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Accessory Retention Flashcards

(74 cards)

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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
Multiple Pins Disadvantages ◦ Increases dentin crazing (4)
◦ Amount of available dentin between pins is decreased ◦ Strength of amalgam restoration is decreased ◦ More difficult to condense around the pins
24
Pin Placement Pins should be placed --- apart from each other MINIMUM of -- apart
5mm 3 mm
25
Pins should be --- from wall of prep * MINIMUM --- from wall
1mm 0.5mm
25
Pin should be --- deep into the dentin
2mm
26
Factors Affecting Pin Placement Type of pin: --- most common 99% used, and most retentive
self threading
27
Surface characteristics of pin:
depth of deformations on the pin ◦ amalgam engages for retention
28
Orientation of Pins:
align pins vertically along long access of tooth ◦ If using multiple pins, slightly angle in different directions ◦ Avoid bending, if possible
29
Factors Affecting Pin Placement (2)
Diameter of Pin Pin breakage
30
Diameter of Pin
◦ increased diameter= increased retention
31
Pin breakage
◦ If pins breaks, place another one 1.5 mm away from broken pin
32
Pin Hole Sizes (4)
Regular Minim 0.021 Minikin 0.017 Minutia 0.0135
33
Regular
◦ 0.027 inch in diameter ◦ Do not use unless hole is stripped
34
Minim 0.021
◦ Most frequently used threaded pin ◦ Start with a 0.021 and if you strip the hole, place a 0.027 pin
35
Minutia 0.0135
◦ not retentive enough in posterior teeth
36
General rule - Use one pin per (3)
missing cusp, axial wall, or line angle
37
Use no more than --- pins/tooth
4 ◦ VERY rarely use more than 1 or 2 pins ◦ Use composite
38
Place the pin in
line angles ◦ Greatest area of bulk
39
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)
LATCH Aluminum shank minimize dentin crazing and breakage of the small drills 20
40
Latch Contra-angle
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
Pinhole Location Depends Upon (2)
Pulpal anatomy External tooth anatomy
42
Pinhole Location Depends Upon Pulpal anatomy External tooth anatomy Determine using: (2)
◦ radiograph ◦ perio probe around the tooth
43
Also consider patient age ◦ older teeth ◦ younger teeth
are more brittle have larger pulp
44
Best Sites for Pin Placement? Best site for placement are at the
line angles (DF, DL, MF, ML)
45
Sites to Avoid for Pin Placement Avoid for pulp exposures (3)
◦ 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
Concavities to watch for
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
Flat area Prepare a flat area prior to pin placement (2)
◦ 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
Distance from DEJ Place pin minimum of --- inside DEJ
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
Increase Distance if Planning to Place Crown
1.0-1.5 mm inside DEJ ◦ Want to avoid exposing the pin during future crown preparation
50
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
0.5
51
Self Threading Pins- Procedure (3)
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
Starting Pilot Hole
Use a 1/4 round bur prior to using the pin drill
53
Orientation of the Pin Drill
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
When Using the Pin drill
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
Placing the Self-Threading Pin
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
What if the Pin is Too Tall? There must be --- of amalgam over the top of the pin, ◦ otherwise the amalgam may fracture
2mm
57
If too tall: (2)
◦ Reduce with handpiece OR ◦ Bend slightly using provided pin tool ◦ Comes with pin kit
58
Cutting the Pin
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
Bending the pin
* Pin bender helps avoid excessive stresses on pin when bending
60
Incorrect Pin Bending
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
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
0.5 ¼ (3-5 mm)
62
Important Points for Pin Placement ALWAYS use rubber dam◦ But especially with pin placement ◦ Risk of
aspiration
63
When using hand wrench
◦ Tie floss around the neck of the hand wrench - even if you use rubber dam.
64
Aspirating Wrenches or Pins Patients have swallowed and even worse --- these hand wrenches
inhaled
65
Pulpal Perforation Pulpal perforation is preferable to a periodontal ligament perforation
◦ 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
Periodontal Perforation A periodontal perforation (3)
◦ 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
Slots and Grooves Placed in dentin -- mm inside the DEJ Slots (4)
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
Locks: (3)
* allow for restorative material to act as “pin” * more tooth structure is removed * BUT slots result in fewer microfractures compared to pins
69
Amalgam Pins (Shavell 1980) Preservation and Restoration of Tooth Structure, Mount, GJ, Hume, WR,1998, Mosby, St. Louis, MO.
- Utilize #245 bur - Drill hole 1mm wide, 2mm deep -Condense amalgam into pin hole
70
Amalgam Advantages as Build Up MaterialBuild up: restoration under crown Amalgam benefits:
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
Combination
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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