Dr Patel's lecture 9/10/2019 Flashcards
What are the components of a resin composite?
Resin matrix
Fillers
Coupling agents
Initiator
What is the resin matrix made up of?
Bis-GMA: HIghly viscous and therefore often mixed with shorter chain monomers (tegDMA). Ratio between Bis-GMA and short chain monomers affects degree of polymerization shrinkage.
What are the types of fillers and what do they do?
Quartz,
The more fillers you have the more bulk you have and affects polymerization shrinkage. Low filler content = high polymerization shrinkage.
WHat are coupling agents for?
Coupling agents is important for combining the resin matrix and fillers
What are initiators?
Initiate polymerization. Composite often has camphorquinone.
How is polymerization shrinkage reduced?
Incremental placement of the composite.
Using a flowable liner underneath restorations.
What is z100 composed of?
z100 has bis-GMA and teg-DMA and has 66% fillers (silica/zirconia)
average particle size 0.6
What is filtek supreme composed of?
bis-GMA, UDMA, TEGDMA
55% silica/zirconia by volume
true hybrid with cluster size of 0.6 to 10 micrometers
It is available in dentine, body, enamel and translucent shades.
How do dentin and enamel differ in terms of adhesion?
Adhesive systems need to accomodate for the type of tooth structure being adhered to.
Enamel requires an acid etch for micromechanical retention. (37% phosphoric acid)
Scotchbond universal is then added to etched (etch increases the bonding capacity)
Dentin is a composite structure and varies with location, depth, and age. Smear layer and smear plug can block the dentinal tubules which must be removed. This prevents permeability of adhesive systems. 2 options t overcome this problem: remove smear layer, and incorporate the smear layer into the bonding system.
Dentin via total etch = removal of smear layer
Etch can be used to remove the smear layer.
What occurs when etch is too concentrated?
Calcium monophosphate precipitation
What are the advantages and disadvantages of removing the smear layer with etch?
Increases permeability,
However,:
It is technique sensitive
Completely exposes the dentinal tubules
Also permits fluid flow via pulpal pressure which can lead to post-op sensitivity
What are the types of etch in terms of
etch-and-rinse aka total-etch
Self-etch
Universal adhesives (aka multi-mode)
How is etch classified?
According to generations
Based on mode of application
Based on number of steps
How long should primary teeth be etched?
In primary teeth there is aprismatic enamel. That area is often hypermineralized.
15 seconds is all that is needed
How long should permanent teeth be etched?
Anywhere from 20 to 60 seconds
How do caries affect the bonding capacity of bonding agents to enamel?
Bonding to caries is not the same as bonding to sound dentin. Bond strength is weaker in caries.
What are the 3 steps to bonding?
Etch:
Stronger acids remove smear layer, demineralize dentin, and widen the dentin tubular orifices
Weaker acids condition the dentin, do not cause substantial dentine demineralisation, and do not completely open the dentinal tubules.
Prime:
Primers contain hydrophilic and hydrophobic sides. The contain HEMA, organic solvents and water.
Solvents displace water in
Bond:
Attaches to hydrophobic resin components. Can be filled or unfilled and contain mainly hydrophobic monomers.
Difference between hybrid layer and ion exchange layer?
Hybrid layer refers to composite ion exchange to GIC
How do the adhesive system monomers differ and what kind of molecules are used?
bis-GMA (big)
bis-EMA
UDMA
TEGDMA
HEMA
The bigger the molecule the more hydrophobic it is.
Different monomers penetrate to different depths into the dentinal tubules based on size.
What are the 2 main methods of bonding of GIC?
2 main methods:
Micromechanical
True chemical bonding
