May 23, 2016 Flashcards
Type of wax used when making definitive impression:
Boxing wax, warmed and sticky wax to hold in place
What do we pour up from the definitive impression?
Working cast
What needs to be captured in the working cast poured up from he definitive impression?
tooth surfaces, residual ridge area (?), other parts of the dental arch, facial structures used to fabricate restoration or prosthesis in the lab
2 other names for working cast:
definitive/ final cast
artificial crowns and fixed partial dentures are made using this technique:
indirect technique
What type of stone do we use to pour the definitive cast?
Jade Stone, Type V
Why do we want Jade stone for the working cast since it has the highest expansion within gypsum materials?
to compensate for the shrinkage of the metal when casting crown
What must be done before taking definitive impression?
surrounding teeth free of voids, teeth involved in anterior guidance intact, all occlusal surfaces accurate, all relevant soft tissue duplicated
Why do we add light body to the occlusal surfaces?
to ensure accurate occlusion of opposing cast
The working cast should be POURED to this thickness with the Jade stone:
20-25 mm above cervical area, leaving palatal portion as exposed as possible
How long does it take for Jade stone to set?
30min (10min to set, 30 minutes to remove)
How to trim the base of the working cast:
parallel to occlusal plane
Thickness to trim the working cast:
10mm above the cervical areas (edentulous area)
Why is it necessary to have 10-15mm extra base just to trim down? ask
Tools to trim the B and L folds of the working cast:
arbor band, cast trimmer, carbide cutter (in a lathe)
How should the working cast be tapered, angle?
at base, 20 degrees, to prevent locking in by undercut
What helps the working cast to come out of the base easily?
smoothness and taper of the way at the base
Positioning of the pin holes of CCC30 preparation:
18, 22 (cingulum), 28 (slightly lingual), 30, 31
Where to mark the location of the pinholes:
occlusal surface of each die, the adjacent teeth and the neighboring edentulous area
How does the Pindex system minimize the rotation of the dies?
anti-rotational mechanism (is this the face that there are 2 legs to each pin? ask)
Why do the dies remain stable after repeated removal and insertion?
because the pins are housed in a sleeve (plastic or metal)
True or False? The size of the drill should be 1 size larger than the pin.
F. same size
How are the holes drilled in the pindex system?
thumbs on oclusal surface of cast, lift handle with the fingers of both hands, move drill up and down or pushing the table down with the cast.
How do you know if you are at proper depth when drilling the pinhole?
the red beam will automatically shut off.
How to remove stone debris from the pinholes:
air chip-blower
Apply this to the heads of the pins before placing them in the pinholes:
cyanoacrylate adhesive
Steps after placement of the pins:
add metal sleeves and plastic caps
Apply this to the stone surface around the pins before placing the cast in a base former:
separating medium, ie Super-sep
Type of stone used to pour up the Pindex working cast around the pins:
microstone (vacumix again), add around pins before flipping into base tray
Allow the microstone base to dry for:
30 min
What to do after base dries for 30min:
trim sides, remove base former and base stopper (plastic caps)
What are the plastic caps called?
base stoppers
When should you grind the metal pins and sleeves with e-cutter or model trimmer?
never
How to cut out the die?
saw blade, “cast must pass completely through the first layer of the stone” ? just pull out, right?
Taper of cuts for the index working cast die:
converged toward base
True or False? It is ok if you damage the finish line when cutting out the die.
F. Don’t damage proximal contacts either
How much beyond the finish line should remain when trimming the die?
0.5 to 1mm of prepared tooth beyond the finish line
True or False? Adequate access to the finish line is imperative.
T
What stone should remain after trimming the die?
the critical few mm’s adjacent and critical to the finish
How to remove the stone that is closer to the finish line:
large then small carbide bur. Don’t touch finish line.
Does the smaller or the larger pin go toward the lingual?
smaller, because the lingual edge is more narrower
How to remove any residual flash:
sharp scalpel, preserve tooth structure immediately apical to finish line
How should the die and cast be labeled before sending to the lab?
each die and adjacent tissues are numbered
Why do we number each die and adjacent tissues?
identification during the lab procedures
How can you protect the trimmed die after marking the finish line with a red pencil?
light coat of die sealer or cyanoacrylate cement that we used for pins (all surfaces)
Do this before mounting casts on the articulator:
utility wax or baseplate wax over the pins/ end of the dowels (remove the red plastic capillaries) (no scoring?)
Why do we place utility wax over the dowels/ pins?
to separate them from the mounting stone (articulator will be upside-down for mounting)
Mounting working cast:
wooden sticks to hold in occlusion, wet cast with paper towel (no scoring?)
