robbypowell's version from 2016-12-12 00:49

Lab 4 (photocuring)

What is the difference in spectral output among a conventional quartz-tungsten-halogen curing unit (QTH), a xenon arc unit (plasma arc; PAC), a blue light emitting diode, and a multiwave LED ligh
WHICH HAS/HAVE (can be more than one)
Question Answer
BROAD spectral emissions and will cure all types initiators (350 –550 nm)PAC (xenon arc/plasma arc) and QTH (Quartz-tungsten-halogen) lights
NARROW spectral emissions and are only really able to cure CQ initiator (430 –470 nm)Blue LED
provides multiple spectral outputs, (390 –410 nm AND 420-480 nm), and so can cure all types of initiators and function LIKE broad-spectrumMulti-wave LED's


Question Answer
does the VALO unit cure to expectations when using recommended exposure time of this composite (10 seconds)?yes
does VALO Turbo 4s setting cure to expected depth when using recommended exposure time of composite (4s)?No
define: light output applied over a defined area (units: mW/cm2)Irradiance
Define: irradiance delivered in an area during a specified time (or put another way) irradiance multiplied by exposure duration –in units of mJ/cm2) (light energy/surface area)* timeRadiant Exposure
Shorter wavelengths (such as 400nm) penetrate to _____ (lesser/greater) depths when curing composite; Longer wavelengths (such as 470nm, i.e. blue) penetrate to _____(lesser/greater) depths400 shallower cure; 470 deeper cure
the span of light wavelengths put out by a photocuring unit (range of wavelengths ex 350-550) is its_______ outputSpectral output
Compared to the study with curing through opaque tubes _______ (lesser/greater) depths would be found in teethGreater (because of reflective and translucent nature of enamel)
"unscrapable" composite at the bottom of cured composite cylinder ____ (Is/isn't) cured to same extent as composite closer to sourceIs not
Based on the lab-test we have done (of the cure depth in opaque cylinder and scrape off what can be scraped off), Depth of Cure should be adjusted how (numerically) to be consistent with Standard Depth of Cure measurements?divide by 2
How far out did the tip have to be before 50% of the tip end light level was lost for the VALO light in each curing mode7-8mm (regardless of power-mode)
T/F: for valo Change in output intensity mode of the unit does not affect the rate at which light is lost based on distance of source from compositeTrue
Is the inverse square law (pertaining to distance of cure source from composite) upheld by the laboratory findings?No; Curing light does not obey inverse square law because it does not act like a point source radiation 360 degrees in space
Is light coming out of the Valo curing light columnated or divergent?Divergent
Because curing light is divergent, The concentration of light over a specified area (irradiance) will ________ (increase/decrease/stay the same) with increasing distance of source from compositeDECREASE
To compensate for decreased light amount with distance (and thus the decrease in ability to optimally photo cure), the exposure _______ can be EXTENDED, so that an equivalent amount of delivered irradiant ENERGY levels can be provided.Duration (make up for it with the other component of Radiant ExposureL TIME)
are irradiance readings obtained when the tip is against the detector element of the radiometer (at a “zero mm” distance) are valid predictors of how the light will perform clinically?No, don't account for Divergence
State a method of ensuring that no composite material will be cured to the end of the curing tip, but yet, providing maximum intensity at the target;For first 2 seconds, hold tip 1-2mm away, then rest against composite
Office fluorescent lighting ______ (does/does not) result in composite cureDoes NOT (although fluorescent light can cause cure composite. The distances that these room lights are from the composites makes them ineffective for curing purposes.)
An operatory light ______ (does/does not) result in pre-mature composite curing.DOES
is use of a blue-blocker paddle effective in preventing pre-mature composite cure?Yes (extremely so)
Will UV light cure composite?Yes! Camphorquinone, the photoinitiator in most composites and bonding agents, has a large UV absorbance. Thus, instead of blue light, UV light can also be used to cure most composites
Is there further curing, shrinking or expansion cured composite when re-irradiated?No further curing; No shrinking; Short-lived expansion from heat, then returns to previous volume when cools
What is the underlying rationale for use of a slow-start method for photo-curing compositeSlower reaction initially to create LESS STRESS and GREATER MARGINAL INTEGRITY ( I thought that Dr. Haddock's experiment that he showed us illustated that there was no difference with this method, though...)
What is a potential problem with the soft-cure method if the same recommended time exposure is usedUndercuring the composite
Define: Light intensity adjusted for the non-linear response of the human eye to different wavelengthsIlluminance (LUX, foot-candles, etc)
Define: Light measurement for purposes of absolute power measurement -NOT related to eye responsiveness (in units of Watts)Radiant Flux
Define: power distributed over an area (same as exitance or radiant emittance), measured in mW/cm2Irradiance
State the wavelength range over which a curing radiometer needs to be responsive to account for potential light-curing energy380 to 490nm (Camphorquinone absorption peak occurs about 465 nm, but effective absorption ranges from 425 to 490 nm.; Other photoinitiators absorb between 380 and 440 nm)
State the proper function of hand-held radiometers in a clinical dental environmentused ONLY for periodic checking of office lights for output; (cannot be used to compare curing potential or irradiance of different curing lights b/c they don't take enough potential differences into effect between lights)


Question Answer
What is the relative loss (percentage of top surface irradiance remaining) of light at 0.5 mm depths from the top(0.5 mm depth) 57-61% loss (39-43% gets through)***
What is the relative loss (percentage of top surface irradiance remaining) of light at 1 mm depths from the top(1.0 mm depth) 79-80% loss (20-21%gets through)
What is the relative loss (percentage of top surface irradiance remaining) of light at 2 mm depths from the top(2.0 mm depth) 92-99% loss (1-8% gets through)***
What is the relative loss (percentage of top surface irradiance remaining) of light at 3 mm depths from the top(3.0 mm depth) 100% loss (0% gets through)
What is the difference between light penetration of shade A1 vs shade A2 composite at same depths?No difference
what two clinical techniques can be used to overcome this great loss of irradiance seen at the depths of composites?Increase POWER output or DURATION of exposure

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