ARTICLE IN PRESS
Biomaterials 25 (2004) 987–994
A thorough physicochemical characterisation of 14 calcium
phosphate-based bone substitution materials in comparison to
natural bone
D. Tadic, M. Epple*
Solid State Chemistry, Faculty of Chemistry, University of Bochum, Universitatsstr. 150, D-44780 Bochum, Germany
Received 10 March 2003; accepted 22 July 2003
Abstract
Fourteen different synthetic or biological bone substitution materials were characterised by high-resolution X-ray diffractometry,
infrared spectroscopy, thermogravimetry, and scanning electron microscopy. Thus, the main parameters chemical composition,
crystallinity, and morphology were determined. The results are compared with natural bone samples. The materials fall into
different classes: Chemically treated bone, calcined bovine bone, algae-derived hydroxyapatite, synthetic hydroxyapatite, peptideloaded hydroxyapatite, and synthetic b-TCP ceramics.
r 2003 Elsevier Ltd. All rights reserved.
Keywords: Bone graft materials; Chemical analysis; Calcium phosphates
1. Introduction
Filling of bone defects is a significant question in
every day clinical work. Autogeneous bone is still the
most effective bone graft substitution material (‘‘gold
standard’’), fulfilling all essential physicochemical and
biological properties, despite its inherent limitations
(availability, post-operative pain) [1–5]. The most
common alternative to the autograft material are
(human) allografts or (animal, e.g. bovine) xenografts.
Allografts have the disadvantages of limited supply and
potential infectivity (e.g. HIV, Hepatitis). With xenografts there are the questions of unfavourable immune
response and also of infectivity.
Autogenous bone is osteogenic (the cells within a
donor graft synthesise new bone at the implantation
site), osteoinductive (new bone is formed by the active
recruitment of host mesenchymal stem cells from the
surrounding tissue, which differentiate into bone-forming osteoblasts), osteoconductive (vascularisation and
new bone formation into the transplant) and highly
biocompatible [6]. This process is facilitated by the
*Corresponding author. Tel.: +49-234-3224-151; fax: +49-2343214-558.
E-mail address: [email protected] (M. Epple).
0142-9612/$ - see front matter r 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0142-9612(03)00621-5
presence of growth factors within the autogenous bone
material (mainly bone morphogenetic proteins [7]).
These characteristics should be present in an ideal
substitute and all bone graft substitution materials can
be described by these characteristics [8].
Synthetic calcium phosphate ceramics [9] with their
excellent biocompatibility are common alternatives to
autogeneous bone, xenograft or allograft materials.
They have gained acceptance for various dental or
medical applications which include, e.g., fillers for
periodontal defects, alveolar ridge augmentation, maxillofacial reconstruction, ear implants, spine fusion,
and coatings for metallic implants [10–15]. Bone grafts
and synthetic calcium phosphates (such as b-tricalcium
phosphate; b-TCP, and hydroxyapatite; HAP) are
commonly used as blocks, cements, pastes, powders
or granules. The aim of this article is to describe
the chemical and physical properties of these bone
graft materials and to compare them to natural bone.
As model for autologous spongiosa, natural bone
samples were analysed. The biological performance
of a synthetic material depends on fundamental
parameters: chemical composition, morphology,
and biodegradability. A wide range of analytical
methods (IR, XRD, TG, REM) was used to investigate
these properties. As each of these methods has its
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D. Tadic, M. Epple / Biomaterials 25 (2004) 987–994
limitations, it is necessary to combine all results to
obtain a comprehensive view.
2. Materials
Fourteen different bone substitution materials were
used. The following data were taken from the manufacturer’s specification. All samples were obtained directly
from the manufacturers in sealed vials and used without
further treatment, except for grinding or cutting to a size
appropriate for analysis.
Bioresorbs, Chronoss, Ceross, Cerasorbs, and
Vitosss are synthetic b-tricalcium phosphates from
high-temperature calcination processes.
Bioresorbs is available as porous granulate (particle
size: 0.5–2 mm) mainly for dental application. Chronoss and Ceross are also granular materials with a
particle size of 0.5–1.4 mm and pore sizes of 100–500 mm
(60% pore volume), also mainly for dental application.
Cerasorbs is available as porous granulate (pore size
>5 mm) in particle sizes of 0.05–2 mm for dental
application and as machined macroporous blocks for
orthopaedic applications. Vitosss is a porous granulate
(pore size 10–1000 mm; porosity approx. 90%; particle
size 3–5 mm) for dental application.
