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23 Fixed Prosth > 11/21 - Substructures, 63-67, 203-210 > Flashcards

11/21 - Substructures, 63-67, 203-210 Flashcards

1
Q

what condition:

sufficient length
wall thickness >/= 1.0 mm
all cusps present

A

moderate loss

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2
Q

preparation features of moderate loss

A

cement base block out of undercuts
classic prep

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3
Q

what condition:

Short preparation
50% of crown remaining
Wall thickness = 1.0 mm
Thickness/length ratio > 1.0
Excessive taper
More serious if an abutment

A

moderate/severe loss

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4
Q

preparation features of moderate/severe loss

A

Modified preparation
Existing features retained
New features added (boxes, grooves, pinholes, vertical walls)

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5
Q

what condition:

<50% of crown remaining
Short preparation-crown ratio
Wall thickness < 1.0 mm
Thickness-height ratio < 1.0

A

severe destruction

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6
Q

preparation features of severe destruction

A

Possible elective devitalization and dowel core
Walls with thickness-height ratio < 1:2 shortened or removed
Walls with thickness-height ratio of 1:1 to 1:2 supported with core
Ferrule effect in preparation
Pin(s) integrated into casting

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7
Q

what condition:

central destruction
enamel (if any) is undermined

A

total coronal loss

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8
Q

preparation features for total coronal loss

A

Dowel core + crown on single-rooted tooth
Pin-retained core + crown on molar

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9
Q

is the base a part of substructure/core/buildup? what is it’s purpose

A

NOT PART! purpose is to protect the pulp

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10
Q

T/F: large central lesion may require a full coverage restoration, but only after tooth is built up with a core

A

TRUE

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11
Q

what is intracoronal restoration that covers cusp

A

onlay

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12
Q

how many clearance needed to pulp for substructure

A

1 mm

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13
Q

if significantly less than 180 degrees of tooth circumference remains between two boxes [of PM], what is susceptible to occur

A

the lingual cusp is susceptible to fracture during function, upon removal of provisional restoration, or at try in of the permanent restoration

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14
Q

pins should always be halfway thru what

A

between pulp and external surface

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15
Q

where do you primarily want to put pins

A

over where cusps are normally or line angles

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16
Q

interproximal caries may preempt the use of what

A

a groove

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17
Q

what can be incorporated into a crown to augment retention and resistance

A

pin (which can also be used to retain a core which in turn will help retain a crown)

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18
Q

if the tooth to be prepared for a cast restoration has been only MODERATELY damaged, what can be done

A

standard MOD only preparation or a three quarter crown preparationwith boxes

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19
Q

if one cusp is destroyed, what can be done

A

widened box with groove augmentation

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20
Q

when half of the crown has been destroyed, what can be done

A

grooves may provide sufficient retention if the supragingival tooth structure in which they are placed has sufficient length. pinholes may be added to the preparation

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21
Q

if three or more cusps have been destroyed, what can be done

A

pin-retained core should be fabricated before proceeding to a full coverage cast restoration

22
Q

T/F: extensive peripheral destruction often requires a full coverage cast restoration if caries has been controlled

A

TRUE

23
Q

what does a widened F-L and gingivally lengthened box provide

A

facial and lingual walls become solid tooth structure and retention will be improved

24
Q

what is a critical factor of restorations

A

biologic width

25
Q

what is the typical distance between margin of crown and bone level

A

2 mm

26
Q

if crown margin is put immediately on bone level, what happens? how does this occur

A

bone recedes 2 mm

recession is bad because it is unpredictable and you get more of a pocket which leads to bone loss

27
Q

what do you do instead of putting crown margin directly onto bone?

A

CROWN LENGETHING

28
Q

what typically accompanies crown lengethening

A

gingival recession

29
Q

what is the normal anatomical crown-root ration for an average central incisor

A

11:14

30
Q

what is the shortening of root

A

extrusion

31
Q

how to determine amount of extrusion needed

A

adding distance of destruction extends beyond the alveolar crest, the biologic width of of 2.0 mm, and the 1.0 mm between the final sulcus bottom and the final crown margin

if destruction extends 1.00 beyond the alveolar crest, 4.0 mm extrusion necessary

32
Q

do current studies show that you should put post in anterior teeth?

A

NO! don’t put post in anterior teeth as of recent studies

33
Q

the length of the dowel should equal what? length of remaining apical fill is what

A

crown length or two-thirds the length of the root, whichever is GREATER. length of remaining apical fill should at least be 4 mm

34
Q

crown lengthening vs extrusion

A

lengthening = bone down
extrusion = tooth up

35
Q

what is critical purpose of ferrule

A

hold tooth together so it doesn’t fracture

36
Q

why do you see a lot of crack on 18 + 31

A

since most distal tooth and they get most load

37
Q

do you do the crown prep first or substructure prep first?

A

in lecture he said do crown prep first but in lab he said to remove the substructure

38
Q

where is pin placed

A

0.5 mm into DEJ only in DENTIN not enamel

39
Q

ferrule must be at least how many mm

A

2mm

40
Q

what material do you use to build up substructure

A

amalgam or composite

41
Q

what type of crown preparation for substructure exercise

A

FCC

42
Q

what rules should be observed to avoid excessive tooth destruction while creating retention in an already weakened tooth

A
  1. central core (pulp and the 1.0 mm thick surrounding layer of dentin) must not be invaded in vital teeth
  2. no wall of dentin should be reduced to a thickness less than its height for the sake of retention
43
Q

no retentive features should extend further into the teeth than ___ mm at the cervical line or from the central fossa

A

1.5 mm

44
Q

if caries removal results in a deeper cavity, any part lying within the vital core should be filled with what

A

glass ionomer cement

45
Q

instead of a groove, what can be placed to accommodate caries removal and provide retention

A

box forms

46
Q

how deep and wide should a groove be

A

1 mm deep and wide

47
Q

are multiple grooves as effective as box forms?

A

YES! but at some point too many grooves can affect the seating of a full veneer crown

48
Q

what are the ways pins can be used

A
  1. pinholes parallel the path of insertion of the preparation, receiving pins that are an integral part of the cast restoration
  2. nonparallel pins placed in the tooth to retain an amalgam or composite resin core in which a classic prep for cast restoration can be formed
49
Q

what materials are best used for a base

A

glass ionomer or polycarboxylate

50
Q

if one-half or more of the clinical crown has been destroyed, what is placed in the tooth

A

amalgam or composite resin core

23 Fixed Prosth (21 decks)

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