JOIJOURNAL OF ORAL IMPLANTOLOGY

The Clinical and Histologic Outcome of Dental Implant inLarge Ridge Defect Regenerated With Alloplast: ARandomized Controlled Preclinical TrialDavid M. Kim, DDS, DMSc1*Marc L. Nevins, DMD, MMSc1

Zhao Lin, DDS, PhD1

Ardavan Fateh, DDS1

Soo-Woo Kim, DMD, MS, DMSc1

Peter Schupbach, PhD2

Myron Nevins, DDS1

The Clinical and Histologic Outcome of Dental Implant inLarge Ridge Defect Regenerated With Alloplast: ARandomized Controlled Preclinical TrialDavid M. Kim, DDS, DMSc1*Marc L. Nevins, DMD, MMSc1

Zhao Lin, DDS, PhD1

Ardavan Fateh, DDS1

Soo-Woo Kim, DMD, MS, DMSc1

Peter Schupbach, PhD2

Myron Nevins, DDS1

A basic tenant of successful osseointegration is that the implant resides in a sufficient quality and quantity of

bone to ensure bone contact and thus stabilization. A prospective, randomized controlled preclinical trial was

conducted to evaluate the bone-to-implant contact (BIC) when placing implants in bone regenerated by 3

different combinations of biphasic calcium phosphate (BCP). Dental implants were placed into the regenerated

ridges of 6 female foxhounds; the ridges were reconstructed with different formulations of BCP in combination

with an hydroxyapatite collagen membrane. They were retrieved after 3 months to perform light microscopic

and histomorphometric analyses. Implants in each group appeared to be stable and osseointegrated. Light

microscopic evaluation revealed tight contacts between the implant threads with the surrounding bone for all 4

groups. The mean BIC ranged from 64.7% to 73.7%. This preclinical trial provided clinical and histologic evidence

to support the efficacy of all 3 formulations of BCP to treat large alveolar ridge defects to receive

osseointegrated dental implants.

Key Words: canine, localized alveolar ridge defect, alloplast, biphasic calcium phosphate, hydroxyapatitecollagen membrane, dental implants, bone-to-implant contact

INTRODUCTION

The basic tenant of successful osseointe-

gration is that the implant resides in a

sufficient quality and quantity of bone to

ensure bone contact and stabilization.

Over the years, dental implants demon-

strated a high success rate.1

Biphasic calcium phosphate (BCP) has been

investigated extensively and has emerged as a

promising bone substitute material.2–10 This graft-

ing material consists of fully synthetic hydroxyapa-

tite (HA) and beta-tricalcium phosphate (b-TCP),

mixed at various ratios. The slowly resorbing HA

acts as stable volume maintainer for bone regener-

ation, whereas the fast dissolution of b-TCP releases

calcium and phosphorous ions that stimulate new

bone formation.

Several studies have shown that BCP is a

biocompatible and effective bone replacement

substitute in sinus augmentation, and implants

placed in BCP grafted sites demonstrate a similar

survival rate compared to other grafting materi-

als.2,3,5,6 However, there are limited citations avail-

1 Department of Oral Medicine, Infection and Immunity, Divisionof Periodontology, Harvard School of Dental Medicine, Boston,Mass.2 Schupbach Ltd, Service and Research for Histology, Microscopyand Imaging, Horgen, Switzerland.* Corresponding author, e-mail: dkim@hsdm.harvard.eduDOI: 10.1563/AAID-JOI-D-12-00242

148 Vol. XXXIX / No. Two / 2013

RESEARCH

able for the application of BCP to treat large alveolarridge defects.9,11 The goal of this study was toevaluate bone-to-implant contact (BIC) when im-plants were placed in bone regenerated by differentcombinations of BCP.

MATERIALS AND METHODS

This prospective, randomized controlled preclinicaltrial utilized 6 female foxhounds to analyze thedental implants placed in bone regenerated withdifferent formulations of BCP.

