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Flashcards in Quiz 2 Deck (77)
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1

what is the consistency of type 1 inlay wax?

medium to hard

2

what is type 1 inlay wax used for?

generally used with the direct technique for making patterns in the oral cavity

3

what temperature is type 1 inlay wax solid at?

37 degrees celcius

4

between type 1 and type 2 inlay wax, which shrinks more?

type 1 shrinks more than type 2

5

what is the consistency of type 2 inlay wax?

softer than type 1

6

what is type 2 inlay wax used for?

more commonly used in the indirect technique

7

what temperature is type 2 inlay wax solid at?

25 degrees celcius

8

what is "suck-back"? how can a reservoir help avoid suck-back?

  • can happen during casting of gold crowns
  • cools last at the greatest bulk of molten area (at the sprue) and sucks away from the thinner areas (metal that has filled the mold)
  • reservoir - molten alloy stays molten longer so that suck-back occurs at the bottom instead of the crown
    • compensation for shrinkage that occurs during the solidification of the casting alloy

9

why are refractory materials added to investments?

it is a material that doesn't burn, so when the investments are put in the oven, the refractory materials will prevent the investment from burning up

10

what is the refractory material that is used in investments?

  • SiO
  • also silica, quartz, and cristobalite

11

what is the absolute minimum chamfer width?

0.5mm (used with gold)

12

why do we want to avoid a smaller chamfer width than 0.5mm?

  • any smaller can cause problems with:
    • difficult casting
    • reading the margin
    • too thin
    • labs are forced to overcontour to compensate

13

what are the problems with under-reducing occlusally on a gold crown preparation?

it can cause thin spots in the crown and make it more difficult for the lab

14

what are the problems with over-reducing occlusally on a gold crown preparation?

it will interfere with retention and resistance

15

during casting, which of the following expands, and which contracts?

wax pattern, stone, investment, cooling alloy

  • contracts - wax pattern and cooling alloy
  • expands - stone and investment

16

do you want your casting to be slight oversized or undersized?

oversized - it is advantageous for accurate seating

17

what are factors that influence resistance?

  • magnitude and direction of dislodging forces
  • geometry of the tooth preparation
  • physical properties of the luting agent

18

what components of tooth preparation geometry can increase resistance?

  • decreased preparation diameter
  • decreased axial wall taper
  • increased crown height
  • proximarl grooves and boxes
  • definite line and point angles (not rounded)

19

what are 4 factors that influence retention?

  • magnitude of dislodging forces
  • geometry of the tooth preparation
  • roughness of the intaglio surface of the fixed restoration
  • material being cemented or bonded

20

what components of tooth preparation geometry can increase retention?

  • increased axial surface area
  • increased preparation height
  • decreased taper of axial walls

21

T or F:

retentive features must be anchored in enamel

 

false

they must be anchored in dentin

22

what are some geometrical features that increase resistance and retention?

grooves, box forms, isthmus

23

2nd molars tend to have short clinical crowns. how can you increase resistance and retention?

  • build the resistance and retention form into the preparation
  • if the prep is less than 4mm in height, consider other features to augment the retention

24

what two techniques can you utilize when using a die to make a crown?

scanning and lost wax technique

25

know the process of how to set up a die, and the order of application of materials when doing a wax-up

prep tooth → PVS impression → pour up stone model in articulator (don't forget silicone separator) → cut die → mark the margin with a red pencil → you can either scan at this point, or if you are doing a wax up, place 2 coats of die sealer → 2 coats of die spacer/relief (1st coat farther from the margin than 2nd coat) → die lube → dip in hot wax → add inlay wax and prepare wax-up → remove wax-up from die → add sprue → investment → put investment in oven for 45 minutes → cast 

26

what is the most effective place on an instrument to apply heat?

shank

27

at what point is the flame the hottest?

top of the meniscus

28

what is a sufficient amount of Au alloy for casting a posterior gold crown?

2 pennyweights and a button

29

is dipping wax softer or harder than inlay wax?

softer

this can be problematic because the wax can more easily be pulled or stretched away from the margins while carving

30

why is it important to insert the die into the dipping wax at a 45 degree angle and then to rotate it vertically and remove?

you will avoid entrapment of air within the central fossa of the preparation