Core build up and Amalgam bonding

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Core build up and Amalgam bonding

• 12th October

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Learning outcomes

• To know the definition of a core build up.
• To understand the advantages and disadvantages of
  amalgam as a restorative material
• To understand the aims of amalgam bonding
• To know the clinical stages to perform a bonded
  amalgam

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Core Definition

• 'that part of a preparation for an indirect
  restoration consisting of restorative material'.

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Types of Core Materials

• Amalgam
• Composite
• Glass Ionomer
• Resin Reinforced Glass Ionomer
• Compomer

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AMALGAM

• Advantages
• Not especially technique sensitive
• Strong in bulk section
• Sealed by corrosion products

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• Disadvantages
• Best left to set for 24 hours before tooth
  preparation
• Weak in thin section
• Mercury content may be of concern to some
  patients and dentists
• Potential electrolytic action between core and
  metal crown
• Not intrinsically adhesive

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• How is the amalgam retained as the core?

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• Retention Form
• Resistance Form

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How is the amalgam retained as the core?

• Mechanical
• Retentive grooves and notches
• Pin Placement
• Adhesion

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• Amalgam Bonding
• A technique to bond amalgam to the cavity.

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Aims Behind Bonded Amalgams

• Conserve more tooth structure by reducing the
  need to remove sound tooth tissue for mechanical
  retention.
• Increased Amalgam retention.
• Reduce marginal leakage
• Reduce the need for dentine pins.
• Potentially reduce sensitivity
• Improve fracture resistance
• Improved amalgam margins

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Materials for Amalgam Bonding

• Resin Cements ( Panavia)
• Adhesive Bonding Agents
• -initially designed for composites
• -OptiBond solo
• -Amalgambond
• -Scotchbond multipurpose

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OptiBond solo
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How do they work?

• Etching dentine opens up dentinal tubules
  enabling adhesive resin to flow into dentine and
  is retained micromechanically
• Adhesive resin adheres to amalgam roughness
  micromechanically and by 4-META adhesive

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Claimed Advantages of Amalgam Bonding Techniques

• Decreased microleakage
• YES
• Increased amalgam retention
• YES, if cavity lacks mechanical retention
• Avoids risk of using pins
• YES, 20 of pins perforate, 80oC rise

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Claimed Advantages of Amalgam Bonding Techniques

• Improved amalgam margins
• Depends on adhesive used. Panavia weakens
  amalgam at margins
• Technique may reduce incidence of ditching
• Tooth reinforcement
• YES, if large cavity
• NO, if small cavity

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Clinical Indications

• Not recommended for routine amalgam cavities with
  sufficient mechanical retention and undercuts.
  No evidence of increased benefit to balance
  increased costs.
• Useful for large multisurface amalgams to avoid
  use of pins
• Useful for amalgam repairs
• Some easier to use than others

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Bonding Agents

• Technique
• Place matrix band ( lightly vaselined)
• Etch 10 phosphoric acid
• Wash and dry
• Apply adhesive ( Kerr Optibond solo)
• Blow off excess solvent
• Light cure
• Pack amalgam

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Limitations of Technique

• Increased cost of restoration
• Technique sensitive?
• Not in use long enough to permit adequate
  evaluation of clinical performance
• Adhesion may breakdown over time

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Amalgam Bonding

• Summary
• Amalgam is an excellent core build-up material
  for posterior teeth
• Excellent interim restoration for posterior teeth
  
• Adhesives can be used to improve retention in
  large amalgam restorations and cores
• Adhesives and preparation features can often
  substitute for pin retention for cores

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References

• R. W. Wassell, E. R. Smart G. St. George. Crowns
  and other extra-coronal restorations Cores for
  teeth with vital pulps. BDJ 2002 May,192(9)
  499-509
• Setcos J.C, Staninec M, Wilson N.H.FThe
  development of resin-bonding for amalgam
  restorations. BDJ 1999 Apr, Vol186 (7) 328-330
• Staninec M, Setcos
• Bonded amalgam restorations current research
  and clinical procedure.Dent Update. 2003
  Oct30(8)430-4, 436