Effects of implant geometry, surface properties, and tgf-β1 on peri-implant bone response: an experimental study in goats
Effects of implant geometry, surface
properties, and TGF-b1 on peri-implant
J. J. J. P. van den BeuckenP. H. M. Spauwen
bone response: an experimental study
Authors' affiliations:
Key words: calcium phosphate coating, electrostatic spray deposition, goat study, implant
C. Schouten, G. J. Meijer, J. J. J. P. van den Beucken,
J. A. Jansen, Department of Periodontology &Biomaterials, Radboud University NijmegenMedical Center, Nijmegen, The Netherlands
P. H. M. Spauwen, Department of Plastic &
Objectives: Despite the high success rates in implantology, the desire to use oral implants in
Reconstructive Surgery, Radboud UniversityNijmegen Medical Center, Nijmegen, The
more challenging clinical situations drives the need for continuing refinements in implant
design and surface properties. In the present study, the effect of implant geometry on
Correspondence to:
implant bone response was evaluated using two geometrically different implant types, i.e.
screw type (St) and push-in type(Pi). Furthermore, the potential beneficial effect of an
Department of Periodontology & BiomaterialsNijmegen Medical Center Radboud University
electrosprayed calcium phosphate (CaP) coating, either or not enriched with the
osteoinductive growth factor TGF-b1, on the osteogenic response was examined.
Material and methods: A total of 54 implants, divided into six groups (n ¼ 9), were inserted
The NetherlandsTel.: þ 31 24 3614006
into the femoral condyles of nine goats. After an implantation period of 12 weeks, retrieved
Fax: þ 31 24 3614657
specimens were evaluated histologically and histomorphometrically. Measurements were
statistically evaluated using SPSS 14.0 and analyzed using a linear regression model.
Results: With respect to implant design, St-implants showed an overall superior biological
healing response compared with Pi-implants. Considering surface properties, the deposition
of an electrosprayed CaP (2–3 mm) coating onto implants significantly increased the amount of
bone–implant contact for both implant types. Additional enrichment of the CaP coating with
the osteoinductive growth factor TGF-b1 did not significantly affect peri-implant bone
Conclusions: The results of this study indicate that a substantial improvement of the
osteogenic response to titanium implants can be achieved by the deposition of an
electrosprayed CaP coating. The enrichment of the coating with 1 mg TGF-b1 has only a
marginal effect.
For decades, an uneventful healing period for
et al. 1994; Testori et al. 2002; Del Fabbro
several months has been advocated for oral
et al. 2006), optimization of the initial bone-
implants to avoid fibrous tissue formation,
healing response after implant placement is
which should result in an appropriate fixa-
still an important issue. In addition, the
tion of the implant within the native bone
desire to use oral implants in more challen-
tissue (Adell et al. 1981). As during this
ging clinical situations drives the need for
Date:Accepted 29 September 2008
healing period the implants should be pre-
continuing refinements in implant design,
vented from any form of loading, patients
surface characteristics, and optimization of
To cite this article:Schouten C, Meijer GJ, van den Beucken JJJP, Spauwen
experience this ‘waiting period' as very in-
the biological healing response following
PHM, Jansen JA. Effects of implant geometry, surfaceproperties and TGF-b1 on peri-implant bone response:
convenient (Gapski et al. 2003). Therefore,
implant placement (Davies 2003).
an experimental study in goats.
despite the high clinical success rates of oral
Over the last few decades, many differ-
Clin. Oral Impl. Res. 20, 2009; 421–429.
doi: 10.1111/j.1600-0501.2008.01657.x
implants (Albrektsson et al. 1988; Buser
ent implant designs have been introduced
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
to optimize the anchorage of an implant in
may result in coating delamination and
bone tissue, i.e. the rapid achievement and
fragmentation, thus influencing the long-
maintenance of direct bone–implant contact
term stability of the implants (Sun et al.
(Pilliar et al. 1991). Implant designs range
2001). Moreover, the crystallinity, composi-
from threaded to non-threaded, cylindrical or
tion, and thickness of the coatings are not
conical, either or not combined with addi-
uniform. Using the magnetron sputter tech-
tional features, such as vents, grooves, in-
nique, thinner (o5 mm), more dense and
dentations, or perforations (Siegele & Soltesz
adherent coatings can be obtained (Jansen
1989; Misch 1999; Sykaras et al. 2000;
et al. 1993), but it is still challenging to vary
Steigenga et al. 2003). Despite the available
the coating composition. These problems
data on the effect of single implant designs,
can be overcome using the Electrostatic
the number of studies that directly compare
Spray Deposition (ESD) technique, which
different implant geometries is limited.
is a simple and versatile technique that
In addition to implant design, implant
allows deposition of thin (2–3 mm) CaP
surface properties are an important factor
coatings with a wide variety of chemical
Fig. 1. Representation of implant designs used in this
in the biological healing response. Conse-
(Leeuwenburgh et al. 2004, 2005) and
study: Screw type (St; left) and Push-in (Pi; right).
quently, surface modifications represent a
tool to enhance the biological response into
burgh et al. 2005, 2006).
a desired direction. The main conse-
Bone-healing responses can be further
and with a smooth surface (Fig. 1) were
quences of the available surface modifica-
stimulated using appropriate growth factors
provided by Dyna Dental Engineering BV
tion techniques can be reduced to effects on
(Fischer et al. 2003). Among these factors,
(Bergen op Zoom, the Netherlands):
surface topography (roughness or texture) or
members of the TGF-b superfamily appear
surface chemistry (or a combination thereof)
to play the most critical role in bone heal-
4.2 mm; length: 10 mm)
(Puleo & Thomas 2006). It has been claimed
ing (Gombotz et al. 1993). For example,
Cylindrical, Pi-implant with grooves
that a certain degree of roughness leads to an
TGF-b1 has been shown to stimulate bone
(diameter: 3.6 mm; length: 10 mm)
increased mechanical stability through sur-
healing in several animal models (Joyce
face enlargement and mechanical interlock-
et al. 1990; Beck et al. 1998). Moreover,
Recombinant human TGF-b1 was ob-
ing with the surrounding bone (Shalabi et al.
previous studies have reported on the abi-
tained from R&D Systems Inc. (Minneapo-
2006; Duyck et al. 2007). In addition, some
lity of TGF-b1 to enhance bone healing
lis, MN, USA). Fluorochromes Alizarin
studies indicate that rougher surfaces in-
around ceramic-coated implants in un-
(Alizarin Complexon dehydrate), Calcein
crease the degree and rate of peri-implant
loaded gap-healing models (Sumner et al.
