EFDA Bases, Liners, and Matrices 2 — Questions and Answers
Question 1: Which material is most commonly used as a cavity liner under composite resin restorations to promote pulpal healing?
- Calcium hydroxide (Correct answer)
- Zinc phosphate cement
- Glass ionomer base
- Zinc oxide eugenol
Correct answer: Calcium hydroxide
Calcium hydroxide is the preferred liner under composites because it stimulates secondary dentin formation and has excellent biocompatibility.
Question 2: A Tofflemire retainer and matrix band are assembled with the retainer positioned on which surface of the tooth?
- Lingual
- Buccal (Correct answer)
- Occlusal
- Incisal
Correct answer: Buccal
The Tofflemire retainer is typically placed on the buccal surface so the knob-tightening mechanism is accessible.
Question 3: What is the primary purpose of using a matrix band when restoring a proximal surface?
- To protect the pulp from thermal shock
- To replace the missing tooth wall during condensation (Correct answer)
- To etch the enamel surface
- To provide a base for the liner
Correct answer: To replace the missing tooth wall during condensation
A matrix band temporarily replaces the missing proximal wall to contain the restorative material and help create proper contour.
Question 4: Which liner has the advantage of releasing fluoride while also bonding chemically to dentin?
- Calcium hydroxide
- Zinc oxide eugenol
- Resin-modified glass ionomer (Correct answer)
- Copal varnish
Correct answer: Resin-modified glass ionomer
Resin-modified glass ionomer liners release fluoride and bond chemically to dentin, making them ideal for caries-prone patients.
Question 5: When placing zinc phosphate cement as a base, why must mixing be done on a cool glass slab?
- To speed up the setting reaction
- To slow the exothermic reaction and extend working time (Correct answer)
- To prevent moisture contamination
- To increase the powder-to-liquid ratio
Correct answer: To slow the exothermic reaction and extend working time
A cool slab dissipates the heat generated during mixing, slowing the exothermic reaction and extending working time.
Question 6: Which wedge placement is correct when using a Tofflemire matrix system for a Class II restoration?
- Occlusal embrasure, buccal to lingual
- Gingival embrasure, lingual to buccal
- Gingival embrasure, buccal to lingual (Correct answer)
- Occlusal embrasure, lingual to buccal
Correct answer: Gingival embrasure, buccal to lingual
The wedge is inserted from the buccal into the gingival embrasure to seal the gingival margin and prevent flash.
Question 7: Which base material is contraindicated under composite resin due to its eugenol content interfering with polymerization?
- Resin-modified glass ionomer
- Calcium hydroxide
- Zinc oxide eugenol (ZOE) (Correct answer)
- Zinc phosphate cement
Correct answer: Zinc oxide eugenol (ZOE)
Eugenol in ZOE inhibits the polymerization of composite resin, preventing adequate setting of the restoration.
EFDA Bases, Liners, and Matrices 2
Which material is most commonly used as a cavity liner under composite resin restorations to promote pulpal healing?