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J Oral Maxillofac Surg68:515-523, 2010

Effect of Zoledronic Acid onOsseointegration of Titanium Implants:

An Experimental Study in anOvariectomized Rabbit Model

Alper Yıldız, DDS, PhD,* Emin Esen, DDS, PhD,†

Mehmet Kürkçü, DDS, MSc, PhD,‡ Ibrahim Damlar, DDS,§

Kenan Daglıoglu, PhD,� and Tolga Akova, DDS, PhD¶

Purpose: Zoledronic acid (ZA), a new-generation intravenous bisphosphonate, exhibits the greatest affinityfor bone mineral with the longest retention, thereby leading to its ability to be dosed at annual intervals in thetreatment of osteoporosis. The purpose of this preliminary study was to evaluate the effects of systemicadministration of a single dose of ZA on osseointegration and bone healing around titanium dental implants.

Materials and Methods: Thirty-six female New Zealand rabbits (aged 6-12 months) were used in thisstudy. Rabbits were randomly assigned to 1 of 3 groups: sham control group (SH), ovariectomy group(OVX), and OVX and ZA group (OVX � ZA). Animals in the OVX and OVX � ZA groups were subjectedto bilateral ovariectomy, whereas animals in the SH group were sham operated. Eight weeks later, 1implant was placed in each tibia of the animals. ZA was administered in the OVX � ZA group during theimplantation, whereas the OVX and SH groups received saline solution infusions. All of the subjects weresacrificed 8 weeks after the implantation, and tibial specimens were harvested. Histomorphometricbone-to-implant contact analysis, resonance frequency analysis, removal torque testing, and digitalradiographic absorptiometry were administered, and the data were statistically analyzed.

Results: Histomorphometric, resonance frequency, and radiodensitometric analyses showed significantimprovement in osseointegration of implants in the OVX � ZA group compared with the OVX group.However, the differences in removal torque results between the groups were not statistically significant.

Conclusions: The results of this study suggest that systemic ZA administration may improve osseointe-gration of titanium implants placed in estrogen-deficient states of bone.© 2010 American Association of Oral and Maxillofacial Surgeons

J Oral Maxillofac Surg 68:515-523, 2010

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n recent decades, the use of titanium endosseous dentalmplants in the treatment of edentulous or partiallydentulous patients has become an alternative to restoreunction and esthetics.1,2 Postmenopausal osteoporosiss a widespread disease and could have serious conse-uences on the long-term success of the dental implantreatment. Many clinicians and researchers have ob-

eceived from Çukurova University, Adana, Turkey.

*Research Assistant, Department of Oral and Maxillofacial Sur-

ery, Faculty of Dentistry.

†Professor, Department of Oral and Maxillofacial Surgery, Faculty

f Dentistry.

‡Associate Professor, Department of Oral and Maxillofacial Sur-

ery, Faculty of Dentistry.

§Research Assistant, Department of Oral and Maxillofacial Sur-

ery, Faculty of Dentistry.

�Veterinary Surgeon, The Experimental Surgery Center, School of

edicine.

¶Assistant Professor, Department of Prosthodontics, Faculty of

entistry.

515

erved that biomaterial osseointegration is impaired insteoporotic subjects.3

The effects of different medications on the osseointe-ration of dental implants have been investigated ineveral studies using osteoporotic animal models. Mostf these studies reported that hormone replacementherapy, bisphosphonates, and intermittent parathor-

This study was partially supported by the Çukurova University

cientific research fund and BioLok International and its represen-

ative in Turkey (UMG Uysal Medikal).

