Dye penetration at a cobalt-chromium alloy--composite resin interface.

This study examined microleakage along the interface of resin systems bonded to cobalt-chromium alloy; a microfine resin with adhesive properties based upon methacrylic acid, and a hybrid resin containing an adhesive phosphate monomer. Specimens were thermocycled between 4 degrees, 37 degrees and 60 degrees C over 1000-10,000 cycles and placed in 0.1% neutral red dye for 7 days. Each was cut diagonally and the interfaces photographed using an optical microscope. Dye penetration was expressed as a percentage of the total length of each edge. The hybrid resin showed significantly less microleakage than the microfine resin.

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 4 mm deep on the cylinders and 2 mm 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 degrees 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 and adhesive based upon methacrylic acid performed significantly less well than a conventional acrylic resin, or a hybrid composite resin with and adhesive monomer.