Journal of Applied Biomaterials & Biomechanics 2005; Vol. 3 no. 1: 18-28
Bone tissue responses to Mg-incorporated
oxidized implants and machine-turned implants
in the rabbit femur
Y-T. SUL1, P. JOHANSSON1, B-S. CHANG2, E-S. BYON3, Y. JEONG3
Department of Biomaterials/Handicap Research, University of Göteborg, Göteborg - Sweden
Department of Periodontics, Kangnung National University, Kangnung - Korea
3
Surface Engineering Department, Korea Institute of Machinery and Materials, Changwon - Korea
1
2
ABSTRACT: Previous studies have demonstrated a significant improvement in the bone response to oxidized titanium implants.
Little is known about the effects of specific oxide properties on the bone tissue responses to titanium implants. This study investigated the bone tissue responses to magnesium (Mg)-incorporated oxidized titanium implants and machine-turned titanium implants in the rabbit femur. The oxidized implants were prepared using micro arc oxidation (MAO) methods. Surface oxide properties were characterized by using various surface analytic techniques, involving scanning electron microscopy (SEM)
equipped with energy dispersive spectrometer (EDS), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and
optical interferometry. Screw shaped titanium implants, 10 machine-turned implants (controls) and 10 Mg-incorporated implants (tests) were inserted in the femoral condyles of 10 New Zealand white rabbits. After a 6-week healing period, resonance
frequency analyses and removal torque measurements of the Mg-incorporated oxidized implants demonstrated significant improvements in implant integration with bone in comparison to machine-turned implants, p=0.007 and p=0.017, respectively.
Bone growth in the pores of the oxidized implants was probably incomplete at a follow-up of 6 weeks, as indicated by SEM and
EDS measurements. Mg-incorporated titanium implants significantly improved bone responses as compared with machineturned control implants. Considering the differences and similarities of the surface oxide properties of controls and test implants, the enhanced bone responses to Mg-incorporated implants could be explained by the Mg surface chemistry of the test implants. (Journal of Applied Biomaterials & Biomechanics 2005; 3: 18-28)
KEY WORDS: Oxidized titanium implant, Surface properties, Bone response, Magnesium surface chemistry, Resonance
frequency analysis, Removal torque test
Received 19/10/04; Revised 18/01/05; Accepted 25/02/05
INTRODUCTION
Novel types of osseointegrated implants have been
developed in conjunction with various surface processing technologies. Surface refinements can be
coupled to improve the clinical performance of titanium implants. In particular, topographical
changes of the implant surface have been widely investigated over the last 10 yrs and applied to a number of clinical implants, i.e. “rougher implants”. Despite the controversial claims in the literature associated with rough surfaces such as peri-implantitis
and corrosion resistance (1-3), the potential for
eliciting mechanical retention still warrants attention to rougher surfaces. Mechanical interlocking
through bone growth in surface irregularities and
biochemical bonding at the implant to bone interface are considered important for implant integration. The latter integration mechanism has inspired
various chemical modifications of titanium surfaces. These chemical modifications can be exemplified by sol-gel processing, ion implantation and
biomimetic approaches functionalizing adhesive
proteins and growth factors (4-9).
Our group has been investigating various types of
oxidized implants; oxide growth behavior in acid
1722-6899/018-11$15.00/0
© Società Italiana Biomateriali
Sul et al
and alkaline electrolytes (10) and various surface
oxide properties of the titanium implant, including
titanium oxides up to a few micrometers thick,
porous oxide structures with different pore sizes,
pore topography, porosity and pore density, different crystal structures and surface oxide chemistry
(11). Bone responses to oxidized implants were significantly improved in different animal and clinical
studies as compared to machine-turned implants
(12-23). However, little is known about the precise
oxide properties that give rise to improved bone responses. Sul et al recently reported on the significance of ion incorporation in titanium oxides such
as S, P, and Ca, respectively, and proposed two osseointegration action mechanisms of the oxidized
implants, i.e. mechanical interlocking via bone
growth in pores and biochemical bonding (17, 19,
23-25).
This study further investigates the role of the surface oxide chemistry in relation to bone responses. Magnesium (Mg) ion-incorporated implants
were prepared using micro arc oxidation (MAO)
methods. Surface oxide properties were characterized by using various surface analytic techniques, involving scanning electron microscopy
(SEM) equipped with energy dispersive spectrometer (EDS), X-ray diffractometry (XRD), X-ray
photoelectron spectroscopy (XPS) and optical interferometry. Bone tissue reactions were evaluated
by resonance frequency analyses and removal
torque measurements after a 6-week follow-up in
the rabbit femur. SEM and EDS analyses were performed to evaluate bone growth in the pores. Mg
ion movements were assessed with XPS on retrieved implants.
