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J Oral Maxillofac Surg68:1667-1675, 2010

Biomechanical Evaluation of EndosseousImplants at Early Implantation Times:

A Study in DogsPaulo G. Coelho, DDS, PhD,* Rodrigo Granato, DDS, MSc,†

Charles Marin, DDS, MSc,‡

Estevam A. Bonfante, DDS, MSc, PhD,§

Jose N.O. Freire, DDS, PhD,� Malvin N. Janal, PhD,¶

Jose N. Gil, DDS, MSc, PhD,# and Marcelo Suzuki, DDS**

Purpose: This study tested the null hypothesis that differences in surgical instrumentation, macroge-ometry, and surface treatment imposed by different implant systems do not affect early biomechanicalfixation in a canine mandible model.

Materials and Methods: The lower premolars of 6 beagle dogs were extracted and the ridges allowedto heal for 8 weeks. Thirty-six (n � 12 each group) implants were bilaterally placed, remaining for 1 and3 weeks in vivo. The implant groups were as follows: group 1, Ti-6Al-4V with a dual acid-etched surfacewith nanometer scale discrete crystalline deposition (Nanotite; Certain Biomet-3i, West Palm Springs,FL); group 2, Ti-6Al-4V with a titanium oxide-blasted fluoride-modified surface chemistry (Osseospeed 4.0S; Astra Tech, Mölndal, Sweden); group 3: Ti-6Al-4V with a bioceramic microblasted surface (Ossean;Intra-Lock International, Boca Raton, FL). Following euthanasia, implants were torqued to interfacefailure and histologically evaluated. General linear modeling (ANOVA) at 95% level of significance wasperformed.

Results: Histology showed that interfacial bone remodeling and initial woven bone formation wereobserved around all implant groups at 1 and 3 weeks. Torque values were significantly affected by time invivo, implant group, and their interaction (P � .016, P � .001, and P � .001, respectively). Regarding torquevalues, group 3, group 2, and group 1 ranked highest, intermediate, and lowest, respectively.

Conclusion: Early biomechanical fixation at 1 and 3 weeks was affected by surgical instrumentation,macrogeometry, and surface treatment present for one of the implant systems tested. The null hypothesiswas rejected.© 2010 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 68:1667-1675, 2010
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sseointegration is a phenomenon in which intimateontact between bone and biomaterials occurs at theptical microscopy level, enabling dental implants toeplace load-bearing tooth organs and restore theirorm and intraoral function.1 Specific to dental im-

*Assistant Professor, Department of Biomaterials and Biomimet-

cs, New York University, New York, NY.

†Instructor, Department of Dentistry, Universidade Federal de

anta Catarina, Florianopolis, Brazil.

‡Instructor, Department of Dentistry, Universidade Federal de

anta Catarina, Florianopolis, Brazil.

§Private Practice, Bauru, SP, Brazil.

�Private Practice, Florianópolis, SC, Brazil.

¶Senior Research Scientist, Department of Epidemiology and

ealth Promotion, New York University, New York, NY.

#Associate Professor, Department of Dentistry, Universidade Fed-d

1667

lantology, implant therapy success ratios often ex-eed 90%.2,3 However, despite the high success rateseported, basic scientists and clinicians have at-empted to decrease treatment time frames by reduc-ng the healing period for establishment of osseointe-

ral de Santa Catarina, Florianopolis, Brazil.

**Assistant Professor, Department of Prosthodontics, Tufts Uni-

ersity School of Dental Medicine, Boston, MA.