(Fluorexon), and Tetracycline were acquired
bone formation (Puleo & Thomas 2006).
1995; Lind et al. 1996a, 1996b, 2001).
from Acros Organics (Geel, Belgium).
Regarding surface chemistry, beneficial
In view of the described effects of im-
effects on bone response have been ascribed
plant design, surface properties, and enrich-
to the deposition of ceramic materials, such
ment with biologically active factors, the
Electrostatic spray deposition (ESD) process
as calcium phosphates (CaP) (Jansen et al.
present study aimed at evaluating these
Before CaP coating deposition, implants
1991; Dorozhkin & Epple 2002) and bio-
parameters in a comparative study design.
were cleansed ultrasonically in nitric acid
glass (Turunen et al. 1998; Wheeler et al.
Therefore, two geometrically different den-
10% (15 min), acetone (15 min), and etha-
2001). These so-called ‘bioactive' materials
tal implants [screw type (St) and push-in
nol (15 min) successively. For CaP coating
have the ability to bond bone directly, with-
type(Pi)] were used in an implantation study
deposition, a vertical ESD setup (Advanced
out an intervening layer of soft tissue,
in goats. Additionally, these implants were
Surface Technology, Bleiswijk, the Nether-
thereby making them suitable as coatings
modified using an electrosprayed CaP coat-
lands) was used, as described previously by
onto bone-anchored implants (Ducheyne
ing, either enriched or not with the osteoin-
Leeuwenburgh et al. (2003). In brief, the
et al. 1992; Dorozhkin & Epple 2002).
ductive growth factor TGF-b1. Implants
basic principle of ESD is the generation of a
Various techniques have been used to deposit
were inserted into the trabecular bone at
so-called electrospray of organic solutions
CaP coatings onto an implant surface,
the medial side of both femoral condyles
containing the inorganic precursors Ca and
among which plasma spraying and mag-
for 12 weeks. Evaluation consisted of quali-
P. This is accomplished by pumping this
netron sputtering are the most widely used.
tative (histology and fluorochrome labeling)
solvent through a nozzle, which is con-
Although the osteoconductive and bone-
as well as quantitative (histomorphometry)
nected to a high-voltage supply. As a result
bonding behavior of plasma-sprayed and
analyses of the peri-implant bone response.
of the applied potential difference, a spray
magnetron sputter coatings has been con-
consisting of charged, micron-sized drop-
firmed by numerous studies (Jansen et al.
lets is formed, which are attracted towards
1993; Dhert 1994; Hulshoff & Jansen 1997;
Material and methods
a grounded and heated substrate. Conse-
Lacefield 1998, 1999; Geesink 2002), there
quently, the droplets impinge onto the
are still some important limitations related
heated substrate, where they lose their
to these techniques. Plasma-sprayed coat-
Prototypes of two geometrically different
charge. After complete solvent evapora-
ings are relatively thick (430 mm), which
oral implants, made of Ti-6AL-4V alloy,
tion, a thin layer (2–3 mm) consisting of
422 Clin. Oral Impl. Res. 20, 2009 / 421–429
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
the inorganic product is left on the sub-
Pi þ CaP þ TGF-b1 (Push-in type with
strate surface.
a CaP coating loaded with TGF-b1).
In this study, implants were coated in
three runs (in turns of 120
Sterility was obtained through autocla-
each, at a substrate holder temperature
vation of non-coated and CaP-coated im-
plants. TGF-b1 enrichment of CaP-coated
1C, a nozzle-to-substrate distance
of 20 mm, and a precursor liquid flow rate
implants was performed after autoclavation
of 2.0 ml/h. Coatings were prepared using
under aseptic conditions.
precursor solutions with a Ca/P ratio of 1.8(Ca(NO3)2 4H2O and H3PO4 were precur-
Surgical procedure
sors for Ca and P, respectively). Subse-
All in vivo work was conducted in accor-
quently, all coated implants were subjected
dance with ISO standards, and protocols of
to an additional heat treatment for 2 h at
the University Medical Center, Nijmegen,
Fig. 2. Location of implant sites in the medial femoral
1C in order to transform the amorphous
the Netherlands. National guidelines for
condyle. The black bars represent the implants.
coatings into crystalline carbonated hydro-
the care and use of laboratory animals were
xyapatite (CHA) coatings (Siebers et al.
observed, and approval of the Experimental
2007). The morphology of the CaP coatings
Animal Ethical Committee was obtained.
Table 1. Scheme for subcutaneous fluoro-
was characterized using scanning electron
A total of 54 implants (nine implants of
chrome administration at timed intervals
microscopy (SEM, Jeol, SEM6310, Tokyo,
each experimental group; n ¼ 9) were im-
Fluorochrome Color
Japan). In addition, X-ray diffraction (XRD)
planted into nine female Saanen goats (2–4
using a thin-film Philips X-ray diffrac-
years of age), with a mean body weight of
tometer (PW3710, Almelo, the Nether-
about 50–60 kg. Surgery was performed
lands) and Fourier Transform Infrared
under general inhalation anesthesia and
Spectrometry (FTIR; Perkin Elmer Instru-
sterile conditions. To reduce the peri-
ments, Zoetermeer, the Netherlands) were
operative infection risk, the prophylactic
used in order to characterize the crystal
antibiotic Albipen was administered sub-
structure and the molecular structure of
cutaneously (Albipen 15%, 3 ml/50 kg pre-
the deposited coatings, respectively.
