"That seems like a good test question" Flashcards
Purpose of acid etch
Increases surface area, adhesive penetrates etched enamel to create a micromechanical bond
How does bond engage enamel?
Through micro-mechanical bonds
What happens when dentin is desiccated?
Collapse of the collagen layer and reduced bond strengths
Optional: place cotton pellet over dentin to avoid desiccation
Smear layer
(6)
Created when dentin is cut
A few microns thick
Composed of denatured collagen, hydroxyapatite, and other cutting debris
Acts like a natural bandage over the cut surface since it occludes many of the dentin tubules with smear plugs
Good protective barrier, relatively weak, can be dissolved with acids
We do not want to bond to the smear layer when using “total etch” bonding systems
Hybrid layer
(3)
Resin interdiffusion zone
Results from resin penetrating and adapting to demineralized intertubular dentin and exposed collagen fibers
Hydrophilic primer/wetting agent applied to wet dentin and prepares for easier penetration of the hydrophobic resin bonding agent that can adapt to the moist dentin and co-polymerize with the composite resin restoration
Adhesive bond strengths to superficial dentin compared to deeper dentin
Superficial dentin and greater than those for deeper
Deeper dentin: more tubules, larger diameter of tubules, reduced amount of intertubular dentin
Opaque vs. translucent composites
(3)
Opaque requires longer curing times
Large class 3 restorations require opaque shades especially when the prep can be seen through the facial to the lingual
Light passes through translucent in large restorations - this will stand out more in a patient
Silane
(4)
Coupling agent for composite
Couples filler to resin matrix
Allows stress transfer from flexible matrix to higher modulus (less flexible) filler
Improves mechanical properties - decreased water sorption along filler-resin interface
