GIs, RMGIs, Class III and V preps Flashcards Preview

SP 16 - Operative final > GIs, RMGIs, Class III and V preps > Flashcards

Flashcards in GIs, RMGIs, Class III and V preps Deck (28)
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What is the difference between Ionomers and Adhesives?

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)


What type of materials are Conditioners used with

Glass Ionomers



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



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


What are the two components of a GI?

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


What is the immediate rxn of a GI?

Acid dissolves the glass
Glass releases Ca+2


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

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


What are the disadvantages of GI?

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


What are the components of RMGI?

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


What is the reaction of RMGI?

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


RMGI Triple Cure

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


What are the advantages of GI and RMGI?

Good seal
Caries inhibition due to F release


What is RMGI better at than GI?

Solubility resistance
Improved strength
Less stiff
Improved optics


What types of patients would you GI or RMGI?

Caries-prone patients


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

Beveled conventional
Modified conventional


Conventional prep design

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


Beveled conventional prep design

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)


Modified Conventional prep design

Beveled enamel margins
Remove defective tooth only
Beveled enamel margins


Describe a Class V prep

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)


What are the advantages of composite with Class Vs?

Adhere to tooth structure so we can be more conservative
Better esthetics


Class V prep dimensions

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


What materials are used in Class III restorations



When do you use a composite in Class III restoration?

When surrounded primarily by enamel


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

When surrounded primarily by cementum and dentin
High caries risk pt


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

Pretty much only in the distal of canines
Don't want Amalgam in an esthetic area


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

Least visible from smile


Conventional Class III Prep

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)


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

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