Bonding Systems

Question 1

What is the purpose of acid etch?

Answer 1

Roughens the surface of enamel, producing a characteristic etched pattern.
Allows micro mechanical interlocking of resin filling material.
Increases the surface energy of enamel- better wettability.

Question 2

Why does the enamel need to be dry during application of a resin?

Answer 2

Moisture contamination prevents flow of the resin into he etched surface.

Question 3

Why is bonding to dentine difficult?

Answer 3

Fluid pumps up from the dentine floor of the cavity, making the surface wet.
Low surface energy
Dentine is hydrophilic, whereas most simple bonding agents are hydrophobic.
Smear layer forms.

Question 4

What is critical surface energy?

Answer 4

The surface tension of a liquid that will just spread on the surface of a solid.

Question 5

What is the purpose of a dentine bonding agent?

Answer 5

Increase the surface energy of the dentine surface and allow composite to flow and stick to the surface.

Question 6

What mechanism is used to bond to dentine?

Answer 6

Molecular entanglement.

Question 7

What mechanism is used to bond to enamel?

Answer 7

Mechanical bonding.

Question 8

What is the smear layer?

Answer 8

Adherent layer of organic debris that remains on the dentine surface after the preparation of dentine during the restoration of a tooth.

Question 9

How is the smear layer removed?

Answer 9

Application of 35% orthi-phosphoric acid to the tooth (acid-etch).

Question 10

What are the components of a dentin bonding agent?

Answer 10

Primer- has a hydrophilic/hydrophobic molecule- hydrophilic to dentine and hydrophobic to the resin- increases the surface energy.
Adhesive- Resin which penetrates into the surface of the dentine attaching to the primers hydrophobic surface- micro mechanical retention.
- forms the hybrid layer.

Question 11

What is the coupling agent found in many primers?

Answer 11

HEMA- hydrophobic.

Question 12

What is the hybrid layer?

Answer 12

Adhesive within the DBA binds tot he collagen found in dentine and the resin that is found in DBA.

Question 13

The surface energy of composite must be higher than the surface energy of the enamel/dentine that it is bonding to- true or false?

Answer 13

False- the surface energy of composite must be lower than the surface energy of enamel and dentine.