Fatigue model to characterize cement-metal interface in dynamic shear.

This study evaluated the interface shear strength between vacuum mixed polymethyl-methacrylate and two types of surface enhancements under static and dynamic shear loading. Cobalt chrome coupons with grit blasted or light plasma sprayed surfaces were tested. For each test, two coupons were mounted in a stainless steel chamber such that they were bonded with a 2-mm cement mantle for each test. Pullout and dynamic fatigue tests were performed on an Instron machine. The mean static pullout strength of the grit blasted surfaces was 13.78 (+/- 2.73) MPa, whereas that of the light plasma sprayed surfaces was 18.46 (+/- 1.98) MPa. The rate of degradation of interface strength caused by fatigue was almost identical for both surface treatments. Qualitative analysis showed that the failed light plasma sprayed surface generated more metal and cement particles. These data suggest that light plasma sprayed surfaces sustain higher loads but have a potential for increased debris generation.