Address correspondence and reprint requests to Dr Coelho:

45 East 24th Street, Room 314a, Department of Biomaterials and

iomimetics, New York University, New York, NY 10010; e-mail:

[email protected]

2010 American Association of Oral and Maxillofacial Surgeons

278-2391/10/6807-0033$36.00/0

oi:10.1016/j.joms.2010.02.050

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1668 BIOMECHANICAL EVALUATION OF ENDOSSEOUS IMPLANTS

ration.4 For that purpose, the most commonpproach is through modification of different implantesign parameters.4,5

Implant design alterations have included changes ints structural material,6,7 its macrogeometry and/orurgical instrumentation,5,8,9 and surface modifica-ions.10-12 Although it is not well defined whetheriocompatible materials other than titanium and itslloys improve the host-to-implant response, alter-tions in macrogeometry and/or surgical instrumenta-ion and surface modifications have demonstrated sig-ificant effects at the early stages of bone healinground endosseous implants.5,8-12

Several studies have demonstrated that dependingn the interplay between final bone drilling and im-lant geometric dimensions, different bone healingechanisms and kinetics may be observed.5,13-15 If

here is intimate surgical fit between bone and im-lant surface, the interfacial bone undergoes remod-ling and is gradually substituted by woven bone thats gradually replaced by mature lamellar bone.13 How-ver, if healing chambers form in regions in whichone and implant are not in intimate contact becausef the interplay between drilling and implant dimen-ions, rapid woven bone filling occurs and long-termmplant stability is ensured by bone modeling andemodeling processes.5,13,14

Among surface modifications, implant texture hasvolved from the as-turned surfaces toward moder-tely rough surfaces because several studies havehown improved histologic and biomechanical host-o-implant response.10,12,16,17 More recently, severaltudies have shown that chemistry alterations to mod-rately rough surfaces, such as the addition of fluorider calcium phosphate in small scales (nanometer orinute scale), have resulted in further improvements

n bone to implant response at early implantationimes in vivo.12,13,15,18-20 Although several experimen-al studies have demonstrated the effectiveness ofurface modifications at early implantation times regard-ess of implant macrogeometry and drilling technique,urther experimentation is desirable to determine whatacrogeometry/drilling dimension/surface modification

esults in optimal bone-to-implant response at early im-lantation times.From a clinical perspective, it is general consensus

hat implant stability immediately and early afterlacement is desirable, because relative motion be-ween implant and bone may risk osseointegra-ion.4,16,21 Histologic studies have shown that implantrimary stability is rendered during placement, andecause of remodeling and subsequent bone apposi-ion bridging old bone and implant surface, biologicalr secondary stability is achieved.8,13,14 This rationaleas led to the presumption that if osteoclastic activity
ndermines primary stability before new bone forma- w
ion prevents implant micromotion, a stability de-rease will take place at early times after implanta-ion.22

Although substantial work has been published regardinghe effects of macrogeometry and implant surface on earlyone-implant interaction,5,8,13,14,17,18,23,24 comparativetudies regarding the effect of implant surgical ins-rumentation/macrogeometry/surface on stability atarly implantation times are sparse in the literature.hus, this investigation tested the null hypothesis thatifferent implant systems presenting distinct surgical

nstrumentation, macrogeometry, and surface wouldot present alterations in biomechanical fixation atarly implantation times in a canine mandible model.

aterials and Methods

This study used 36 endosseous implants with vari-tions in bulk geometry and surface treatment fromhree manufacturers (12 of each type).

The implant groups were as follows: group 1, Ti-Al-4V threaded implant with a dual acid-etched sur-ace with nanometer scale discrete crystalline depo-ition (Nanotite; Certain Biomet-3i, West Palmprings, FL); group 2, Ti-6Al-4V threaded implant (pre-enting microthreads in the cervical third) with aitanium oxide-blasted fluoride-modified surfacehemistry (Osseospeed, 4.0 S; Astra Tech, Mölndal,weden); group 3, Ti-6Al-4V threaded implant (pre-enting microthreads in the cervical third) with aioceramic microblasted surface (Ossean; Intra-Locknternational, Boca Raton, FL). The group 1 and 3evices presented the same physical dimensions withespect to diameter (4 mm) and length (10 mm).roup 2 implants had a 4-mm diameter and 11-mm

mplant length.Following approval of the bioethics committee for

nimal experimentation at the Universidade Federale Santa Catarina, Brazil, 6 beagle dogs with closedrowth plates (between 18 and 24 months of age) inood health were acquired for the study and followed2-week in-house period before surgery.All surgical procedures were performed under gen-

ral anesthesia. The preanesthetic procedure com-rised intramuscular administration of atropine sul-

ate (0.044 mg/kg) and xylasin chlorate (8 mg/kg).eneral anesthesia was then obtained following an

ntramuscular injection of ketamine chlorate (15 mg/g).Bilateral extractions of all 4 premolars (P1, P2, P3,

nd P4) were performed. The procedure involved aull thickness mucoperiosteal flap, teeth sectioning inhe buccolingual direction so individual roots coulde extracted by means of root elevators and forceps
ithout bone wall damage. The soft tissue was closed