Study animals and biomaterials

The study protocol was approved by the Institu-tional Animal Care and Use Committee at PARF inMassachusetts. Six female hounds (age 2–3 years,weight 20–24 kg) which were bred exclusively forbiomedical research purposes, were obtained froma licensed vendor. They were acclimated for 2weeks prior to the research commencement, andwere fed an appropriate diet with ad libitum accessto water. The biomaterials utilized for this studywere alloplastic BCPs in different formulationstogether with a barrier membrane:

� Group A (Osteon I, Dentium Co, Ltd, Seoul, SouthKorea): 70% HA and 30% b-TCP (particle size 0.5-to 1.0-mm, porosity 77%, macropore size 300–500lm, crystallinity 97%, crystal size 0.059 lm); 7sites.

� Group B (Osteon II, Dentium): 30% HA and 70% b-TCP (particle size 0.5- to 1.0-mm, porosity 70%,macropore size 250 lm, crystallinity 97%, crystalsize 0.043 lm); 7 sites.

� Group C (Osteon II collagen, Dentium): a mixtureof 30% HA, 70% b-TCP (particle size 0.5- to 1.0-mm, porosity 70%, macropore size 250 lm,crystallinity 97%, crystal size 0.043 lm), andcollagen; 92% graft and 8% collagen by volume;7 sites.

� Group D: negative control (no grafting).

The barrier membrane used in bone grafting wasHA-collagen membrane (Genoss Co, Ltd, Suwon,South Korea).

General and local anesthesia

All surgical procedures were performed undergeneral and local anesthesia in sterile conditions.

Xylazine hydrochloride (2.2 mg/kg, intramuscularly)and tiletamine hydrochloride/zolazepam hydrochlo-ride (10 mg/kg, intramuscularly) were administeredinitially, followed by inhalation of 1.5% to 2%isoflurane as a general anesthesia for the durationof the procedure. Local anesthesia (2% lidocainewith 1:100 000 epinephrine) was provided at thesurgical sites.

Surgical extraction and defect creation

The bilateral mandibular first, second, third, andfourth premolars (P1–P4) were extracted. Standard-ized alveolar ridge defects (approximately 12 mmmesiodistally and 10 mm apicocoronally) were thencreated by removing the buccal plate and leavingthe lingual wall intact. Periosteal releasing incisionswere made, and the flaps were adapted to achievetension-free, primary closure. There was a healingperiod of 2 months after the surgery to eliminateany spontaneous bone regeneration.

Ridge augmentation procedure

Two months after extraction and alveolar ridgedefect creation, ridge augmentations were per-formed to repair the defects (Figure 1a). Each sitewas randomized to receive 1 of 4 treatmentmodalities (groups A–D). A crestal incision wasmade for surgical access, followed by mucoperios-teal flaps to expose the mental foraminae. The graftmaterials were condensed into the defects accord-ing to a randomized distribution pattern so that notwo adjacent sites received the same material. HA-collagen membranes were used to cover all sitesand were stabilized with stainless steel pins(Dentium). Tension-free primary flap closure wasachieved by periosteal releasing incision andinterrupted sutures. The animals received thestandard postsurgical infection and pain controlconsisting of cefazolin sodium (20 mg/kg, intramus-cularly) and buprenorphine HCl (0.02 mg/kg,intramuscularly). The sutures were removed after14 days, and the animals were fed a soft diet duringthe entire healing period and treatment phase.

Implant placement

The surgical sites healed for 3 months at which timeradiographs and photographs were taken. Fullthickness flaps were elevated to expose theregenerated ridges (Figure 1b). The osteotomy

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Kim et al

was prepared by a 2.4-mm diameter trephine bur(Dentium) with the bone cores harvested forhistologic analysis, and the results were presentedin a previous report.11 The submerged implants hada sandblasted, large grit, and acid-etched surface(Dentium Superline) with a diameter of 3.6 mm andlength of 10 mm (Figure 1c).

Histologic staining and histomorphometricanalysis

The animals were sacrificed 3 months after theimplant placement (Figure 1d), and the sampleswere fixed in 10% formalin and submitted forhistologic analysis.

