ASTM F1926-99
(Test Method)Standard Test Method for Evaluation of the Environmental Stability of Calcium Phosphate Coatings
Standard Test Method for Evaluation of the Environmental Stability of Calcium Phosphate Coatings
SCOPE
1.1 This test method covers calcium phosphate coatings intended for use in surgical implant applications.
1.2 Aspects of the biological response to calcium phosphate materials in soft tissue and bone have been reported from laboratory studies and clinical use.
1.3 The requirements of this specification apply to calcium phosphate coatings such as calcium hydroxyapatite (see Specification F1185), beta-tricalcium phosphate (see Specification F1088), and biphasic mixtures thereof with or without intentional addition of other minor components (< 10%).
1.4 The coating(s) shall be representative of that produced for sale. It shall have been produced and processed under standard manufacturing conditions.
1.5 The coatings may be applied to porous, nonporous, textured, and other implantable topographical substrate forms representative of the end-use product.
1.6 The calcium phosphate coating may constitute the only coating on a substrate or be one of a multiple coated device.
1.7 This test method is limited to the laboratory evaluation of the dissolution rate of a calcium phosphate coatings. No correlation of the results to in vivo performance is implied.
1.8 The values stated in both inch-pound units and SI units are to be regarded separately as the standard. The values given in parentheses are for information only.
1.9 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 1926 – 99
Standard Test Method for
Evaluation of the Environmental Stability of Calcium
Phosphate Coatings
This standard is issued under the fixed designation F 1926; 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 E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers calcium phosphate coatings
F 1088 Specification for Beta Tricalcium Phosphate for
intended for use in surgical implant applications.
Surgical Implantation
1.2 Aspects of the biological response to calcium phosphate
F 1185 Specification for Ceramic Hydroxylapatite for Sur-
materials in soft tissue and bone have been reported from
gical Implantation
laboratory studies and clinical use (1-10).
1.3 The requirements of this specification apply to calcium
3. Terminology
phosphate coatings such as calcium hydroxyapatite (see Speci-
3.1 Definitions of Terms Specific to This Standard:
fication F 1185), beta-tricalcium phosphate (see Specification
3.1.1 calcium phosphate—any one of a number of inorganic
F 1088), and biphasic mixtures thereof with or without inten-
chemical compounds containing calcium and phosphate ions as
tional addition of other minor components (< 10 %).
its principal constituents.
1.4 The coating(s) shall be representative of that produced
3.1.2 coating—a layer of material mechanically or chemi-
for sale. It shall have been produced and processed under
cally adhering to the surface of a substrate.
standard manufacturing conditions.
1.5 The coatings may be applied to porous, nonporous,
4. Dissolution Media
textured, and other implantable topographical substrate forms
4.1 Any water used for preparing reagents or dissolution
representative of the end-use product.
media shall be deionized or distilled and have less then 0.1
1.6 The calcium phosphate coating may constitute the only
++
ppm each of residual Ca , phosphorus, and total solids.
coating on a substrate or be one of a multiple coated device.
4.2 Unbuffered Water Media—Deionized or distilled water
1.7 This test method is limited to the laboratory evaluation
–5 –5 –5
containing 8 3 10 M NaCl, 8 3 10 M CaCl , and 5 3 10
of the dissolution rate of a calcium phosphate coatings. No
MK (PO ).
3 4
correlation of the results to in vivo performance is implied.
4.3 pH 5.5 MES Buffer Media—1.0 M MES, [2-(N-
1.8 The values stated in both inch-pound and SI units are to
morphplino)ethanesulfonic acid] having a pH of 5.5 at 37 °C 6
be regarded separately as the standard. The values given in
–5 –5
0.5 °C and containing 8 3 10 M NaCl, 8 3 10 M CaCl ,
parentheses are for information only.
–5
and 53 10 MK (PO ).
3 4
1.9 This standard does not purport to address all of the
4.3.1 A buffer concentration of 1.0 M will usually provide
safety concerns, if any, associated with its use. It is the
sufficient buffer capacity to keep the solution within 6 0.1 pH
responsibility of the user of this standard to establish appro-
units of the initial value. If this is not the case, the buffer
priate safety and health practices and determine the applica-
capacity should be adjusted accordingly.
bility of regulatory limitations prior to use.
4.3.2 The pH must be adjusted to 5.5 at 37 6 0.5° C.
4.4 pH 7.4 TRIS Buffer Media—1.0 M TRIS, [Tris(hy-
2. Referenced Documents
droxymethyl)aminomethane] having a pH of 7.4 at 37 °C 6
2.1 ASTM Standards:
–5 –5
0.5 °C and containing 8 3 10 M NaCl, 8 3 10 M CaCl ,
–5
and 5 3 10 MK (PO ).
3 4
This test method is under the jurisdiction of ASTM Committee F04 on Medical 4.4.1 A buffer concentration of 1.0 M will usually provide
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
sufficient buffer capacity to keep the solution within 6 0.1 pH
F04.13 on Ceramic Materials .
Current edition approved May 10, 1999. Published September 1999. Originally
published as F 1926 - 98. Last previous edition F 1926 - 98.
2 3
The boldface numbers given in parentheses refer to a list of references at the Annual Book of ASTM Standards, Vol 14.02.
end of the text. Annual Book of ASTM Standards, Vol 13.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F1926–99
units of the initial value. If this is not the case, the buffer
capacity should be adjusted accordingly.
4.4.2 The pH must be adjusted to 7.4 at 37 6 0.5° C.
5. Analytical Parameters
5.1 The following procedure should be performed with each
of the media listed:
5.1.1 The dissolution rate shall be measured under the
conditions of a constant ratio of initial coating mass (mg) to
total dissolution media volume (mL), and initial pH. The
milligrams of coating to millilitres of dissolution media ratio
shall typically be between 1.0 and 0.1.
5.1.2 The pH of the dissolution media (60.01 pH units),
FIG. 2 Test Specimen and Coating
dissolved Ca++ concentration (6 1 ppm), and dissolved
phosphorus (as P) concentration (6 1 ppm) shall be measured
as soon as practical after the start of the experiment and at
appropriate time intervals thereafter to allow the determination
of their changes with time.
6. Analytical Procedures
6.1 Make pH measurements with an appropriately cali-
brated pH meter and probe.
6.2 Measure Ca++ concentrations potentiometrically, colo-
rimetrically, by atomic absorption (AA) or inductively coupled
plasma (ICP) spectroscopy, or by inductively coupled plasma
mass spectroscopy (ICP/MS).
6.3 Total phosphorus concentrations shall be measured by
an appropriate method (for example, inductively coupled
plasma (ICP) spectroscopy, inductively coupled plasma mass
spectroscopy (ICP/MS), and phosphomolybdate complex
method) (11).
6.4 It is recommended that an appropriate bacteriostat (for
example, 0.1 v/v % Hibiclens or 0.1 w/v % sodium azide) be
added to the dissolution media prior to the start of an
experiment.
7. Dissolution Apparatus
7.1 The dissolution vessel (see Fig. 1) shall be of such
design to easily accommodate the test specimen (see Fig. 2)
and stirrer assembly (see Fig. 3), the specific ion-electrode
assembly, and the pH electrode assembly. It shall also be
FIG. 3 Stirrer Shaft Assembly
capable of being isolated from the atmosphere by an oxygen
and carbon dioxide free inert gas purge.
7.2 It shall be of appropriate dimensions to contain the
required volume of dissolution media at a level to facilitate
sufficient stirring action from the stirrer blades.
7.3 The stirrer assembly shall consist of a stirrer motor
FIG. 1 Dissolution Apparatus capable of maintaining a constant stirring rate of at least 80
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F1926–99
rpm. The distal end of the stirrer shaft shall be threaded to mate 9.8 As soon as practical after the introduction of the test
with the male threaded portion of the test specimen and also specimen to the dissolution media, record the initial pH and the
allow for the placement of the stirrer propeller immediately dissolved Ca++ and phosphorus concentrations.
above the test specimen (see Fig. 3).
9.9 Repeat the measurement of the pH, dissolved Ca++, and
7.3.1 Stirrer Propeller —(2.5 in. (63.50 mm) diameter,
dissolved phosphorus concentrations at appropriate time inter-
0.875 in. (22.22 mm) blades, three blades, 45° pitch, stainless
vals to define their dissolution rate curves.
steel).
9.9.1 A typical initial sampling rate shall be at least
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