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ith resorbable sutures (3-0 Vicryl, Ethicon, Lang-ome, PA).Following a healing period of 8 weeks, 1 implant of

ach design was placed by 1 experienced implantolo-ist in each of the 6 animals, 3 per mandible side;mplant configuration placement was interpolated athe distal, central, and proximal positions. Two weeksater, 1 implant of each design was placed in the otheremiarch following the same distribution of the pre-ious implant placement procedure. The animalsere euthanized 3 weeks after the first implant place-ent surgery, and each dog provided implants that

emained for 3 and 1 weeks in vivo. Such experimen-al distribution allowed the comparison of the sameumber of implants per design per mandibular regionnd time in vivo.

For implant placement, a mucoperiosteal flap wassed to expose the alveolar bone (Fig 1A), the distal

mplant was placed 0.5 cm from the first molar, and theemaining 2 implants (central and mesial) were sequen-ially placed 1 cm from each other (Fig 1B). All implantsere placed following the manufacturer’s surgical pro-

ocol (Table 1), and the soft tissue was closed withesorbable sutures (3-0 Vicryl, Ethicon; Fig 1C). Postsur-ical medication included antibiotics (penicillin, 20.000I/kg) and analgesics (ketoprofen, 1 mL/5 kg) for aeriod of 48 hours postoperatively. The euthanasia waserformed by anesthesia overdose.For biomechanical testing, the bone blocks with

mplants were adapted to an electronic torque ma-hine equipped with a 200 N-cm torque load cellTest Resources, Minneapolis, MN). Custom ma-hined tooling was adapted to the implants’ internalonnections, and the retrieved bone was carefullyositioned to minimize angulation during testing. The

mplants were torqued to interfacial fracture at a ratef approximately 0.19618 rad/s, and the maximumorque value was recorded for each specimen. Theorque machine was set to stop automatically when

torque drop of 25% from the highest load wasetected. The rationale for this procedure was toinimize interface damage, allowing its histomorpho-

ogic evaluation.15,23-25

Following biomechanical testing, the bone blocksere kept in 10% buffered formalin solution for 24ours, washed in running water for 24 hours, andradually dehydrated in a series of alcohol solutionsanging from 70% to 100% ethanol. Following dehy-ration, the samples were embedded in a methacry-

ate-based resin (Technovit 9100; Heraeus Kulzer, Wehr-eim, Germany) according to the manufacturer’s in-tructions. The blocks were then cut into slices�300-�m thickness) aiming the center of the im-lant along its long axis with a precision diamond sawIsomet 2000; Buehler, Lake Bluff, IL), glued to acrylic
lates with an acrylate-based cement, and a 24-hour c
etting time was allowed before grinding and polish-ng. The sections were then reduced to a final thick-ess of 30 �m by means of a series of SiC abrasiveapers (400, 600, 800, 1,200, and 2,400; Buehler) in arinding/polishing machine (Metaserv 3000, Buehler)nder water irrigation.26 The sections were then to-

uidine blue stained and referred to optical micros-

IGURE 1. A, A mucoperiosteal flap was used to access thelveolar bone and allow implant placement (B) 8 weeks afterxtraction of premolars. One implant of each design was placed inhe mandible, bilaterally (3 per mandible side with site interpola-ion). C, Resorbable sutures were used to close the soft tissue.

oelho et al. Biomechanical Evaluation of Endosseous Implants.Oral Maxillofac Surg 2010.

opy evaluation. The histologic features were qualita-

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ively evaluated at 50� to 200� magnification (LeicaM2500M; Leica Microsystems, Wetzlar, Germany).Statistical evaluation of torque measures employedmixed-model analysis of variance (ANOVA) with 1

etween-subjects factor (3 levels of implants). Statis-ical significance was indicated by P levels less than%, and post hoc testing employed the Fisher leastignificant difference test.

esults

The surgical procedures and follow-up demon-trated no complications regarding procedural condi-ions or other immediate clinical concerns. However,

postoperative complication was detected in one-week group hemimandible, which was excludedrom the study because of clinical instability of allmplants after euthanization.