MATERIALS AND METHODS
Implant design and preparation
Screw shaped implants with a pitch-height of 0.5
mm, an outer diameter of 3 mm, a total length of
7.2 mm, a 3.2 mm square head and an inner threaded hole of 2 mm, were manufactured from 5 mm
rods of commercially pure titanium. Machineturned implants were used in the control group.
Test group implants were Mg ion-incorporated, oxidized implants (test Mg implants). The test Mg implants were prepared using the MAO process at
high forming voltages and current densities at galvanostatic mode in an Mg containing mixed electrolyte system. The electrochemical oxidation
method employed was as described in our previous
study (10, 11).
Surface characteristics of test magnesium implants and controls
Surface chemical analysis was investigated by XPS
(Escalab 250, VG Scientific Ltd). The XPS spectra
were recorded using normal Al Kα radiation
(1486.8 eV) with a probing beam size of 200 µm.
The outermost surface of the implants was etched
with Ar ion with an ion energy of 5 keV and a beam
current of 0.3 µA for 150 sec, corresponding to 2
nm in thickness, resulting in surface contaminant
removal. The surface oxide of the test Mg implants
and the controls consisted mainly of TiO2. XPS
survey spectrum of the test Mg implants revealed
the presence of the Mg elements, Ti, O, C and some
traces of P and S (Fig. 1). The relative atomic Mg
TABLE I - ATOMS DETECTED BY XPS MEASUREMENTS ON THE MACHINE-TURNED IMPLANTS (CONTROLS), THE
Mg-INCORPORATED OXIDIZED IMPLANTS (TESTS) AND RETRIEVED TEST IMPLANTS
Atoms
Control implants
Test implants
Retrieved test implants
Ti 2p
O 1s
Mg 2p
C 1s
S 2p
P 2p
Na 1s
N 1s
Ca 2p
Cl 2p
22.51
51.74
18.79 (22.12)
53.38 (58.25)
7.58 (9.33)
15.19 (6.49)
1.21 (0.81)
3.86 (3.0)
0.71 (3.33)
14.08 (18.09)
0 (1.15)
70.87 (60.05)
–
18.95
0.61
0.83
1.4
2.18
0.82
0.5
–
–
–
–
–
1.53 (2.85)
0.38 (1.65)
10.50 (6.17)
1.03 (4.32)
1.9 (2.38)
Figures in parentheses are the relative atomic concentrations after 150 sec of Ar+ sputter cleaning, corresponding to 4 nm
thick oxide
19
Bone tissue responses to Mg-incorporated oxidized implants and machine-turned implants in the rabbit femur
Fig. 1 - XPS survey spectra of the implants. a) asreceived surface of machine-turned implants,
b) as-received surface of
Mg implants, c) as-received surface of retrieved Mg implants.
Specimen was prepared
by cryofracture technique, d) Retrieved Mg
implants by unscrewing
(removal torque test) after sputter cleaning for
150 sec.
Fig. 2 - SEM images
show a machine-turned
control surface and a
porous test surface structure.
concentration was approximately 7.6% at the as-received surface and 9.3% after Ar+ sputter cleaning
for 150 sec; 15% of C at the as-received surface was
rapidly reduced after sputter cleaning. This could
indicate that C is a surface contaminant. Table I
summarizes the relative atomic concentrations at
the as-received surface and the Ar+ sputter-cleaned
surface. SEM micrographs in Figure 2 show the
porous surface structure of the test implants and
the groove characteristics of the machine-turned
20
orientation in the controls. An image analysis system (Image Inside, Focus Co, Ltd) was used for the
pore characteristics of the test implants. The mean
surface porosity was 23.7% (n = 3, sd = 0.1). The
pore size was ≤1.5 µm in diameter. The pore density (pore population/scanning area) was 3.25. The
mean oxide thickness was 3.4 µm (n = 15, sd = 0.6)
in the test Mg implants as measured with SEM (Fig.
