Fabrication de substituts osseux macroporeux
à base de phosphate de calcium
Since its creation, Biocetis realizes bones substitutes macro porous used in surgery. The bone graft, the filling of losses of bones substances, or the repair and the reconstruction are very frequent in traumatological or orthopaedic surgery. The origins of products can be human, animal or synthetic. The bones substitutes of Biocetis have this three origins.
The most common bones substitutes are with calcium. More exactly hydroxyapatite (HA) (Link English Wikipedia ) and tricalcium phosphate phase β (β-TCP) (Link English Wikipedia ). There are excellent materials because their chemical compositions are very similar to the bone with good biological properties and a perfect biocompatibility. We also use the term of “bioceramic” to indicate the constitution of the substitute’s material.
The substitute’s structure is too important that allows an easier and faster biocompatibility in the human body.To reach this objective, the structure depends on the porosity which answers two criteria: the quantity of macropore and the number of interconnection between pores. During an analysis on a conventional ceramic, various problems were detected:
- – A heterogeneous distribution of the macroporosity;
- – A dimension of macropores and porous volumes badly controlled;
- – The macroporosity’s morphology unpredictable;
- – A weak diameter of interconnection between macropores and badly analyzed.
The ceramic creates by Biocetis allows to respond to this differents problems.
The aim of Biocetis research was to resolve these problems. Solve have been found in material of product’s edifice. Indeed, habitual procedures use a foam assembly a sponge to be the calcium slurry’s shelf. The problem is that this foam produces random pores and interconnections. So then, Biocetis has decided on use marble of Poly(methyl methacrylate) (PMMA link Wikipedia English) to realize the edifice, and to use two thermal treatment to do disappear marbles. It’s possible to do vary pores size with marbles size, and network enters marbles also.
the first step consists in the product’s edifice realization. This edifice is marble in PMMA assembly diving in acetone. Then, it’s possible to influence two parameters :
- – Macro-porous’ size depending to marble size;
- – Network size depending to duration of marble dissolution in acetone.
- After, that edifice is cleaning for remove all acetone’s mark.
This is during this stage that the chemical composition is made. Slurry is made from mix with HA, β-TCP, water and organics additive. Here, it’s possible to modify the substitute resorption, more HA are present, more the time will be long (15-20 year for 100% HA), more β-TCP are present more the time will be (3-4 years for 100%). All of this is mixed for obtain slurry.
During this stage, the slurry is flowing on the edifice. Then all dry to let the assembly to become solid. After this, the excess are cleaned to make pores in next step appear.
4. Passing in oven
at low temperature
The assembly are placed in a first oven with a temperature between 200 °C and 300°C during around 48h. The operation objective is to do to disappear by evaporation PMMA marble, this is that create macro-porous and network between this.
After, the elements are placed in another oven, with a temperature between 1000°C and 1200 °C, during around 24h. The operation objective is to consolidate the ceramic.
The substitutes are realized, we need to pack. The produce is placed in a double sheath flat shims, all of this in “clean” room.
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