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Operative 2 > Accessory Retention > Flashcards

Accessory Retention Flashcards

1
Q

When Do We Need Accessory
Retention?

A

Often used with large restorations
◦ Especially amalgam

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1
Q

Accessory Retention
(2)

A

◦ This just means additional retention
◦ More than the primary retentive features of your prep

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1
Q

Often used with large restorations
◦ Especially amalgam
(3)

A

◦ Amalgam relies completely on mechanical retention
◦ Accessory retention does NOT seal or increase strength!
◦ NO effect on resistance form

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2
Q

Accessory Retention
Required when the

A

residual tooth structure
does not provide
adequate retention

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3
Q

Indications for Pin Placement
(3)

A

To improve retention
Extensive preparations
Prognosis of a tooth is uncertain

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4
Q

To improve retention

A

◦ when more conservative methods can’t be used

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5
Q

Extensive preparations

A

◦ Especially those missing a cusp

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6
Q

Prognosis of a tooth is uncertain
(2)

A

◦ eg. perio prognosis questionable
◦ Sometimes it is the only treatment of choice if the tooth is sclerosed and we cannot access pulp canals for additional retention

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7
Q

Contraindications
(5)

A

Severe loss of tooth structure
Endodontically treated teeth
Large pulp canals
Difficult access
Tooth already serves as abutment for partial denture

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8
Q

Advantages of Pin
Placement
(4)

A

Economical
One appointment
Alternative to extraction
Pins remove minimal tooth structure compared to other
methods

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9
Q

Economical
(2)

A

◦ 70% of four surface amalgams are successful at 5 years compared
to gold crowns (84% success) (Martin & Bader, 1997)
◦ 72% of amalgam restorations survive for 15 years including those
with cuspal coverage (Smales, 1991)

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10
Q

Pins remove minimal tooth structure compared to other
methods

A

◦ less than slots, grooves and amalgapins

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11
Q

Disadvantages of Pin
Placement Introduces stresses in the dentin which can lead to

A

crazing and even fracture

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12
Q

The pin does not strengthen the amalgam
(2)

A

◦ its only function is to provide additional
retention and or resistance.
◦ Pins reduce the compressive and transverse strength
of amalgam

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13
Q

Disadvantages of Pin
(3)

A

Placement Possibility for perforation
Microleakage around pin
Anatomy harder to carve

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14
Q

Possibility for perforation
(2)

A

◦ Into pulp
◦ Into periodontal ligament

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15
Q

Types of Accessory Retention
Vital Teeth
(3)

A

◦ Pins
◦ Slots and grooves
◦ Amalgapins

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16
Q

Endodontically Treated Teeth –
Non-Vital
Do not use pins in non-vital teeth
(3)

A

◦ endodontically treated teeth are brittle
◦ Pins can concentrate stress
◦ Lead to fracture

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17
Q

Endodontically Treated Teeth –
Non-Vital
Do not use pins in non-vital teeth
◦ endodontically treated teeth are brittle
◦ Pins can concentrate stress
◦ Lead to fracture
Alternatives:
(2)

A

Amalgam Core
◦ Retention from pulp chamber
Post Retained Amalgams
◦ Post placed in actual canal, not dentin

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18
Q

Pin is always placed in

A

dentin

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19
Q

What Types of Pins are
Available?
(3)

A

Cemented Friction Lock Self-Threading

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20
Q

Self Threading (Going 1966) Pin hole is 0.002” smaller than pin

A

Pins self threads into dentin
◦ Use hand wrench or
◦ Latch grip on slow speed
5-6 times as retentive as the cemented pin
High crestal and apical stresses; Crazing and
microleakage
◦ Greater stresses in dentin
There should be at least 1.0 mm dentin around pin hole
Used at UMKC most frequently

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21
Q

Self Threading
Self threading pins are

A

self shearing
o They break off on their own as you turn them with hand wrench or slow speed

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22
Q

Multiple Pins
Advantage

A

◦ Increases retention

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23
Q

Multiple Pins
Disadvantages ◦ Increases dentin crazing
(4)

A

◦ 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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24
Q