operative and Albipen LA, 7.5 ml/50 kg for
three holes were made on the medial side of
3 days post-operative, Intervet BV, Boxm-
the condyle (proximal, medial, and distalwith an interimplant distance of 1 cm).
eer, the Netherlands). Anesthesia was
For growth factor loading, TGF-b1 was
initiated by an intravenous injection of
After preparation, the holes were irrigated
dissolved in sterile 4 mM HCl containing
(AUV Wholesale, Cuijk,
and the implants were inserted. In each
1 mg/ml bovine serum albumin (BSA;
the Netherlands). Subsequently, the goats
femur, three implant sites were located,
Sigma Aldrich, Zwijndrecht, the Nether-
were intubated and connected to an inhala-
resulting in six sites per goat (Fig. 2). To
lands). Administration was achieved by
tion ventilator with a constant volume of a
ensure complete randomization, the im-
direct adsorption of the growth factor onto
mixture of nitrous oxide, isoflurane, and
plants were placed according to a balanced
the CaP-coated implants. Aseptic condi-
oxygen. Before the insertion of the im-
split-plot design. However, to avoid cross-
tions were maintained throughout the
plants, each animal was immobilized on
over effects, all implants containing TGF-
adsorption process. A volume of 6 ml of
its back and the hind limbs were shaved,
b1 were grouped together and placed in left
the HCl/BSA solution (containing 1.0 mg
washed, and disinfected with povidone–
femurs only. After insertion of the im-
TGF-b1) was pipetted onto each implant.
iodine. For implantation of the implant in
plants, the soft tissues were closed in
After loading, implants were immediately
the femur, a longitudinal incision was
separate layers, and the skin was closed
made on the medial surface of the left and
transcutaneously using resorbable Vicryl
1C for 1 h, and placed in a
24-well plate for overnight lyophilization.
the right femur. Subsequently, landmarks
4 0 sutures (Ethicon Products, Amers-
were placed in the femoral condyle, and a
foort, the Netherlands). To reduce pain
radiographic image was made to localize
after surgery, all goats received Finadyne
Experimental animal groups
the trabecular bone. After exposure of the
(AUV Wholesale, Cuijk, the Netherlands)
In the animal study, a total of six different
femoral condyle, a 2 mm pilot hole was
for 2 days postoperatively. Postoperative
experimental groups were used:
drilled, which was gradually widened with
radiographs were conducted to check
1. St (Screw type), non-coated;
drills of increasing size until the final
implant placement.
2. St þ CaP (Screw type with a CaP
diameter was reached. The final drill, For
dynamics of bone growth, four goats re-
both the St and the Pi implants had a
ceived sequential fluorochrome labels at 1,
3. St þ CaP þ TGF-b1 (Screw type with a
diameter of 4 mm. The bone defect pre-
6, 9, and 11 weeks postoperatively (Table 1).
CaP coating loaded with TGF-b1);
paration was performed with a gentle sur-
All labels were administered subcuta-
4. Pi (Push-in type), non-coated;
gical technique, using low rotational drill
5. Pi þ CaP (Push-in type with a CaP
speeds (800–1200 rpm) and continuous
At 3 months postimplantation, euthanasia
external cooling with saline. In this way,
was performed with an overdose of
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
423 Clin. Oral Impl. Res. 20, 2009 / 421–429
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
Nembutal , and the implants with sur-
the implant: for the St-implant, starting at
rounding tissue were retrieved for histolo-
the first coronal screw thread, and for the Pi-
gical evaluation.
implant, starting at the beginning of the firstconcave thread (total standardized distance
of interest of 4000 mm).
After the animals were sacrificed, thefemoral condyles were retrieved, excess
Fluorochrome labeling
tissue was removed, and, using a diamond
For fluorochrome labeling analysis, a
circular saw, the condyles were divided
reflectant fluorescence microscope was
into smaller specimens suitable for histo-
used (Leica Microsystems AG). In addi-
logical processing. Finally, each specimen
tion, a Zeiss filter No. 05, consisting of a
contained only one implant with surround-
395–440 nm band-pass excitation filter,
Fig. 3. Scanning electron micrograph of the porous
ing bone. Subsequently, the tissue blocks
was used for visualization of the different
CaP coating as deposited using electrostatic spray
were fixed in 10% neutral-buffered forma-
deposition (ESD).
lin solution, dehydrated in a graded seriesof ethanol (70–100%), washed with acet-
Statistical analysis
one, and embedded in methyl methacrylate
Measurements were statistically evaluated
retrieved and used for histological and
for 4 weeks. After polymerization, non-
using SPSS 14.0 (SPSS Inc., Chicago, IL,
USA). Data obtained with histomorphome-
(10–20 mm) of the implants were prepared
try regarding bone–implant contact were
implants implants implants
(at least three of each implant), using a
analyzed using a linear regression model.
retrieved used for
modified sawing microtome technique
The dependent variable was represented by
(van der Lubbe et al. 1988), and stained
‘bone contact,' whereas the independent
with methylene blue and basic fuchsin.
variables were represented by ‘implant
Specimens from the four goats that
design', ‘presence of CaP,' and ‘presence
received fluorochromes were processed
of TGF-b1.' Using this model, the effect of
to obtain both unstained and stained
the independent variables on bone–implant
contact could be evaluated. The signifi-
cance level was set at a probability (P) value
nDuring implantation one St þ CaP þ TGF-b1
smaller than 0.05.
implant was lost, and replaced by one
To evaluate the trabecular bone response to
wDuring explantation one non-coated
the implants, histological as well as histo-
Pi-implant could not be retrieved.
zDuring histological preparation one
morphometrical analyses were performed.
Coating characterization
non-coated St-implant, one St þ CaP þ TGF-b1,
Histological evaluation using a light micro-
SEM observations showed a uniform sur-
one Pi þ CaP, and one Pi þ CaP þ TGF-b1
scope DMRD (Leica Microsystems AG,
face coverage of the implant. The electro-
implant were damaged.