3) on a cross-section view and <17 nm in the controls as measured with an auger electron spec-
Sul et al
troscopy (11, 23). The crystal structure was measured with low-angle XRD with a thin film collimator (X`Pert PRO-MNR, Philips Ltd) on the plate
type of the specimen. The step size was 0.02° between 15° and 70° of the measured scan. The spectra were recorded using Cu Kα radiation (0.154056
Å). XRD patterns showed a mixture of anatase and
rutile phases for the test Mg implants (Fig. 4) and
an amorphous phase for the controls. The surface
roughness measured with optical interferometry
(MicroXamTM) revealed an Sa (arithmetic average
height deviation) of 0.68 µm (± 0.2), Sdr (developed surface ratio, i.e. the ratio of the increment
of the interfacial area of a surface over the sampling area) of 26.3% (± 11.1), Sds (the number of
summits of a unit sampling area) of 0.12 µm–2
(± 0.04) for the test Mg implants and an Sa of 0.55
µm (0.21), Sdr of 10.6% (± 3.9), Sds of 0.09 µm–2
(± 0.04) for the controls.
~10 µm
10.00 µm
4.19 µm
3.70 µm
4.14 µm
8.51 µm
3.52 µm
4.50 µm
Fig. 3 - The oxide thickness in a cross-sectional view of the test
implant. Ni plating was performed before resin mounting.
Animals and surgical technique
Ten mature (mean weight of 2.8 kg) New Zealand
white rabbits were used in this study, which was
approved by the local animal ethics committee at
the University of Göteborg, Sweden. Each rabbit
received one test and one control implant in the
femur close to the condyle region. For surgery
the rabbits were anesthetized with intramuscular
injections of fentanyl and fluanison (Hypnorm
Vet, Janssen, Saunderton, UK) at a dose of 0.5 ml
per kg body weight and intraperitoneal injections
of diazepam (Valium, Roche, France) at a dose of
2.5 mg per rabbit. The skin and fascial layers were
opened and closed separately. The periosteal layer was gently pulled away from the surgical area
and was not resutured. During all surgical drilling
sequences, low rotary drill speeds (not exceeding
2000 rpm) and saline cooling were used. The rabbits were kept in separate cages and immediately
after surgery, they were allowed full weight-bearing. After a 6-week follow-up, the rabbits were sacrificed by intravenous Pentobarbitalum® (Apoteksbolaget, Uppsala, Sweden) injections.
Evaluations of the bone response
The 20 implants were evaluated with resonance
frequency measurements. Seven test implants and
seven control implants were removal torque tested. Three test implants and three control implants were retrieved and used for SEM and XPS
investigations. Histological and histomorphometric analyses were not performed because of the
limited animal number (n = 10). In fact, RTQ test,
Fig. 4 - XRD diffraction patterns on cp titanium plates abraded
by 800 grit SiC paper and oxidized in the same manner as the test
Mg screw implant (acceleration voltage of 35 kV and current of
25 mA). A refers to anatase phase and R to rutile phase.
histological and histomorphometric analysis
could not be performed on the same samples.
Resonance frequency measurements
RFA is a non-destructive technique to demonstrate the implant stability in terms of interfacial
stiffness (ISQ). The frequency response of the
system was measured by attaching the transducer, i.e. an L-shaped cantilever beam, to the
screw implant. The excitation signal was given
21
Bone tissue responses to Mg-incorporated oxidized implants and machine-turned implants in the rabbit femur
over a range of frequencies (typically, 5-15 ISQ
with a peak amplitude of 1 V) and the first flexural resonance measured (26).
were prepared with ultrasonic treatment to eliminate bone particles left on the implant surface.
Statistics
Removal torque tests
The removal torque instrument is electronic
equipment involving a strain gauge transducer
used for testing the implant stability (the peak
loosening torque, in Ncm) in the bone bed; and
therefore, can be regarded as a three dimensional (3D) test roughly reflecting the interfacial shear strength between bone tissue and the
implant (25, 27). This technique is routinely
used and well documented in our laboratories
(25-28). The device ensures a fixed rotation
rate in contrast to hand controlled devices to
eliminate “operator errors”, and it has been
shown to achieve high reproducibility and low
operator sensitivity. The static torque is applied
to the implant at a linear rate of 9.5 Ncm/s
(personal communication C-A Wannerskog, Detektor AB, Göteborg, Sweden).
We used a newly developed alignment table to
ensure that the rotation axis was kept in a
straight line between the transducer and the implant. This alignment table was designed to allow a 3D adjustment at the micrometer scale.
Statistical analyses were performed using the
Wilcoxon signed rank test. Differences were considered statistically significant at p<0.05, highly significant at p<0.01 and not significant at p>0.05.