Address correspondence and reprint requests to Dr Yildiz: De-

artment of Oral and Maxillofacial Surgery, Çukurova University

aculty of Dentistry, Balcali, Adana, Turkey; e-mail: dtalperyildiz@

ahoo.com

2010 American Association of Oral and Maxillofacial Surgeons

278-2391/10/6803-0005$36.00/0

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516 ZOLEDRONIC ACID AND IMPLANT OSSEOINTEGRATION

one (PTH 1-34) administration improved bone qualityround implants in osteoporotic subjects.4-9

Bisphosphonates are the most widely prescribededication for the treatment of osteoporosis.10 Bisphos-honates are pyrophosphate analogs containing a phos-hate-carbon-phosphate bond, which is stable to chem-

cal and enzymatic hydrolysis; they strongly bind toydroxyapatite (HA) crystals and potently inhibit oste-clast-mediated bone resorption while minimally inhib-

ting osteoblast activity.9,11 Zoledronic acid (ZA), aew-generation intravenous bisphosphonate, exhibits

he greatest affinity for bone mineral with the longestetention, thereby leading to its ability to be dosed atnnual intervals in the treatment of osteoporosis.12

isphosphonates might have the potential to improvehe osseointegration of dental implants. They may en-ance the ability of bone to integrate with the implant,

eading to more rapid and improved osseointegration.here have been few studies evaluating the effects ofisphosphonates on implant osseointegration in osteo-orotic animal models. These studies showed thatystemic administration of alendronate and ibandronatend local delivery of pamidronate and ZA from HAoating of implants improved osseointegration of dentalmplants in estrogen-deficient states of bone.7,8,13-15 Na-ai and Nagahata7 evaluated the effect of alendronate onitanium implant osseointegration in an ovariectomizedat model. The results of this study indicated that alen-ronate improved the mechanical stability of implantslaced in estrogen-deficient bone. Kurth et al8 analyzedhe effect of ibandronate treatment on osseointegrationf HA-coated and titanium implants in ovariectomizedats. They showed that integration of HA-coated im-lants was significantly enhanced by administration of

bandronate. The results of similar studies showed im-roved bony integration of implants to low-density boney local release of the bisphosphonates pamidronatend ZA from surface coatings of implants.14,15 However,o date, no article has been published evaluating theffects of systemic administration of ZA on the os-eointegration of titanium dental implants in an estro-en-deficient animal model.The purpose of this preliminary study was to evaluate

he effects of systemic administration of a single dose ofA on bone healing around titanium dental implants invariectomized rabbits by histomorphometry, radioden-itometry, and biomechanical tests. The hypothesis ofhis study is that the negative effects of estrogen defi-iency on osseointegration of titanium implants will beeversed after systemic administration of ZA.

aterials and Methods

ANIMALS

Thirty-six adult female New Zealand rabbits aged 6

o 12 months with a mean weight of 3 kg were a

ncluded in this study. The rabbits were housed inndividual cages with a circadian light rhythm of 12ours. Standard pelleted laboratory chow (Tavas AS,dana, Turkey) and water ad libitum were available to

he rabbits. All animal procedures were approved byhe ethics committee and performed in complianceith the guidelines for the care and handling of ex-erimental animals of the medical research center atukurova University, Adana, Turkey.

EXPERIMENTAL DESIGN

Rabbits were randomly assigned to 1 of 3 groups:ham control group (SH) (n � 12), ovariectomy groupOVX) (n � 12), and OVX and ZA group (OVX � ZA)n � 12). Bilateral ovariectomies were performed inhe OVX and OVX � ZA groups under general anes-hesia with intramuscular injection of 40 mg/kg ofetamine hydrochloride (Alfamine; EgeVet, Izmir,urkey) and 5 mg/kg of xylazine (Alfazine; EgeVet).or the sham ovariectomy (SH) group, the ovariesere examined and returned to the original positionnder the same protocol. After 8 weeks, implant sur-ery was carried out with rabbits under general anes-hesia. Drug administration was performed before im-lant surgery with an infusion pump. We administered.1 mg/kg of ZA (Zometa; Novartis, Basel, Switzerland)s a single intravenous infusion over a period of 10inutes before implant surgery to the animals in theVX � ZA group, whereas saline solution infusionsere given to the animals in the SH and OVX groups.ne implant was placed in each tibia of all animals.efore implant surgery, the legs were shaved, washed,nd decontaminated with an antiseptic iodine solu-ion. Fascio-periosteal flaps were elevated in the me-ial surface of the proximal metaphysis of the tibia,nd implant sites were prepared. Dental implantsith resorbable blast media surfaces (6.0 mm in

ength and 4.0 mm in diameter; BioLok International,eerfield Beach, FL) were used in this study. Implant

engths were modified for this study by the manufac-urer. After implantation, the fascia and skin werelosed in separate layers with resorbable sutures.ostoperative daily injections of 1 mg/kg of tramadolydrochloride (Contramal; Abdi Ibrahim, Istanbul,urkey) and 50 mg/kg of cefazolin sodium (Cefamez-

ne; Eczacıbası, Istanbul, Turkey) were administeredor 3 days. Eight weeks after implant surgery, animalsere killed by intravenous injection of 100 mg/kg ofentobarbital sodium (Pental; Bilim Pharmaceuticals,stanbul, Turkey). Tibial specimens including the im-lants were bilaterally removed by en bloc resection.Twelve implants in each group were subjected to

emoval torque testing, and the others were preparedor histomorphometric analysis. All of the implantshat successfully completed the healing period were

lso prepared for digital radiographic absorptiometry

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nalysis. Twenty implants in each group were sub-ected to resonance frequency analysis (RFA).

HISTOMORPHOMETRIC ANALYSIS

Implants that were not subjected to removal torqueesting were prepared for histomorphometric analy-is. The specimens were fixed in 10% buffered forma-in, dehydrated in increasing concentrations of etha-ol (70% to 99%) over a period of 10 days, andmbedded in methylmethacrylate (Technovit 7200LC; Heraeus Kulzer, South Bend, IN). Fifty-microme-

er-thick, undecalcified sections were prepared by usef a diamond-coated saw cutting and grinding systemExakt, Norderstedt, Germany). Sections were stainedith toluidine blue, and digital images were obtainedy a digital camera attached to a light microscopeOlympus DP 70; Olympus, Tokyo, Japan) at a mag-ification rate of �40. The percentage of bone-to-

mplant contact (BIC) at the lateral sides of the im-lants was calculated with image analysis softwareImageJ 1.33u; National Institutes of Health, Bethesda,D). Because the surface at the bottom of implantsas a machined surface (implants were cut to aeight of 6 mm during the manufacturing process),he apical surfaces were not included in the BICalculations.

REMOVAL TORQUE TEST

The tibial samples were wrapped in saline solu-ion–soaked gauze and stored at �20°C and werehen thawed at room temperature on the day of me-hanical testing. The bone samples containing im-lants were fixed in acrylic blocks and placed in aesting apparatus (Fig 1). Gradually increasing un-crewing torque was applied to the implants, and theeak torque value required for loosening the implantsas recorded with a digital torque gauge (Lutron

IGURE 1. Removal torque testing setup. A digital torque gaugeLutron TQ-8800) was used to measure the removal torque of themplants.

pildiz et al. Zoledronic Acid and Implant Osseointegration. J Oralaxillofac Surg 2010.

Q-8800; Lutron Electronic Enterprise, Taipei, Tai-an).

RESONANCE FREQUENCY ANALYSIS

Twenty implants were randomly selected in eachroup and subjected to RFA. Transducers were at-ached to the implants, and resonance frequencyalues were recorded for each implant (Osstell In-egration Diagnostics, Savedalen, Sweden) as im-lant stability quotient (ISQ) values. ISQ valuesere recorded right after the implantation (ISQ-I)

nd when the animals were sacrificed, 8 weeksostoperatively (ISQ-F).