Wetzlar, Germany) consisted of a concise
sprayed CaP coatings revealed a porous,
description of the observed tissues reaction,
reticular surface morphology (Fig. 3). Heat
including the structure and arrangement of
treatment increased coating crystallinity
number of implants placed, retrieved after
cells, implant, and tissue–implant inter-
and yielded in a CHA structure as con-
implantation, and included in the histolo-
face. In addition, a computer-based image
firmed with XRD and FTIR (data not
gical and histomorphometrical analyses.
analysis technique (LEICA QWIN PRO-
shown). Additionally, XRD measurements
Of the 54 installed implants, a total of 53
IMAGE analysis software; Leica Imaging
showed reflection peaks of TiO
implants could be retrieved. One implant
Systems, Cambridge, UK) was used for
was not found during retrieval. Throughout
1 2y for heat-treated CaP
histomorphometrical evaluation. The quan-
coatings, which were absent in non-heat-
the histological processing, five implants
titative measurement was performed for
treated CaP coatings. The coatings were
were damaged, and hence not included for
three different sections per implant, on
crack free after the heat-treatment at
analyses. A total of 48 implants were used
each side of the 2D histological image. The
for analyses.
average of these six measurements was usedfor statistical analysis. The quantitative
Descriptive histological evaluation
parameter assessed was the bone–implant
Light microscopic examination of the
contact (at magnification 25). Therefore,
All nine goats remained in good health
the amount of bone contact was defined as
during the experimental period without
sections of the implants and its surround-
the percentage of implant length at which
any postoperative wound-healing compli-
ing tissue demonstrated that one of the
there is direct bone-to-implant contact with-
cations. At sacrifice, no signs of inflamma-
implants (non-coated Pi) was inserted
out intervening soft tissue layers. Measure-
tion or adverse tissue reaction could be seen
very close to the growth plate cartilage,
ments were performed along the length of
around the implants. Table 2 depicts the
but no contact between the implant and
424 Clin. Oral Impl. Res. 20, 2009 / 421–429
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
the growth plate was seen. Also, for an-other implant (St þ CaP þ TGF-b1), in-flammatory
the implant surface. Generally, in allsections, bone apposition, bone remodel-ing, and ingrowth of newly formedbone into the threads of the implantswere observed.
In all St-implants, except for one, a close
contact between the implant and surround-ing bone was observed. The screw threadswere almost completely filled with bone(Fig. 4, St-implants), but around one non-coated St-implant, an intervening fibroustissue layer was present at the crestal areaof the implant. In the sections of four
Fig. 4. Representative histological sections of Screw-type (St) and Push-in (Pi) implants after 12 weeks of
Pi-implants (three non-coated, and one
implantation in the femoral condyles of goats.
CaP coated), a gap was observed betweenthe surrounding bone and the implant sur-face (Fig. 4, Pi-implants), resulting in noimplant–bone contact at all. In all other Pi-implants a close bone-to-implant contactwas observed.
For all St- and Pi-implants, except for
one, the CaP-coated equivalents, whetheror not enriched with TGF-b1, showeda close bone-to-implant contact (Fig. 4,CaP coated implants). In these sections,the presence of bone on top of the threadand conducting over the implant surfaceinto the threads was observed.
Fig. 5. Fluorescence microscopy images of histological sections of fluorochrome-administered experimentalanimals. Colors indicate bone formation at 1 (blue; calcein blue), 6 (red; alizarin-complexon), 9 (green; calceingreen), and 11 (yellow; tetracycline) weeks post-implantation.
Fluorescence microscopyConsecutive fluorochrome markers, laiddown in the form of bands, were observedaround the implants in the sequenceof their administration (Fig. 5a and b).
In contrast to the labels, alizarin com-plexon (red), calcein (green), and tetracy-cline (yellow), the presence of the calceinblue label, administered 1 week afterimplantation, could not be clearly identi-fied.
Detailed observation of the images
showed the yellow line to be very close tothe implant surface and bone marrowspaces in the trabecular bone, and the greenand red lines more towards the peripheralareas (away from the implant surface) withabout equal distances between the lines.
Fig. 6. Fluorescence microscopy images of histological sections of fluorochrome-administered experimental
This band formation was absent in images
animals. The color indicates bone formation at 9 weeks post-implantation (green; calcein green). Images
of the non-coated groups.
indicate bone formation predominantly in the implant vicinity.
Fluorochromes in the non-coated groups
of both implant types, i.e. St and Pi,showed a less intense fluorescence signal
TGF-b1 or not (Fig. 6a and b). In general,
a more pronounced signal was seen at sites
The results of the bone–implant contact
groups, i.e. CaP coated, enriched with
where new bone was formed.
measurements and the outcome of the
2009 The Authors. Journal compilation c
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425 Clin. Oral Impl. Res. 20, 2009 / 421–429
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
roborates published data of other experi-ments, in which different animal modelswere used (Steigenga et al. 2003; Watzaket al. 2005). An explanation for the higherimplant–bone contact for St-implants isthat, relative to their length, St-implantsoffer the surrounding bone a larger surfacearea compared with Pi-implants. Moreover,the manufacturer's recommendations forinsertion of the St-implants actually involvescrewing implants into an undersized defect,whereas the advice for Pi-implants is to pushthe implants into an oversized defect. Con-sequently, the placement of St-implants isassociated with shear forces at the interface,
Fig. 7. Results of histomorphometric analyses of Screw-type (St) and Push-in (Pi) implants in femoral condyles
hence loosening small bone fragments.
of goats. Bone-implant contact of St- and Pi-implants after 12 weeks of implantation is displayed for thedifferent experimental groups. Bars represent the mean þ standard deviation. No interaction between the
These bone fragments are likely to be
experimental variables was found. Significantly higher bone implant contact for St-implants compared with Pi-
pressed in between the trabecular voids and
implants. nSignificantly different compared with non-coated controls.
in between the screw threads during implantplacement, enhancing new bone formation(Shalabi et al. 2006). In addition, during
Table 3. Bone contact percentages and statistical testing of the experimental variables
implant placement, a degree of compression
Bone-implant contact
95% Confidence Interval
will take place along the implant–bone inter-face, which further enhances implant
stability (O'Sullivan et al. 2004). When
such an undersized approach is used for
Implant design (Pi ¼ 1, St ¼ 0)
CaP (with ¼ 1, without ¼ 0)
cylindrical Pi-implants, there may be an
TGF-b1 (with ¼ 1, without ¼ 0)
increased risk of (i) failing to place the
implant fully into the drill hole and (ii)
Indicates statistically significant effect (Po0.05).
