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27 Cards in this Set
- Front
- Back
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Why is bonding sought after?
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enhances marginal seal
enhances retention and allows more conservative tooth prep strengthens tooth (tie/bind together) |
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What are the different types of bonding?
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micromechanical e.g. bonding resin to enamel with acid-etch technique
chemical adhesion e.g. bonding of GIC to either enamel or dentin formation of hybrid intermediate layer e.g. dentine bonding agents |
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What type of bonding is predictable?
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bonding to enamel
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What type of bonding is more difficult to achieve?
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bonding to dentin
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Why is bonding to dentin more difficult to achieve?
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more variation in composition (inorganic and organic)
tubule fluid in surface of dentin dentin is vital- don't want injurious agents smear layer |
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What is the smear layer?
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particles of dentin tubules, has to be removed to expose the tubules or modified to become part of a dentin/smear layer/ restoration complex
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How do you get micro mechanical bonding?
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acid etch on enamel
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What does acid etch do to enamel?
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creates microscopic irregularities
different etch patterns depending on rods |
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What forms locking resin tags on enamel?
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unfilled resin applied to etched enamel flows into irregularities
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explain the chemical adhesion
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ionic bond-->between carboxyl group and calcium and phosphate ions from hydroxyapatite
bonds greatest to enamel enhanced by conditioning |
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What are the limitations of chemical adhesion?
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limited by strength of GIC
failure is between cohesive within cement and no adhesive between cement and tooth structure |
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Why can't composite bond even mechanically to dentin?
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because most are hydrophobic- they will retreat from moisture in the tubules before they can set
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What do you need to get resin-dentin bonding?
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need to be able to alter the structure of the smear layer and outer tubules
need to be able to displace outer tubule fluid need intermediate dentin bonding agent |
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What are the 3 main components of resin-dentin bonding systems?
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conditioner
primer adhesive/sealer/bond |
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What is s 3 stage system in resin-dentin bonding?
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separate conditioner, primer and bond
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What is a 2 stage system in resin-dentin bonding?
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conditioner and primer or the primer and adhesive
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What is a 1 stage system in resin dentin bonding?
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individual components separate within a container
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What is conditioner made of?
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made of acid e.g. phosphoric acid, maleic acid, oxalic acid
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What does conditioner do to smear layer?
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dissolves the smear layer to allow it to be washed away or
sublimes the smear layer to allow it to be redeposited (within primer) in the tubules hydroxyapetite crystals are also dissolved leaving a delicate collagen framework supported by fluid |
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What is a primer?
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a resin monomer with a double ended molecule
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What end of primer bonds with dentin?
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hydrophilic end +
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What end of primer bonds to resin?
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hydrophobic end O
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explain how a primer works
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monomer is dissolved in a solvent like ethanol or acetone to displace water and allow the resin to penetrate the collagen.
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What system do you apply primer to wet/moist dentin?
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when the smear layer is dissolved
fluid supports the collagen framework until it is replaced by resin |
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When is primer applied to dry dentin and not washed off?
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when the system relays on the smear layer being solubilised.
primer solution is acidic and self-etching |
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What is the bond?
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resin monomer coating
bonded to the hybrid resin-collagen layer to give a methacrylate rich layer for the composite resin to bond to. e.g. Bis-GMA, UDMA |
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What can happen is intimate bonding is not achieved?
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leakage and pulpal sensitivity is severe
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