Midterm 1 Flashcards
how is it possible for adhesive resin to bond high noble indirect restorations?
Adhesive resin cements work on 4-META technology so you can use it to bond high noble indirect restorations as long as you tin plate the intaglio surface
what type of crown should you do with a cast post and core, and why?
- PFM
- you wouldn’t want to use something like zirconia because you’d get show-through from the CPC
what is the lingual axial reduction for an anterior PFM preparation for metal? what about porcelain?
it is the same for both: 0.5-1.0
*lingual axial reduction is not the same as lingual concavity reduction
what are the areas of importance that you should inspect for detail and accuracy when checking your stone models for crown and bridge?
- prepared tooth/teeth
- adjacent tooth/teeth, especially proximal surfaces
- occlusion
- *you should also check these when inspecting your impression*
what type of margin is used for a cast post and core? what is the purpose of the cast post and core margin?
- bevel margin
- serves as another ferrule to resist root fracture
- making the bevel margin isn’t always possible
For an anterior PFM crown, what is the lingual concavity reduction for metal and porcelain?
- metal lingual - 0.5-1.0mm
- porcelain lingual - 1.0-1.5mm
Placement of the keyway for a cast post and core is lingual. Why?
- Keeping it lingual can help prevent fracture
- You have more tooth structures to the lingual
- It will also prevent the temporary from appearing dark
when using triple function articulators, the set should be ___ when the model is poured up
passive (tray can’t be torqued or twisted while stone is setting)
when cutting the die from the cast, why is it important to keep the cuts parallel?
So you can put the die back in easily – otherwise you’d have to take off the other pieces
What clinical situations require you to take a full arch impression as opposed to a dual arch impression?
- 2nd molar
- 3 or more teeth
- canines
Is it advised to enlarge the canal to create a bigger diameter post to strengthen the restoration?
no, never
what is an advantage and disadvantage of having a large base on your die?
- advantage: easier to hold when you are trimming it
- disadvantage: you will be forced to trim perpendicular to the axis of the preparation at times
after trimming the die, what are the next steps up to the point of the wax-up?
- apply 2 coats of die sealer; use compressed air to thin it
- apply die relief; first coat applied 2-3mm from margins; second coat completely covers first coat and is applied 1-2mm of margins (should NOT touch the margins)
- begin wax-up
T or F:
when trimming the triple tray impression to fit the articulator, opposing sides must be parallel
false
they can be somewhat divergent if needed
when pouring up the FGC stone model for the articulator, which arch should be poured up first?
the arch with the die
If you have a high noble casting (75% gold), can you bond that into place?
You can if you tin plate it; you have to bond it with adhesive resin cement
When shaping the die apical to the margin, you want to shape it so that it will maintain ___
axial wall contours
you are less likely to abrade the margins if you do this
what is the difference between a thin and thick biotype?
thin biotypes have thinner gingival thickness and are more susceptible to gingival recession, whereas thick biotypes have thicker gingiva and are usually not a problem
what stone type is used when pouring up the FGC stone model for the articulator, and what is it important to remember to do with the articulator before pouring?
- type IV
- you need to remember to spray silicone separator into the appropriate index of the articulator
is the bevel margin on a cast post and core preparation critical?
no - it is ideal, but you can still do a CPC if you can’t get the bevel margin
when taking an impression for a cast post and core, how should the impression material be injected?
- inject around the head of the blue pastic analog post, starting in the anti-rotational keyway
- move to margins of tooth preparation
- add balance of syringe material all around the area of the tooth
- insert the impression tray
what type of restoration should be strongly considered on a tooth with more than 1/2 of coronal tooth structure missing?
cast post and core
which of the following anterior PFM framework designs is/are unfavorable?
- opposing tooth contacts porcelain
- opposing tooth contacts the porcelain/metal junction
- opposing tooth contacts metal
opposing tooth contacts the porcelain/metal junction
what should you use to finalize the marginal area of your die when trimming?
25 blade in a red handle
why is the wingless preparation the preferred design for an anterior PFM crown?
- better esthetics
- slightly less retentive
- easier
why are cast post and cores made with a tapered post?
