EFDA Bases, Liners, and Matrices 4 — Questions and Answers
Question 1: A sectional matrix system (e.g., Palodent) is preferred over the Tofflemire system for Class II composites because it:
- Is less expensive and easier to sterilize
- Provides better proximal contact and contour (Correct answer)
- Does not require the use of wedges
- Can be used for all tooth surfaces simultaneously
Correct answer: Provides better proximal contact and contour
Sectional matrix systems produce tighter, more anatomically correct proximal contacts compared to the circumferential Tofflemire band.
Question 2: Copal varnish is applied in a cavity preparation primarily to:
- Bond the amalgam chemically to dentin
- Seal dentinal tubules and reduce microleakage under amalgam (Correct answer)
- Stimulate secondary dentin formation
- Replace the smear layer with a protective barrier
Correct answer: Seal dentinal tubules and reduce microleakage under amalgam
Copal varnish seals dentinal tubules to reduce microleakage and postoperative sensitivity under amalgam restorations.
Question 3: Which matrix system would be MOST appropriate for restoring a severely broken-down molar with missing proximal and buccal walls?
- Tofflemire band
- Celluloid strip
- Copper band or custom matrix (Correct answer)
- Automatrix
Correct answer: Copper band or custom matrix
A copper band or custom-fabricated matrix is best for teeth with extensive wall loss that standard matrix systems cannot adequately contain.
Question 4: What is the correct consistency of zinc phosphate base when mixed for use as a base (not a luting cement)?
- Thin, watery consistency for easy flow
- Putty-like consistency that holds its shape (Correct answer)
- Creamy paste that flows freely
- Thick but pourable syrup consistency
Correct answer: Putty-like consistency that holds its shape
A base consistency for zinc phosphate is thick and putty-like, providing adequate bulk and resistance to compressive forces.
Question 5: The purpose of a wooden or plastic wedge used with a matrix band is to:
- Anchor the matrix retainer to the tooth
- Separate the teeth slightly and seal the gingival margin (Correct answer)
- Create room for the liner at the gingival floor
- Hold the matrix band flat against the occlusal surface
Correct answer: Separate the teeth slightly and seal the gingival margin
The wedge separates the teeth to compensate for band thickness and seals the gingival margin to prevent material flash.
Question 6: Glass ionomer cement used as a base is placed in which preparation zone?
- Only on the enamel walls
- The axial and pulpal floors over exposed dentin (Correct answer)
- Along the cavosurface margin
- On top of the calcium hydroxide liner only
Correct answer: The axial and pulpal floors over exposed dentin
Glass ionomer base is applied over exposed dentin on pulpal and axial floors where thermal and chemical protection is needed.
Question 7: Which of the following best describes the 'sandwich technique' in restorative dentistry?
- Placing two layers of composite between two enamel walls
- Using a glass ionomer base beneath a composite resin restoration (Correct answer)
- Alternating layers of amalgam and composite
- Placing calcium hydroxide between two glass ionomer layers
Correct answer: Using a glass ionomer base beneath a composite resin restoration
The sandwich technique uses a glass ionomer base bonded to dentin topped with composite resin, combining fluoride release with esthetic results.
EFDA Bases, Liners, and Matrices 4
A sectional matrix system (e.g., Palodent) is preferred over the Tofflemire system for Class II composites because it: