J. Camilo Rolda´n Sinus ﬂoor augmentation with S Yahya Ac ...coimplante.odo.br/Biblioteca/Enxertos prp/the presence of...N 2500, Hoffmann-La Roche AG, Gren-zach-Wyhlen, Germany)

Sinus floor augmentation withsimultaneous placement of dentalimplants in the presence of platelet-richplasma or recombinant human bonemorphogenetic protein-7

J. Camilo RoldánS�ren JepsenChristian SchmidtHelge KnüppelDavid C. RuegerYahya AçilHendrik Terheyden

Authors’ affiliations:J. Camilo Roldán, Christian Schmidt, HelgeKnüppel, Yahya Açil, Hendrik Terheyden,Department of Oral and Maxillofacial Surgery,University of Schleswig-Holstein, Campus Kiel,GermanyS�ren Jepsen, Department of Periodontology,Operative and Preventive Dentistry, University ofBonn, GermanyDavid C. Rueger, Stryker Biotech, Hopkinton, MA,USA

Correspondence to:Juan Camilo Roldán MD, DMDDepartment of Oral and Maxillofacial SurgeryUniversity of Schleswig-HolsteinCampus KielArnold-Heller-Str. 1624105 KielGermanyTel.: þ49 431 597 2820Fax: þ49 431 597 2950e-mail: [email protected]

Key words: anorganic bovine bone, bone morphogenetic proteins, dental implants,

platelet-rich plasma, sinus floor augmentation

Abstract: The aim of the present study was to evaluate the possible benefit of platelet-rich

plasma (PRP) in sinus grafting as compared with recombinant human bone morphogenetic

protein-7 (rhBMP-7). For this purpose, we performed a bilateral sinus augmentation with

anorganic bovine bone and simultaneous insertion of a titanium screw implant in five

miniature pigs. Six hundred microliters of PRP and 15%-vol. autologous bone, which was

collected with a trap during preparation of the implant recipient site, were added to the

right sinus and 420ml rhBMP-7 to the left sinus. A polychrome sequential labeling was

performed. The animals were sacrificed 6 weeks after surgery. Undecalcified ground

sections were evaluated by microradiography, digitized histomorphometry and under

fluorescent light. The mean bone–implant contact using rhBMP-7 was 45.8% and 5.7%

under PRP (P¼0.002). The mean height of newly mineralized bone in the augmented area

using rhBMP-7 amounted to 8.3mm as opposed to 3.6mm under PRP (P¼0.013). Using PRP,

the mean area of the newly formed bone was enhanced (51.3%) as compared with rhBMP-7

(33.1%); however, this difference was not statistically significant (P¼0.081). In conclusion,

under the selected experimental conditions the use of rhBMP-7 led to superior outcomes

with regard to the osseointegration of dental implants and the height of new bone as

compared with the use of PRP.

The advanced atrophy of the maxilla and

the subsequent pneumatization of themax-

illary sinus imply a challenge for the im-

plant rehabilitation. Boyne & James (1980)

introduced the sinus augmentation with

autogenous bone graft for implant surgery.

This technique became a standard method

with good results (Raghoebar et al. 1997;

Lorenzetti et al. 1998). Nevertheless, the

limited amount of disposable bone of the

jaws for grafting purposes and the need for

iliac bone to fulfill the expected bone

volume for reconstruction make it neces-

sary to find a substitute of autologous bone

to reduce morbidity and patient discomfort

associated with bone grafting (Smiler &

Holmes 1987). The introduction of hydro-

xylapatite (Smiler & Holmes 1987) and of

the anorganic bovine bone (Wentzel et al.

1995; Hürzeler et al. 1996; Hass et al.

1998; Valentini et al. 1998) to augment

the sinus floor showed a realistic alterna-

tive to the autologous bone. The most

critical aspect of the latter approach is the

longer time needed for bone healing (Moy

et al. 1993; Lorenzetti et al. 1998; Yildirim

et al. 2001). Lynch et al. (1991) reported

about the increase of the bone–implant

contact (BIC) after the application of re-

combinant human platelet-derived growth

factor (rhPDGF) and recombinant human

Insulin growth factor-I (rhIGF-I) 7 days

after operation. In 1998, Marx et al.

(1998) introduced the local application ofCopyright r Blackwell Munksgaard 2004

Date:Accepted 8 January 2004

To cite this article:Roldán JC, Jepsen S, Schmidt C, Knüppel H, RuegerDC, Açil Y, Terheyden H. Sinus floor augmentationwith simultaneous placement of dental implants in thepresence of platelet-rich plasma or recombinant humanbone morphogenetic protein-7.Clin. Oral Impl. Res. 15, 2004; 716–723doi: 10.1111/j.1600-0501.2004.01070.x

716

autologous platelet-rich plasma (PRP) to

accelerate the maturation of grafted bone

in maxillofacial surgery. Growth factors

released by platelets like PDGF, IGF-I and

transforming growth factor-b (TGF-b) areinvolved in reparative processes including

osteogenesis (Ross et al. 1986; Noda &

Camilliere 1989; Pfeilschifter et al. 1990;

Nash et al. 1994). Lynch (1999) proposed

the use of PRP in combination with a bone

substitute for the treatment of small bone

defects in periodontal and implant surgery.

Since 2000, clinical studies have been

published to evaluate the benefit of PRP

in sinus surgery (Kassolis et al. 2000;

Rosenberg & Torosian 2000; Lozada et al.

2001; Philippart et al. 2003; Rodriguez

et al. 2003;Wiltfang et al. 2003). At present,

there are no data available from experimen-

tal in vivo studies on the histomorpho-

metric evaluation of new bone formation

and osseointegration of dental implants in

the presence of PRP.

Bonemorphogenetic proteins (BMPs), on

the other hand, are able to induce me-

senchymal stem cells to differentiate into

osteoblasts and to produce new bone tissue

(Urist 1965). BMPs have been shown to

shorten the healing time of sinus augmen-

tation in combination with a bone substi-

tute and to increase the osseointegration of

dental implants (Boyne et al. 1997; Ha-

nisch et al. 1997; Margolin et al. 1998;

Terheyden et al. 1999). Therefore, the aim

of the present study was to evaluate the

pattern of bone formation using PRP com-

pared with the well-documented effects of

a recombinant BMP in the miniature pig

model for sinus augmentation.

Material and methods

The study was approved by the Ministry of

Nature, Environment and Forestry of Schles-

wig-Holstein in accordance with the ethics

committee of this institution (V 252-72241.

121-14). Five miniature pigs (Ellengard Göt-

tingen Minipigs ApS, Dalmose, Denmark),

18 months of age, which weighed 40kg,

were operated. They were fed with 2 �250 g standard soft diet (Altromin 9023s

Atronium International GmbH, Lange,

Germany) and water ad libitum.

Anesthesia was induced with 30mg Ke-

tamine (Ketavets, Upjohn GmbH, Hep-

penheim, Germany) and 1mg Xylazine

(Rompuns 2%, Bayer AG, Leverkusen,

Germany). An intratracheal intubation

was performed with a Miller size 4 laryn-

goscope and a standard straight 5.5mm ID

tube with cuff (Portex, Kent, UK). An-

esthesia was maintained with gas (66%

N2O and 32% O2 (Forenes, Abbot

GmbH, Wiesbaden, Germany)). One gram

Clemizol–Penicillin (Clemizol–Penicillins

i.m. forte, Grünenthal GmbH, Aachen,

Germany) was given preoperatively as a pro-

phylactic antibiotic. Postoperative pain relief

was achieved before extubation by inject-

ing 500mg metamizol i.m. (Novalgins,

Hoechst AG, Bad Soden, Germany), con-

tinuing with 2 � 50mg/day p.o. Tramadol(Tramals, Grünenthal GmbH, Aachen,

Germany).

Preparation of PRP

Seventeen milliliters of blood were col-

lected in two vacuum tubes of 8.5ml

each (S-Monovettes, CPDA-1, Starstedt

AG, Nümbrecht, Germany) from the

vena jugularis interna in general anesthesia

just before surgery. The method proposed

by Marx et al. (1998) on how to prepare

PRP was modified according to the small

sample of blood after a statistically vali-

dated method (Roldán et al. 2004). The

volumes handled were proportional to the

volumes described by Marx et al. (1998).

The PRP was produced as follows: the

whole blood was centrifuged for 7min at

1700 rpm without brake. The plasma was

decanted down to the erythrocyte sediment

and then centrifuged again for 10min at

3000 rpm with brake. Finally, the plasma

was decanted and the sediment was resus-

pendedwith 2.3ml plasma, resulting in the

same concentration of PRP as the one

described by Marx et al. (1998). The plate-

lets in whole blood and PRP were counted

manually in the Neubauer chamber in

which the thrombocytes were stained

with a specific reagent (TTV 55-Thrombo-

zyten-Einzeltests KABE Labortechnik

GmbH, Nümbrecht-Eisenroth, Germany).

The PRP was kept in a sample shaker for

a mean of 30min at room temperature.

The PRP for clinical usewas activatedwith

human lyophilized thrombin (Tissucols,

Baxter, Heidelberg, Germany). The throm-

bin was combined with CaCl2 10% in

a proportion of 250 IU thrombin/500 mlCaCl2 10%. Three hundred and eighty

microliters of activated thrombin were

mixed with 600ml PRP. Nine hundred

and eighty microliters of this solution

were used in combination with the anor-

ganic bovine bone and 15% vol. autologous

bone for implantation in the right sinus.

Experimental procedure

After harvesting of blood to prepare PRP, the

cheek was shaved and cleaned with povi-

done–iodine solution and drapedwith sterile

towels. The augmentation of the sinus was

achieved by an infraorbital access and sub-

periosteal preparation of the facial maxillary

bone, the crista zygomaticoalveolaris and

the malar prominence, as previously de-

scribed (Terheyden et al. 1999). The access

to the sinus was achieved by thinning the

facial wall with a surgical bur. The Schnei-

derian membrane was carefully elevated

within the sinus, particularly below the

malar prominence, where the dental im-

plant in a latero-cranial direction was in-

serted. The malar bone, as an implant site,

was reduced to a height of 5mm for stan-

dardization according to the clinical situa-

tion (Tidwell et al. 1991; Triplett & Schow

1996). Solid screw titanium implants (SLA-

ITIs, Strauman AG, Waldenburg, Switzer-

land), 16mm long with a diameter of

4.1mm, were used. The right sinus was

augmentedwith 3ml anorganic bovine bone

(Bio-Osss Granulat 0.25–1mm, E. Geis-

tlich Söhne AG, Wolhusen, Switzerland),

15%-vol. autologous bone collected during

preparation of the implant recipient site

with a bone trap in a suction device (Kno-

chenfilter T2, SchlumbohmOHGs, Broch-

stedt, Germany) and 600ml PRP. The leftsinus was augmented with 3ml Bio-Osss

and 420ml recombinant BMP-7 (rhBMP-7)(Stryker Biotech, Hopkinton MA, USA) in

600ml acetate buffer. No autologous bonewas grafted into the left sinus.

Polychrome sequential labeling

A polychrome sequential labeling of miner-

alizing tissues according to Rahn (1976)

was performed as previously described (Ter-

heyden et al. 1999). Intraperitoneal injec-

tion of fluorochromes under i.m. anesthesia

with 250mg Zolazepam/250mg Tiletamin

(Tilests 500 Parke-Davis, Freiburg, Ger-

many) started 2 weeks after the surgical

procedure and continued for 3 weeks with

one labeling per week as follows: xylenolor-

ange (6% in 2%NaHCO3 solution, 1.5ml/

kg body weight), calcein green (1% in 2%

NaHCO3 solution, 5ml/kg body weight),

Roldán et al . Sinus floor augmentation in presence of PRP or rhBMP-7

717 | Clin. Oral Impl. Res. 15, 2004 / 716–723

alizarin complexon (3% in 2% NaHCO3solution, 0.8ml/kg body weight) and dox-

ycyclines (1mg/kg body weight, Doxy-

cyclin-Rathiopharm SFs, Rathiopharm

GmbH & Co., Ulm, Germany).

Sacrifice

The animals were sacrificed 6 weeks post-

surgery in general anesthesia (see above)

by an intravital and intracardial perfusion.

For this purpose, the ascending aorta, after

a median thoracotomy, was canulated

through an incision of the left ventricle.

Prior to this, heparin 40 IU/kg (Liquemins

N 2500, Hoffmann-La Roche AG, Gren-

zach-Wyhlen, Germany) had been admi-

nistered. The right atrium was opened by

an incision to release the venous blood

flow. Two liters of Ringer solution was

perfused at a temperature of 36–371C under120mmHg pressure in order to wash out

the blood. Subsequently, the animals were

perfused for tissue fixation with a 500ml

solution composed of 25% glutaraldehyde

(2.5%), formaldehyde (1.5%) and Sören-

sen’s phosphate buffer (100mMKH2PO4,

100mMNa2HPO4 � 2H2O, pH 7.4). Acoronal computed tomography (CT) Scan

(Siemens Somatom Plus, Siemens AG,Mu-

nich, Germany; 120kV, 33mA) was con-

ducted. The explanted sinus was immersed

in 10% formalin, Sörensen’s phosphate buf-

fer and 70% isopropyl alcohol for 10 days.

