Retaining large amalgam restorations Flashcards

1
Q

Retention

A

Provided by convergent cavity walls

Loss of cusps gives loss of retention

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2
Q

Features to increase retention

A
Grooves
Channels, slots
Bonding
Pins
Use composite
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3
Q

Channels, slots etc

A

Use available tooth structure for retention
Slots
Amalgapins
Shelves

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4
Q

Slots

A

Inverted cone bur

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5
Q

Amalgapins

A

Minimum: 0.8mm diameter

2mm deep

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6
Q

Shelves

A

Need to be 2mm high?

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7
Q

Success

A

Place features where they will resist likely loads

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8
Q

Bonded amalgam

A

Other techniques are ‘invasive’
Risk to pulp and periodontium
A means to retain an amalgam restoration without macromechanical retention
Self curing
Bonds to dentine
Amalgam condensed into it whilst both unset to form mechanical interlock

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9
Q

Bonded amalgam: the process

A

Methacrylate or composite resin
HEMA: hydroxylethyl methacrylate
NMSA: N-methacryloyl 5-aminosalicylic acid
MDP: 10-methacryloyloxydecyl dihydrogen phophate
A bond to dentine and metal?

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10
Q

Bonded amalgam: clinical trials

A

Lower sensitivity?
Retention rates exceed that of pins
Less iatrogenic damage

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11
Q

Problems with bonding

A

Loss of bond layer
Oxygen inhibition
Weakening of amalgam
Adhesion to matrix band

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12
Q

Pins

A
Historically many forms
Stainless steel self-tapping
Must be surrounded by 0.5mm of sound dentine
One per missing wall/ cusp
Keep in axis of tooth
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13
Q

Location

A

Avoid:

  • bifurcation
  • curved roots
  • thin dentine
  • pulp
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14
Q

Pin placement

A
Maximise all other retention
Find flat, anatomically safe location
Mark centre with 1/2 round bur
Select drill angle
Drill hole
Clean
Place pin
Adjust pin if required
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15
Q

Pain or bleeding

A

Pulp: endodontics
Perio: trim surgically if it protrudes

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16
Q

Pins not advised presently

A
Often traumatic
Placement at high speed results in poor thread
Cause dentine fractures
Surplus lining reduces retentive action
Inappropriate with composite