Resin Composites 2 Flashcards
what is the optimum absorption of camphorquinone?
460-480nm = visible blue light
what kind of activation lights have been used in the past?
-quartz tungsten halogen GTH
-fibre optic light guide - on use fibres break, reduced efficiency for light transmissions
- cooling/timing mechanisms
heat
broad spec filtered to eliminate harmful wavelengths
LED’ s = what kind of spectrum?
have a low?
what kind of heat?
bulky or small?
narrow spectrum
less bulky
low heat
low current
avoid what with LED’s?
sequential activations
what is LED quality control like?
low
how to increase coverage with LED lights?
multi LED curing lights
Zach and Cohen 1965 found?
- 5 degrees caused pulipitis in 15% monkey teeth
11. 1degrees caused pulipitis in 60%
with an LED unit wait how long until using again?
at least 30 seconds before curing again
if not = heat builds up at LED tip = discomfort and tissue irritation
Plasma Arcs - xenon bulbs how do they work?
spark, potential difference across gas and gas ionises to form plasma
plasma arcs - how much power output?
what do they need?
ten times QTH
need efficient cooling
apply plasma arc for how long?
was stops sequential activations?
2-3 seconds
timer prevents sequential activations
Argon lasers give out?
blue light
Argon lasers narrow wavelength means?
do not coincide with all materials
Argon lasers have a collimated beam which allow?
greater depth cure with minimum heat production
how to look after a unit?
avoid contact with RC
regularly check the output
How to use a lamp checker?
apply to light from new because measurements are relative
what is abrasive wear?
hard asperites penetrate the polymer matrix removing material by shearing and cutting
what is erosive wear?
impact of asperites produce damage of polymer matrix
what is fatigue?
Localised deformities of polymer = subject to repeated stresses = failure
In vitro staining by silver staining can see what 3 stages of wear?
- little wear, no substance damage
- higher wear, more considerable damage
- catastrophic wear b/c extensive subsurface damage
what is resin matrix softening?
Inhibition of polymerisation b/c entrapped air pockets
b/c chem scattering = foods, plaque acids
stress concentrates at resin filler and what happens?
thermomechanical fatigue
watersorption
polymerisation shrinkage
mechanical stresses on restoration