- because you put a taper on the axial walls of the preparation, and so you want to mirror that
- it is an indirect restoration and it will be inserted into the tooth, so the taper helps it go in easier because it should match the canal walls
what are some important considerations in cementing a final cast post and core restoration?
- post and crown should be cemented simultaneously with a chemical cure, self-adhesive cement such as C&B metabond or panavia
- vertical pressure should be applied during cementation, and patient should NOT bite on the restoration during the set
- remove excess cement during the rubbery stage (don’t cause gingival bleeding, and don’t wait until cement is set before removing it)
When trimming your die, what is the dangerous direction of the cutting edge to rotate? how can this be avoided?
- Perpendicular to the axis of the die or parallel to the margin
- Instead, you want the long axis of your cutting instrument to be parallel to the axis of the preparation
when taking an alginate impression, you should insert the tray from from front to back or back ro front?
front to back
Why do we start cutting the cast apart from the base of the index side rather than the die side (aka you go apical to occlusal)?
Less chance of having that saw blade come up against the margin
If you get anterior gingival recession in someone with a high smile line, is that problematic?
yes
what should you do to the canal before taking an impression for a cast post and core?
dry it with a paper point
what is a diagnostic tooth preparation?
done before the actual preparation clinically; it gives the operator a preview of what’s coming; it’s kind of like a trial run
in the lock-and-key preparation technique, where should the anti-rotational keyway be placed? why?
- on the lingual/palatal aspect
- it could cause a fracture if it’s not on the lingual
- it’s more compatible with the forces that are placed on the teeth
- you tend to have more tooth structure on the lingual/palatal
why is it important to extend stone toward the distal when pouring up the stone model of the cast post and core?
to create an index, allowing the arches to fit together like a puzzle piece
what are the reduction measurements for a FGC?
- occlusal reduction/clearance
- functional cusp: 1.5-2.0mm
- non-functional cusp: 1.0-1.5mm
- functional cusp bevel: 1.5-2.0mm
- axial reduction: 0.5-1.0mm at margin
- margin type: chamfer
- non-functional cusp bevel: 0.3-0.7mm wide
- softened acute line and point angles
What happens if the analog post gets hit when the patient bites down?
just trim it
for the midterm, what is the range for incisal reduction for an anterior PFM preparation?
2-3mm
why don’t you need as much lingual reduction for an anterior PFM?
Because there is usually metal on the lingual (in other words, you don’t need as much porcelain)
- lingual concavity reduction for metal is 0.5-1.0mm
- lingual concavity reduction for porcelain is 1.0-1.5mm
T or F:
maxillary keyways should be palatal, and mandibular keyways should be buccal
false
they should both be palatal/lingual
how should PVS impressions be removed from the patient’s mouth once set?
- opposing arch comes off first
- remove impression from the prepared tooth arch by pulling entire impression out parallel with the post’s line of draw to avoid torquing or tipping
when cementing a temporary crown, why is it important to only apply cement to the base of the acrylic and not on the post?
cause you’ll cement the gat dang post to the teeth! then how are ya gonna get it out? SMH.
T or F:
You can get a more consistent bite registration component with a triple bite tray (aka dual arch impression) rather than two separate full arch impressions
true
if a tooth is badly broken down, what type of restoration will hold up best?
cast post and core
when pouring up the stone model of the cast post and core, which arch should be poured first?
the one with the prepared tooth
can zirconia crowns be used with any preparation design?
yes, even though we have an ideal prep
how should vacuum mixers be stored?
with water inside
In a posterior PFM preparation, what is the axial reduction? where should it be heavier?
- 1.2-1.7mm
- heavier on buccal transitioning to lighter on the lingual
when fabricating a temporary for a cast post and core, why is it important that the metal post is toward the lingual/palatal?
if it is too facial, it can show through and give the temporary and darker appearance
when doing an impression pour up for a cast post and core, how much stone and how much water should you use? what about when pouring up the FGC stone model for the articulator?
- 100g of stone and 21ml of water for CPC (single arch)
- 100g of stone and 20ml of water for FGC (two arches, otherwise it’s half for a single arch)
what cement should be used on a temporary?
polycarboxylate cement