How to place the wax:
sectionally or from #18-#30, peel off after mounting stone is smoothed
What is used for slow speed mixing on the Vac-U-Mixer?
drive chuck
Black knob on Vac-U-Mixer:
Vibrator
What should be with the lid (lead) of the Vac-U-Mixer?
O ring
Metal piece sticking out of lid (lead) of the Vac-U-Mixer:
slotted drive nut
Before using the Vac-U-Mixer bowl, make sure:
it is dry
Mix __ mL of water with the Jade Stone:
15.5 mL with 70g of stone
True or False? you must mix the Jade stone before using the Vac-U-Mixer.
T, 20-30 seconds
Rotate the bowl in this direction to lock the Vac-U-Mixer in place.
clock wise
Why should you press the bowl and lid (lead) of the Vac-U-Mixer together?
to seat bowl on O ring in lid (lead)
Connect what to what after closing the Vac-U-Mixer lid (lead)?
metal nozzle (at end of vacuum hose) to top of lid (lead)
How to start the Vac-U-Mixer:
insert slotted drive nut into drive chuck, starts automatically
Why do we move the manual switch to the on position during mixing?
so pump continues to run after the Vac-U-Mixer is disengaged Why? Ask
The vacuum gauge of the Vac-U-Mixer should be between:
25 and 30
Mixing time for plaster, stone in mixer (check): Microstone?
10-15
Mixing time for die material in mixer (check): (jade stone?)
20-30
What do you do after disengaging the Vac-U-Mixer?
move mixing bowl to vibrator (to help get lid (lead) off?)
Steps after mixing is completed:
disconnect vacuum, open lid (lead), turn to “off” position, wash lid (lead), bowl, and hand spatula (sequence?)
Which stones have lower expansion rates than Jade Stone?
Resin rock, Lind rock, Hard rock, then Gypsum (backward alphabetical)
Which type of sleeves are the most stable?
metal
Placement of pinholes in the anterior:
over cingulum
How to trim the mounting cast:
1mm of microstone (around gingiva? check)
Stone to use when pouring second pour of the definitive impression: we use the same impression?
Jade stone, called solid cast
True or False? The Solid cast should be pindexed.
F. This cast is only for technician
Are large/small carbide burs synonymous with e-cutters?
ask
Blade strokes should be in either of these 2 directions when trimming the die:
O-G (G-O, right?) or horizontally
Where to add utility wax
pinhole area or entire rim of cast
Why do we want such a large space (more than the width of one piece of wax) in the anterior portion of our cast?
ask, this happened in one video, not the other
Point of defining finish line in red pencil:
tells the lab technician EXACTLY where the finish line should be placed
How big of a gap should you have between the base and the working cast?
none
What is the vibrator used for?
removing the nozzle after mixing (and lead/lid?)
How does the vibrator help to remove the lid (lead)?
ask
In what shape should you trim the working cast?
arch
True or False? Super-Sep should be applied to the metal pindex pins as well as the facial border of the cast.
F to the pins, T to the facial border
The position of each saw cut should be:
parallel to the dowel with a pencil (?) so dowel should be perfectly centered BL?
Which teeth are we making die of?
29, 30
The cast must pass completely through:
the first layer of stone (?) just needs to lift out, right?
How do you protect the fragile die when sawing them out?
with a soft cloth
How should you trim the margins of the die?
don’t!
Why does unprepared tooth structure adjacent to the tooth being prepped have to be preserved?
to identify contour of the tooth
Purpose of covering the dowels with wax before mounting:
to separate them from the mounting stone
% expansion of Jade stone:
18%
Function of the metal sleeve and red rubber tips:
increase life span of model, prevents wear
Spray the definitive impression with this before pouring up:
debubblizer, then remove with air syringe
Working time when pouring up the definitive impression:
5-7 minutes
How do you avoid trapping air bubbles when pouring up the definitive impression?
debubblizer and adding stone a little at a time
Setting time after pouring up the definitive impression:
10 minutes, separate after 30 minutes
Stone for working cast, “” “” around the pins, and “”” second pour:
Jade, microstone, Jade
Pour this/these with Jade stone:
working cast, solid cast
Pour this/these with microstone:
base for working cast
What are dowels?
The ends of tube pins?
How to speed the setting time of the cyanoacrylate when adhering the pins in the cast:
1 drop of PMMA monomer
How to trim the microstore base:
1-2mm of land area for the base
From which angle should you mark the finish line?
from the occlusal angle
What maxillary cast are we mounting against?
use existing maxillary cast
