Shear bond strength of resin-mediated amalgam-dentin attachment after cyclic loading

Several in vitro studies have suggested that a resin-mediated attachment mechanism can provide tooth reinforcement with silver amalgam restorations. This study investigated the ability of this attachment to withstand simulated occlusal function. Forty bovine incisors were divided into four groups. Prepared tooth surfaces were treated with a dentin bonding system (All-Bond 2) followed by amalgam (Tytin) condensation into a split mold. Samples were tested for shear bond strength after no cyclic loading or after 1000 and 5000 cycles with a weight of 700 grams (1.5 lb) at one strike per second. Mode of failure was assessed by microscopic investigation of fracture sites. The 24-hour shear bond strength (7.11 +/- 1.93 MPa) of Tytin spherical amalgam to dentin was progressively reduced after cyclic loading. Bond failure invariable occurred at the interface between the adhesive resin and amalgam. It was concluded that occlusal function may significantly reduce tooth reinforcement with bonded amalgam restorations.