RESULTS
Surface characteristics of the implant
The surface oxide properties of the implants used
prior to insertion in bone are described above.
Table II summarizes the surface oxide characteristics of the titanium implants used.
Resonance frequency measurements
The Mg-incorporated test implants demonstrated
highly significant resonance frequency values when
compared to the machine-turned control implants
(p = 0.005). The mean values of the RFA were 67.4 ISQ
(Sd = 1.0, range 66-69) for the test implants and 64.0
ISQ (Sd=1.4, range 62.5-66.5) for the controls (Fig. 5).
SEM and XPS measurements of the retrieved implants
Removal torque tests
Three test implants and three control implants
were retrieved and frozen in liquid nitrogen, followed by the cryofracture technique (29) to prepare specimens for SEM, EDS and XPS examinations. In addition, specimens for XPS examinations
The Mg-incorporated test implants revealed a significantly greater removal torque in comparison
with the machine-turned control implants (p =
0.017). The mean values of the removal torque
were 19.2 Ncm (Sd = 5.4; range 12-30 Ncm) for the
TABLE II - SURFACE OXIDE CHARACTERISTICS OF THE MACHINE-TURNED IMPLANTS (CONTROLS) AND THE
Mg-INCORPORATED OXIDIZED IMPLANTS (TESTS)
Oxide characteristics
Machine-turned implant
Mg-incorporated oxidized implant
Chemical composition
Mainly TiO2. Contaminant: C.
Morphology
Non-porous structure with
machine-turned grooves ≤10 µm
None
None
None
17 ± 6 nm
Amorphous
Sa 0.55 µm (0.21), Sdr 10.6%
(± 3.9), Sds 0.09 µm–2 (± 0.04)
Mainly TiO2 and Mg ≤9.3%.
Contaminant: C. Traces: P and S
Porous structure with a great
number of craters
≤1.5 µm
23.7% (± 0.1)
3.25
3400 ± 600 nm
Anatase + rutile
Sa 0.68 µm (± 0.2), Sdr 26.3%
(± 11.1), Sds 0.12 µm–2 (± 0.04)
Pore size
Porosity
Pore density
Oxide thickness
Crystal structure
Roughness
22
Sul et al
Fig. 5 - Mean resonance frequency values (ISQ) after a follow-up
of 6 weeks, indicating highly statistically significant differences
between machine-turned implants and Mg-incorporated oxidized
implants (p = 0.005).
Fig. 6 - Mean removal torque values (Ncm) after a follow-up of 6
weeks, indicating statistically significant differences between machine-turned implants and Mg-incorporated oxidized implants
(p = 0.017).
test implants and 10.1 Ncm (Sd = 3.2; range 7-16
Ncm) for the controls (Fig. 6).
at 168.05 to 169.5 eV. Table I summarizes the relative atomic concentrations detected by XPS measurements.
SEM analyses of the retrieved test implants
Scanning electron microscopy observations of the
Mg-incorporated implant retrieved after a 6-week
healing period, demonstrated that bone growth in
the porous structures was probably incomplete until
bone tissue first formed around the pores and spread
over the implant surface (Fig. 7). SEM pictures and
EDX analyses in Figure 8 clearly indicate that fracture
during the cryofracture process did not occur at the
interface of the bone and porous surface of the oxidized implant but, in general, appeared in the bone.
XPS measurements of magnesium-incorporated test
implants retrieved after a 6-week healing period
XPS survey spectrum of the Mg-incorporated test
implants retrieved from the bone bed additionally
showed Ca, N, Cl and Na (Fig. 9) when compared
to atoms detected in the test implants before implant insertion in the bone, including Ti, O, Mg, C,
P and S. After Ar+ sputtering for 150 sec, the Ca 2p
binding energy shifted ≈ at 347.35 to 346.65 eV.
