Biological environments are particularly corrosive: they can generate relatively acidic pH values, associated with the formation of oxide radicals (super oxides, hydro peroxides) and molecules with strong chelating capabilities. These phenomena may lead to a biodegradation of ceramics, at times desired and at times accidental.
Overall, biodegradation appears connected to the solubility of these ceramics. Thus, very insoluble calcium phosphates, corresponding to stoechiometric apatites are non biodegradable, while those that are relatively more soluble are biodegradable. It seems that this general rule is equally valid for other types of ceramics. We can distinguish between the phenomena of passive biodegradation not involving cells and the phenomena of biodegradation activated by the cells.
12.3.3.1. Passive degradation by biological fluids
Modes of passive degradation are not different from what we can observe in other aqueous media. We may, for example, observe a dissolution at grain boundaries associated with the release of particles and hydrolysis phenomena, sometimes limited to the surface of the material. In the case of multiphase ceramics,
phenomena connected to the transfer of material between phases of different solubility may appear. The release of particles in tissues or biological fluids may sometimes produce inflammatory reactions which we will analyze later. Certain plasma sprayed coatings of calcium phosphate can be associated with small
proportions of calcium oxide, whose hydration is accompanied by a large increase in molar volume, leading to the formation of cracks and to a detachment from the metallic substrate
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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