Theory

Question 1

Describe the retention of glass ionomer (two ways).

Answer 1

1) direct chemical bonding to tooth structure

2) mechanical retention via gingival retentive groove

Question 2

Name two ways in which a gingival retentive groove assists retention.

Answer 2

1) mechanical retention

2) increased surface area for chemical bonding

Question 3

What is dentine conditioner made of?

Answer 3

10% polyacrylic acid

Question 4

Name three roles of dentine conditioner.

Answer 4

1) remove smear layer
2) cleanse surface of debris (protein, oils, etc)
3) optimize adaptation and bonding of GI

Question 5

Glass Ionomers are based on a(n) _____ reaction.

Answer 5

Acid-Base Reaction

Question 6

What are the liquid and powder components of glass ionomers?

Answer 6

polyalkenoic acid liquid

calcium fluoroaluminosilicate glass powder

Question 7

RMGIs set by a(n) _____ reaction and partly by a ______.

Answer 7

RMGIs set by an acid-base reaction and partly by a photochemical polymerization.

Question 8

Describe IN DETAIL the setting mechanism of glass ionomers.

Answer 8

Dissolution of the surface of the glass particles with the release of calcium and aluminium ions, which then combine with the polyacrylic acid to form calcium and aluminium polyacrylate chains. The calcium chains form first, and aluminium chains thereafter.

The setting mechanism is an acid-base reaction between the polyalkenoic acid liquid and the glass powder which leads to a diffusion-based adhesion between the glass particles and the matrix.

Question 9

T/F: Glass Ionomers bind chemically to mineralized tissues.

Answer 9

True.

Question 10

Why do we apply single bond (unfilled resin) after etching and before the CR?

Answer 10

To seal the interface between the CR and the acid-etched enamel, developing micro mechanical retention. Also to seal the dentine tubules

Question 11

What is etch made of?

Answer 11

35-37% Orthophosphoric acid

Question 12

Describe the retention of a CR restoration.

Answer 12

Micromechanical bonding of the resin to the preferentially etched enamel.

Question 13

Name four reasons we place a GI lining under a CR.

Answer 13

1) seal dentine tubules
2) replace lost dentine
3) provide fluoride-releasing agent
4) protect the pulp from any incompletely cured low molecular weight component of the bonding resin

Question 14

T/F: Retentive undercuts are not required for CR Class I.

Answer 14

True! Retentive undercuts are required for Class I amalgam, but not for CR.

Question 15

List two goals of condensation of amalgam.

Answer 15

1) adapt amalgam to the margins, walls, and line angles
2) minimize voids within amalgam
3) leave the amalgam in its strongest state
4) bring excess mercury-rich amalgam to the surface, for removal, thereby decreasing the final Hg:alloy ratio of the amalgam

Question 16

What is the major cause of “isthmus region fracture” of Class II amalgam restorations?

Answer 16

Failure to provide adequate occlusal depth (referred to as “resistance form”

Question 17

What are the two ways we ensure that there is proper retention form in a Class II amalgam?

Answer 17

1) retentive undercuts (prevents movement towards occlusal) as well as diverged walls
2) occlusal lock (prevents movement towards proximal)