Core build up and Amalgam bonding 12 th October

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

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

Types of Core Materials Amalgam Composite Glass Ionomer Resin Reinforced Glass Ionomer Compomer

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

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

How is the amalgam retained as the core?

Retention Form Resistance Form

How is the amalgam retained as the core? Mechanical Retentive grooves and notches Pin Placement Adhesion

Amalgam Bonding A technique to bond amalgam to the cavity.

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

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

OptiBond solo

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

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, 80 o C rise

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

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

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

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

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

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): Setcos J.C, Staninec M, Wilson N.H.F The development of resin-bonding for amalgam restorations. BDJ 1999 Apr, Vol186 (7): Staninec M, Setcos Bonded amalgam restorations: current research and clinical procedure. Dent Update Oct;30(8):430-4, 436