ASTM F1854-98
(Test Method)Standard Test Method for Stereological Evaluation of Porous Coatings on Medical Implants
Standard Test Method for Stereological Evaluation of Porous Coatings on Medical Implants
SCOPE
1.1 This test method covers stereological test methods for characterizing the coating thickness, void content, and mean intercept length of various porous coatings adhering to nonporous substrates.
1.2 Porous coatings with significant gradients in the porosity from the substrate to the surface will require use of the alternate sample orientation method outlined in 8.2.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: F 1854 – 98
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Stereological Evaluation of Porous Coatings on Medical
1
Implants
This standard is issued under the fixed designation F 1854; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 This test method covers stereological test methods for 4.1 Mean Coating Thickness—Measurement grid lines are
characterizing the coating thickness, void content, and mean oriented perpendicular to the substrate interface. On each of the
intercept length of various porous coatings adhering to non lines in the group, the distance from the substrate interface to
porous substrates. the last contact with the porous coating material is measured.
1.2 Porous coatings with significant gradients in the poros- The average of the line lengths over the group of lines is the
ity from the substrate to the surface will require use of the local mean coating thickness.
alternate sample orientation method outline in 8.2. 4.2 Volume Percent Void—A regular grid of points is
1.3 The values stated in SI units are to be regarded as the superimposed on a field from the working surface. The
standard. percentage of points that are in contact with void areas in the
1.4 This standard does not purport to address all of the coating correlates with the volume percent of void present.
safety concerns, if any, associated with its use. It is the 4.3 Mean Void Intercept Length—Measurement grid lines
responsibility of the user of this standard to establish appro- are oriented parallel to the substrate interface. The number of
priate safety and health practices and determine the applica- times the lines intercept voids is used with the volume percent
bility of regulatory limitations prior to use. void to calculate the mean void intercept length.
2. Referenced Documents 5. Significance and Use
2.1 ASTM Standards: 5.1 These test methods are recommended for elementary
2
E 3 Methods of Preparation of Metallographic Specimens quantification of the stereological properties of porous coatings
2
E 883 Practice For Metallographic Photomicrography and the solid substrates to which they are bonded.
5.2 These test methods may be useful for comparative
3. Terminology
evaluations of different coatings or different lots of the same
3.1 Definitions: coating.
3.1.1 field—the image of a portion of the working surface
5.3 All three methods should be performed on the same
upon which measurements are performed. working surface.
3.1.2 intercept—the point on a measurement grid line pro-
5.4 A statistical estimate can be made of the distributions of
jected on a field where the line crosses from solid to void or the mean coating thickness and the volume percent void. No
vice versa.
estimate can be made of the distribution of intercept lengths
3.1.3 measurement grid lines—a evenly spaced grid of
unless the void is a regular geometric shape that can be defined
parallel lines all of the same length mathematically.
3.1.4 porous coating—coating on an implant deliberately
6. Apparatus
applied to contain void regions with the intent of enhancing the
fixation of the implant. 6.1 The procedures outlined in this test method can be
3.1.5 substrate—the solid material to which the porous performed manually or by an automated procedure. The
coating is attached. following apparatus are necessary for manual calculations.
3.1.6 substrate interface—the region where the porous coat- 6.2 Microscope, or other suitable device with a viewing
ing is attached to the substrate. screen or photomicrographic capability of at least 125 by 175
3.1.7 working surface—the ground and polished face of the mm should be used to image the working surface.
metallographic mount where the measurements are made. 6.3 Transparent Sheet, with measurement grid lines or
points is superimposed on the viewing screen or photomicro-
graph for the measurements. The grid lines grids of points
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This test method is under the jurisdiction of ASTM Committee F-4 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee should be uniformly spaced and parallel with at least five
F04.15 on Material Test Methods.
parallel lines.
Current edition approved February 10, 1998. Published June 1998.
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Annual Book of ASTM Standards, Vol 03.01.
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F 1854
7. Metallography 9.1.3 The transparency of the measurement grid lines is
superimp
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