CaP, calcium phosphate; TGF-b1, transforming growth factor-b1.
detrimental effects of bone tissue compres-sion, potentially causing local cellular da-mage, resulting in cell death, necrosis, and
statistical analyses are depicted in Fig. 7
The results of this study showed a signifi-
ultimately bone resorption (O'Sullivan et al.
and Table 3, respectively. Considering
cant effect on the bone-healing response
2004). Because of the visco-elastic properties
geometry, a significantly higher (12.5%)
of both implant geometry and CaP
of bone, an oversized bone cavity is always
bone–implant contact was observed for
coating, whereas additional enrichment of
drilled for cylindrical implants, implicating
St-implants compared with Pi-implants
CaP-coated implants with TGF-b1 did
less primary stability as compared with
(P ¼ 0.004). Furthermore, surface modifi-
not further enhance peri-implant bone
To improve bone–implant contact, bio-
coating showed a significantly higher
A prerequisite for successful orthopedic
active materials, such as CaP ceramics,
(19.7%) bone contact (Po0.001) compared
and dental implant placement is to obtain
have been used successfully. These materials
with their non-coated equivalents. The
a good primary stability of the implant in the
are characterized by their potential to form a
enrichment of CaP-coated implants with
surrounding bone (Albrektsson et al. 1981).
very tight, chemical bond with the surround-
TGF-b1, however, was not statistically
The establishment of such a mechanically
ing bone, i.e. ‘bone–bonding' (Ducheyne
significant (8.0%; P ¼ 0.147) compared
stable interface prevents the development
et al. 1992). Because of their favorable bio-
with CaP-coated implants.
of an intervening layer of fibrous tissue
logical behavior, bulk CaP ceramics have
(Shalabi et al. 2006). In view of the currently
been widely used in the orthopedic and
available implant systems, it needs to be
dental field. As bulk materials, however,
emphasized that the degree of primary
the mechanical properties of CaP ceramics
stability, besides bone quality, largely
are too weak, limiting their use in load-
The aim of this study was to evaluate
depends on implant design and insertion
bearing situations. Consequently, CaPs are
the effect of implant geometry on bone-
modality. For this reason, the current study
applied as coatings onto mechanically strong
healing responses in an in vivo goat
included two geometrically different implant
(metallic) implants. Numerous studies have
femoral condyle model. Furthermore, the
designs (St; Pi). With respect to implant
already confirmed the osteoconductive and
potential beneficial effect of an electro-
geometry, the results of this study indicate
bone–bonding behavior of CaP coatings (Jan-
sprayed CaP coating, enriched or not with
that bone–implant contact is superior for
sen et al. 1991; Hulshoff & Jansen 1997).
TGF-b1, on bone healing was evaluated.
St- over Pi-implants. This observation cor-
Similar positive data were obtained in an
426 Clin. Oral Impl. Res. 20, 2009 / 421–429
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
animal gap study, showing that gaps of
the combination of TGF-b1 with a non-
phate-coated implants. Loading an electro-
1 mm can only be bridged by bone if a
coated implant was not included. It should
sprayed b-tricalcium phosphate coating with
CaP coating is applied, whereas uncoated
be realized that most growth factors, includ-
TGF-b1 also resulted in a burst release of
implants demonstrated no bone contact at all
ing TGF-b1, are very expensive. Only a
490% (Siebers et al. 2006). Analogous to
(Clemens et al. 1997).
significant extra effect, beyond the effect of
this relatively fast and almost complete in
Various deposition methods have been
a CaP coating alone, may value these high
vitro release of TGF-b1, the release in the
proposed to apply CaP coatings onto im-
costs. To prove such an effect, only the
current study may have resulted in subopti-
plants, among which plasma spraying and
combination of CaP-coated implants and
mal amounts of TGF-b1 both spatially and
magnetron sputtering are the most widely
TGF-b1 was selected. Over the last decade,
temporarily. Therefore, the need for a slow
used. A major drawback of both coating
several studies have been performed to eva-
and more gradual release still exists and has
techniques is the lack of control over the
luate the effects of TGF-b1 in vitro and in
to be investigated. A possible solution can be
final coating composition and morphology.
vivo, which obtained rather mixed results.
found by the incorporation of the growth
Consequently, promising CaP phases, like
For example, 2 mg TGF-b1 applied in a 3%
factor into the carrier material, as proposed
carbonate apatite, which comprise a chemi-
methylcellulose gel was able to regenerate a
by Liu et al. (2004), who incorporated BMP-
cal composition closest to bone and teeth,
critical-size defect in a rabbit skull within 28
2 during the deposition of a biomimetic
cannot be deposited (Jansen et al. 1993; De
days; 0.1- and 0.4 mg showed less bone for-
CaP coating onto a titanium implant by
Groot et al. 1994; Leeuwenburgh et al.
mation (Beck et al. 1991). In a non-critical-
co-precipitation. More research is needed to
2004). To overcome these problems, the
size rabbit skull model, the combination of a
find a suitable technique for the incorpora-
ESD technique was used in the present
Ti fiber mesh implant with 2 mg TGF-b1
tion of biologically active compounds in
study to deposit carbonated apatitic CaP
induced orthotopic bone formation (Vehof
order to create a more gradual release, or an
coatings. Leeuwenburgh et al. (2003) al-
et al. 2002). Further, in a canine model,
optimized combination of a burst and sus-
ready confirmed the feasibility of the ESD
porous coated implants showed a more
tained release profile.
