Bonding of amalgam to composite: tensile strength and morphology study.
OBJECTIVE
The present study was based on the premise that it may be possible to produce useful dental restorations by bonding freshly triturated amalgam to a cured composite restoration (Group 1 specimens), or by bonding uncured composite to hardened amalgam (Group 2 specimens).


METHODS
To determine the validity of this premise, a phosphonate adhesive resin cement was used to produce simulated, layered dental restorations for each test group.


RESULTS
The mean tensile bond strength of 24 hour-old Group 1 specimens (6.74 MPa +/- 1.63 MPa) was almost twice that of 24 hour-old Group 2 specimens. Cohesive failure of the amalgam-substrate layer was a prominent feature of the fracture pattern of Group 1 specimens. On the other hand, rupture of all Group 2 specimens occurred mainly along the adhesive-amalgam interface. Findings from SEM examination of the layers of amalgam, adhesive cement, and resin composite of intact Group 1 specimens suggested that inclusions of adhesive resin cement may be the cause of the persistent cohesive failure of the amalgam layer.


CONCLUSIONS
It may be possible to improve the strength of bonded couples made from freshly triturated amalgam and cured resin composite by minimizing the thickness of the adhesive layer.
Garcia-Barbero
A E
AE
Department of Conservative Dentistry, Complutense University School of Dentistry, Madrid, Spain.
Garcia-Barbero
J
J
Lopez-Calvo
J A
JA
D003188:Composite Resins / Q000737:chemistry; D003723:Dental Amalgam / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D019279:Resin Cements; D013499:Surface Properties; D013718:Tensile Strength
D003188:Composite Resins; D003738:Dental Cements; D010710:Phosphates; D019279:Resin Cements; C065770:Herculite XR; C041332:amalcap; D003723:Dental Amalgam; C052304:Panavia EX