Chapter 05 Principles of Bonding

Chapter 05  Principles of Bonding

Complete Chapter Questions And Answers
 

Sample Questions

MULTIPLE CHOICE

1. The most commonly used etchant or conditioner for tooth bonding is _____ in concentrations ranging from 10% to 38%.
a.
acetic acid
b.
phosphoric acid
c.
hydrochloric acid
d.
sodium perborate

ANS: B
The most commonly used etchant or conditioner for tooth bonding is phosphoric acid in concentrations ranging from 10% to 38%. Acid removes mineral from the surface to create roughness or microscopic porosity.

REF: p. 45 TOP: Basic Principles of Bonding (Preparation for Bonding)

2. When a resin bonding agent hardens, it creates projections that lock into the tooth, creating a _____ bond. The resin bonding agent will then form a _____ bond to other resins placed over it, such as composite resin.
a.
chemical; chemical
b.
chemical; mechanical
c.
mechanical; chemical
d.
mechanical; mechanical

ANS: C
When a resin bonding agent hardens, it creates projections that lock into the tooth, creating a mechanical bond. The resin bonding agent will then form a chemical bond to other resins placed over it, such as composite resin. The chemical bond, called a primary bond, is a true adhesion between atoms or molecules of the composite resin and the bonding resin.

REF: p. 45 TOP: Basic Principles of Bonding (Bonding to the Etched Surface)

3. When acid etching for bonding, it is desirable to have a _____ surface energy and a _____ angle of contact.
a.
high; high
b.
high; low
c.
low; high
d.
low; low

ANS: B
When acid etching for bonding, it is desirable to have a high surface energy and a low angle of contact. The high surface energy helps attract the resin to the etched surface. Surfaces that are poorly wet will cause beading of the liquid, similar to water on a newly waxed car. On an unwaxed car, the water easily spreads out and has a low angle of contact. Bonding agents are usually not very viscous (thick), so they will flow readily and wet the etched surface.

REF: p. 46 TOP: Basic Principles of Bonding (Surface Wetting)

4. Which of the following statements is true concerning bond strength?
a.
The bond strength to dentin is usually greater than to enamel.
b.
Bonding to enamel usually achieves consistently high bond strengths of around 60 MPa (megapascals).
c.
The dentin near the dentinoenamel junction (DEJ) has more dentinal tubules, and they are larger in diameter than in dentin closer to the pulp.
d.
Wetter dentin with more holes is more difficult to bond to consistently than shallower dentin.

ANS: D
Wetter dentin with more holes is more difficult to bond to consistently than shallower dentin. Bonding to enamel usually achieves consistently high bond strengths of around 30 MPa (megapascals). The bond strength to dentin is usually less than to enamel and varies according to how deeply into dentin the cavity preparation extends. The dentin near the dentinoenamel junction (DEJ) has fewer dentinal tubules, occupying 14% of the dentin surface, and they are smaller in diameter than in dentin closer to the pulp. Deeper dentin contains more tubules, and they are larger in diameter, occupying 20% to 30% of the dentin surface.

REF: p. 46 TOP: Basic Principles of Bonding (Bond Strength)