Cements & Bonding Flashcards
1) What are the fundamental parts of adhesion to tooth structure?
2) As a result, what are formed that micromechanically interlock with hard tissue?
3) What is the essential first step of all adhesion mechanisms?
1) a) removing HA to create micropores
b) infiltration of resin monomers into micropores
c) subsequent polymerization
2) resin tags are formed
3) wetting - an adhesive needs to form intimate contact with the surface, spread over it, and penetrate by capillary action
(Phillips Science of Dental Materials)
1) How can you increase the surface energy of dentin, enamel, and synthetic materials?
2) What does this promote?
3) To achieve strong bonding through the micromechanical interlocking mechanism, what must monomers adapt to?
1) roughen the surface
2) wettability of the surface by adhesive monomers
3) monomers must adapt to enamel and fill surface irregularities and/or infiltrate into a demineralized collagen network in dentin
(Phillips Science of Dental Materials)
What is the smear layer?
How thick is it?
Layer of debris and organic film left on the surface of enamel and dentin after mechanical cutting
Typically 1-2µm, but can be thicker depending on abrasives used
(Phillips Science of Dental Materials)
What is a hybrid layer?
A layer of resin-infiltrated dentin formed when hydrophilic resin infiltrates acid-demineralized collagen fibers in etched dentin
What happens if dentin is too dry during resin bonding? What happens if it is too wet?
If too dry, the collagen network will collapse, preventing resin infiltration.
If too wet, resin cannot fully replace the water in the collagen network.
What step in resin bonding is required to maintain a hydrated collagen network while removing excess water?
priming
If dentin is too dry, the collagen network collapses, preventing resin infiltration
What is a primer?
a solution containing hydrophilic functional monomers dissolved in acetone/ethanol/water
HEMA (2-hydroxyethylmethacrylate) is a widely-used primer
What is the pH of acid etchants?
1-2
4th gen bonding
3-step:
etch
prime
bond
5th gen bonding
2-step:
etch
prime + bond
Advantages of immediate dentin sealing
1) improved bond strength: allows hybrid layer to develop stress-free
Polymerization of the adhesive layer is not completed immediately after curing. By delaying restoration delivery at least 24 hours, the dentin bond strength may increase by up to 25 percent.
2) bonding to freshly-cut dentin:
avoids contamination by impression, provisional, and oral cavity materials
3) may reduce post-op sensitivity (conflicting info)
4) may decrease bacterial leakage during provisional phase
Disadvantages of immediate dentin sealing
1) technique-sensitivity
2) time (additional steps = more time)
How do you do immediate dentin sealing?
bonding agent is applied immediately after tooth preparation (instead of waiting for the time of delivery)
6th gen bonding
2-step:
prime + etch
bond
What types of bonding agents are recommended for immediate dentin sealing?
4th (3-step)
6th (2-step: etch+prime -> bond)