PepGen P-15s is a calcined bovine bone (1100 C;
hydroxyapatite) coated with a pentadecapeptide (P-15, a
part of the sequence of collagen). It is available as
granulate with a particle size of 0.25–0.42 mm and used
in dental applications.
Endobons and Cerabones are high-temperature
sintered bovine bone materials (>1200 C), containing
the sintered inorganic part of bone (hydroxyapatite).
They are usually administered as highly porous blocks
(pore size typically 1 mm; porosity typically 50%) with
dimensions in the centimeter-range. Cerabones is also
available as granulate (not studied here). These materials are used in orthopaedic surgery.
Algipores is a algae-derived hydroxyapatite. It is
prepared by the hydrothermal conversion of the original
calcium carbonate of the algae in the presence of
ammonium phosphate at about 700 C. This process
preserves the porosity of the algae. It is available as
granulate with particle sizes of 0.3–2 mm and pores in
the range of 5–10 mm and used for dental application.
Ostims is a nanocrystalline precipitated hydroxyapatite that still contains about 40% of water. It has a
viscous, fluid-like consistence and can therefore be
directly injected into a defect. Note the difference to
self-hardening bone cements as this is a fluid dispersion.
It can be used in dental and orthopaedic surgery.
BioOsss is the inorganic component of bovine bone
(i.e., the mineral). All organic material is removed by a
stepwise annealing process (up to 300 C), followed by a
chemical treatment (NaOH) that leaves a porous
hydroxyapatite bone chip material. The particle size of
the granulate is 0.25–2 mm. It is used mainly in dental
surgery.
Kiel bone is a bovine bone graft material that was
treated chemically with chloroform/methanol and H2O2
to remove all organic components except of the
collagen. It is not in clinical use anymore. It was
available as centimeter-sized block.
Tutoplasts is obtained as either human or bovine
graft material after a multi-step chemical treatment
(osmolysis, NaOH, H2O2, acetone). It is available as
granulate (particle size 0.25–2 mm) and as centimetersized block or cylinder. The interconnecting porosity of
the bone is still present in both cases (pore sizes of some
hundred mm).
The data for synthetic hydroxyapatite synthesised by
precipitation (purchased from Merck Chemical Division, Darmstadt, Germany) and human callus bone and
human tumor bone were taken from our earlier study
on the structure of bone and bone substitution
materials [16].
3. Methods
High-resolution X-ray powder diffractometry (XRD)
was carried out in transmission geometry (ground
samples on Kapton foil) at beamline B2 at HASYLAB/DESY, Hamburg, Germany, with wavelengths of
( (depending on the individual experiabout l ¼ 1:2 A
ment) [16]. For Ceross, Chronoss, Bioresorbs, Vitosss and PepGen P-15s, diffraction data were
measured on a Bruker AXS D8 Advance laboratory
( Infrared spectroinstrument (Cu Ka radiation, 1.54 A).
scopy (IR) was carried out with a Perkin-Elmer 1720 instrument (KBr pellet, transmission mode, 400–
4000 cm1, resolution 2 cm1, 10 scans). Thermogravimetric analysis (TGA) was carried out with a TG/DTAS II, Seiko Exstar 6000 instrument (5–15 mg; 25–
1000 C; 10 K min1; dynamic oxygen atmosphere;
300 ml min1; Al2O3 crucibles). Scanning electron microscopy (SEM) was carried out with a LEO 1530
instrument on gold-sputtered samples.
4. Results and discussion
Fig. 1 shows the macroscopic morphologies of the
different materials. Bioresorbs, Chronoss, Ceross,
Cerasorbs, Vitosss, PepGens, Algipores, BioOsss,
and Tutoplasts are available as granulate with typical
particle sizes of a few hundred mm to a few millimeters.
Ostims is a fluid paste with nanoscopic apatite particles
in aqueous dispersion. Cerabones, Endobons, and
Tutoplasts have the bone-like structure with interconnecting porosity as they are all derived from natural
ARTICLE IN PRESS
D. Tadic, M. Epple / Biomaterials 25 (2004) 987–994
Bioresorb®
Chronos®
β-TCP
ceramics
Ceros®
Cerasorb®
Vitoss®
Hydroxyapatite-based materials
PepGen® P-15
Cerabone®
Ostim®
CO2m’’; peak at 37.3 2Y) [17]. Traces of CaO are also
seen in Cerabones at the same position in 2Y: The
inorganic phase of PepGens is also a highly crystalline
hydroxyapatite (with no traces of CaO). Algipores is a
moderately crystalline hydroxyapatite phase with no
detectable foreign phases.
Ostims is prepared by rapid precipitation, keeping
the crystals within the nanometer range. This is
indicated by the broad diffraction peaks in Fig. 2c that
correspond to synthetic hydroxyapatite. No foreign
phases are visible. Interestingly, the crystallinity is close
to that of BioOsss that is prepared from bovine bone.
Even smaller crystals lead to even broader diffraction
peaks. All bone-like samples fall into this category (Fig.
2d). They all contain hydroxyapatite-like mineral and
there are no distinct differences. The only exception
is a content of octacalcium phosphate (OCP;
Ca8H2(PO4) 5H2O) in Tutoplasts (bovine) as indicated
by asterisks in Fig. 2d (peaks between 21 and 24 2Y).
The diffraction peak broadening by small crystallites
can be semi-quantitatively estimated by the Scherrer
equation [18] (Table 1):
b1=2 ¼ ðKl57:3Þ=ðD cos YÞ:
BioOss®
Tutoplast®
Fig. 1. Macromorphology of the different bone graft materials.
bone by either thermal or chemical treatment. In
contrast, blocks of Cerasorbs are prepared by coldisostatic pressing, followed by mechanical drilling of
millimeter-sized holes.
The results of the X-ray diffraction experiments that
are indicative for the chemical composition (presence of
crystalline phases) are shown in Fig. 2.
Four of the five b-TCP ceramics show small amounts
of impurities besides the major phase (peaks marked
with asterisks in Fig. 2a). They all exhibit a high
crystallinity as indicated by the narrow diffraction
peaks. Bioresorbs contains some b-Ca2P2O7 (calcium
pyrophosphate; peak at 30.8 2Y) and a-TCP (peak at
22.9 2Y). Chronoss and Ceross contain some a-TCP
and some hydroxyapatite (peak at 31.6 2Y). Vitosss
contains some b-Ca2P2O7 (peaks at 29.0 and 30.2 2Y).
In all cases, the amount of foreign phases is very small.
Cerabones and Endobons are prepared by hightemperature calcination from bovine bone, and consequently the hydroxyapatite is highly crystalline (very
narrow diffraction peaks). Endobons also contains
small amounts of calcium oxide (CaO) that results from
decomposition of the carbonate content of the original
bone mineral (carbonated apatite; ‘‘CaCO3-CaO+
989
ð1Þ
Here, b1=2 is the peak width (as full-width at half
maximum) in 2Y; K is a constant that we set to 1 (as
( D is the
often done), l is the X-ray wavelength in A,
average domain size (roughly the crystallite size) and Y
is the diffraction angle of the corresponding reflex. This
equation gives an estimate of the crystallite size. It
should be noted, however, that structural disorder and
strain phenomena, e.g. caused by carbonate substitution, can also lead to a peak broadening effect [18].
Therefore, the given values should be mainly used for
comparison among the samples.
All bone samples have essentially the same anisotropic crystal size, i.e. about 25 nm in c-direction [(0 0 2)
and (0 0 4)] and about 9 nm in a-direction [(2 1 0)/(1 2 0)
and (1 3 0)/(3 1 0)]. The Tutoplasts process does not
change the mineral particle size. BioOsss and Ostims
have slightly larger particles (about double as much in
each direction). In the case of BioOsss, this may be due
to the heating during the preparation as Rogers et al.
reported first structural changes in the mineral phase
between 200 C and 400 C [17]. Synthetic hydroxyapatite and Algipores show almost isotropic particles
about three times larger than bone mineral particles in
each direction. For the highly crystalline samples
Cerabones, Endobons and PepGens, the diffraction
peak width is at the minimum given by the experimental
setup, therefore only a lower limit for the crystallite size
can be given (but see below for SEM pictures).
The infrared spectra are shown in Fig. 3. All b-TCP
ceramics are identical and show only the expected
calcium phosphate bands (Fig. 3a). The hydroxyapatitebased ceramics in Fig. 3b show only calcium phosphate
ARTICLE IN PRESS
D. Tadic, M. Epple / Biomaterials 25 (2004) 987–994
990
Bioresorb
Chronos
*
*
(R)
(R )
*
Ceros
Cerasorb
*
20
25
(a)
Vitoss
*
30
35
PepGen
(R)
P15
intensity
*
intensity
(R )
*
*
(R)
*
Endobon
*
Cerabone
(R)
(R)
(R)
Algipore
40
20
25
(b)
diffraction angle / ˚2 θ
(R)
30
diffraction angle / ˚2 θ
35
40
Kiel
Bone
(synthetic)
Ostim
(R)
Tumor
Bone
intensity
intensity
hydroxyapatite
Callus
Bone
(R)
* * ** *
Tutoplast
(bovine)
(R)
Tutoplast
(human)
(R)
BioOss
20
(c)
25
30
diffraction angle / °2θ
35
40
(d)
20
25
30
diffraction angle / ˚2 θ
35
40
( The
Fig. 2. X-ray diffraction data for all investigated samples. All data were either measured at or converted to the Cu Ka wavelength (1.54 A).
displayed range in 2y was chosen to optimally represent the relevant features.
Table 1
Estimation of the domain size from diffraction peak broadening of all investigated materials in nanometers
Diffraction line index
(
2y [ ] at Cu Ka (l ¼ 1:54 A)
PepGens
Endobons
Cerabones
Algipores
Synthetic hydroxyapatite
Ostims
BioOsss
Kiel bone
Tumor bone
Callus bone
Tutoplast (bovine)s
Tutoplast (human)s
(1 1 1)
(0 0 2)
(2 1 0)
(1 2 0)
(1 3 0)
(3 1 0)
(1 1 3)
(2 2 2)
(2 1 3)
(1 2 3)
(0 0 4)
22.9
>64
>71
>64
59
30
21
29
19
24
20
21
14
25.9
>54
>64
>80
65
38
36
36
24
22
21
27
27
29.0
>54
>67
>65
45
25
22
23
10
12
10
17
18
39.8
>56
>63
>84
40
29
21
17
8
9
9
8
9
43.8
>42
>64
>56
29
40
24
21
23
20
24
21
13
46.7
>57
>62
>57
44
26
19
21
19
18
18
12
16
49.5
>43
>64
>58
38
33
25
25
15
14
14
17
19
53.1
>44
>64
>88
36
42
35
29
25
22
22
20
22
bands in a sharp and split way, as indicative for the high
crystallinity. Algipores shows some carbonate bands
(approx. 1400 cm1) that are probably due to remnants
of the production process (from calcium carbonate
algae). Although PepGens contains a bioactive peptide,
there are no bands of organic material (as seen below).
This is due to the small amount present. In Fig. 3c,
nanocrystalline hydroxyapatite ceramics are shown. The
phosphate bands are generally broader because of the
small crystallite size. In addition, there are bands of
water, and, except for Ostims, of carbonate. This shows
that synthetic hydroxyapatite as well as BioOsss
contain small amounts of incorporated carbonate. The
bone samples that are shown in Fig. 3d all contain
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D. Tadic, M. Epple / Biomaterials 25 (2004) 987–994
991
(R)
Chronos
Ceros
(R)
(R)
(R)
Cerasorb
Vitoss
(R)
(R)
PepGen
absorbance / a.u.
absorbance / a.u.
Bioresorb
(R)
Endobon
(R)
Cerabone
O-H
P-O
4000
3500
3000
(a)
2500
2000
1500
wave number / cm
1000
(R)
Algipore
C-O
P-O
P-O
P-O
500
4000
-1
3500
3000
(b)
2500 2000 1500 1000
-1
wave number / cm
500
Bone
(Kiel)
Ostim
(R)
BioOss
absorbance / a.u.
absorbance / a.u.
Hydroxyapatite
synthetic
Bone
(tumor)
Bone
(callus)
(R)
O-H
O-H
P-O
C-O
H-P-O
N-H
O-H
P-O
4000
3500
3000
2500
2000
1500
1000
500
4000
-1
wave number / cm
(c)
(d)
3500
C-H
3000
2500
2000
C-O
P-O
O-H
1500
Tutoplast
(bovine)
(R)
Tutoplast
P-O (human)
H-P-O
(R)
1000
500
-1
wave number / cm
Fig. 3. Infrared spectroscopy on the bone graft materials with the bands assigned to structural features.
100
~9 % water
95
sample mass / %
90
85
80
~ 26 % organic material
75
70
65
~ 3,6 % CO2
60
100
200
300 400 500
temperature / ˚C
600
700
800
900
Fig. 4. Typical thermogravimetric curve of Tutoplasts (bovine),
showing the three regions of mass loss that can be used to derive the
chemical composition.
collagen and organic tissue in variable amounts. In
addition to the bands of calcium phosphate, we can see a
multitude of bands that are related to the organic
material and incorporated water.
All samples were subjected to thermogravimetric
analysis [19] to determine the content of water, organic
material (like collagen), and mineral (calcium phos-
phate). A typical curve is shown in Fig. 4 (Tutoplasts
human). As derived from earlier experiments with mass
spectrometric analysis of the released gases, three ranges
of mass loss can be assigned to specific processes [16].
From room temperature to about 200 C, incorporated
water is lost. Above about 300 C, organic material like
collagen, fat tissue, proteins start to burn. At about
400 C, only the mineral phase (calcium phosphate) is
left. If the mineral contains some carbonate in the form
of carbonated apatite, there is a mass loss between about
400 C and 900 C [16,20]. Therefore, it is possible to
determine the mineral content and its carbonate content
from such TG experiments. Note that all biological
apatites are carbonated apatites [15].
Table 2 shows all compositional data as determined
from TG experiments (average of two experiments). All
b-TCP phases, except for Vitosss, show no mass loss,
indicating the absence of any volatile or combustible
material. In the case of Vitosss, a small mass loss was
registered between 200 C and 400 C. This may be due
to an organic binder used for granulation. All calcined
hydroxyapatite samples (PepGens, Cerabones, and
Endobons) show no mass loss, as expected due to the
preparation of these materials by high-temperature
calcination. The amount of peptide in PepGens is too
small to result in a detectable mass loss.
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992
Table 2
Chemical composition, as derived from thermogravimetric experiments. The nature of the mineral phase was derived from previous diffraction
experiments
Bioresorbs
Chronoss
Ceross
Cerasorbs
Vitosss
PepGens
Endobons
Cerabones
Algipores
Ostims
BioOsss
Kiel bone
Tumor bone
Callus bone
Tutoplasts (bovine)
Tutoplasts (human)
H2O
(wt%)
Soft tissue+organic
bone matrix (wt%)
Mineral
phase (wt%)
Formal content
of CaCO3 (wt%)
Content
of TCP
Formal content
of HAP (wt%)
Formal ratio
apatite: CaCO3 (w:w)
0
0
0
0
0
0
0
0
0.3
40.4
3
7.8
5.7
6.9
9
9.5
0
0
0
0
1.2
0
0
0
2.4
0
0
28.7
21.2
47.7
26
34
100
100
100
100
98.8
100
100
100
97.3
\quad 59.6
97
63.5
73.1
45.4
65
56.5
0
0
0
0
0
0
0
0
2.3
0
3.4
3.7
5.2
1.4
8
7.5
100
100
100
100
98.8
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
100
100
100
95
59.6
93.6
59.8
67.9
44
57
49
—
—
—
—
—
—
—
—
41
—
28
16
13
31
7
6.5
Note the traces of impurities in some cases (Fig. 2).
Algipores contains small amounts of water, probably
a small amount of organic material and some carbonate,
as indicated by the weight loss at high temperature
(decomposition of carbonated hydroxyapatite to hydroxyapatite and calcium oxide). Ostims contains about
40 wt% of water; the remainder is a carbonate-free
hydroxyapatite. BioOsss contains a small amount of
water but no detectable combustible material. The
inorganic phase is a carbonated hydroxyapatite. The
materials that still contain all or most of the organic
bone matrix (Kiel bone, natural bone, Tutoplasts) have
a similar composition with some water content (6–
10 wt%), some organic material (20–50 wt%) and
carbonated hydroxyapatite as mineral phase.
It is interesting to see that the carbonate content in the
bone-like materials (BioOsss, Kiel bone, Tutoplasts) is
highly variable. If we formally compute a weight ratio of
Ca5(PO4)3OH to CaCO3 in these samples, we obtain
values between 6 and 30. As the range in natural bone
samples is also highly variable (we found ratios from 13
to 37 in four bone samples [16]), we can conclude that
the identity with bone mineral is still present, even after
extensive chemical and moderate thermal treatment.
