimal.
Question 5: The 'C-factor' (configuration factor) in composite restorations refers to:
- The concentration of filler particles
- The ratio of bonded to unbonded surfaces affecting shrinkage stress (Correct answer)
- The curing light intensity
- The cavity classification number
Correct answer: The ratio of bonded to unbonded surfaces affecting shrinkage stress
A high C-factor (more bonded walls than free surfaces) increases polymerization shrinkage stress, which can debond the restoration or fracture enamel.
Question 6: To prevent galvanic shock after placing a new amalgam, the clinician should check for:
- Occlusal contacts only
- Adjacent or opposing gold restorations in contact (Correct answer)
- The patient's blood pressure
- Dentin hypersensitivity
Correct answer: Adjacent or opposing gold restorations in contact
Dissimilar metals (amalgam and gold) in contact create a galvanic cell producing an electric current that causes sharp, transient pain (galvanic shock).
Question 7: When light-curing composite resin, the curing tip should be held:
- At least 10mm from the restoration surface
- As close as possible to the composite surface without touching (Correct answer)
- At a 45-degree angle pointing away
- Directly on the matrix band
Correct answer: As close as possible to the composite surface without touching
Maximum irradiance and depth of cure are achieved when the curing tip is as close as possible (1–2mm) to the composite surface without direct contact.
EFDA Amalgam and Composite Restorations 4
Zinc-containing amalgam alloys should NOT be contaminated with moisture during condensation because this causes: