Fatigue strength tests of multifunctional resorbable composite plates in simulated biological conditions
Journal Title: Engineering of Biomaterials / Inżynieria Biomateriałów - Year 2018, Vol 21, Issue 147
Abstract
The article is part of a series of publications presenting the results of mechanical tests of multi-functional resorbable fixation plates. Tests were con-ducted on prototype plates in conditions simulating natural biological environment. The examinations were meant to assess the so-called “implant working time” or fatigue strength of the fixation plates. This parameter is particularly important in the case of elements subjected to time-varying loads due to the possibility of alterations to the material structure, strain strengthening or development of defects leading to the implant failure. Composite materials consisting in a polymer matrix modified with ceramic particles are quite sensitive to variable loads. Moreover, the complex geometry of the tested plates makes them more vulnerable to destruction with the critical cross-sections located at the fixing holes. Another key aspect is the biological environment where the implants will perform their functions. The temperature, pH and chemical composition are factors directly affecting the way and rate of degradation of the resorbable polymer. Degradation affects the strength characteristics, obviously weakening the material. The tests were performed on a model composed of PMMA blocks playing the role of bones with the tested plate attached with metal screws. The model was mounted in a fatigue machine and subjected to cyclic stretching. Two variants of the examinations were performed. Firstly, the model was tested in “dry” conditions; secondly - in a closed container filled with fluids simulating the biological environment (the Ringer’s solution heated to ~37°C used as the medium). The results revealed that the plates tested in “dry” conditions were endowed with different characteristics as compared to the plates exposed to the simulated biological environment.
Authors and Affiliations
K. Gryń, B. Szaraniec, J. Chłopek
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