Adhesive composite resins for artificial teeth: a laboratory investigation of bond strength to a cobalt-chromium alloy

Adhesive resin systems are reported to improve the bond strength between resins and cast cobalt-chromium alloy. This investigation compares the behaviour of three resin systems. Cylinders and beams of cobalt-chromium, with 0.6-mm-diameter retention beads regularly cast onto the bonding surfaces, were air-abraded and ultrasonically cleaned. Resin veneers 4mm deep on the cylinders and 2mm on the bars were polymerized by heat and pressure or by light. Specimens were water-stored for 7 or 90 days, including thermocycling between 4, 37 and 60 °C, before testing in a Universal Testing Machine to examine the shear bond strength or the effect of the bonded resin spine on the flexural strength of the beams using a three-point bend test. Specimens were examined with an optical microscope to attempt to determine the nature of the failures that occurred. The investigation showed that, overall, the heat- and pressure-cured urethane dimethacrylate resin with an adhesive based upon methacrylic acid performed significantly less well than a conventional acrylic resin, or a hybrid composite resin with an adhesive monomer.