There were chemical shifts in the binding energy of
N 1s ≈ at 400.2 to 398.95 eV, Cl 2p ≈ at 197.9 to
197.55 eV and no changes in the Na 1s binding energy ≈ at 1072.4 eV (Fig. 9). XPS analyses in Figure
10 on the retrieved test implant surfaces demonstrated chemical shifts in the binding energy of Mg
2p ≈ at 50.05 to 49.20 eV, O 1s ≈ at 529.70 to 530.55
eV, Ti 2p ≈ at 459.05 to 457.70 eV, C 1s ≈ at 284.30
to 283.70 eV, P 2p ≈ at 132.9 to 133.6 eV and S 2p ≈
DISCUSSION
Previous studies from our research group introduced chemically modified surface oxide of the titanium implant, i.e. S-, P- and Ca-incorporated oxide surfaces (17, 19, 23, 24). Ca cation-incorporated implants demonstrated greater bone response
than S or P anion-incorporated implants, as estimated by both biomechanical and histomorphometrical investigations. Mg cation of the test Mg implants were electrochemically incorporated in the
TiO2 matrix from an Mg containing mixed electrolyte system during the MAO process in the same
manner as previously described for Ca cations (19,
23). Therefore, from a surface modification technology point of view, the MAO process seems to be
ideal for the creation of modified oxide chemistry,
pore topography and the crystal structure of implant surfaces.
Which surface properties of oxidized implants that
play an important role for the bone response have
previously been addressed at our laboratories and
elsewhere (12, 13, 15, 16, 19-21, 23-25). Sul et al reported that the thickness, pore characteristic, crystal structure and chemical composition of the surface oxide are considered as surface properties that
could have an effect on the improved bone responses to the oxidized implants (15, 16, 19). More
recently, Sul conducted a comparative study of the
bone response to S-, P- and Ca-incorporated im23
Bone tissue responses to Mg-incorporated oxidized implants and machine-turned implants in the rabbit femur
a
b
c
d
Fig. 7 - SEM observations on retrieved test implants; Mg-incorporated
oxidized implant retrieved from bone using
cryofracture technique.
a) Bone tissue formed
and branched out the implant surface. b) Bone tissue further spread over
pores of oxidized implants. c) d) Bone tissue
is unlikely to go into the
pores before bone formation commences around
the marginal border of
pores. Therefore, immediately after bone formation
the porous structures of
the oxidized implants are
still visible, indicating
that the pores were not
completely filled with
bone tissue. e) Bone tissue
is about to grow into the
pores. f) Forefront of bone
tissue spreading over a
porous structure. Fr represents the fracture line
that occurred during the
cryofracture process (the
arrow head = the porous
oxide surface area of the
retrieved oxidized implant, the arrow = the tissue area surrounding a
pore of the oxidized implant surface, * = the
fractured area during the
cryofracture process).
*
e
f
plants (23). Those implants presented sharply distinguished surface chemistries, but rather similar
surface properties of porous structures and surface
roughness. Porous structures and surface chemistry, particularly Ca surface chemistry, have been
suggested as an explanation for the stronger and
faster bone response reported in Ca-incorporated
implants. Mechanical interlocking and biochemical
bonding at the bone to implant interface have been
proposed as the action mechanism for the enhanced osseointegration of oxidized implants.
24
However, in this study, mechanical interlocking via
bone growth in the pores of the oxidized implants
seems to be an unlikely reason for the improved
bone response since SEM (Fig. 7) and EDS analyzes
(Fig. 8) indicated only poor bone growth in and
through the porous structures of the Mg implants.
Although a great number of nano- and micro-fabricated implants have been investigated, the optimal
pore size for bone growth is known to be unclear.
Pore characteristics including pore size, porosity,
pore topography and pore density seem to have an
Sul et al
Fig. 8 - EDX analyses on three different locations of an arrow
head, arrow and * in Figure 7 indicate that mineralization has
not occurred at the tissue area surrounding a pore of the oxidized
implant surface (arrow head) and also at the porous oxide surface area of the retrieved oxidized implant (arrow), and that the
fractured area (*) is mature bone tissue (a, b and c represent the
chemical compositions of the areas indicated by an arrow head,
arrow and * in Figure 7, respectively).
effect on adhesive proteins, cellular responses and
bone growth (30-33). Bone growth into the pores is
most likely dependent not only on pore topography
but also on the implant materials used, the healing
period after implantation and the chemical properties of the implants. Pineda et al reported that pore
sizes of about 200 µm diameter promoted bone
growth in a rabbit model (34). However, the bigger
the pore size and porosity of the surface structure
are the mechanical properties will be adversely affected (35). Our study indicates that the completion of bone growth in a pore size ≤1.5 µm in diameter needs longer than a 6-week healing period.
The present experimental design had a limitation
in clearly revealing the effect of the crystal structure on the improved bone response. As suggested
in our previous studies (15), however, the crystal
structure of a mixture of anatase and rutile could in
part favor the improvement of the bone response.