All torque values per implant group, animal, im-lantation site, and animal are presented in Table 2.he general linear modeling (ANOVA) biomechanicalesults are presented in Table 3 and showed that timen vivo, implant group, and the interaction betweenmplant group and time in vivo significantly affectedorque values (P � .016, P � .001, and P � .001,espectively). Implantation site within arch (distal,entral, and proximal) and the interaction betweenmplant group and time in vivo/implantation site, andhe 3-way interaction between implant site, time inivo, and implant group did not significantly affectorque values (P � .98, P � .69, P � .81, and P � .52,espectively).

The overall increase in torque values from 1 to 3eeks is depicted in Table 4, and the overall differ-

nces in torque between groups presented in Table 5.t 1 week, group 3 presented a significantly higher

orque than groups 2 and 1. For implant group 1,omparable levels of torque were observed at bothmplantation times, whereas a significant increase inorque value was observed for implant group 2 as

Table 1. DETAILED DRILLING SEQUENCE FOR EACH IMP

Group 1 Group

ound drill Guide drill.0-mm twist drill 2.0-mm twist drillilot drill 3.2-mm twist drill.25-mm twist drill 3.7-mm twist drillountersink drill 4.0-mm cortical dr

3.85 twist drillrilling speed: 1,200 rpmunder irrigation

Drilling speed: 1,5under irrigation

bservation: Drilling sequencerecommended bymanufacturer for dense bone

Observation: Drillirecommended bmanufacturer for

oelho et al. Biomechanical Evaluation of Endosseous Implants.

ime in vivo elapsed from 1 to 3 weeks. ComparableCJ

evels at 1 and 3 weeks were also observed for group. However, groups 2 and 3 presented comparablealues at 3 weeks, and these values were significantlyigher than group 1 (Table 6).

SYSTEM

Group 3

1.5-mm initial drill2.5-mm twist drill2.8-mm twist drill3.2-mm twist drill3.5-mm twist drillCountersink drillDrilling speed: 1,200 rpm under

irrigation, 400 rpm for last 2 drillsuence

bone

Observation: Drilling sequencerecommended by manufacturer fordense bone

Maxillofac Surg 2010.

Table 2. IMPLANT DISTRIBUTION PER ANIMAL,SITE, TIME IN VIVO, AND THEIR RESPECTIVETORQUE VALUES

ImplantTime

In VivoDogNo.

Site (Distalto Proximal)

Torque toFailure (N-cm)

roup 1 1 1 1 25.1roup 1 1 2 2 15.1roup 1 1 3 3 18.3roup 1 1 4 1 15roup 1 1 5 2 20.1roup 1 1 6 3 23roup 2 1 1 2 31.3roup 2 1 2 3 27.3roup 2 1 3 1 26.7roup 2 1 4 2 19.8roup 2 1 5 3 18.3roup 2 1 6 1 17.5roup 3 1 1 3 109.2roup 3 1 2 1 107.1roup 3 1 3 2 123.4roup 3 1 4 3 126roup 3 1 5 1 90.5roup 3 1 6 2 89.4roup 1 3 1 1 24.5roup 1 3 2 2 41roup 1 3 3 3 20.1roup 1 3 4 1 15.1roup 1 3 5 2 27.6roup 2 3 1 2 72.3roup 2 3 2 3 92.2roup 2 3 3 1 87.3roup 2 3 4 2 53roup 2 3 5 3 66.3roup 3 3 1 3 117.3roup 3 3 2 1 101.9roup 3 3 3 2 102.3roup 3 3 4 3 57.8roup 3 3 5 1 86.8

