This in vitro study was to investigate bond strength between dental amalgam and a) composite or b) Glass-Ionomers (GI) to mimic restoration repair.

Materials and Methods:
Cylindrical substrates of amalgam were made and ground (sanding paper #500). Repair materials were fixed to amalgam in groups of 20 specimens. Composite and three different bonding agents were tested in 3 modes; 1) short term (48 hr water storage), 2) water storage for 60 days, 3) thermo-cycling (TC) 5000/5-55°C. For the two Self-etch bonding-agents, the amalgam surface was not etched with acid. Three glass-ionomer products were tested in the same modes, two of them with and without dentine conditioner (optional from manufacturer). Altogether 24 groups were tested for sheer bond strength according to ISO/TS 11405.

None of the GIs adhered to the amalgam surface, resulting in bond strength value of 0 MPa. Composite testing: Mode 1) 6.5-8.3 MPa, Mode 2) 6.4-7.7 MPa, Mode 3) 0.6-2.2 MPa. There was no significant difference between mode 1 and 2. Mode 3 differed significantly from mode 1 and 2.

GIs did not bond to amalgam. Composite-amalgam repair bond strength is low compared to previous results on bonding composite to composite. TC seems to be detrimental to composite-amalgam repair-interface.

Bonding of Composite and Glass-Ionomer to Amalgam.
Staxrud F, Mulic A.
J Dent Oral Biol. 2018; 3(6):1145.