Pin Placement
Pins should be placed — apart from each other
MINIMUM of – apart

A

5mm
3 mm

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25
Q

Pins should be — from wall of prep
* MINIMUM — from wall

A

1mm
0.5mm

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25
Q

Pin should be — deep into the dentin

A

2mm

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26
Q

Factors Affecting Pin Placement
Type of pin: — most common 99% used, and
most retentive

A

self threading

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27
Q

Surface characteristics of pin:

A

depth of deformations on the
pin
◦ amalgam engages for retention

28
Q

Orientation of Pins:

A

align pins vertically along long access of
tooth
◦ If using multiple pins, slightly angle in different directions
◦ Avoid bending, if possible

29
Q

Factors Affecting Pin Placement
(2)

A

Diameter of Pin
Pin breakage

30
Q

Diameter of Pin

A

◦ increased diameter= increased retention

31
Q

Pin breakage

A

◦ If pins breaks, place another one 1.5 mm away from broken pin

32
Q

Pin Hole Sizes
(4)

A

Regular
Minim 0.021
Minikin 0.017
Minutia 0.0135

33
Q

Regular

A

◦ 0.027 inch in diameter
◦ Do not use unless hole is stripped

34
Q

Minim 0.021

A

◦ Most frequently used threaded pin
◦ Start with a 0.021 and if you strip the hole, place a
0.027 pin

35
Q

Minutia 0.0135

A

◦ not retentive enough in posterior teeth

36
Q

General rule - Use one pin per
(3)

A

missing cusp, axial wall, or line
angle

37
Q

Use no more than — pins/tooth

A

4
◦ VERY rarely use more than 1 or 2 pins
◦ Use composite

38
Q

Place the pin in

A

line angles
◦ Greatest area of bulk

39
Q

Twist Drill
Use in — head of handpiece
◦ Slow speed or electric on slow speed (5000 rpm)
— acts as a heat absorber
Minuta and minikin twist drill have a built-in wobble to
Discard after — uses (too dull)

A

LATCH
Aluminum shank
minimize dentin
crazing and breakage of the small drills
20

40
Q

Latch Contra-angle

A

Drill the pin hole with the slow speed drill (300 rpm)
using air to cool* Pin placement raises the pulpal temperature 4oF - do not use excessive
speed

41
Q

Pinhole Location Depends Upon
(2)

A

Pulpal anatomy
External tooth anatomy

42
Q

Pinhole Location Depends Upon
Pulpal anatomy
External tooth anatomy
Determine using:
(2)

A

◦ radiograph
◦ perio probe around the tooth

43
Q

Also consider patient age
◦ older teeth
◦ younger teeth

A

are more brittle
have larger pulp

44
Q

Best Sites for Pin
Placement? Best site for placement are at the

A

line angles (DF, DL, MF, ML)

45
Q

Sites to Avoid for Pin Placement
Avoid for pulp exposures
(3)

A

◦ Mesio facial 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 & 2nd
molars

46
Q

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
Max 1st & 2nd molars

47
Q

Flat area Prepare a flat area prior to pin placement
(2)

A

◦ Otherwise the drill may slip and you may
inadvertently angle it into the pulp or periodontal
ligament
◦ Alternatively you may not drill the correct pin hole
height (generally 2mm in depth)

48
Q

Distance from DEJ Place pin minimum of — inside DEJ

A

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

49
Q

Increase Distance if Planning to Place
Crown

A

1.0-1.5 mm inside DEJ
◦ Want to avoid exposing the pin during future crown preparation

50
Q

Distance from Axial Wall Pins should be a minimum of — mm from any wall to allow room for
condenser and condensation of amalgam around the pin

A

0.5

51
Q

Self Threading Pins-
Procedure
(3)

A
  1. Determine ideal pin location and drill pilot hole with ¼
    round bur into dentin (optional)
  2. Drill pin hole using provided twist drill
    ◦ Place in latch head of electric handpiece
  3. Line up pin in pilot hole
    ◦ Turn hand wrench OR slow-speed handpiece until pin self-
    shears
    ◦ Non-electric handpieces should have torque converter added
52
Q