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COELHO ET AL 1671

The nondecalcified sample processing after con-rolled torque to interface failure testing showed sim-lar bone-to-implant response. Higher magnification ofhe bone-implant interface region showed that theondecalcified sections obtained following biome-hanical testing presented minimal morphologic dis-ortion due to mechanical testing bone disruptionnd/or thin section processing (Figs 2-4). Intimateone-to-implant interaction was observed for all im-lant groups (Figs 2-4).At 1 week, initial woven bone formation was ob-

erved around all implant groups. Irrespective of theresence of microthreads in implant geometry,hroughout the whole bone-implant interface perim-ter, all groups presented a combination of regions ofnitial woven bone formation and gap regions be-ween old bone and implant surface characteristic ofnterfacial bone modelling-remodeling stages (Figs 2A,A,B, and 4A,B). Bone cracking due to implant place-ent was also observed at regions of microthreads

Figs 3A and 4A), and large pitch threaded regionsFigs 2A, 3B, and 4B).

At 3 weeks, irrespective of experimental group,ewly formed woven bone bridging the old bone and

mplant surface filled the interfacial modelling-remod-ling regions observed at 1 week, resulting in contin-

Table 4. IMPLANTATION TIME AND TORQUE (N-cm)STATISTICAL SUMMARY IN WHICH SIGNIFICANTDIFFERENCES WERE OBSERVED BETWEEN 1 AND 3WEEKS (P � .016)

Time InVivo Mean SE df

95% CILowerBound

95% CIUpperBound

Week 50.17b 3.662 15 42.36 57.97Weeks 65.28a 4.228 15 56.27 74.30

bbreviations: CI, confidence interval; SE, standard error.The same superscript letters denote statistically homoge-

eous groups.

Table 3. GENERAL LINEAR MODELING ANALYSIS OF VA

Source Numerator df

ntercept 1ime in vivo 1

mplant group 2ite 2ime in vivo*implant group 2ime in vivo*site 2

mplant group*site 4ime in vivo*implant group*site 4

sterisk represents interaction between variables.



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ous bone-implant structures (Figs 2B, 3C,D, and 4C,). Bone cracking at the thread tips was seldombserved at 3 weeks as the bone in intimate contactith the implant thread tips underwent remodeling

Figs 2B, 3C,D, and 4C,D).

iscussion

Over the past 40 years, surgical and prostheticrotocols substantially deviating from the classical-stage protocol27 have been suggested, typically un-er the rationale of implant design modifications thatould enable improved healing or biomechanical be-avior.10,11,17,18,28 Although a substantial amount ofesearch has been devoted to increasing the host-to-mplant response at early implantation times,10,11,17,18,28,29

ittle information has been published to date concern-ng the host-to-implant response considering the in-erplay between surgical protocols and implant bulkesign.5 This investigation tested the null hypothesishat different implant systems presenting distinct sur-ical instrumentation, macrogeometry, and surfaceould not present alterations in biomechanical fixa-

CE STATISTICS SUMMARY

Denominator df F P

15 246.12 .00015 0.989 .01615 68.57 �.00115 0.014 .98615 12.29 .00115 0.372 .69515 0.393 .81115 0.829 .527


Table 5. STATISTICAL SUMMARY FOR IMPLANTGROUP TORQUE (N-cm) IN WHICH SIGNIFICANTDIFFERENCES WERE OBSERVED BETWEEN GROUPS(P < .001)

ImplantGroup Mean SE df

95% CILowerBound

95% CIUpperBound

roup 1 22.08 4.84 15c 11.75 32.41roup 2 49.94 4.84 15b 39.61 60.26roup 3 101.16 4.84 15a 90.84 111.50

bbreviations: CI, confidence interval; SE, standard error.The same superscript letters denote statistically homoge-

eous groups.

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ion at early implantation times in a canine mandibleodel.The implant systems used in this study were com-ercially available and presented distinct implant ge-

metry and surfaces, as well as surgical instrumenta-ion. Group 1 implant presented a moderately roughurface with discrete hydroxyapatite crystalline dep-sition at the nanometer scale,20 group 2 presented aoderately rough surface presenting minute content

f fluoride obtained by a sequence of grit-blasting andcid etching procedures,13 and group 3 presented aoderately rough structure along with a nanometer

cale roughness pattern with calcium and phosphateinute quantities, obtained by a grit-blasting me-

hod.19 All surfaces evaluated in the study have shownuperior performance compared with their moder-tely rough predecessors at early times in differentnimal models.13,19,20 From a geometric perspective,he implants used in this study present commonlysed thread designs; microthreads were included inroups 2 and 3 but not group 1.Previous investigations using the same animalodel have described the early events of bone heal-

ng around implants of varied shapes and surfa-es.5,8,9,14 It has been demonstrated that a blood clotn close proximity to the implant surface at the im-lant surface region is established immediately after

mplant placement, and over the next hours to severalays, a sequence of cellular and vascular events orig-

nates a granulation tissue with varied degrees ofnflammatory cell content.5,8 Then, the formation of

oven bone is detected at 1 week5,8 and substantialnterfacial remodeling is observed over the next 3 to

weeks5,8,9 until lamellar bone is observed in prox-mity with the implant surface. Thus, the rationale forhoosing in vivo evaluation times of 1 and 3 weeksas to evaluate the various implant groups’ interac-

PLANT GROUP—TIME IN VIVO INTERACTIONVED (P � .001)

df95% CI

Lower Bound95% CI

Upper Bound

4 15 5.91 32.952 15 9.124 40.344 15 9.96 37.002 15 60.79 92.014 15 94.08 121.122 15 79.124 110.34

groups.


IGURE 2. A, Optical micrograph of the bone-implant interface ingroup 1 thin section shows woven bone formation in proximityith implant surface at 1 week. Bone cracking induced by implantlacement occurred in some large pitch threaded areas (arrow).ote regions of initial woven bone formation and regions betweenld bone and implant surface representative of interfacial boneodeling/remodeling stages. B, At 3 weeks, newly formed wovenone replacing the modeled/remodeled interfacial bone region,esulting in a more continuous bone–implant structure.

Table 6. TORQUE (N-cm) STATISTICAL SUMMARY FOR THE IMTORQUE IN WHICH SIGNIFICANT DIFFERENCES WERE OBSER

Implant Group Time In Vivo Mean SE

Group 1 1 Week 19.43b 6.33 Weeks 24.73b 7.3

Group 2 1 Week 23.48b 6.33 Weeks 76.40a 7.3

Group 3 1 Week 107.6a 6.33 Weeks 94.73a 7.3

bbreviations: CI, confidence interval; SE, standard error.The same superscript letters denote statistically homogeneous

oelho et al. Biomechanical Evaluation of Endosseous Implants. J Oral

ion with bone at times that would comprise the

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nset and an intermediate period of woven boneeposition and interfacial remodeling in dog mandi-les.5,8,9

Our histologic observations are in direct agreementith previous studies5,8,9 in which, irrespective of

xperimental group, initial woven bone formationlong with bone remodeling at the interfacial regionas detected at 1 week and extended to 3 weeks.5,8,9

ll groups evaluated presented higher amounts ofoven bone at the interfacial region at 3 weeks,hich may be explained by subsequent interfacialone remodeling and woven bone formation be-ween 1 and 3 weeks. The observation of bone crack-ng at the implant thread tip regions at 1 week for allpecimens and its near inexistence at 3 weeks sug-ests the extent of the region of high bone activityformation and remodeling) temporally changed overime. Such observation reflects the dynamic nature of

IGURE 3. A, Optical micrograph of a group 2 thin section bone–if woven bone formation and gaps in the space separating old blacement is observed at the microthreaded region (arrow) as wellD) at the large pitch thread regions, newly formed woven bone is shetween bone and implant surface is observed.


he bone–implant interface at early implantation i

imes despite the 3 systems’ differing surgical drillingechniques, geometries, and surfaces.

