[Fatigue properties of junction of crown and bridge resin and metal frame. 1. Effects of retention beads and adhesive].

The bending fatigue test of crown and bridge resin facing metal frame was carried out under a scanning electron microscope, and the fracture and propergation behavior of junction was studied. The resin facing metal frame with retention beads had a static breaking stress of about 100 kgf/mm2. The resin facing metal frame, when bonded with adhesive, had the stress of about 36 kgf/mm2. The specimens with retention beads and bonded with adhesive were not destroyed at cycles of 10(6) under the bending fatigue stress of below 40% and 50% of the static breaking stress, respectively. Marginal micro gaps between resin and metal frame with retention beads were observed before the fatigue test, and were increased with the number of cycles. Then fracture of the specimen occurred from the resin of the retention beads side. In the specimen bonded with adhesive, marginal micro gaps between resin and metal frame were observed during the fatigue test, and the partially cohesive fracture occurred.