5/26 - Custom Tray, 298-302 Flashcards
how far to extend custom tray
3 mm below gingival crest
how many layers of wax to use for custom tray? this is equivalent to what?
2 layers
this is equivalent of 3 mm of PVS
dimensions of tissue stops on custom tray
3x3 mm
how many tissue stops should be placed on custom tray
3 - tripoded on non-functional cusps and incisal edges
where to place tissue stops on custom tray
non functional cusps and incisal edges
when creating custom tray, should you squish the wax real flat
NO! you’ll use the 3 mm thickness
what should you place on pink wax to help with custom tray relief once material is cured (per grady)
small amounts of vaseline
how should you cut the Triad material to aid with forming the tray
down the middle creating a horshoe shape
what should you do to custom tray to prevent material from flowing out the back of the tray? what does this do
create an extension that covers the distal aspect of the last tooth. this allows for capture of distal margin of posterior prep
how should you form handle when making custom tray for mandibular arch
straight up and a little out
how many times will you bake tray? what happens at each bake?
2x2 minute bakes
1st 2 minutes: just place it in with model and pink wax
2nd 2 minutes: remove model and pink wax and just place in custom tray
what should you do after baking custom tray
feel with fingers to remove rough spots and finish the rough edges
why do we have to smooth out the custom tray
it can hurt patient (cutting, etc.)
T/F: if you wouldn’t place it in your mouth, do not place in patient’s mouth
TRUE
what should the inside of the tray be painted with for the impression material used?
uniform coat of adhesive
what are the mandibular nonfunctional cusps
lingual cusps
why are custom resin trays used in elastomeric impression techniques
are more accurate in uniform, thin layers of 2-3 mm (shil)
why do some authors advise against the use of stock trays
uneven bulk of impression material is conductive to distortion
what is the mean difference between custom and stock trays
1 mm
does tray space have an effect on dimensional accuracy of monophasic PVS impressions
NO
are stock trays or custom trays provide more sufficient accuracy for single-tooth preps, particularly if PVS or polyether is used
stock trays (per shill)
are the adhesives between different tray materials interchangeable
no
bonding strength of adhesives with PVS materials can be improved by:
50% by ___
140% by ___
50%: adding perforations to tray
140%: roughening inner surface of acrylic resin tray with 80 grit silicon carbide paper
per shill, why should we not use petrolatum? what should be used instead
the waxy layer on the inner surface will diminish bonding by the tray adhesive applied before placement of impression material, resulting in distortion of impression.
use aluminum foil over wax and stone cast to provide separation
should the tray touch retromolar areas
yes
tray should be prepared how many hours in advance of making impression
at least 6 hours (since it could shrink as much as 8%)
significant linear changes occur during the first ___ of tray fabrication and continue for up to ___
40 minutes; 6 hours
how can an acrylic resin tray be stabilized against further shrinkage and distortion
boiling it before placing impression material
should elastomeric impressions be stored in moist environment
no bc acrylic resin tray may imbibe water and distort