Starting Pilot Hole

A

Use a 1/4 round bur prior to using the pin drill

53
Q

Orientation of the Pin Drill

A

Follow External Tooth Anatomy

Use perio probe to check external surface alignment
Knowledge of the anatomy of tooth
◦ ie furcations, grooves etc
Align pin-drill with external surface to check alignment
Check angulation twice from various angles

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
◦ this clears the dentinal shavings
After placing pin hole, check for bleeding
◦ if you perforate, you will usually see blood easily
◦ Can use a paper point (endo) if you suspect a perforation but do not see bleeding

55
Q

Placing the Self-Threading
Pin

A

Use hand wrench or latch on slowspeed
Make sure you have a positive stop
Quarter turn reverse at the end
◦ count total quarter turns
◦ reduces stress

56
Q

What if the Pin is Too Tall?
There must be — of amalgam over
the top of the pin,
◦ otherwise the amalgam may fracture

A

2mm

57
Q

If too tall:
(2)

A

◦ Reduce with handpiece
OR
◦ Bend slightly using provided pin tool
◦ Comes with pin kit

58
Q

Cutting the Pin

A

Stabilize the pin with a forceps and cut
away the excess with a bur
Cut perpendicular to pin
◦ if you cut parallel to pin the pin will unscrew and
become loose.
After any of these procedures - check
that the pin is still retained
◦ If it is loose - remove and use a larger
size pin

59
Q

Bending the pin

A
  • Pin bender helps avoid
    excessive stresses on pin
    when bending
60
Q

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 dentine.
1.0 mm of amalgam around bent pin.

61
Q

Summary of Procedure for Drilling
Pinholes Place – mm inside DEJ
Place pilot hole with a – round bur
Confirm correct angulation
Continuous drilling
◦ in and out one time
Interpin distance

A

0.5
¼
(3-5 mm)

62
Q

Important Points for Pin Placement
ALWAYS use rubber dam◦ But especially with pin placement
◦ Risk of

A

aspiration

63
Q

When using hand wrench

A

◦ Tie floss around the neck of the hand wrench - even if you use rubber dam.

64
Q

Aspirating Wrenches or Pins Patients have swallowed and even worse —
these hand wrenches

A

inhaled

65
Q

Pulpal Perforation
Pulpal perforation is preferable to a periodontal ligament perforation

A

◦ extirpation of the pulp solves the problem
◦ It may also be possible to attempt to pulp cap the perforation with calcium hydroxide depending on the endodontic prognosis of the tooth

66
Q

Periodontal Perforation A periodontal perforation
(3)

A

◦ usually results in an abscess
◦ treated by uncovering the perforation, removing the part of the pin that
extend through and/or plugging this area with amalgam
◦ less predictable prognosis.

67
Q

Slots and Grooves
Placed in dentin – mm inside the DEJ
Slots
(4)

A

0.5

◦ Similar to grooves, but larger
◦ created with 33 1/2 inverted cone bur
◦ 0.5-1.0 mm wide and 1mm deep
◦ should be undercut slightly to provide retention

68
Q

Locks:
(3)

A
  • allow for restorative material to act as “pin”
  • more tooth structure is removed
  • BUT slots result in fewer microfractures compared to pins
69
Q

Amalgam Pins (Shavell
1980)
Preservation and Restoration of Tooth Structure, Mount, GJ, Hume, WR,1998, Mosby, St. Louis, MO.

A
  • Utilize #245 bur
  • Drill hole 1mm wide,
    2mm deep
    -Condense amalgam into pin hole
70
Q

Amalgam Advantages as Build Up
MaterialBuild up: restoration under crown
Amalgam benefits:

A

oCan visualize when preparing crown
oEase of manipulation
oGood mechanical properties
oNot as technique sensitive as composite resin
oGood dimensional stability
oGood wear resistance
oRelatively inexpensive

71
Q

Combination

A

Slots, locks, grooves, amalgapins, and pins can all be
combined to provide retention and resistance for a complex
amalgam restoration
Place slots, locks, grooves before placing pinhole

Operative 2 (12 decks)

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