The presence of materials may modify cell activity and affect tissue
reconstruction. We have known for many years how to grow eukaryotic cells on different materials and studies have been made on a wide variety of ceramics. Concerning ceramics used in orthopedics, there is a succession of events which ends in the integration of the implant. The sketch in Figure 12.2 details these events in the case of a bioactive ceramic.
1. Equilibrium of the ceramic surface and the solution. Eventual release of mineral ions, adsorption of
ions and/or of proteins.
2. Nucleation and growth of a layer of carbonated apatite analogous to bone mineral from
supersaturated biologic fluids. This layer contains a number of bioactive proteins.
3. Cells go towards the modified surface on which these will settle and become differentiated in order to
give rise to osteoblasts.
4. The osteoblasts multiply and colonize the surface of the biomaterial.
5. The cell layer synthesizes a collagenic organic matrix.
6. The organic matrix mineralizes and the new bone is deposited.
12.3.2.1. Surface phenomena
Biological fluids are generally supersaturated with respect to the apatite of bone tissues. The presence of nucleation and crystal growth inhibitors of calcium phosphates, however, generally prevent the phenomena of uncontrolled mineralization. In this environment, the nucleation and the crystalline growth of apatitic calcium phosphate analogous to bone mineral are relatively easy. It has been shown that all bioactive compounds which facilitate the formation of bone tissues also favor nucleation of calcium phosphates. Several authors in fact now consider this property as a direct measurement of the biological activity of ceramics. We can
distinguish ceramics which simply play the role of a nucleate or without bringing mineral ions from those which modify in biological environment with release of mineral ions and accelerate the formation of a layer of neo-formed apatite
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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