DIGITAL RADIOGRAPHIC ABSORPTIOMETRY

Digital radiographs of the tibial bone specimensere obtained from the lateral aspect, with an alumi-um step wedge attached to the sensor of the digitaladiography device (RVG; Trophy Radiologie, Vin-ennes, France). The aluminum step wedge consistedf 10 steps, with a thickness ranging from 0.5 to 5m. The same aluminum step wedge was used for all

adiographs. The x-ray unit (Philips Densomat; Phil-ps, Eindhoven, The Netherlands) was set at 65 kilo-olt peak, 300 mA, and 0.16 milliseconds. The x-rayone was directed perpendicular to the sensor, at aistance of 20 cm. Digital images were converted toIFF format by use of image software (Adobe Photo-hop CS2; Adobe Systems, San Jose, CA). Bone densityas measured with image analyzing software (ImageJ

.33u). The gray level of each step of the aluminumtep wedge was measured and used for calibration ofhe software (Fig 2). Aluminum-equivalent bone den-ity around the implants was measured. The resultsre expressed as millimeters of aluminum.

STATISTICAL ANALYSIS

Statistical analysis was performed with SPSS soft-are, version 15 (SPSS, Chicago, IL). Data regardingFA, removal torque test, and BIC percentages weretatistically analyzed by use of the Kruskal-Wallis non-arametric test, and multiple comparisons were per-

ormed by use of the Mann-Whitney U test. Pairedata from initial and final RFA measurements (ISQ-Ind ISQ-F) were analyzed with the Wilcoxon signedank test. Statistical analysis of radiographic absorpti-metry was performed by use of 1-way analysis ofariance (Scheffé test). A P value of .05 was consid-red significant.

esults

Despite all efforts, 1 animal in each of the SH, OVX �A, and OVX groups was sacrificed early because ofibial bone fractures and wound infection after im-

lant surgery and was excluded from the study. The

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emaining 33 animals were considered in our evalua-ion.

HISTOMORPHOMETRY

One implant in each of the OVX and SH groups wasxcluded from histomorphometric analysis becausef failure of osseointegration. The highest BIC per-entage was detected in the SH group, with a meanalue of 53.017% � 7.8366%, as compared with6.025% � 5.8081% in the OVX group and 43.084% �.3701% in the OVX � ZA group (Table 1, Fig 3).

REMOVAL TORQUE TEST

One implant failed to osseointegrate in each of theVX and OVX � ZA groups. One implant could note placed in the SH group because of a longitudinalone crack. The mean removal torque value was

IGURE 2. Densitometry measurement of tibial specimen withluminum step wedge. The area selected for radiodensitometricnalysis is marked with a rectangle.

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Oralaxillofac Surg 2010.

Table 1. COMPARISON OF PERCENTAGE OF BIC, REMO

SH [Mean � SD (n)]

IC (%) 53.017 � 7.8366 (10)TQ (N-cm) 31.83 � 11.030 (10)ensity (mm of aluminum)(aluminum equivalent) 2.760 � 0.2611 (20)

Abbreviation: RTQ, removal torque test.*Statistically not significant.

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Oral Max

1.83 � 11.030 N-cm in the SH group, followed by0.71 � 6.509 N-cm in the OVX � ZA group and1.02 � 10.386 N-cm in the OVX group. There waso significant difference between the groups (P �

056) (Table 1, Fig 4).

RESONANCE FREQUENCY ANALYSIS

The results of RFA measurements are shown inable 2. Failed implants and the samples obtained

rom the animals that were sacrificed early were alsoxcluded from RFA statistics. The final ISQ level of 1mplant could not be measured in the OVX � ZAroup because of difficulty in attaching the trans-ucer properly because of excessive bone appositionround the implant neck. (Samples were excluded forimplants in the SH group, 4 implants in the OVX �A group, and 2 implants in the OVX group.) Theifferences between the initial and final ISQ values inach group were statistically significant. Initial RFAeasurements in the OVX and OVX � ZA groups

howed significantly lower ISQ-I values comparedith the SH group (SH vs OVX, P � .007; SH vs OVX �A, P � .001). There was no significant differenceetween the ISQ-I values in the OVX and OVX � ZAroups. The final RFA measurements showed statisti-ally significant differences between the ISQ-F valuesn the OVX � ZA and OVX groups (P � .012) and SHnd OVX groups (P � .001). The difference betweenhe ISQ-F values in the SH and OVX-ZA groups wasot significant (Fig 5).

