Biodegradable magnesium alloys could be the next generation of implant material for oral and maxillofacial surgeries e.g. jawbone traumata or facial reconstruction. This scope of application implies that the implant material stays first in contact with the patient´s saliva until wound closure. Thereafter the implant is exposed to a different, cellular environment in which the degradation and mechanical properties still must be ensured. Therefore, the environmental conditions for the implant are strongly various compared to those found in blood vessels or bone tissue. Obviously these different environmental conditions have an influence of the biodegradation behaviour of the implant material.
The focus of the present study is to detect the influence of electrolyte composition on the degradation behaviour of Mg-Ca-Zn alloys. One issue is the individual consideration of the different environment conditions; here open wound and closed wound. The other aspect is to consider the influence of the corrosion behaviour by interaction to simulate the specific conditions.
The research approach involved the identification of the degradation behaviour of Mg-0.6 wt.% Ca-0.8 wt.% Zn and Mg-0.6 wt.% Ca-1.8 wt.% Zn alloys in four different saliva electrolytes and Hanks´ balanced salt solution. Due to the complexity of natural saliva it is only possible to simulate the conditions by using artificial saliva so far. Here the artificial saliva was varied by the amount of the organic substance urea and by the percentage of the glycoprotein mucin. Hanks´ balanced salt solution feigned the cellular environment after wound closure. To evaluate the degradation behaviour immersion testing were carried out.
The results showed that mucin and urea have a corrosion-inhibiting effect on both alloys. Furthermore, with respect to formation of corrosion products, it was observed that during the corrosion process a three-layered system is formed. This consists of a magnesium hydroxide layer, a bright, thin, smooth layer and a particulate layer of (Ca,Mg)x(PO4)y.