Abstract
The aim of the present investigation was to determine the effects of the embedding material mechanical properties on the in vitro fatigue endurance of femoral hip stems as determined following ISO standards. Acrylic cements are usually employed as embedding media; due to the high cost of surgical cements, acrylic cements for dental applications are commonly used. Two acrylic cements for dental applications were tested to determine their static mechanical properties and compared with those found for three surgical cements. The same two dental cements were also compared as embedding media in a series of ISO 7206/3 fatigue tests on a mini-size Cr-Co stem; prosthesis stress analysis using strain gauges was also performed. The mechanical tests on the different cements showed that behind the definition of acrylic cement are materials with considerably different mechanical static properties. The fatigue campaign confirmed the influence of embedding media on the results obtained from the ISO 7206/3 fatigue test. Under a load of 4200 N the stem failed after four million cycles when using one cement; it did not fail after ten million cycles when using another cement. Stress analysis with strain gauges substantially confirmed these findings.
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