GIs, RMGIs, Class III and V preps

Question 1

What is the difference between Ionomers and Adhesives?

Answer 1

Ionomers - need a clean, intact dentin surface with exposed minerals. They attach via chelating with HA surfaces
Adhesives - need a demineralized dentin surface with exposed collagen (Hybrid layer)

Question 2

What type of materials are Conditioners used with

Answer 2

Glass Ionomers

Question 3

Conditioners

Answer 3

Mild organic acids
They solubilize and remove the smear layer
But they leave the smear plugs intact
They do not demineralize dentin or enamel

Question 4

Etchants

Answer 4

Inorganic acid
35% H3PO4
Completely removes smear layer and plugs
Demineralizes surface dentin
Leaves a collagen rich surface with numerous pores

Question 5

What are the two components of a GI?

Answer 5

Powder = acid soluble glass
Liquid = 50% water, 50% polyacid copolymers (long chain polymers [ph = 1])

Question 6

What is the immediate rxn of a GI?

Answer 6

Acid dissolves the glass

Glass releases Ca+2

Question 7

What is the rxn of a GI 1-3 days later?

Answer 7

Al replaces the Ca
This increases the strength
F is released
Acid side groups cal also chelate with glass and HA

Question 8

What are the disadvantages of GI?

Answer 8

Slow setting
Early dissolution
Optical properties  (opaque)
Poor stain resistance
Poor strength

Question 9

What are the components of RMGI?

Answer 9

Powder = acid soluble glass (same as GI)
Liquid = 35% water, 35% methyacrylate modified polyacid copolymers, 30% HEMA (pH = 2)

Question 10

What is the reaction of RMGI?

Answer 10

Same as GI

The only difference is RMGI undergoes polymerization shrinkage, but swells due to water sorption, with a net 0 change

Question 11

RMGI Triple Cure

Answer 11

LC, SC, and acid-base rxn
Free radical react immediate immediately (protects from early solubility)
Acid-base rxn occurs slowly (properties improve over time)

Question 12

What are the advantages of GI and RMGI?

Answer 12

Good seal

Caries inhibition due to F release

Question 13

What is RMGI better at than GI?

Answer 13

Solubility resistance
Improved strength
Less stiff
Improved optics

Question 14

What types of patients would you GI or RMGI?

Answer 14

Caries-prone patients

Question 15

What are the three different prep designs for a class V?

Answer 15

Conventional
Beveled conventional
Modified conventional

Question 16

Conventional prep design

Answer 16

90' cavosurface margin
Follow the curvature of the tooth
Amalgam only
Uniform depth into dentin (0.5mm)
M and D walls slightly diverge
Gains retention via incisal grooves

Question 17

Beveled conventional prep design

Answer 17

Composites only
Use when enamel prep walls aren’t under high stress
Increases the interface that the prep has with the adhesive, and that the adhesive has with the composite (increased retention)
Uniform depth (0.5mm into dentin)

Question 18

Modified Conventional prep design

Answer 18

Beveled enamel margins
Remove defective tooth only
Beveled enamel margins

Question 19

Describe a Class V prep

Answer 19

Pulpal floor follows the curvature of the cavosurface margin
0.2-0.5mm into dentin
90’ cavosurface angle
M-D walls slightly diverge
Deeper incisally than gingivally
Spoon bur to remove remaining caries
1/4 round bur to make retention grooves (for amalgam)

Question 20

What are the advantages of composite with Class Vs?

Answer 20

Adhere to tooth structure so we can be more conservative

Better esthetics

Question 21

Class V prep dimensions

Answer 21

Gingival margin is 0.5mm above gingiva
1.5mm I-G height
Axial depth = 1.2mm @ incisal, 1.0mm @ gingival
Gingival floor follows tooth contour
M-D length should reach line angles of tooth
90’ cavosurface margins

Question 22

What materials are used in Class III restorations

Answer 22

Composite
RMGI
Amalgam

Question 23

When do you use a composite in Class III restoration?

Answer 23

When surrounded primarily by enamel

Question 24

When do you use a RMGI in a Class III restoration?

Answer 24

When surrounded primarily by cementum and dentin

High caries risk pt

Question 25

When do you use an Amalgam in a Class III restoration?

Answer 25

Pretty much only in the distal of canines

Don’t want Amalgam in an esthetic area

Question 26

Why is the lingual approach most common for Class III restorations?

Answer 26

Least visible from smile

Question 27

Conventional Class III Prep

Answer 27

Incisal wall contact
Gingival wall has clearance
I-G cavosurface margins are 90’ angles
Facial depth slightly breaks contact (approx 1.0-1.5mm deep)
Axial depth = 0.2-0.5mm into dentin (1.0 mm on lateral, 1.5mm on central)

Question 28

How does a Beveled Conventional Class III prep differ from conventional?

Answer 28

All other things are the same
But there is a 45’ lingual bevel (0.5-1.0mm)
Incisal contact is maintained