The influence of long term water immersion on shear bond strength of amalgam repaired by resin composite and mediated by adhesives or resin modified glass ionomers

ObjectiveTo assess the shear bond strength between amalgam and resin composite mediated by either multipurpose adhesive systems or RMGI when subjected to long term immersion in saline.MethodsPart I: Cylindrical specimens (6 mm × 6 mm) composed of equal parts of sandblasted set amalgam (Oralloy) and composite (Z-100), with a thin layer of either Scotchbond Multipurpose, All Bond 2, Amalgam Bond Plus, High Q Bond Plus or Vitrebond in between were fabricated (n = 100 × 5). Each group was divided into 3 subgroups, immersed in saline at 37 °C for either 48 h, 3 or 6 months, followed by thermocycling (5000; 5/55 °C) and shear bond strength testing (SBS). Part II: Identical specimens were fabricated with intermediary of either Ketac Cem, Fuji Lining LC, Rely X Luting, Fuji Plus or Meron Plus (n = 100 × 5). Immersion periods, followed by thermocycling and SBS testing as in Part I.Two representative specimens from each subgroup were sectioned and inspected under SEM.ResultsThe two classes of intermediary agents yielded SBS which differed mainly in the 6 months incubation period. While multipurpose adhesives provided SBS values of ∼9–10 MPa RMGI provided higher SBS of ∼16 MPa. All Bond 2 and Amalgam Bond Plus exhibited deterioration of SBS during the 6 month period as well as Rely X Luting. Gap sizes between 0.5 and 3 μm exist between all intermediaries and the amalgam; on the other hand all intermediaries exhibit gap-free interfaces between the adhesives/RMGI and the composite.ConclusionsVitrebond in particular and RMGIs in general can serve as an excellent coupler of resin composite to amalgam, providing a durable bond.