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Fixed Prosthodontics II > Quiz 1 > Flashcards

Quiz 1 Flashcards

1
Q

what material do we use to take bite registrations?

A

PVS

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2
Q

why is it important for the coefficients of thermal expansion of porcelain and metal to be as close as possible?

A

if the coefficient of thermal expansion of porcelain is too far off from metal, the stresses between the materials would be too great

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3
Q

what is the difference, with respect to bonding, between porcelain and zirconia and porcelain and metal?

A
  • porcelain and zirconia do not form a chemical bond
  • porcelain and metal form a chemical bond
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4
Q

suck-down matrices are made from a ___ sheet using a ___

A

polypropylene sheet using a vacuuform

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5
Q

what are the PFM crown preparation measurements for a metal lingual preparation?

A
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6
Q

what are 4 examples of PFM facial margins?

A
  • 90 degree shoulder
  • 120 degree shoulder
  • shoulder with a bevel
  • heavy chamfer
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7
Q

what are the two categories of anterior PFM design and which is the preferred design?

A

winged and wingless (preferred)

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8
Q

what is the advantage of vacuum firing porcelain?

A

makes porcelain more dense and increases strength

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9
Q

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 ___

A

the tooth was prepared in a single facial plane

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10
Q

are current generation caries detector dies alone enough to determine adequate caries removal?

A

no

caries detection is a multi-faceted exercise and no one technique is adequate; you can use an explorer to feel for caries

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11
Q

what is the metal collar location on a porcelain lingual PFM?

A
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12
Q

what is the metal collar location on a metal lingual PFM?

A
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13
Q

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

A

esthetics

you want to bury the margin at least 0.5mm

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14
Q

what are the 6 applications of a suck-down matrix?

A
  • 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
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15
Q

what are the ideal reduction ranges for a PFM crown preparation on an anterior tooth? what is the margin type?

A
  • 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
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16
Q

are suck-down matrices as accurate as putty?

A

no

17
Q

what are some issues with inadequate occlusal reduction?

A

it can lead to fractured porcelain, over-contoured crown, broken temps, perforations, etc.

18
Q

where do you want the index on a suck-down?

A

on soft tissue

19
Q

when making the pour-up model for a suck-down matrix, what stone type is used?

A

type III buff stone

20
Q

what are the contraindications for a PFM crown?

A
  • 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
21
Q

what are the basic steps in making a suck-down matrix?

A
  • 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
22
Q

in an anterior PFM crown preparation, the incisal reduction of 2.0-2.5mm allows for ___

A

proper porcelain translucency

23
Q

in treatment sequencing, when is fixed prosthodontics completed?

A

it is usually the last treatment to be completed. there are some exceptions, but this is a general rule.

24
Q

what are the ideal reduction range for a PFM preparation on a posterior tooth? what is the margin type?

A
  • 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
25
Q

do porcelain and metal have the same coefficient of thermal expansion?

A

no. it is very similar, but the coefficient of thermal expansion of porcelain is a tiny bit higher

26
Q

why are PFM crowns an excellent choice for removable partial denture abutments in the esthetic zone?

A

the incorporation of occlusal or cingulum rests and proximal and reciprocal guide planes in metal

27
Q

in a posterior PFM crown preparation, the incisal reduction of 2.0-2.5mm allows for ___

A

proper thickness of porcelain

28
Q

what are the indications for a PFM crown?

A
  • teeth that require complete coverage and considerable attention to esthetics
  • excellent choice for bridge retainers
  • excellent choice for removable partial denture abutments in the esthetic zone
29
Q

what are the PFM crown preparation measurements for a porcelain lingual preparation?

A
30
Q

on a PFM crown, where is the metal?

A

at the thinnest point (0.3mm), called the coping

31
Q

in an anterior preparation for a PFM crown, where should the heavy chamfer (1.2-1.7mm) or 120 degree shoulder margin be placed?

A

in all esthetically critical areas of the preparation

32
Q

what type of bond is formed between porcelain and metal?

A

oxides from the porcelain form a chemical bond with the metal

33
Q

in a PFM crown, if the opaque layer is too close to the surface, what can it cause?

A

it will create an increase in value over that area

34
Q

what is a bite registration?

A

an impression taken of the patient’s upper and lower teeth in a biting position; used to assist in fabricating crowns and other prosthodontics

Fixed Prosthodontics II (4 decks)

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