Effect of repeated sterilization

The worsening of the material properties due to regular use in clinical practice, and the associated reprocessing, should be taken into account, particularly for polycarbonate. In the load cycle with PC, there is clear evidence of stress cracking and embrittlement after just a few reprocessing steps. PEEK and PA12, on the other hand, show good media and sterilization resistance, and no measurable decrease in strength even after 75 cycles. Steam sterilization provides the most critical loading step for all the investigated materials. However, the effect of media - in particularly under mechanical stresses due to external loads or inherent stresses - and cleaning and disinfection - additionally have a damaging effect, which should be taken into account. Realistic loading of medical products in an alternating cycle consisting of the effect of media under load, cleaning and disinfection, and sterilization, is more damaging than the long-term loading under only one loading type that is usually used in material fatigue testing. Nevertheless, clear trends can be recognized just through simple continuous load tests and information determined about the material's basic suitability. As so often, these material tests cannot replace the suitability test of a part under service conditions.