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Prosthesis > denture processing > Flashcards

denture processing Flashcards

1
Q

Which casts require relining?

A
  • new dentures (lose adaptation
  • old dentures (bone resorption)
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2
Q

What is rebasing?

A

replacement of entire denture base with a new material

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3
Q

relining and rebasing should be done without changing which relationship?

A

occlusal

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4
Q

When is relining indicated?

A

when denture loses its adaptation to tissues due to bone resorption while other points (occlusion, aesthetics, occlusal vertical dimension and denture base material) are all satisfactory

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5
Q

What is the procedure of relining of complete denture?

A
  • remove the denture out of the patient’s mouth for 48 hours to give time for the mucosa to rest
  • reduce the denture borders 2mm (to allow the flow of impression material to reach
    the depth of vestibule)
  • remove undercuts from the fitting surface of the denture.
  • take impression while the patient is closing in centric occlusion under closed mouth technique (to preserve occlusion)
  • make boxing and pour the cast
  • make flasking
  • throw away the impression material to make space for new acrylic resin
  • pack heat cured acrylic resin in the place of impression material
  • curing (45° for 20 minutes) (long curing cycle)
  • deflasking then laboratory remounting
  • finishing and polishing
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6
Q

If both upper and lower dentures need to be relined, which one is relined first and why?

A

lower denture as upper denture is supported by the palate but lower denture is not supported

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7
Q

What to do if vertical dimensions are not correct?

A

remake

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8
Q

What are the steps of rebasing?

A
  • remove the denture out of the patient’s mouth for 48 hours to give time for the mucosa to rest
  • reduce the denture borders 2mm and drilling 3 holes through the palate to allow the flow of impression material to reach the
    depth of vestibule
  • remove undercuts from the fitting surface of the denture
  • take impression while the patient is closing in centric occlusion under closed mouth technique to preserve occlusion (to preserve VDO)
  • make boxing and pour the cast
  • mount the cast and the denture on Hooper articulator or simple hinge articulator (to preserve occlusion and VDO)
  • grind the denture base and throw it
  • make new denture base from wax
  • flasking → wax elimination → packing of acrylic resin → curing → deflasking →
    laboratory remounting → finishing and polishing
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9
Q

When is rebasing done?

A

when denture contains cracks but occlusion must be right

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10
Q

What does polishing of denture consist of?

A

making denture smooth and glossy without changing its contour

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11
Q

When is finishing and polishing done?

A

after laboratory remounting (processing)

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12
Q

What is the procedure of wax elimination?

A

placing flask in hot water

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13
Q

What happens before wax elimination?

A

flasking

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14
Q

What happens after wax elimination?

A

acrylic resin packing

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15
Q

What happens after flasking is done?

A

wax is flushed out with hot water

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16
Q

How is the cast remounted?

A

cast has indices or v-notches

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17
Q

When is laboratory remounting done?

A

after processing and before finishing and polishing

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18
Q

Who does the laboratory remounting?

A

lab technician

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19
Q

Why do we remount the cast?

A

refining of occlusion

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20
Q

What needs to be done if cusps are high in centric relation only?

A

deepen opposing fossa

21
Q

What needs to be done if cusps are high in centric and eccentric relations?

A

grinding working and non-working cusps

22
Q

What are the working sides of teeth of casts?

A
  • BULL
  • buccal upper
  • lingual lower
23
Q

What is grinded in both sides?

A

non-functional cusps

24
Q

What should acrylic resin be glued to?

A

teeth

25
Q

What is the procedure of acrylic resin packing?

A
  • put cellophane on cast before adding acrylic resin
    a- dd acrylic resin then close the flask and bench press
  • remove cellophane and excess
  • add cellophane again and close the flask, then open to remove excess, put cellophane then close the flask and bench press
  • repeat until no excess is left
  • cure in oven
  • cooling
  • deflasking
26
Q

In which stage is acrylic resin packing done?

A

dough stage

27
Q

Why is long cycle better than short cycle?

A

short cycle causes crazing

28
Q

Which cycle is better for curing: long or short?

A

long

29
Q

What are the ways of packing acrylic resin?

A
  • injection method
  • open flask method (easier)
30
Q

What are the types of flasks?

A
  • flask for upper cast
  • flask for lower cast
31
Q

What are the components of a flask?

A
  • base (in the form of a cup)
  • middle part
  • top part (lid)
32
Q

What are the steps of flasking?

A
  • place cast in lower part of flask and fill it up with stone until level of cast and then ass separating medium
  • place second part of flask and add stone but don’t cover occlusal surface of teeth with stone then add separating medium again
  • add last layer of stone then close flask and it should touch occlusal surface of teeth
  • put flask in hot water and wax should melt
  • throw away trial denture base and add acrylic resin
33
Q

Why is the lower flask higher than upper?

A

presence of retromolar pad

34
Q

Do we add separating medium on occlusal surface of teeth?

A

no

35
Q

What is cap layer?

A
  • last layer that covers occlusal surface
  • this makes sure teeth don’t dislodge
36
Q

What happens before deflasking?

A

acrylic resin packing

37
Q

What happens after deflasking?

A

laboratory remounting

38
Q

What happens during deflasking?

A

flask cools to room temperature

39
Q

What is the objective of deflasking?

A

remove denture from investment material without breaking the denture or dislodging denture from cast for laboratory remounting

40
Q

What should the contour of the labial and buccal flange be and why?

A
  • concave
  • help stabilisation of denture
  • adaptation of oral muscles
  • muscles are stronger than the denture
41
Q

What should the contour of the lingual flange be and why?

A
  • convex then concave
  • convexity directly beneath the teeth
  • tongue may lie in this undercut and dislodge the lower denture
  • concavity away from teeth in the middle of the flange (not at any undercuts)
42
Q

Why should the palate be kept thin?

A
  • pronunciation of “s” sound
  • it is the space between tongue and rugae area
  • tongue never touches the rugae area
43
Q

What is lisping?

A
  • “th” sound replaces “s” sound
  • the the tongue is crowded against palate particularly on posterior region
44
Q

What are the causes of lisping?

A
  • increase in thickness of acrylic at rugae area
  • backward arrangement of upper anterior teeth which leads to no space to pronounce “s”
45
Q

What is whistling?

A

”s” sound is pronounced too sharply

46
Q

What causes whistling?

A
  • forward arrangement of upper anterior teeth
  • decrease thickness of acrylic in rugae area (insufficient waxing up)
  • low V.D.O. (short teeth and excessive freeway space)
47
Q

Why do we stipple gingiva?

A

to show rough appearance

48
Q

What should be contoured properly when contouring the root?

A

canine eminence

Prosthesis (7 decks)

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