NDAEB Dental Materials and Equipment 1 — Questions and Answers
Question 1: Dental amalgam is formed when mercury reacts with which alloy?
- Gold and platinum alloy
- Silver-tin alloy (Correct answer)
- Zinc and copper alloy
- Nickel-chromium alloy
Correct answer: Silver-tin alloy
Dental amalgam is created when liquid mercury is combined with a silver-tin alloy powder, forming a stable, hardened restorative material.
Question 2: Which type of composite resin is BEST suited for high-stress posterior restorations?
- Microfilled composite
- Flowable composite
- Packable (condensable) composite (Correct answer)
- Nanofilled composite
Correct answer: Packable (condensable) composite
Packable composites have the highest filler loading and greatest wear resistance, making them the preferred choice for posterior restorations under occlusal stress.
Question 3: Glass ionomer cement is unique among restorative materials because it continuously releases which beneficial ion?
- Calcium
- Phosphate
- Fluoride (Correct answer)
- Sodium
Correct answer: Fluoride
Glass ionomer cement releases fluoride ions over time, providing a cariostatic effect that helps prevent secondary decay around restorations.
Question 4: What does 'working time' mean when referring to dental restorative materials?
- Time from mixing to complete final set
- Time from start of mixing during which the material can be manipulated (Correct answer)
- Total shelf life of the material before use
- Time the patient must wait before eating
Correct answer: Time from start of mixing during which the material can be manipulated
Working time is the period beginning at the start of mixing during which a dental material can be properly manipulated, adapted, and placed before it begins to set.
Question 5: What is the primary purpose of placing a base material in a deep tooth preparation before restoring?
- To improve the color of the restoration
- To provide pulpal protection from thermal and chemical stimulation (Correct answer)
- To increase the working time of the restorative material
- To chemically bond the restoration to enamel
Correct answer: To provide pulpal protection from thermal and chemical stimulation
A base is placed in deep preparations to insulate the pulp from thermal and chemical irritation caused by restorative materials and temperature changes.
Question 6: What is the purpose of acid etching enamel before placing a composite resin restoration?
- To sterilize the tooth surface before bonding
- To remove carious dentin completely
- To create micro-porosities for mechanical retention of the bonding resin (Correct answer)
- To chemically activate the composite material
Correct answer: To create micro-porosities for mechanical retention of the bonding resin
Phosphoric acid etching creates microscopic irregularities in enamel that allow the bonding resin to penetrate and form tags, creating strong mechanical retention.
Question 7: Which dental restorative material forms a true chemical bond with both enamel and dentin without requiring a separate bonding agent?
- Zinc phosphate cement
- Glass ionomer cement (Correct answer)
- Composite resin
- Amalgam
Correct answer: Glass ionomer cement
Glass ionomer cement bonds chemically to calcium in tooth structure through an ionic reaction, making it the only common restorative material that adheres chemically to both enamel and dentin.
NDAEB Dental Materials and Equipment 1
Dental amalgam is formed when mercury reacts with which alloy?