Histology

Undecalcified specimens were prepared ac-

cording to themethod described by Donath

& Breuner (1982). The process consists in

a gradual dehydration of the specimen

in ethyl alcohol and a final embedding in

acrylic resin (Fluka Chemie AG, Buchs,

Switzerland). The block was cut in the

coronal plane after placing an implant abut-

ment that indicated the axis of the implant

body. The retrieved specimens, in 0.5mm

slices, were fixed on an acrylic carrier and

ground and polished down to approxi-

mately 90 ml. A microradiograph (Type1A, Microchrome Technology Inc., San

José, CA, USA) was taken at 3mA and

25kV using a microradiography device

(Faxitron X-ray systems, Hewlett Packard

GmbH, Böblingen, Germany). The histo-

morphometry of the total core was evalu-

ated after digitalization of the microscope

image. The software detected a variety of

different gray tones, which allowed to

distinguish the newly mineralized bone

(Q500MCs, Leach Cambridge Ltd., Cam-

bridge, UK). Fluorescence microscopy was

performed under UV light. The parameters

to be evaluated according to Parfitt et al.

(1987) were the following:

� Bone–implant contact: Mineralizedbone in direct contact to the implant

(%), where 100% is the total length of

the implant in the augmented sinus.

� The area of newly mineralized bone inthe lower third of the augmented area

(mm2)

� Height of newly mineralized bone inthe augmented area (mm).

Statistical analysis

The data for the three outcome variables

were analyzed with a paired t-test. The

correlation in the thrombocyte count in

whole blood and PRP was analyzed with

a Spearman test. The significance level

was set at Po0.05.

Results

Validity of the preparation of PRP

The mean number of thrombocytes in

whole blood was 450.20 � 103 cells/ml.The PRP mean platelet count was

1.592 � 103 cells/ml. Thus, the concentra-tion of the thrombocytes in PRP was in-

creased by a factor of 3.5. The thrombocyte

count in whole blood in the different ani-

mals was variable, ranging from 173 � 103

to 620 � 103 cells/ml. No statistically sig-nificant correlation between the thrombo-

cyte concentration in the whole blood and

in PRP could be observed (P¼ 0.1).

CT scan

Six weeks after the operation no signs of

infection in themaxillary sinus, of any loss

of implant integration or any apparent

differences in the imaging of the augmenta-

tion with PRP or with rhBMP-7 could be

observed (Fig. 1).

Fig. 1. Coronal CT Scan (Siemens Somatom Plus, 120 kV, 33mA) of the midface of a miniature pig 6 weeks

after sinus-lift with anorganic bovine bone in association with platelet-rich plasma and 15%-vol. autologous

bone on the right side and with bone morphogenetic protein-7 on the left side. A titanium screw implant was

primarily inserted into the zygomatic bone in a latero-cranial direction on both sides. No sinus pathology or

apparent difference in the radio-opacity of the augmentation is seen on both sides. The right maxillary sinus is

outlined in red, the left sinus in blue; the infraorbital nerve (n) is demarked in yellow on both sides.



Microradiography

In the presence of PRP, the apposition of

new bone could be seen in the proximity of

host bone but not on top of the augmenta-

tion (Fig. 2a). The formation of new bone

in the presence of rhBMP-7 appeared to be

homogeneous in the whole augmented area

and limited to the area augmented with

bone substitute (Fig. 2b).

Toluidine blue histology

No inflammatory reaction was seen on

any section and individual animal. An

enhancement of bone apposition in the

proximity of host bone in the presence

of PRP was clearly detected; however,

the osseointegration of the dental im-

plants was not improved in this site. The

tip of the dental implant was surround-

ed by connective tissue in all cases treated

with PRP (Fig. 3a). In contrast, bone

marrow was observed in the whole aug-

mented sinus in the presence of rhBMP-7

and the implants were surrounded

by newly formed bone in all the cases

(Fig. 3b).

Fluorescence microscopy

The apposition of new bone was observed

in the presence of rhBMP-7 after the second

week postsurgery; in the presence of PRP it

occurred 1 week later, as indicated by the

second labeling (Fig. 4). Bone apposition

was enhanced on the sinus floor showing

wider labeled bands in both experimental

groups. No bone apposition was seen on

the tip of the implants in sites treated with

PRP. In the presence of rhBMP-7, however,

a homogeneous bone apposition on the top

of the implants and around the Bio-Osss

Fig. 2. Solid screw titanium implant (ITIs) in the maxillary sinus augmented with anorganic bovine bone (Bio-Osss) 6 weeks postoperatively. (a) Situation following

application of platelet-rich plasma and 15%-vol. autologous bone graft: the apposition of new bone takes place in a gradual fashion from the host bone to the top of the

augmentation. The sinus wall is outlined in red, see Fig. 1. (b) Situation following application of recombinant human bonemorphogenetic protein-7: Homogeneous new

bone formation in thewhole augmented sinus. The formation of new bonewas determined by the shape of the implantedmaterial and did not exceed it. The sinus wall is

outlined in blue, see Fig. 1. (Microradiography of undecalcified ground sections.)

Fig. 3. Solid screw titanium implant (ITIs) in the maxillary sinus augmented with anorganic bovine bone (Bio-Osss) 6 weeks postoperatively. (a) Situation following

application of platelet-rich plasma and 15%-vol. autologous bone graft: The apposition of new bone takes place in a gradual fashion from the host bone to the top of the

augmentation. Enhanced bone apposition on the sinus floor is evident; however, osseointegration is not improved. Bio-Osss particles on top of the dental implant are

surrounded by connective tissue. The sinus wall is outlined in red; the arrow indicates apposition of new bone on the implant. (b) Situation following application of

recombinant human bone morphogenetic protein-7: Homogeneous new bone formation with bone marrow in the whole augmented sinus. Osseointegration of the

titanium implant is seen on its entire length. The sinus wall is outlined in blue; the arrow indicates apposition of new bone on the tip of the implant (toluidine blue

staining).



particles could be seen after the second

postoperative week.

Histomorphometry

In all but one specimen, apposition of bone

on dental implants was seen in the PRP

group. The mean BIC in the presence of

PRP amounted to 5.76%, whereas in the

rhBMP-7 group BIC was observed over the

entire implant length with a mean value of

45.8%. This difference was statistically

significant (P¼ 0.002). The mean heightof the newly formed bone in the augmented

area in rhBMP-7 treated sites was 8.3mm,

which is in contrast to a mean height

of 3.6mm in the PRP group (P¼ 0.013).The area of the newly mineralized bone

on the sinus floor was larger in the pre-

sence of PRP (51.32%) than in the presence

of rhBMP-7 (33.12%); however, this

difference was not significant (P¼ 0.081)(Table 1).

Discussion

Since the first description of local applica-

tion of PRP produced by a gradient density

cell separator (Electro Medics 500s, Med-

tronics, Minneapolis, MN, USA) to accel-

erate the maturation of bone transplants in

maxillofacial surgery (Marx et al. 1998),

many methods have been proposed to pro-

duce PRP by using a conventional centri-

fuge to facilitate its application for implant

surgery in clinical practice (Landesberg et al.

2000; Weibrich et al. 2001). In the present

study, we chose a validated method to

produce PRP (Roldán et al. in press), which

resembles the method of Marx et al. (1998),

but is adapted to the handling of smaller

volumes of blood according to the animal

model. The mean value of the concentra-

tion factor of thrombocytes in PRP was 3.5,

which is comparable with the factor 3.4

reported by Marx et al. (1998). Neverthe-

less, a statistical correlation between the

thrombocyte count in whole blood and in

PRP was not seen, possibly due to the small

sample size (n¼ 5). Moreover, a high varia-bility in the thrombocyte count in the

whole blood of the experimental animals

was observed (maximum: 620 � 103 cells/ml and minimum: 173 � 103 cells/ml). Thisis a critical aspect because the application of

thrombocytes and the contained growth

factors is not standardized. Experiments on

local application of recombinant growth

factors showed a dose-dependent effect

(Noda & Camilliere 1989; Pfeilschifter et al.

1990; Nash et al. 1994; Ripamonti et al.

1997). The effect of the local application of

growth factors also depends on the applica-

tion site (Fujimoto et al. 1999), age and

animal model (Ripamonti et al. 1997).

The effect of TGF-b has been shown to bebiphasic depending on the dose; at a high

concentration an inhibition of osteoblast

proliferation has been seen (Centrella et al.

1994; Fujimoto et al. 1999). Further inves-

tigations have to be undertaken to clarify

the interaction of growth factors at higher

levels in a PRP model.