DIGITAL RADIOGRAPHIC ABSORPTIOMETRY

One sample in each of the SH, OVX � ZA, and OVXroups was excluded from the radiodensitometricnalysis. The mean aluminum thickness equivalent ofhe gray pixel values in the SH, OVX � ZA, and OVXroups was 2.760 � 0.2611 mm of aluminum, 2.731 �.2366 mm of aluminum, and 2.523 � 0.2527 mm ofluminum, respectively (Table 1). The differences be-ween the SH and OVX groups (P � .014) and the SHnd OVX � ZA groups (P � .033) were statisticallyignificant (Fig 6).

ORQUE VALUES, AND DENSITOMETRY VALUES

OVX � ZAean � SD (n)]

OVX[Mean � SD (n)] P Value

4 � 5.3701 (11) 36.025 � 5.8081 (10) P � .0011 � 6.509 (10) 21.02 � 10.386 (10) P � .056*

1 � 0.2366 (21) 2.523 � 0.2527 (21) P � .006

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iscussion

Osteoporosis is a skeletal disease characterized by aeduction in bone mass and microarchitecturalhanges in bone, which leads to increased bone fra-ility and increased risk of fracture.16,17 Several stud-es have reported that the medical status of the pa-ient has been associated with failure of dentalmplants. Recently, the number of patients with seniler postmenopausal osteoporosis presenting for im-lant treatment has increased with the growth of thelderly population.1 It is well known that osteoporo-is results in reduced jaw bone mass as well as alter-tions of alveolar bone structure. The negative effects

IGURE 3. Histologic views of SH (A), OVX (B), and OVX � ZAC) groups (toluidine blue stain, original magnification �40).

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Oralaxillofac Surg 2010.

f osteoporosis on alveolar bone density have been o

hown in numerous studies.18-20 Bisphosphonates arehe most widely used drugs for the treatment of os-eoporosis.

In previous animal studies, the effects of bisphos-honates on osseointegration of implants have beenvaluated. Duarte et al5 evaluated whether alendro-ate influences bone healing around titanium im-lants inserted in ovariectomized rats. The results ofhis study showed that alendronate and estradiol treat-ent had positive effects on osseointegration. They

oncluded that alendronate may prevent the negativenfluence of estrogen deficiency on bone healinground titanium implants inserted in ovariectomizedats. Giro et al13 investigated the influence of estrogeneficiency and its treatment with estrogen and alen-ronate on the removal torque of osseointegrated tita-ium implants. The results of this study showed theegative effects of osteoporosis on the removalorque of implants and enhancement of the removalorque with alendronate treatment.

Oral surgical procedures including dental implantsre not recommended for cancer patients being ad-inistered intravenous bisphosphonates because of

he risk of bisphosphonate-related osteonecrosis ofhe jaws.21 However, some authors claim that there isot a risk of bisphosphonate-related osteonecrosis ofhe jaws developing as a result of implant surgery inatients taking bisphosphonates with the doses used

or the treatment of osteoporosis.22,23 To our knowl-dge, there is no published clinical study evaluatinghe success of dental implants in subjects receivingnnual bisphosphonates for the treatment of osteopo-osis. In this study the effects of ovariectomy-inducedstrogen deficiency and its treatment with systemicA administration on the osseointegration of titanium

mplants were evaluated.Ovariectomy is the most widely used method to

btain an animal model of postmenopausal osteopo-osis.1 Although rats are primarily used for this pur-ose, the lack of intracortical remodeling in thesenimals compromises the physiologic investigationf cortical bone. However, rabbits achieve skeletalaturity shortly after reaching complete sexual de-

elopment at approximately 6 months, and theyhow significant intracortical remodeling, unlikeats.24 Studies comparing bone density in estrogen-eficient rabbit models that were established solelyhrough ovariectomy showed that negative effects ofvariectomy on bone density and new bone forma-ion appear after about 12 weeks.19,25-27 Cao et al19

