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FIXED > lecture 4 > Flashcards

lecture 4 Flashcards

1
Q

parts of a crown prep:

A

-axial wall
-interproximal wall
-finish line (chamfer finish line)
-occlusal anatomy

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2
Q

the design of the prep finish line dictates the shape and bulk of

A

restorative material in the marginal area of the restoration

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3
Q

a full coverage restoration can survive in the biologic environment of the oral cavity only if the

A

margins are closely adapted to the surface finish of the prep

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4
Q

types of finish line designs:

A

-knife edge
-chamfer (light and heavy)
-shoulder
-beveled shoulder

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5
Q

used primarily for full metal crowns only
especially gold crowns: gold’s malleability it can be burnished, adapted, and polishd to a precise fit with this margin design

A

knife edge (margin design)

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6
Q

disadvantages of knife chamfer

A

-difficult to see finish line in an impression or scan
-metal can be thin and is susceptible to distortion under heavy occlusal load
-often leads to an over-bulking of crown material to compensate for thinness along margin
-easy to miss creating distinct end of finish line and instead axial wall never terminates

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7
Q

for knife edge chamfer, to compensate for thin marginal area, labs will:

since margin thin and susceptible to distortion

A

overbulk crown at margin

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8
Q

indications for knife edge margins

A

tipped, molar, possible to be conservative in abnormal area

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9
Q

most conservative prep design

A

knife edge
(use a flame or needle shaped diamond bur)

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10
Q

light chamfer

A

metal crowns
zirconia crowns

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11
Q

heavy chamfer

A

-ceramic crowns
-zirconia crowns
-metal-ceramic crowns

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12
Q

use what bur to create chamfer

A

round ended diamond bur

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13
Q

axial depth more than ____bur, can create lipped edges of the margin which leave unsupported enamel likely to chip or break leaving an open and exposed margin

A

1/2 the bur

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14
Q

advantages of chamfer:

A

-well suited to full metal crowns and zirconia crowns
-ease of seating crown and placing of crown
-ease of detecting margin on impression or scan
-if full metal, chamfer is easy to wax and cast
-provides adequate thickness of restoration material at margin area

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15
Q

heavy chamfer good for:
chamfer good for:

A

heavy chamfer:
-high strength porcelain crowns, buccal of metal ceramic crowns

chamfer:
-full metal crowns, palatal/lingual of MCC’d, resin bonded crowns

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16
Q

light chamfer is ___mm deep into axial wall

A

0.3-0.5mm

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17
Q

light chamfer produces ____degree margin with rounded internal angle

A

30-45 degrees

18
Q

chamfer combines knife edge burnish-ability with bulk of material for all what type of crowns

A

metal crowns

19
Q

heavy chamfer provides room for ____ceramic margin.

internal rounded angle decreases material stress in this area
how deep?
what bur use?

A

thicker ceramic margin

1-1.2mm deep

large round ended diamond bur

20
Q

for shoulder margin, want close to a _____degree angle.

used primarily for what kind of crowns:

what bur used:

A

90 degree (rounded angle)

metal ceramic crowns and all ceramic crowns where thickness of material is important [decreases stress on restoration]

flat end diamond bur used

21
Q

some shoulder finish lines can include this at 3-45 degree angle which is often used for onlays and inlays, metal ceramic crowns where there is metal collar

A

bevels

-allows for adaptability of metal to ensure marginal fit

22
Q

rough margin=

A

plaque accumulation = recurrent decay

23
Q

significant roughness of prep finish line can prevent

A

close adaptation of crown margin

24
Q

deep chamfer and rounded angles means=

A

crowns last longer

25
Q

the finish line designs vary based on:

A
  1. restoration material
  2. location in mouth
  3. desired results
26
Q

similar to chamfer finish line but comes with 90 degree cavosurface angle with large radius rounded internal angle.

best finishes for ceramic crown

A

heavy chamfer

27
Q

crown prep concerns:

A

-pulp becomes irritate and inflamed during crown preparation
-rise in pulp temp by 10 degrees significantly increases the change of pulpal necrosis

28
Q

to prevent pulpal issues with prep, must do what:

A

-use lots of water
-sharp bars
-light pressure
-high speed
-diamond burs

29
Q

margin design instrumentation
preparation:
finishing:
caries removal:

A

preparation:
high speed handpiece
air/water spray
diamond burs

finishing:
slow speed handpiece
fine diamond burs (possibly carbide burs)
hand instruments too

caries removal:
slow speed with 2,4,6 round bur
spoon excavators

30
Q

these burs remove enamel and dentin by grinding it away

A

diamond burs (leave rougher surface)

31
Q

these burs remove tooth by shearing it away

A

carbide burs (smoother)

32
Q

what burs are most efficient and 2-3 times faster?

A

diamond burs

33
Q

these burs cut precision prep features with smooth surfaces

often used to place extra retention retention features in a crown prep such as seating groove

A

carbide burs

34
Q

hand instruments can also be used to help smooth finish lines

A

chisel
hatchet
hoe
margin trimmer

35
Q

advantages and disadvantages of full metal crowns

A

adv:
-gentle to opposing teeth
-can be thin
-conservative preps
-recurrent decays less likely
-very durable
-if missing contact, can add material
-long lasting

disadv:
esthetics

36
Q

what margin design for full metal crown prep

A

can use knife edge, but usually a light chamfer is recommended .3-.5mm

[reduce until half a bur is in axial wall]

37
Q

in full metal crown prep,
axial walls are reduced to create a tapered wall between ____ and ___degrees but can have TOC up to:

axial walls can be reduced as little as ___mm, but can be reduced more in needed

A

6-10 degrees
but can have up to 20 degrees

as little as .5mm

38
Q

full metal crown prep, occlusal reduction depth of

A

1-1.5mm

39
Q

need to do this to prevent pressure points and possible fracturing of a restorative material

A

ling angles and corners need to be rounded

use fine grit diamond bur

40
Q

metal free
hard and tough
less translucent than natural teeth
tooth-colored ceramic like material

A

zirconia

FIXED (8 decks)

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