In the literature, no data are reported on

the influence of PRP on BIC. BMPs, pre-

viously shown to be an effective approach

to enhance osseointegration of dental im-

plants applied in a mineral or collagen

scaffold (Bessho et al. 1999; Terheyden

et al. 1999), were chosen as a control group

Table 1. Parameters (mean values and standard deviation) of bone formation 6 weeks aftersinus augmentation with 3 ml anorganic bovine bone (Bio-Osss) and primary insertion of atitanium implant (ITIs) combined with 600ll of PRP (in 15%-vol. autologous bone) or420ll of rhBMP-7

Bio-Osss-15%-vol.autologous bone/PRP

Bio-Osss/rhBMP-7

P-valuesBMP vs. PRP

Bone–implant contact (%) 5.76 � 11.8 45.80 � 18.58 0.002n

Area of newly mineralized boneon the sinus floor (%)

51.32 � 20.83 33.12 � 13.65 0.081

Height of the newly mineralizedbone in the augmented area (mm)

3.58 � 3.3 8.35 � 2.74 0.013n

nStatistically significant difference (t-test).

rhBMP, recombinant human bone morphogenetic protein; PRP, platelet-rich plasma.

Fig. 4. Basal aspect of the augmented sinus with anorganic bovine bone (Bio-Osss) and primary inserted ITIs-Implant 6 weeks postoperatively. (a) Situation following

application of platelet-rich plasma and 15%-vol. autologous bone graft: Beginning of the bone apposition after the third postoperatively week (calcein green). The arrow

indicates newly formed non-fluorochrom-labeled bone, indicating bone formation after the fifth postoperative week; implant (n). (b) Situation following application of

recombinant human bone morphogenetic protein-7: Homogeneous bone apposition after the first labeling, injected in the second postoperative week; implant (n).

(Fluorescence microscopy in composite slides technique).



in order to evaluate the efficiency of PRP

to improve BIC. In the present study, the

achieved BIC 6 weeks following PRP ap-

plication was 5.76% compared with

45.8% in the presence of rhBMP-7. The

achieved BIC in the PRP model has to be

considered inadequate in a clinical setting

and does not show a benefit compared with

reported studies on sinus augmentation

with Bio-Osss alone, as shown by Hass

et al. (1998), who informed about a BIC of

27.4% 12 weeks after sinus augmentation

in sheep. Others reported about a BIC of

63% in beagles (Schlegel et al. 2003) or

38% in miniature pigs (Terheyden et al.

1999) after an observation period of 6

months. Lynch et al. (1991) demonstrated

a statistically significant enhancement of

the BIC 7 days after the application of

rhPDGF und rhIGF-I. This positive effect

of growth factors on osseointegration sug-

gests that in the present study the required

concentration of growth factors contained

in PRP may not have been achieved.

The mean BIC in sites conditioned with

rhBMP-7 was 45.8%. Terheyden et al.

(1999), using the same experimental

model, reported a mean BIC of 80% after

6 months for the rhBMP-7 group. The

present study shows the strong effect of

BMP at the very beginning after applica-

tion. In vitro studies by the same authors

on Bio-Osss loaded with rhBMP-7 showed

a release of 98% of BMP into simulated

body fluid within 24h (Jepsen et al. 1999).

The evaluation of the effectiveness of BMP,

compared with PRP after 6 weeks, is there-

fore appropriate. An evaluation of the effect

of BMP or PRP after 6 or 9 months is not

appropriate, because a bone integration of

anorganic bone in the absence of bone-

stimulating factors is to be expected after

that time (Hürzeler et al. 1996; Hass et al.

1998; Valentini et al. 1998).

The area of newly mineralized bone on

the sinus floor is expected to be larger in

the vicinity of the residual host bone (Qui-

ñones et al. 1997). In the present study, the

area of newly mineralized bone on the floor

of the sinus was higher in the presence of

PRP (51.32%) than under the influence of

rhBMP-7 (33.12%), although this differ-

ence was not statistically significant. The

observed increase in trabecular bone area

on bone grafts treated with PRP by Marx

et al. (1998) declined from the second to

the sixth month after surgery. Schmitz &

Hollinger (2001) discussed this work, and

extrapolated the curve of the area of the

trabecular bone in the bone graft to 1 year

and concluded that in the long term there

may be no observable advantage in bone

density of treated bone grafts with PRP.