valuated the effects of ovariectomy on bone densityf the mandible of rabbits, and 12 weeks after ovari-ctomy of rabbits, they found a significant loss ofandibular bone density. Öberg et al25 studied the

ffect of antigen-extracted allogeneic bone on healing

f tibial bone defects in an ovariectomized rabbit

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odel. They performed tibial bone surgery 4 weeksfter ovariectomy and observed the animals for 8eeks. The results showed incompletely healed boneefects in the ovariectomized group compared withham-operated animals 12 weeks after ovariectomy.n another study Arslan et al26 compared the boneensity of an area that had undergone distractionsteogenesis in ovariectomized and sham-operatedabbits, and they reported a significant reduction ofew bone formation in the surgical gap in the ovari-ctomized group 6 weeks after ovariectomy. A similarodel was used in the study by Jung et al.27 They

nalyzed the osseointegration of implants in an ovari-ctomized rabbit model. Their results showed de-reased BIC and mechanical integration of implants inhe ovariectomized group 2 months after ovariecto-y/sham operation. When the 16-week length of our

tudy is taken into consideration, it can be predictedhat ovariectomized rabbits were influenced by estro-en deficiency during the osseointegration period.Rabbit tibias have been frequently used as a recip-

ent sight for placement of titanium implants in os-eointegration studies. Different methods have beensed for evaluation of the bony integration around

FIGURE 4. Com

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Ora

Table 2. COMPARISON OF INITIAL AND FINAL RESONA

SH[Mean � SD (n)]

FA ISQ-I 68.18 � 3.807 (17)FA ISQ-F 72.94 � 2.709 (17)ifference in ISQ 4.76 � 2.173 (17)value (ISQ-I vs ISQ-F) P � .001

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Oral Max

mplants. In our study histomorphometry, removalorque test, RFA, and digital radiographic absorptiom-try were preferred as objective measurement tech-iques.Histomorphometric results showed the negative ef-

ects of ovariectomy on the osseointegration process.nalysis of histologic sections showed increased cor-

ical porosity in the OVX group compared with theH group. Inversely, the percentage of BIC was sig-ificantly decreased in the OVX group compared withhe SH group. Administration of ZA seemed to im-rove the BIC of implants placed in the tibial bone ofstrogen-deficient rabbits. The results indicated 19%igher BIC values in the OVX � ZA group comparedith the OVX group (P � .010). However, the differ-

nces in BIC between the SH and OVX � ZA groupsas still statistically significant (P � .006). These

esults suggest that the administration of a single dosef ZA seems to enhance bone regeneration aroundental implants in estrogen-deficient subjects; how-ver, by this application, the BIC percentages did noteach the level of control subjects (SH group).

Mechanical stability of the implants was evaluated byse of RFA and removal torque measurements. The

n of BIC values.

illofac Surg 2010.

FREQUENCY VALUES

VX � ZAn � SD (n)]

OVX[Mean � SD (n)] P Value

� 3.981 (16) 64.06 � 4.207 (18) P � .003� 2.019 (16) 68.26 � 4.176 (18) P � .001� 2.530 (16) 4.17 � 2.816 (18) P � .001� .001 P � .001

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ccuracy of these methods has been proved in severaltudies.28-31 Differences in mean removal torque valuesere not statistically significant (P � .056). This mighte the result of an insufficient number of samples thatould be assigned for removal torque testing (Table 1).According to RFA analysis, initial measurements

howed lower ISQ values in the OVX and OVX � ZAroups compared with the SH group. This resulthows that in ovariectomized animals the primarytabilization of implants decreases, which might beelated to negative effects of estrogen deficiency onhe bone quality. The final ISQ values of the implantsn the SH and OVX � ZA groups were also signifi-antly higher than those in the OVX group. Becausehe highest increase in ISQ values was detected in theVX � ZA group, it may be concluded that ZA ad-

FIGURE 5. Comparison

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Ora

FIGURE 6. Comparison of densitome

ildiz et al. Zoledronic Acid and Implant Osseointegration. J Oral Max

inistration significantly contributed to bone qualitynd implant stabilization in poor-quality bone (Table 1).

