ISO 23317:2012 pdf free download – Implants for surgery- In vitro evaluation for apatite-forming ability of implant materials.
It has been revealed that materials of various kinds bond to living bone through a layer of apatite. It has been shown that this apatite layer can be reproduced on their surfaces in an acellular and protein-free simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma, and that apatite thus formed is similar to the bone mineral in its composition and structure.
This evaluation of apatite-forming ability on implant material in SBF is useful for evaluating its in vivo bone-bonding ability preliminary to animal experiments. When a bioactive material is implanted in a living body, a thin layer rich in Ca and P forms on its surface. The material then connects to the living tissue through this apatite layer without a distinct boundary. It has been shown that this apatite layer can be reproduced on the surfaces of materials in SBF as well, and that apatite thus formed is similar to bone mineral in its composition and structure. As bioactivity increases, apatite forms on the material surface in a shorter time in proportion to this increase. The formation of apatite layers can be detected by thin film X-ray diffraction spectrometry and/or scanning electron microscopy.
The natite formed in the SRF is. however. simibr to hone ntite in the fo11owings.
6.3.9 Step 8
Pour the pH-adjusted solution from the beaker into a 1 1 volumetric flask. Rinse the surface of the beaker with distilled water several times and add the washings to the flask. Fix the stirring bar with a magnet to prevent it from falling into the volumetric flask.
6.3.10 Step 9
Add the distilled water up to the marked line (it is not necessary to adjust exactly because the volume becomes smaller after cooling). Put a lid on the flask and close it using a plastic film.
6.3.11 Step 10
After mixing the solution in the flask, keep it in the water bath to cool it down to 20°C.
6.3.12 Step 11
After the solution temperature has fallen to 20°C, add distilled water up to the marked line.
6.4 Confirmation of ion concentration of SBF
Prepared SBF shall have the ion concentrations given in Table 1. In order to confirm the ion concentrations of the SBF, chemical analysis of the SBF is recommended because SBF is a metastable solution supersaturated with respect to apatite.
It is also recommended that the apatite-forming ability of standard glasses in the prepared SBF be examined. Chemical compositions of the standard glasses for evaluating apatite-forming ability are shown in Figure B.1. When standard glasses A, B and C for evaluating apatite-forming ability are soaked in SBF, an apatite layer should be detected by TF-XRD pattern after soaking for about 12 h, 24 h and 120 h.
6.5 Preservation of SBF
Prepared SBF should be preserved in a plastic bottle with a lid put on tightly and kept at (7,5 ± 2,5)°C in a refrigerator. The SBF shall be used within 30 d of preparation.
It is recommended that the final product of SBF be sterilized by filtration to eliminate any dust particles and bacteria from the fluid, since dust can promote the heterogeneous nucleation of apatite and bacteria often phagocytose apatite formed in SBF. The sterilization should be carried out just after the preparation and/or just before evaluation for apatite-forming ability. For sterilization just after preparation (before preservation), the whole amount of as-prepared SBF is filtered using a peristaltic pump through a sterile vented filter unit with a pore size of 0,22 lim at the flow rate of 85 ml/min to 100 mI/mm. For sterilization just before starting evaluation for apatite-forming ability, the SBF is filtered using a syringe attached with a sterile vented filter unit with a pore size of 0,22 jim. Either or both sterilization methods can be selected.