Physics and Chemistry of Light Curing - mechanism Flashcards
What is the polymerisation reaction?
process of reacting monomer molecules together in a chemical reaction to form 3D networks or small polymer chains
What are the advantages of light curing?
extended working time
command set
more consistent means of polymerisation obtained
more even distribution of the chemicals within the paste as its blending is optimised
the (tertiary) amine required in the material lower
higher levels of monomer to polymer
What percent of monomer to polymer is achieved in light activated materials? (clinical)
50-70
What is the effect of unconverted monomer?
can lead to leaching out of the material in the long term and degradation of the restoration with time
What is the laboratory percentage conversion of monomer to polymer?
95-97%
What are the disadvantages of light curing?
expensive
systems need to be compatible - excitation wavelength of chemicals and wavelength of light
adequate energy and correct wavelength
problems with light attenuation - ways that the light passes through the material
What does the initiation of the light process rely on?
photo-initiator
What is the photo-initiator?
chemical activated by light of a specific wavelength
When light breaks down the photo-initiator, what is produced?
atoms or molecules
What are the steps in the mechanism of photo-polymerisation?
What does the activated chemical react with?
amine
What is this reaction called, light breaks down the photo-initiator chemical to produce atoms or molecules?
amine
What are free radical?
atoms, molecules or ions with unpaired electrons and are highly chemically reactive
What initiated the polymerisation reaction?
free radicals
What kind of reaction is the photo-polymerisation mechanism?
chain reaction
What are the basic steps in the mechanism for the setting reaction of light activated resin?