technique for the deposition of thin CaP
effective bone ingrowth with a dose
In summary, this study demonstrates
coatings with a defined surface morphology,
of 120 mg TGF-b1, compared with a dose of
that the peri-implant healing response fol-
by varying the deposition parameters. More-
335 mg TGF-b1 (Sumner et al. 1995). In the
lowing implant placement is dependent on
over, by varying the Ca/P precursor solution
present study, no significant effects of TGF-
both implant design and surface modifica-
ratio, and applying an additional heat treat-
b1 on bone healing were observed. The
tion. With respect to implant design,
ment, this technique is able to control the
reason for this lack of beneficial effects of
St-implants show an overall better bio-
coating composition and crystallinity (Leeu-
TGF-b1 remains unclear. A possible expla-
logical healing response over Pi implants.
wenburgh et al. 2004). Despite the im-
nation may be the dose–response effect for
Considering surface modification, the de-
proved mechanical strength and interfacial
TGF-b1. However, as shown in the available
position of an electrosprayed CaP coating
adhesion, no data are available yet that can
literature, higher doses do not necessarily
onto implants significantly increased the
provide information regarding whether the
generate more bone formation, as there is an
amount of bone–implant contact. Further,
coating remains stable after implantation.
optimum dose. Therefore, in the present
enrichment of the CaP coating with the
However, the observed biological response
study, it was decided to load the implants
osteoinductive growth factor TGF-b1 did
in the present study proves that during the
with 1 mg TGF-b1. In addition to the dose-
not show an additional effect on peri-im-
initial bone-healing process, the CaP coat-
response effect, data have been published
plant bone response. The results of this
ing exerted its biological effect by enhancing
suggesting a positive correlation between
study consequently indicate that a substan-
the bone formation around the implanted
the in vivo osteoinductive activity of TGF-
tial improvement of the osteogenic re-
materials. Additionally, as a result of the
b1 and the amount of protein retained at the
sponse to titanium implants can be
heat-treatment, oxidation of the titanium
site of implantation. Consequently, if less
obtained by the deposition of an electro-
substrate occurred, which was demon-
growth factor is retained, a higher dose is
sprayed CaP coating. The enrichment of
strated through XRD analysis. Although
the coating with 1 mg TGF-b1 has only a
the authors are aware of the effects of heat-
response. Although growth factor retain-
marginal effect.
treatment on the mechanical properties of
ment was not assessed in this study, the
titanium, the current study did not evaluate
amount of TGF-b1 remaining on the im-
this parameter.
plants in the present study might have been
In addition to the deposition of a CaP
below the optimal osteoinductive level. Sev-
would like to acknowledge Dr E.M.
coating, the potential beneficial effect of
eral in vitro studies have been performed to
Bronkhorst for his assistance with the
TGF-b1 on the peri-implant bone response
determine the release characteristics of TGF-
statistical analyses, and Dyna Dental
was also evaluated in this study. It is recog-
b1. For instance, a burst release of 70% of
Engineering BV (Bergen op Zoom,
nized that TGF-b1 might have effects in the
TGF-b1 was observed from a titanium fiber
the Netherlands) for providing the
vicinity of the implant; however, thorough
mesh implant (Vehof et al. 2002). Lind et al.
implants. This study was financially
histological observations did not support this
(1996b) found a burst release of 80% of
supported by the Dutch Program for
suggestion. With respect to the study design,
TGF-b1 adsorbed onto tricalcium phos-
Tissue Engineering (DPTE; NGT. 6730).
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
427 Clin. Oral Impl. Res. 20, 2009 / 421–429
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
Adell, R., Lekholm, U., Rockler, B. & Branemark,
Duyck, J., Slaets, E., Sasaguri, K., Vandamme, K. &
Leeuwenburg, S.C., Heine, M.C., Wolke, J.G.C.,
P.I. (1981) A 15-year study of osseointegrated
Naert, I. (2007) Effect of intermittent loading and
Pratsinis, S.E., Shoonman, J. & Jansen, J.A.
implants in the treatment of the edentulous jaw.
surface roughness on peri-implant bone formation
(2006) Morphology of calcium phosphate coatings
International Journal of Oral and Maxillofacial
in a bone chamber model. Journal of Clinical
for biomedical applications deposited using elec-
Surgery 10: 387–416.
Periodontology 34: 998–1006.
trostatic spray deposition. Thin Solid Films 503:
Albrektsson, T., Branemark, P.I., Hansson, H.A. &
Fischer, U., Hempel, U., Becker, D., Bierbaum, S.,
Lindstrom, J. (1981) Osseointegrated titanium
Scharnweber, D., Worch, H. & Wenzel, K.W.
Lind, M., Overgaard, S., Glerup, H., Soballe, K. &
implants. Requirements for ensuring a long-last-
(2003) Transforming growth factor beta1 immobi-
Bunger, C. (2001) Transforming growth factor-
ing, direct bone-to-implant anchorage in man.
lized adsorptively on Ti6Al4V and collagen type I
beta1 adsorbed to tricalciumphosphate coated im-
Acta Orthopaedica Scandinavica 52: 155–170.
coated Ti6Al4V maintains its biological activity.
plants increases peri-implant bone remodeling.
Albrektsson, T., Dahl, E., Enbom, L., Engevall, S.,
Biomaterials 24: 2631–2641.
Biomaterials 22: 189–193.
