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Operative II > Accessory Retention > Flashcards

Accessory Retention Flashcards

1
Q

accessory retention is often used with:

A

large restorations, especially amalgam

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2
Q

does accessory retention increase strength

A

no

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3
Q

when is accessory retention required

A

when the residual tooth structure does not provide adequate retention

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4
Q

what are the indications for pin placement

A
  • to improve retention when more conservative methods cant be used
  • extensive preparations, especially those missing a cusp
  • if prognosis of a tooth is uncertain
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5
Q

what are the contraindications for pin placement

A
  • severe loss of tooth strucutre
  • endodontically treated teeth
  • large pulp canals
  • difficult access
  • tooth already serves as abutment for partial denture
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6
Q

what are the advantages for pin placement

A
  • economical
  • one appointment
  • alternatie to extraction
  • pins remove minimal tooth structure compared to other methods such as slots grooves and amalgapins
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7
Q

how is pin placement economical

A
  • 70% of four surface amalgams are successful at 5 years compared to gold crowns
  • 72% of amalgam restorations survive 15 years including those with cuspal coverage
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8
Q

what are disadvantages of pin placement

A
  • introduces stresses in the dentin which can lead to crazing and even fracture
  • possibility for perforation into pulp or PDL
  • microleakage around pin
  • anatomy harder to carve
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9
Q

what is the pins function

A

to provide additional retention and or resistance

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10
Q

pins reduce the _____ and _____ strength of amalgam

A

compressive and transverse

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11
Q

what are the types of accessory retention in vital teeth

A
  • pins
  • slots and grooves
  • amalgapins
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12
Q

what accessory retention should be used in endodontically treated teeth- non vital

A
  • do not use pins in non vital teeth
  • use amalgam core or post retained amalgams
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13
Q

why should you not use pins in non vital teeth

A
  • endodontically treated teeth are brittle
  • pins can concentrate stress and lead to fracture
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14
Q

where does the amalgam core get retention from

A

pulp chamber

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15
Q

where are post retained amalgams posts placed

A

in actual canal, not dentin

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16
Q

what are the steps in pin placement

A
  • broken cusp
  • drill pilot holes
  • drill pin holes
  • place pins
  • place restoration
  • prepare crown prep
  • avoid perforation
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17
Q

pin is always placed in_____

A

dentin

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18
Q

what types of pins are available

A
  • cemented
  • friction lock
  • self threading
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19
Q

describe self threading pins

A
  • pin hole is 0.002” smaller than pin
  • pin self threads into dentin
  • use hand wrench or latch grip on slow speed
  • high crestal and apical stresses; crazing and microleakage
  • greater stresses in dentin
  • should be at least 1.0mm of dentin around pin hole
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20
Q

self threading pins are ______ more retentive as the cemented pin

A

5-6 times

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21
Q

what pin is used at UMKC most frequently

A

self threading

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22
Q

self threading pins are _____. what does this mean?

A
  • self shearing
  • they break off on their own as you turn them with hand wrench or slow speed
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23
Q

what are the advantages of multiple pins

A

increases retention

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24
Q

what are the disadvantages of multiple pins

A
  • increases dentin crazing
  • amount of available dentin between pins is decreased
  • strength of amalgam restoration is decreased
  • more difficult to condense around the pins
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25
Q

how far apart should pins be placed from each other

A

5mm. minimum of 3mm

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26
Q

how far away should pins be from wall of prep

A

1mm. minimum 0.5mm

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27
Q

how deep should pins be into dentin

A

2mm

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28
Q

what are the factors affecting pin placement

A
  • type of pin
  • surface characteristics of pin
  • orientation of pins
  • diameter of pin
    -pin breakage
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29
Q

what type of pin is the most retentive

A

self threading

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30
Q

what are the surface characteristics of the pin that affect pin placement

A

depth of formations on the pin
- amalgam engages for retention

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31
Q

how does the orientation of pins affect pin placement

A
  • align pins vertically along long axis of the tooth
  • if using multiple pins slightly angle in different directions
  • avoid bending
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32
Q

increased diameter of pin = ______ retention

A

increased

33
Q

what do you do if pin breaks

A

place another 1.5mm away from broken pin

34
Q

use one pin per:

A

missing cusp, axial wall or line angle

35
Q

use no more than ____ pins per tooth

A

4

36
Q

where do you place the pin and why

A

in line angles because greatest area of bulk

37
Q

describe the twist drill

A
  • use in latch head of handpiece on slow speed or electric on slow speed 5000 rpm
  • aluminmum shank acts as a heat absorber
  • minuta and minikin twist drill have built in wobble to minimize dentin crazing and breakage of the small drills
  • discard after 20 uses because too dull
38
Q

how do you use the latch contra angle

A
  • drill the pin hole with the slow speed drill 300 rpm using air to cool
  • pin placement raises the pulpal temperaturee 4 degrees F- do not use excessive speed
39
Q

pinhole location depends on:

A
  • pulpal anatomy
  • external tooth anatomy
  • patient age
40
Q

determine pulpal anatomy and external tooth anatomy using

A
  • radiograph
  • perio probe around the tooth
41
Q

what are sites to avoid for pin placement

A
  • MF corner of max and mand 1st molar
  • distal mand molars and max lingual of molars
  • Mid facial, mid mesial and mid distal furcations of max 1st and 2nd molars
42
Q

why are there specific sites to avoid in molars

A

to avoid pulp exposures

43
Q

what are the concavities to watch for

A
  • mesial concavity over max 1st PM
  • mid- lingual and mid-facial of mand 1st and 2nd molars
  • mid-facial, mid mesial, and mid distal furcations of max1st and 2nd molars
44
Q

why do you want to prepare a flat area prior to pin placement

A
  • the drill may slip and yuo may inadvertently angle it into the pulp or periodontal ligament
  • alternatively you may not drill the correct pin hole height- generally 2mm in depth
45
Q

place pin _____ inside DEJ

A

minimum 0.5mm
- preferably 1.0mm inside DEJ
- or pins should be a minimum of 1.0mm from the external surface of the tooth, whichever is greater

46
Q

what do you want to avoid during future crown prep

A

expose the pin

47
Q

what do you do to the pins if planning to place crowns

A

increase distance

48
Q

how far should pins be from axial wall

A
  • a minumum of 0.5mm from any wall to allow room for condenser and condensation of amalgam around the pin
49
Q

what is the self threading pins procedure

A
  • determine ideal pin location and drill pilot hole with 1/4 round bur into dentin
  • drill pin hole using provided twist drill- place in latch head of electric hand piece
  • line up pin in pilot hole- turn hand wrench OR slow speed handpiece until pin self- shears.
50
Q

non electric handpieces should have what added

A

torque converter

51
Q

describe the orientation of the pin drill

A
  • follow the external tooth anatomy
  • use perio probe to check external surface alignment
  • knowledge of the anatomy of the tooth
  • align pin drill with external surface to chekc alignment
  • check angulation twice from various angles
52
Q

what should the handpiece angulation be

A

follow long axis of the tooth

53
Q

what should the pin placement be parallel with

A

external surface of tooth and with pulp, halfway between each

54
Q

when using the pin drill:

A
  • place the pin hole in one movement- avoid stopping and starting
  • continue to reverse the drill as the pin drill is removed
  • after placing pin hole, check for bleeding
55
Q

why do you continue to reverse the drill as the pin drill is removed

A

to clear the dentinal shaving

56
Q

what do you use if you suspect a perforation but do not see bleeding

A

a paper point (endo)

57
Q

when placing the self threading pin, make sure you have a ____

A

positive stop

58
Q

what should you do at the end of placing the self threading pin and why

A

quarter turn
- count total quarter turns
- reduces stess

59
Q

there must be ______ of amalgam over the top of the pin. why?

A

2mm; otherwise it may fracture

60
Q

what should you do if pin is too tall

A

reduce with handpiece or bend slightly using provided pin tool

61
Q

how do you cut the pin

A
  • stabilize the pin with a forceps and cut away the excess with a bur
  • cut perpendicular to pin
62
Q

what do you do if you cut parallel to the pin

A

it will unscrew and become loose

63
Q

what do you do if the pin is loose after cutting it

A

remove and use a larger size pin

64
Q

what does the pin bender do

A

helps avoid excessive stress on pin when bending

65
Q

describe incorrect pin bending

A
  • do not use a condenser or any other instrument to push on the pin and flatten it
  • bending the pin with a condenser will further concentrate stresses in the crestal region of dentin
  • 1 mm of amalgam around bent pin
66
Q

what is the summary of procedure for drilling pinholes

A
  • place 0.5mm inside DEJ
  • place pilot hole with 1/4 round bur
  • confirm correct angulation
  • continuous drilling: in and out one time
  • interpin distance 3-5mm
67
Q

what are the important points for pin placement

A
  • always use rubber dam
  • when using hand wrench tie floss around the neck of the hand wrench- even if you use rubber dam
68
Q

which is preferable: pulpal perforation or periodontal ligament perforation

A

pulpal

69
Q

what solves the problem of pulpal perforatino

A

extirpation
- or possible to attempt a pulp cap with CaOH

70
Q

a periodontal perforation:

A
  • usually results in an abscess
  • treated by uncovering the perforation, removing the part of the pin that extends through and/or plugging this area with amalgam
  • less predictable prognosis
71
Q

slots:

A
  • similar to grooves but larger
  • created with 33 1/2 inverted cone bur
  • 0.5-1.0mm wide and 1mm deep
  • should be undercut slightly to provide retention
71
Q

where are slots and grooves placed

A

in dentin 0.5mm inside DEJ

72
Q

locks:

A

-allow for restorative material to act as pin
- more tooth structure is removed
- but slots result in fewer microfractures compared to pins

73
Q

amalgam pins:

A
  • use #245 bur
  • drill hole 1mm wide and 2mm deep
  • condense amalgam into pin hole
74
Q

what are amalgam benefits

A
  • can visualize when preparing crown
  • ease of manipulation
  • good mechanical properties
  • not as technique sensitive as composite resin
  • good dimensional stability
  • good wear resistance
  • relatively inexpensive
75
Q

matrix band should not shift during:

A

condensing and initial set of the amalgam

76
Q

what features can be combined to provide retention and resistance for a complex amalgam restoration

A

slots, locks, grooves, amalgapins

77
Q

when should you place slots, locks, and grooves

A

before placing pinhole

78
Q
A

Operative II (10 decks)

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