Quiz 1 Flashcards
what material do we use to take bite registrations?
PVS
why is it important for the coefficients of thermal expansion of porcelain and metal to be as close as possible?
if the coefficient of thermal expansion of porcelain is too far off from metal, the stresses between the materials would be too great
what is the difference, with respect to bonding, between porcelain and zirconia and porcelain and metal?
- porcelain and zirconia do not form a chemical bond
- porcelain and metal form a chemical bond
suck-down matrices are made from a ___ sheet using a ___
polypropylene sheet using a vacuuform
what are the PFM crown preparation measurements for a metal lingual preparation?
what are 4 examples of PFM facial margins?
- 90 degree shoulder
- 120 degree shoulder
- shoulder with a bevel
- heavy chamfer
what are the two categories of anterior PFM design and which is the preferred design?
winged and wingless (preferred)
what is the advantage of vacuum firing porcelain?
makes porcelain more dense and increases strength
a patient is unhappy with the esthetics of an anterior metal-ceramic crown, complaining that it looks too opaque in the incisal third. the reasn for this is most likely ___
the tooth was prepared in a single facial plane
are current generation caries detector dies alone enough to determine adequate caries removal?
no
caries detection is a multi-faceted exercise and no one technique is adequate; you can use an explorer to feel for caries
what is the metal collar location on a porcelain lingual PFM?
what is the metal collar location on a metal lingual PFM?
a sub-gingival margin is often required on the facial aspect of PFM crown preparations. in these situations, if the margin ends up being supra-gingival, ___ will be compromised
esthetics
you want to bury the margin at least 0.5mm
what are the 6 applications of a suck-down matrix?
- can be used in multiple areas of the mouth
- can be cut into segments for easier insertion and retrieval
- can be made in small segments
- can be used for the fabrication of provisional restorations
- can be used as a reduction guide for tooth preparation
- can be used as a short term ortho retainer
what are the ideal reduction ranges for a PFM crown preparation on an anterior tooth? what is the margin type?
- incisal reduction - 2.0-2.5mm
- 1.7-2.2mm for porcelain
- 0.3-0.5mm for metal
- facial reduction - 1.2-1.7mm
- facial chamfer - 1.5mm
- lingual concavity - follow contour of tooth
- 1.0mm metal lingual
- 1.5mm porcelain lingual
- lingual chamfer - 0.5-1.0mm
- two-plane facial reduction - gingival 1/3 to incisal 2/3
- chamfer margin
are suck-down matrices as accurate as putty?
no
what are some issues with inadequate occlusal reduction?
it can lead to fractured porcelain, over-contoured crown, broken temps, perforations, etc.
where do you want the index on a suck-down?
on soft tissue
when making the pour-up model for a suck-down matrix, what stone type is used?
type III buff stone
what are the contraindications for a PFM crown?
- patients whose mouth preparation has not been completed (ie. active caries, untreated perio, etc.)
- young patients with large pulp chambers
- whenever a more conservative approach would suffice
- whenever maximum esthetics is indicated and feasible
what are the basic steps in making a suck-down matrix?
- take alginate impression
- pour up model using type III buff stone
- apply block out resin
- cure for 1 minute in triad curing unit
- trim base to within 7-10mm of teeth (horseshoe shape)
- place matrix material (polypropylene sheet) in vacu-former, heat until sheet is clear and sagging approx. 1/2” at the center
- meanwhile, soak model in water to point of saturation, then spray with separator
- turn on vacuum and drop coping sheet to platform
- trim
in an anterior PFM crown preparation, the incisal reduction of 2.0-2.5mm allows for ___
proper porcelain translucency
in treatment sequencing, when is fixed prosthodontics completed?
it is usually the last treatment to be completed. there are some exceptions, but this is a general rule.
what are the ideal reduction range for a PFM preparation on a posterior tooth? what is the margin type?
- occlusal reduction - 2.0-2.5mm
- axial reduction lingual - 1.2-1.7mm *should be on the narrower side
- axial reduction buccal - 1.2-1.7mm *should be on the wider side
- functional cusp bevel - 0.3-0.7mm wide
- nonfunctional cusp bevel - none
- two-plane facial reduction - gingival 1/3 to occlusal 2/3
- margin above gingiva - 0.5mm
- chamfer margin