Engquist, B., Eriksson, A.R., Feldmann, G., Frei-
Gapski, R., Wang, H.L., Mascarenhas, P. & Lang,
Lind, M., Overgaard, S., Ongpipattanakul, B.,
berg, N., Glantz, P.O., Kjellman, O., Kristersson,
N.P. (2003) Critical review of immediate implant
Nguyen, T., Bunger, C. & Soballe, K. (1996a)
L., Kvint, S., Ko¨ndell, P.A
˚ ., Palmquist, J., Wern-
loading. Clinical Oral Implants Research 14:
Transforming growth factor-beta 1 stimulates
˚ strand, P. (1988) Osseointegrated oral
bone ongrowth to weight-loaded tricalcium phos-
implants. A Swedish multicenter study of 8139
Geesink, R.G. (2002) Osteoconductive coatings
phate coated implants: an experimental study in
consecutively inserted Nobelpharma implants.
for total joint arthroplasty. Clinical Orthopaedics
dogs. Journal of Bone and Joint Surgery. British
Journal of Periodontology 59: 287–296.
and Related Research 395: 53–65.
Volume 78: 377–382.
Beck, L.S., Deguzman, L., Lee, W.P., Xu, Y., McFa-
Gombotz, W.R., Pankey, S.C., Bouchard, L.S.,
Lind, M., Overgaard, S., Soballe, K., Nguyen, T.,
tridge, L.A., Gillett, N.A. & Amento, E.P. (1991)
Ranchalis, J. & Puolakkainen, P. (1993) Con-
Ongpipattanakul, B. & Bunger, C. (1996b) Trans-
Rapid publication. TGF-beta 1 induces bone
trolled release of TGF-beta 1 from a biodegradable
forming growth factor-beta 1 enhances bone heal-
closure of skull defects. Journal of Bone and
matrix for bone regeneration. Journal of Bioma-
ing to unloaded tricalcium phosphate coated
Mineral Research 6: 1257–1265.
terials Science Polymer Edition 5: 49–63.
implants: an experimental study in dogs. Journal
Beck, L.S., Wong, R.L., DeGuzman, L., Lee, W.P.,
Hulshoff, J.E. & Jansen, J.A. (1997) Initial interfacial
of Orthopaedic Research 14: 343–350.
Ongpipattanakul, B. & Nguyen, T.H. (1998)
healing events around calcium phosphate (CaP)
Liu, Y., Hunziker, E.B., Layrolle, P., De Bruijn, J.D.
Combination of bone marrow and TGF-beta 1
coated oral implants. Clinical Oral Implants
& De Groot, K. (2004) Bone morphogenetic protein
augment the healing of critical-sized bone
Research 8: 393–400.
2 incorporated into biomimetic coatings retains its
defects. Journal of Pharmaceutical Sciences 87:
Jansen, J.A., van de Waerden, J.P., Wolke, J.G. & de
biological activity. Tissue Engineering 10: 101–108.
Groot, K. (1991) Histologic evaluation of the
Misch, C.E. (1999) Implant design considerations
Buser, D., Weber, H.P., Bragger, U. & Balsiger, C.
osseous adaptation to titanium and hydroxy-
for the posterior regions of the mouth. Implant
(1994) Tissue integration of one-stage implants:
apatite-coated titanium implants. Journal of Bio-
Dentistry 8: 376–386.
three-year results of a prospective longitudinal
medical Materials Research 25: 973–989.
O'Sullivan, D., Sennerby, L. & Meredith, N. (2004)
study with hollow cylinder and hollow screw im-
Jansen, J.A., Wolke, J.G., Swann, S., Van der
Influence of implant taper on the primary and
plants. Quintessence International 25: 679–686.
Waerden, J.P. & de Groot, K. (1993) Application
secondary stability of osseointegrated titanium
Clemens, J.A., Klein, C.P., Sakkers, R.J., Dhert,
of magnetron sputtering for producing ceramic
implants. Clinical Oral Implants Research 15:
W.J., de Groot, K. & Rozing, P.M. (1997) Healing
coatings on implant materials. Clinical Oral
Implants Research 4: 28–34.
Pilliar, R.M., Deporter, D.A., Watson, P.A. & Vali-
implants in trabecular bone of the goat. Journal
Joyce, M.E., Roberts, A.B., Sporn, M.B. & Bolander,
quette, N. (1991) Dental implant design–effect on
of Biomedical Materials Research 36: 55–64.
M.E. (1990) Transforming growth factor-beta and
bone remodeling. Journal of Biomedical Materials
Davies, J.E. (2003) Understanding peri-implant
the initiation of chondrogenesis and osteogenesis
Research 25: 467–483.
endosseous healing. Journal of Dental Education
in the rat femur. Journal of Cell Biology 110:
Puleo, D.A. & Thomas, M.V. (2006) Implant
67: 932–949.
surfaces. Dental Clinics of North America 50:
De Groot, K., Wolke, J.G.C. & Jansen, J.A. (1994)
Lacefield, W.R. (1998) Current status of ceramic
State of the art: Hydroxylapatite coatings for
coatings for dental implants. Implant Dentistry 7:
Shalabi, M.M., Gortemaker, A., Van't Hof, M.A.,
dental implants. Journal of Oral Implantology
Jansen, J.A. & Creugers, N.H. (2006) Implant
20: 232–234.
Lacefield, W.R. (1999) Materials characteristics
surface roughness and bone healing: a syste-
Del Fabbro, M., Testori, T., Francetti, L., Taschieri,
of uncoated/ceramic-coated implant materials.
matic review. Journal of Dental Research 85:
S. & Weinstein, R. (2006) Systematic review of
Advances in Dental Research 13: 21–26.
survival rates for immediately loaded dental im-
Leeuwenburgh, S.C., Wolke, J.G., Schoonman, J. &
Siebers, M.C., Walboomers, X.F., Leewenburgh,
plants. International Journal of Periodontics and
Jansen, J.A. (2003) Electrostatic spray deposition
S.C., Wolke, J.G., Boerman, O.C. & Jansen, J.A.
Restorative Dentistry 26: 249–263.