Fürst et al. (2003) performed sinus eleva-

tion procedures in mini-pig using hydroxy-

lapatite for augmentation. PRP was added

to the test side; however, no dental implant

was inserted. An enhanced bone density

was seen on the base of the sinus in the

presence of PRP 3 weeks after surgery; at 6

weeks the bone density declined and at 12

weeks there was no difference to the con-

trol side (Fürst et al. 2003). The observed

enhancement of the trabecular bone area at

the beginning of the observational period

could be of no clinical interest in the long

term, as it has to be realized that the

trabecular bone area will undergo contin-

uous remodeling in response to the me-

chanic and the endocrine demands.

In the present study, the mean height of

newly mineralized bone in the augmented

areawas 8.3mm in the presence of rhBMP-

7, which corresponded to the total height of

the implanted anorganic bovine bone. In

the presence of PRP, the achieved value

was 3.6mm. It is expected that the aug-

mentation of the sinus with Bio-Osss in

the absence of bone-stimulating factors has

to be integrated into new bone, if it takes

6–9 months (Hürzeler et al. 1996; Hass

et al. 1998; Valentini et al. 1998). The very

slow resorption rate of Bio-Osss, a prop-

erty of this material that is often criticized

(Skoglund et al. 1997), could be of advan-

tage in sinus surgery (Schlegel et al. 2003),

because it permits a full bone integration of

implanted anorganic bovine bone before

the resorption of the scaffold starts, as

demonstrated by Hürzeler et al. (1996)

and Hass et al. (1998).

The rationale of adding autologous bone

to PRP was to supply osteoblasts to support

the proposed mitogenic effect of PRP (Wei-

brich et al. 2002). As shown in the extra-

skeletal model in the rat PRP is not os-

teoinductive and could not enhance bone

formation on Bio-Osss in skeletal sites

(Roldán et al. 2004). Because of the known

osteoinductive effects of BMPs, no autolo-

gous bone was grafted into the correspon-

dent sinus.

Autologous bone (15% vol.) collected

during the preparation of the implant site

was mixed with Bio-Osss to enhance bone

formation in the presence of PRP as it is

recommended when Bio-Osss is applied in

the clinical setting (Yildirim et al. 2001). In

spite of the addition of autologous bone to

Bio-Osss in the PRP model, vital bone

could only be seen in the proximity to the

sinuswalls. In the future, it has to be tested

if the addition of more autologous bone can

improve the osteogenesis in a PRP model.

However, if more bone than 15% vol. has

to be applied, it will be necessary to harvest

the additional bone-graft from a second

donor site. The augmentation of the sinus

with Bio-Osss in the presence of rhBMP-7

was carried out without the addition of

autologous bone. Nevertheless, homoge-

neous bone formation was seen in the

whole implanted area.

To our knowledge, this is the first report

to compare the effect of rhBMP-7 and PRP

in implant surgery. PRP could not improve

the osseointegration of dental implants in

regenerated sinus bone after an observation

time of 6 weeks. Our data support the

concept that recombinant BMPs in combi-

nation with an appropriate matrix carrier

may become clinically effective to improve

and accelerate osseointegration of dental

implants.

Acknowledgements: The authors

thank Mrs. M. Hermann and G. Otto, of

the Department of Experimental

Maxillofacial Surgery of the University

of Kiel, for their excellent technical

assistance.

Résumé

Le but de l’étude présente a été d’évaluer le bénéfice

possible du plasma riche en plaquettes (PRP) dans le

greffage sinusal comparé à la protéine-7 morpho-

génétique osseuse humaine recombinante (rhBMP-

7). Un épaississement du sinus bilatéral a été effec-

tué avec de l’os bovin anorganique et l’insertion

simultanée d’un implant vis en titane chez cinq

mini-porcs. Six cents ml de PRP et 15% /vol d’osautogène, qui avait été prélevé dans une trappe

durant la préparation du site implantaire receveur,

ont été placés dans le sinus droit et 420 ml de rhBMP-7 dans le sinus gauche. Un marquage séquentiel

polychrome a ensuite été effectué. Les animaux ont

été euthanasiés six semaines après la chirurgie. Des

coupes épaisses non-décalcifiées ont été évaluées par

microradiographies, histomorphométrie digitale et

sous lumière à fluorescence. Le contact os-implant

moyen en utilisant rhBMP-7 était de 45,8% et 5,7%

sous PRP (p¼ 0,002). La hauteur moyenne de l’os



minéralisé nouveau dans la partie épaissie rhBMP-7

montait à 8,3 mm contre 3,6 mm pour le PRP

(0,013). En utilisant PRP, l’aire moyenne de l’os

néoformé était augmentée (51,3%) comparée à

rhBMP-7 (33,1%), cette différence n’étant cepen-

dant pas significative (p¼0,081). En conclusion,sous des conditions expérimentales sélectionnées,

l’utilisation de rhBMP-7 apporte des avantages

supérieurs en ce qui concerne l’ostéoı̈ntégration

des implants dentaires et la hauteur de l’os néoformé

comparé à l’utilisation du PRP.

