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crown > working cast and dies > Flashcards

working cast and dies Flashcards

1
Q

What is the relevant soft tissue that should be reproduced?

A

part of palatal and facial mucosa

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2
Q

Do we have to take impression of the vestibule?

A

no

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3
Q

What is the most commonly used material for making dental die

A

gypsum

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4
Q

What are the most commonly used types of gypsum?

A

dental stone type 3 and high-strength type 4

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5
Q

Which type of gypsum is used for mounting on articulator?

A

model plaster type 2

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6
Q

How is gypsum supplied?

A

in the form of powder mixed with water in certain ratios

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7
Q

Why can’t ceramic restoration be used with gypsum die?

A

gypsum can’t withstand high temperatures so it’s used with refractory dies

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8
Q

What are refractory dies used for?

A

all ceramic restoration and laminate veneers

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9
Q

Is the dowel pin technique used nowadays?

A

no

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10
Q

Is the di-lock tray technique used nowadays?

A

rarely

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11
Q

Is the pendix system technique used nowadays?

A

yes, it is the most commonly used method for a working cast with a removable die

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12
Q

What does the dowel pin consist of?

A

head and tail

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13
Q

Where does the head enter in the dowel and pin technique?

A

inside coronal part of the die

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14
Q

What does the tail look like in dowel and pin technique?

A

all sides are circular except one side is flat to provide stability

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15
Q

Why do we use 2 pins in dowel and pin technique?

A

more accurate than using one pin

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16
Q

Is long dowel pin more retentive than short dowel pin?

A

yes

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17
Q

How is the sawing technique made?

A

parallel or slightly diverging but never converging

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18
Q

What happens if there is insufficient opening of contact?

A

incorrect crown and bridge as it can affect the finish line during sawing technique

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19
Q

What does the dental cast have to look exactly like?

A

the patient

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20
Q

Why do we take upper and lower cast impression if the dentist is working only on the upper arch?

A

for the lab to know how the teeth are in occlusion , how tall the teeth are and their contact

21
Q

What are the requirements of a working cast?

A
  • must produce both prepared and unprepared tooth surface and should be free of voids (air bubbles)
  • all surfaces of teeth involved in anterior guidance and occlusal surface of all unprepared teeth must allow for precise articulation of opposing casts
  • all relevant soft tissues should be reproduced
22
Q

What are the requirements of die material?

A
  • reproduction of surface details accurately (cusps, fissures, contact)
  • high hardness to resist scratching
  • dimensionally accurate (no shrinkage)
  • high mechanical properties (not break easily)
  • compatible with impression material and separating medium
  • colour contrast
  • easy to section and easy to trim (even if its strong)
23
Q

What are the types of die materials used?

A
  • amalgam (historical and not used anymore)
  • electroplated discs (historical and not used anymore)
  • resin (not used anymore)
  • gypsum
  • refractory die
  • flexible die material
  • 3D printed casts
  • virtual casts (CAD software)
24
Q

Why is resin not used anymore?

A

shrinkage problem

25
Q

Why is electroplated disc not used anymore?

A
  • toxic
  • very expensive
  • takes a very long time
26
Q

What are the 5 forms of dental gypsum?

A
  • impression plaster type 1
  • model plaster type 2
  • dental stone type 3
  • high strength type 4
  • high strength high expansion type 5
27
Q

Is impression plaster type 1 used nowadays?

A

no

28
Q

What are the advantages of gypsum?

A
  • inexpensive
  • easy to use
  • consistent results
29
Q

What are the disadvantages of using gypsum?

A

relatively poor abrasion resistance

30
Q

What are refractory dies?

A

special type of ceramic supplied in powder and liquid, mixed and fired according to manufacturer construction to form the die

31
Q

What is the property of refractory dies?

A

can withstand high temperatures

32
Q

What are flexible die materials?

A

similar to heavy body silicon and polyether material in consistency

33
Q

What are flexible die materials used to make?

A

temporary restorations and indirect composite resin inlay or onlay

34
Q

What are the advantages of flexible die materials?

A
  • body light consistency
  • more rapid setting
  • easy to remove restoration or onlay
35
Q

What do we need to do to get 3D printed casts?

A
  • intra-oral scanner
  • scanning of teeth
36
Q

Which type of impression is more accurate: physical or digital?

A

digital

37
Q

What are the properties of virtual cast

A
  • scanning
  • quicker and easier
38
Q

What is the classification of working cast and die system?

A
  • working cast with separate die (warpage and distortion may happen)
  • working cast with removable die
39
Q

What are the types of working cast with removable die?

A
  • dowel pin technique
  • pindex system
  • di-lock tray
40
Q

What does the dowel pin technique require?

A

sawing technique (between teeth’s contacts) and it consists of first pour (head is found) and second pour (tail is found)

41
Q

What is the pindex system?

A
  • forms a pinhole and then add super glue until it dries
  • head of dowel pin is inserted to have a removable die
42
Q

Is using double pins better than using a single dowel pin?

A

yes

43
Q

What is the name of the super glue used in pindex system?

A

cyanoacrylate or amir alpha glue

44
Q

What is the function of a die spacer?

A
  • allows space for the luting cement
  • allows space for easy removal of wax pattern from the die after its construction
  • creates space between internal surface of casting and of prepared surface of the tooth everywhere except immediately adjacent to the margin (1mm short of finish line)
  • one or two coats are applied
44
Q

Where is the die spacer applied?

A

all the die except that finish line to allow adaptation of the margin to the finished line

45
Q

Why do we add grooves in the di-lock tray?

A

help to put back the sawed die in the correct place

45
Q

What is used for die preparation?

A
  • a bur is used to trim under the finish line area to accentuate the finish line
  • a marker is used t define the finish line
  • a red pencil (non-carbon) could attach to the wax and contaminate the future casting
46
Q

What is ditching?

A

removing fine details using a fine instrument (it makes a ditch)

47
Q

What is a die hardener?

A
  • painted on the die to increase its surface hardness
  • placed all over the die (extends beyond finish line)
  • allow time to harden and set
  • prevents scratching

crown (6 decks)

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