The surface chemistry of the Mg titanate of the test
implants could explain the significant improve-
ments in implant stability and bonding strength in
this study. Mg in the most stable state appears as a
divalent cation. Mg2+ and Ca2+ are known to play essential roles in the binding interactions of the integrin superfamily of cell-surface receptors and the
ligand proteins such as fibronectin, vitronectin, fibrinogen and some cell-cell adhesion receptors (3638). Therefore, integrin-ligand interactions modulate cell anchorage, polarity, migration, proliferation and differentiation. Our XPS analyses results
(Fig. 9) indicated that the Mg ions of the test implants moved into the surrounding bone tissue during the 6-week healing period. In addition, Na, Cl
and Ca appeared on the outer surface layer of the
retrieved Mg implants. This could imply Mg ion
movements and ion exchange at the interface between the outer surface of the implant and the
body fluid and/or bone tissue. Chemical shifts of
binding energy occurred at all major surface atoms
of the retrieved test implants including Ti, O, Mg, P
and S (Fig. 9) when compared to non-inserted test
implants. Ca binding energy decreased on the retrieved test implants. A few previous studies have
shown interfacial ion exchange between body fluid/bone tissue and implant surface, presumably following chemical bonding.
In addition, the N binding energy at 400.2-400.60
eV suggests an organic matrix exists on the retrieved Mg implant surfaces. After ion sputtering
for 150 sec, the N binding energy shifted to 398.95
eV. This indicates the presence of NH3 groups (Fig.
10) (39) in peptide sequences of proteins surrounding the implants, probably including adhesive bone matrix proteins. These chemical shifts in
the binding energy of the chemicals mentioned
above could indicate a biochemical bonding between the Mg titanate of the test implant and the
surrounding bone tissue. Parise et al found that the
platelet receptor GP IIb-IIIa bound more strongly
to fibronectin in the presence of Mg2+ than in the
presence of Ca2+ (40). Zreiqat et al recently investigated the effect of Mg ions (Al2O3-Mg2+) on cell adhesion, integrin expression and intracellular signaling molecule activation (41). They reported an increase in cell adhesion, significantly enhanced levels of integrin receptors, signaling proteins and collagen type I as compared to native Al2O3. The findings of Parise et al and Zreiqat et al can be applied to
the interpretation of a biochemical bonding mechanism of Mg-incorporated titanium implants, suggested in our study. However, our study did not give solid evidence for biochemical bonding. Further investigations are needed focusing on the roles of the Mg
titanate surface chemistry and for the better understanding of the chemical bonding taking place.
25
Fig. 9 - XPS high resolution
of the elements, Ca, N, Cl
and Na that were not detected on the as-received test
surface before implant insertion, but appeared on the
retrieved test implants.
Intensity (arb unit)
Intensity (arb unit)
Bone tissue responses to Mg-incorporated oxidized implants and machine-turned implants in the rabbit femur
Binding energy (eV)
Intensity (arb unit)
Intensity (arb unit)
Binding energy (eV)
Binding energy (eV)
Binding energy (eV)
Binding energy (eV)
Binding energy (eV)
Intensity (arb unit)
Intensity (arb unit)
Intensity (arb unit)
Binding energy (eV)
Intensity (arb unit)
Intensity (arb unit)
Intensity (arb unit)
Binding energy (eV)
Binding energy (eV)
Binding energy (eV)
Fig. 10 - Comparisons of XPS spectra at Mg 2p, O 1s, Ti 2p, C 1s, P 2p and S 2p between the as-received test surface before implant
insertion and the retrieved test implant surface.
26
Sul et al
CONCLUSIONS
Considering the differences and similarities in the
surface oxide properties of the controls and the test
implants, the enhanced bone responses to Mg-incorporated implants could be explained by the Mg
surface chemistry of the test implants. This study
concludes that biochemical bonding can occur
faster than micropore-mediated mechanical interlocking, which occurs later than a 6-week healing
period in rabbit bone (Sul et al in preparation).
ACKNOWLEDGEMENTS
This study was supported by research grant of the Biochallenge Project from the Ministry of Science and Technology
(MOST) of Korea and MediSciTec Inc (Korea).
The authors wish to thank Dr. Mi-Sook Won in Korea
Basic Science Institute for her technical support in
the XPS analyses.
Address for correspondence:
Dr. Young-Taeg Sul, PhD
Department of Biomaterials/Handicap Research
Institute for Surgical Sciences
Göteborg University, Box 412,
SE-405 30 Göteborg - Sweden
[email protected]
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