Zusammenfassung

Sinusbodenelevation mit gleichzeitiger Platzierung

von dentalen Implantaten mit plättchenreichem

Plasma oder rekombiniertem menschlichem kno-

chenmorphogenetischem Protein-7

Das Ziel der vorliegenden Studie war, dem mögli-

chen positiven Effekt von plättchenreichem Plasma

(PRP) im Vergleich zu rekombiniertem menschli-

chem knochenmorphogenetischem Protein-7

(rhBMP-7) bei der Sinusbodenelevation zu untersu-

chen. Zu diesem Zweck wurde bei fünf Minipigs

eine bilaterale Sinusbodenelevation mit anorga-

nischem bovinem Knochen und gleichzeitig die

Implantation eines Schraubenimplantats durchge-

führt. Sechshundert ml PRP und 15%-vol. autologerKnochen, welcher bei der Präparation des Implan-

tatbettes gewonnen wurde, wurden im rechten Si-

nus dazu gefügt und 420 ml rhBMP-7 wurden in denlinken Sinus eingebracht. Es wurde eine polychrome

Sequenzmarkierung durchgeführt. Sechs Wochen

nach dem Eingriff opferte man die Tiere. Die nicht

entkalkten Schliffpräparate wurden mittels Mikror-

adiographie, digitalisierter Histomorphometrie und

unter fluoreszierendem Licht untersucht. Der

mittlere Knochen-Implantat-Kontakt betrug mit

rhBMP-7 45.8% und mit PRP 5.7% (P¼0.002).Die mittlere Höhe an neu gebildetem mineralisier-

tem Knochen im Augmentat erreichte 8.3mm bei

rhBMP-7 und 3.6mm bei PRP (P¼ 0.013). Mit PRPwar die Fläche an neu gebildetem mineralisiertem

Knochen grösser (51.3%) als mit rhBMP-7 (33.1%),

jedoch war dieser Unterschied nicht statistisch sig-

nifikant (P¼ 0.081). Es wird die Schlussfolgerunggezogen, dass unter den ausgewählten experimentel-

len Bedingungen die Verwendung von rhBMP-7 im

Vergleich zu plättchenreichem Plasma zu besseren

Resultaten bezüglich Osseointegration von Dental-

implantat und der Höhe von neuem Knochen führt.

Resumen

La intención del presente estudio fue evaluar el

posible beneficio del plasma rico en plaquetas

(PRP) en el injerto del seno en comparación con la

proteı́na-7 morfogenética ósea humana recombi-

nante (rhBMP-7). Para este propósito, llevamos a

cabo aumento del seno bilateralmente con hueso

bovino anorgánico e inserción simultanea de un

implante roscado en cinco cerdos miniatura. Se

añadieron 600 ml de PRP y 15%-vol. de huesoantólogo, que fue recolectado usando una trampa

durante la preparación del lugar receptor del im-

plante, al seno derecho y 420 ml de rhBMP-7 alseno izquierdo. Se llevó a cabo un marcado poli-

cromo secuencial. Los animales se sacrificaron seis

semanas tras la cirugı́a. Se evaluaron las secciones

descalcificadas microrradiograficamente, histomor-

fometricamente y bajo luz fluorescente. El contacto

hueso a implante medio usando rhBMP-7 fue 45.8%

y 5.7% bajo PRP (P¼ 0.002). La altura media delhueso neomineralizado en el área aumentada usando

rhBMP-7 llegó a 8.3mm frente a 3.6mm bajo PRP

(P¼ 0.013). Usando el PRP, el área media de huesoneoformado aumentó (51.3%) en comparación con

rhBMP-7 (33.1%), sin embargo esta diferencia no fue

estadı́sticamente significativa (P¼ 0.081). En con-clusión, bajo las condiciones experimentales selec-

cionadas, el uso se rhBMP-7 condujo a unos

resultados superiores respecto a la osteointegración

de implantes dentales y a la altura del nuevo hueso

en comparación con el uso de plasma rico en

plaquetas.

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