Fig. 5 shows representative SEM pictures that
illustrate the typical morphology of these classes of
materials. In Fig. 5a, Cerasorbs shows the granular
appearance of a sintered material with visible micropores at high magnification. In Fig. 5b, the calcined
bovine bone (Cerabones) has the interconnecting
porous structure of the original bone. In higher
magnification, primary crystallites of sintered hydroxyapatite are visible with particle sizes of a few
micrometers. In Fig. 5c, the chemically converted algae
structure of Algipores can be seen. The graded porosity
(resembling cortical and cancellous bone, but on a much
(a)
(b)
(c)
(d)
Fig. 5. SEM pictures of four representative bone graft materials. (a)
Cerasorbs, (b) Cerabones, (c) Algipores and (d) Tutoplasts
(bovine).
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993
Table 3
Summary of all data obtained for the different materials. The mechanical stability of granulates refers to their ability to retain a cm-sized threedimensional shape
Sample
Chemical composition
Crystallinity Morphology
Expected
biodegradability
Mechanical stability
BioResorbs
b-TCP, traces of calcium
pyrophosphate and a-TCP
b-TCP, traces of a-TCP and
HAP
b-TCP, traces of a-TCP and
HAP
b-TCP
High
Porous granulate
Moderate
Low
High
Porous granulate
Moderate
Low
High
Porous granulate
Moderate
Low
High
Porous granulate; drilled
porous blocks
Porous granulate
Moderate
Moderate
Low (granulate) to high
(blocks)
Low
Porous
Porous
Porous
Porous
Slow
Slow
Slow
Moderate
Low
High
High
Low
Paste
Porous granulate
Porous block (bone-like)
Fast
Fast
Fast
None
Low
High
Porous block (bone-like)
Fast
High
Porous block (bone-like)
Fast
High
Porous block (bone-like)
Fast
High
Porous block (bone-like)
Fast
High
ChronOSs
Ceross
Cerasorbs
Vitosss
PepGens
Endobons
Cerabones
Algipores
Ostims
BioOsss
Kiel bone
Callus bone
Tumor bone
Tutoplasts (bovine)
Tutoplasts (human)
b-TCP, traces of calcium
High
pyrophosphate and possibly
organic binder
HAP
High
HAP, traces of calcium oxide High
HAP, traces of calcium oxide High
Carbonated HAP, traces of
Moderate
organic binder (?)
HAP dispersed in water
Nano
Carbonated HAP, water
Nano
Carbonated HAP, water,
Nano
organic bone matrix
Carbonated HAP, water,
Nano
organic bone matrix
Carbonated HAP, water,
Nano
organic bone matrix
Carbonated HAP, traces of
Nano
OCP, water, organic bone matrix
Carbonated HAP, water,
Nano
organic bone matrix
smaller dimension) is due to the biological requirements
of the algae. At high magnification, we can see the
primary particles of a micrometer or less. In Fig. 5d, the
chemically treated bovine bone material Tutoplasts is
shown. As in Fig. 5b, we can see the interconnecting
macroporosity of bone; however, as this material was
not sintered, it still contains the collagen matrix. At high
magnification, we do not see sintered hydroxyapatite
but the fibrous structure of the original bone.
Table 3 summarises all structural and morphological
information in a concise way. It can be seen that these
materials strongly differ in their composition. It is also
clear the mere denomination ‘‘calcium phosphate
ceramics’’ is by no means sufficient to fully characterise
a material. With respect to biodegradability, it is
possible to make some reasonable predictions, based
on literature data. b-TCP ceramics are faster degradable
than HAP ceramics [21–23]. In addition, there is a
difference between sintered HAP ceramics and precipitated HAP ceramics, the former showing a very slow (if
any) biodegradation. If the crystallite size of the HAP
ceramics is very small (like in bone) and/or if there is
carbonate incorporated, the biodegradation is strongly
enhanced due to a higher solubility [22–26]. Even more
strongly, this applies to bone grafts that still contain the
collagen matrix. In these cases, usually a fast biode-
granulate
block (bone-like)
block (bone-like)
granulate
gradation is observed and a biological potency of the
incorporated bone matrix is postulated [7,27].
5. Conclusions
14 different bone graft materials were investigated,
and the results were compared to synthetic hydroxyapatite and natural bone samples (as reference for
autologous bone). Their composition and morphology is
strongly different, therefore the materials cover a wide
range of applications, ranging from permanent implants
to rapidly degradable implants with osteogenic potency.
Acknowledgements
This project was supported by the Fonds der
Chemischen Industrie (Frankfurt am Main, Germany).
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