(ESD) of calcium phosphate coatings. Journal
(2006) Transforming growth factor-beta1 release
Dhert, W.J. (1994) Retrieval studies on calcium
of Biomedical Materials Research Part A 66:
from a porous electrostatic spray deposition-
phosphate-coated implants. Medical Progress
derived calcium phosphate coating. Tissue Engi-
Through Technology 20: 143–154.
Leeuwenburgh, S.C., Wolke, J.G., Schoonman, J.
neering 12: 2449–2456.
Dorozhkin, S.V. & Epple, M. (2002) Biological
& Jansen, J.A. (2004) Influence of precursor
Siebers, M.C., Wolke, J.G., Walboomers, X.F.,
and medical significance of calcium phosphates.
solution parameters on chemical properties of
Leeuwenburgh, S.C. & Jansen, J.A. (2007) In
Angewandte Chemie International Edition 41:
calcium phosphate coatings prepared using Elec-
vivo evaluation of the trabecular bone behavior
trostatic Spray Deposition (ESD). Biomaterials
to porous electrostatic spray deposition-derived
Ducheyne, P., Bianco, P., Radin, S. & Schepers, E.
25: 641–649.
calcium phosphate coatings. Clinical Oral Im-
(1992) Bioactive Materials: mechanisms and
Leeuwenburgh, S.C., Wolke, J.G., Schoonman, J. &
plants Research 18: 354–361.
Bioengineering Considerations. In: Ducheyne,
Jansen, J.A. (2005) Influence of deposition
Siegele, D. & Soltesz, U. (1989) Numerical investi-
P., Kokubo, T. & van, Blitterswijk C.A., eds.
parameters on chemical properties of calcium
gations of the influence of implant shape on
Bone-bonding Biomaterials. 1–12. Leiderdorp,
phosphate coatings prepared by using electrostatic
stress distribution in the jaw bone. International
the Netherlands: Reed Healthcare Communica-
spray deposition. Journal of Biomedical Materials
Journal of Oral & Maxillofacial Implants 4:
Research Part A 74: 275–284.
428 Clin. Oral Impl. Res. 20, 2009 / 421–429
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
Schouten et al . Effects of implant geometry, surface properties and TGF-b1
Steigenga, J.T., al-Shammari, K.F., Nociti, F.H.,
tional Journal of Oral & Maxillofacial Implants
plastic embedded bone with implants. Stain Tech-
Misch, C.E. & Wang, H.L. (2003) Dental implant
15: 675–690.
nology 63: 171–176.
design and its relationship to long-term implant
Testori, T., Del Fabbro, M., Feldman, S., Vincenzi,
Vehof, J.W., Haus, M.T., de Ruijter, A.E., Spauwen,
success. Implant Dentistry 12: 306–317.
G., Sullivan, D., Rossi Jr, R, Anitua, E., Bianchi,
P.H. & Jansen, J.A. (2002) Bone formation in
Sumner, D.R., Turner, T.M., Purchio, A.F.,
F., Francetti, L. & Weinstein, R.L. (2002) A
transforming growth factor beta-I-loaded titanium
Gombotz, W.R., Urban, R.M. & Galante, J.O.
multicenter prospective evaluation of 2-months
fiber mesh implants. Clinical Oral Implants
(1995) Enhancement of bone ingrowth by trans-
loaded Osseotite implants placed in the posterior
Research 13: 94–102.
forming growth factor-beta. Journal of Bone and
jaws: 3-year follow-up results. Clinical Oral Im-
Watzak, G., Zechner, W., Ulm, C., Tangl, S., Tep-
Joint Surgery America 77: 1135–1147.
plants Research 13: 154–161.
per, G. & Watzek, G. (2005) Histologic and
Sun, L., Berndt, C.C., Gross, K.A. & Kucuk, A.
Turunen, T., Peltola, J., Makkonen, T., Helenius,
histomorphometric analysis of three types of den-
(2001) Material fundamentals and clinical perfor-
H. & Yli-Urpo, A. (1998) Bioactive glass granules
tal implants following 18 months of occlusal
mance of plasma-sprayed hydroxyapatite coatings:
and polytetrafluoroethylene membrane in the
loading: a preliminary study in baboons. Clinical
a review. Journal of Biomedical Materials
repair of bone defects adjacent to titanium and
Oral Implants Research 16: 408–416.
Research 58: 570–592.
bioactive glass implants. Journal of Materials
Wheeler, D.L., Montfort, M.J. & McLoughlin, S.W.
Sykaras, N., Iacopino, A.M., Marker, V.A., Triplett,
Science: Materials in Medicine 9: 403–407.
(2001) Differential healing response of bone
R.G. & Woody, R.D. (2000) Implant materials,
Van der Lubbe, H.B., Klein, C.P. & de Groot, K.
adjacent to porous implants coated with hydro-
designs, and surface topographies: their effect on
(1988) A simple method for preparing thin (10
xyapatite and 45S5 bioactive glass. Journal of
osseointegration. A literature review. Interna-
microM) histological sections of undecalcified
Biomedical Materials Research 55: 603–612.
2009 The Authors. Journal compilation c
2009 John Wiley & Sons A/S
429 Clin. Oral Impl. Res. 20, 2009 / 421–429
Source: http://www.dynadental.es/app/download/9107218721/Study+Helix+DC2+-+Schouten+et+al+-+ENG.pdf?t=1391945123
Seminar: Does life science have a future in Sweden? Stockholm, October 8, 2014 The Third Industrial Revolution: Three main drivers, many Dr David Brown, PhD, FRSC, FRSM Cambridge, UK email: [email protected] +44 (0) 7766 686 345 A brief history since the discovery of Viagra Viagra catalysed rapid corporate growth
UNIVERSITE LUMIERE LYON II - 2006-2007 Institut d'Etudes Politiques de Lyon Mémoire de fin d'études : Section Relations Internationales La gouvernance du VIH/Sida en Thaïlande : Etude du réseau PHPT (Program for HIV Prevention and Treatment) Soutenu le 6 juin 2007 Directeur de mémoire : Gwenola Le Naour séminaire gestion des risques et politiques publiques