The intimate contact between newly formed bonend the 3 groups’ different surfaces suggest that theyre all highly biocompatible and osseoconductive.uch observation is in direct agreement with previ-usly published experimental animal studies.13,19,20

lthough our previous investigations15,23-25 have mea-ured bone-to-implant contact values from histologicamples that were biomechanically tested with theame methods used in the current investigation, thosetudies15,23-25 used experimental implant designs thatllowed biomechanical testing on a plane (cylindricalhaped implants without threads, unlike threaded im-lants that change in position along their long axisuring testing, potentially causing higher interfacialisruption).In contrast with our histologic findings in which all

interface shows bone modeling/remodeling represented by areasd implant surface at 1 week. Bone cracking induced by implant

arge pitch thread regions (arrow). C, At the microthreads and also3 weeks, filling the gaps present at 1 week, where intimate contact


mplantone anas (B) lown at

mplant groups presented similar interaction with

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one at 1 and 3 weeks in vivo, significant differencesere observed in biomechanical testing. The general

inear modeling (ANOVA) test detected a significantncrease of torque values over implantation time

hen all implant groups were included. Significantlyigher torque values were also observed betweenroups, with group 3, group 2, and group 1 rankedighest, intermediate, and lowest, respectively. Al-hough these observations are informative becausehe different implant systems were placed accordingo their manufacturer’s instructions, it should beoted that mainly because of the different geometriconfiguration between systems, any attempt to com-are the torque values obtained in this study to stan-ard insertion torque values commonly observed forumans or to compare the torque values obtainedetween experimental implant groups would be of

imited value.Directly related to the null hypothesis, which stated

IGURE 4. A, Optical micrograph of group 3 bone-implant interfat 1 week at the microthread and (B) also at the large pitch threadeand D, At 3 weeks, both regions of microthreads (C) and also lar

y newly formed woven bone.


hat no differences in biomechanical behavior would a

e detected over time for all groups, our resultshowed that 2 groups maintained their torque valuest the period of onset of woven bone formation andnterfacial bone remodeling and a period during

hich substantial bone activity takes place in the dogandible model, rejecting the null hypothesis. Our

esults, however, strongly suggest that the interplayetween surgical instrumentation, implant geometry,nd surface directly influences implant systems’ sta-ility at early implantation times. However, becausehis investigation was limited to only 2 evaluationoints in vivo, temporal stability decreases and in-reases among systems may have been hindered.hus, experimental multivariable studies concerningpecific effects of implant design aspects over a largerumber of evaluation times are warranted.

cknowledgments

ws woven bone formation in close proximity with implant surfacens, where bone cracking is induced by implant placement (arrow).h threads (D) present a continuous implant–bone structure bridged


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This study was supported in part by the Department of Dentistryt Universidade Federal de Santa Catarina, Brazil. The implants used

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COELHO ET AL 1675

ere purchased from all manufacturers except Intra-Lock Interna-ional, which donated the implants. The authors acknowledgealuable discussions with Dr Robert J. Miller before and during thereparation of the article.

eferences1. Albrektsson T, Branemark PI, Hansson HA, et al: Osseointe-

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4. Lemons JE: Biomaterials, biomechanics, tissue healing, andimmediate-function dental implants. J Oral Implantol 30:318,2004

5. Berglundh T, Abrahamsson I, Lang NP, et al: De novo alveolarbone formation adjacent to endosseous implants. Clin OralImplants Res 14:251, 2003

6. Lemons J, Dietch-Misch F: Biomaterials for dental implants. In:Misch CE, editor. Contemporary Implant Dentistry. Saint Louis,MO, Mosby, 1999, pp 271-302

7. Bottino MC, Coelho PG, Henriques VA, et al: Processing, char-acterization, and in vitro/in vivo evaluations of powder metal-lurgy processed Ti-13Nb-13Zr alloys. J Biomed Mater Res A88:689, 2009

8. Abrahamsson I, Berglundh T, Linder E, et al: Early bone forma-tion adjacent to rough and turned endosseous implant surfaces.An experimental study in the dog. Clin Oral Implants Res15:381, 2004

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