In this study, digital radiographic absorptiometry wassed to assess bone density around implants. Densitom-try measurements with digital radiographic absorpti-metry have a strong correlation with those obtainedith other bone densitometry techniques.32-34 Opera-

or errors have been reduced with the improvementn radiographs obtained under standard conditions.he development of computer-assisted imaging hasontributed to the precision of the radiographs.32

one mineral density (BMD) measurements showed aignificant difference between the groups (P � .006).ean aluminum-equivalent bone density in the OVX

roup was significantly lower than that in the SHroup (P � .014). Mean BMD in the OVX group had

al and final ISQ values.

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522 ZOLEDRONIC ACID AND IMPLANT OSSEOINTEGRATION

ecreased by 9.4% 16 weeks after ovariectomy, indi-ating reduced trabecular bone density and reducedortical bone thickness of the tibiae. Previously, Morit al35 found similar results, showing a decrease inibial BMD values by approximately 12% in rabbits 1onth after applying ovariectomy and a low-calcium

iet. Differences in mean BMD between the SH andVX � ZA groups were not statistically significant.his result shows the efficiency of ZA in preventing

he reductive effects of osteoporosis on the corticalone thickness of rabbit tibias.Aside from their inhibitory effects on osteoclasts,

nabolic effects of bisphosphonates were also shownn in vitro studies. The improving effects of bisphos-honates on osteoblast proliferation, maturation, andifferentiation were shown in these studies.36-39 Im etl36 showed a significantly increased osteoblastic cellumber and enhanced gene expression of bone mor-hogenetic protein 2, type I collagen, and osteocalcinith alendronate and risedronate in cell cultures. Vi-

reck et al37 studied the effects of pamidronate andoledronate on osteoprotegerin messenger ribonu-leic acid levels and protein production in primaryuman osteoblasts and suggested that enhancementf osteoprotegerin by bisphosphonates could be re-

ated to their stimulatory effects on osteoblastic dif-erentiation. Fromigué and Body38 showed that iban-ronate and zoledronate stimulated the proliferationf human osteoblast by up to 30%. They concludedhat the beneficial effects of bisphosphonates on boneass could be partly mediated through a direct action

n osteoblasts.The results of our study show enhanced bone gen-

ration and improvement in implant osseointegrationue to application of ZA in an estrogen-deficient statef bone. This might be explained by anti-osteoclasticnd anabolic effects of ZA.

This experimental study showed that systemic ad-inistration of a single dose of ZA improved thesseointegration of titanium dental implants thatere placed in the tibial bone of osteoporotic rabbits.

t is believed that osseointegration of dental implantsn osteoporotic subjects requires a prolonged periodf time compared with normal individuals because of

mpaired bone quality. The results of this study sug-est that the osseointegration period for dental im-lants might be reduced in osteoporotic bone byystemic administration of ZA. This assumption maye verified by further clinical studies assessing theuccess of dental implants placed in patients receiv-ng annual ZA doses for treatment of osteoporosis.

cknowledgment

The authors thank Dr Ufuk Tatli for technical assistance.

eferences1. Duarte PM, Cesar Neto JB, Goncalves PF, et al: Estrogen defi-

ciency affects bone healing around titanium implants: A histo-metric study in rats. Implant Dent 12:340, 2003

2. Branemark PI: Osseointegration and its experimental back-ground. J Prosthet Dent 50:390, 1983

3. Marco F, Milena F, Gianluca G, et al: Peri-implant osteogenesisin health and osteoporosis. Micron 36:630, 2005

4. Qi MC, Zhou XQ, Hu J, et al: Estrogen replacement therapypromotes bone healing around dental implants in osteoporoticrats. Int J Oral Maxillofac Surg 33:279, 2004

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