Fixed samples were dehydrated in a gradedseries of ethanol (60%, 80%, 96%, and absoluteethanol) using a dehydration system with agita-

tion and vacuum. The blocks were infiltrated withKulzer Technovit 7200 VLC-resin (Heraeus Kulzer,Wehrheim, Germany). Infiltrated specimens wereplaced into embedding molds, and polymerizationwas performed under blue and white light.Polymerized blocks were sectioned in a mesiodis-tal direction and parallel to the long axis of eachimplant. The slices were reduced by microgrindingand polishing using an Exakt grinding unit (EXAKTAdvanced Technologies GmbH, Norderstedt, Ger-many) to an even thickness of 30–40 lm. Sectionswere stained with Sanderson’s rapid bone strainand counter-stained with acid fuchsin and exam-ined using both a Leica MZ16 stereomicroscopeand a Leica 6000DRB light microscope (LeicaMicrosystems, Glattbrugg, Switzerland). Histomor-phometric measurements were performed by

FIGURES 1 AND 2. FIGURE 1a. A healing period of 2 months was allowed following the creation of chronic bony defects beforeeach site of the jaw was randomized to receive 3 different bone grafting materials (groups A, B, and C), in addition to anegative control site (group D, defect only). Hydroxyapatite-collagen membranes were used to cover all grafted sites andwere stabilized with stainless steel pins. FIGURE 1b. The surgical sites were allowed to heal for 3 months prior to the implantplacement. Graft consolidation was noted in all 3 groups, but some grafted sites were distinguishable from the surroundinghost bone due to the visible presence of remaining graft particles. FIGURE 1c. Trephine burs were used to harvest a bonecore from each site, and the dental implants were then placed into the trephined sites. FIGURE 1d. Dental radiographs taken3 months after the implant surgery revealed the presence of radiopaque granules surrounding the dental implants withoutnoticeable bone loss. FIGURE 2a. Group D (negative control) specimen demonstrated the maintenance of the crestal bonelevel up to the cover screw and histologic features that were indicative of successful osseointegration. FIGURE 2b. A highmagnification of the implant threads demonstrated tight contact with the surrounding bone.

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Outcome of Dental Implant in Regenerated Large Ridge Defect

using a software (ImageAcess, Imagic, Glattbrugg,

Switzerland) to calculate the percentage of min-

eralized bone, soft tissue components (connective

tissue and/or bone marrow), and residual graft

particles along the bone-implant-contact surface.

Statistical analysis

Means and standard deviations were calculated for

all quantitative data. Due to the sample size,

collected data of each group were compared by

Kruskal-Wallis test with Mann-Whitney U test for

pairwise comparisons after Bonferroni correction to

adjust for multiple statistic testings. P , .05 was

considered to be statistically significant. The statis-

tical analysis was performed using a commercially

available software program (SPSS for Windows,

version 19.0, IBM Corp, Somers, NY).

RESULTS

No adverse events were observed during the

implant healing stage. All implants appeared to be

stable and osseointegrated (Figures 2a through 3f).

They were surrounded by radiopaque granules

without noticeable bone loss upon radiographic

evaluation (Figure 3a through c). Light microscopic

evaluation revealed tight contacts between the

implant threads with the surrounding bone for all 4

FIGURE 3. Dental implants from tested groups (groups A, B, and C) demonstrated the maintenance of the crestal bone levelup to the cover screw and histologic features that were indicative of successful osseointegration. High magnifications ofimplants threads (Figure 3d and f) revealed tight contact with the newly regenerated bone. Graft remnants can be noted inall 3 groups (Figure 3a,d¼ group A, Figure 3b,e ¼ group B, Figure 3c,f ¼ group C).

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Kim et al

groups, indicating successful osseointegration (Fig-ures 2b and 3d through f).

Histologically, all implants demonstrated os-seointegration. Light microscopy revealed excellentBIC in all groups. The mean BIC was 64.7% (groupA), 73.7% (group B), 68.2% (group C), and 83.1%(group D) with some residual graft particles presentaway from the implant surface (Figure 4). Nostatistically significant difference was noted amonggroups A through D in terms of BIC (P ¼ .173,Kruskal-Wallis test). New bone was found in contactwith the implant surfaces with less BIC in themarrow space of the mandible. The newly formedbone was dense with normal bone marrow spacesand blood vessels.

DISCUSSION

Previous studies have shown that BCP bonesubstitute material can be successfully utilized toreconstruct large alveolar bone defects.9,11 Thisstudy provided clinical and histologic evidence thatregenerated bone can lead to dental implantosseointegration with survival of all implants.

BCP has been widely used as an augmentationmaterial in sinus lift studies.2,3,5,6,12 Cha et al12

reported 95.56% cumulative survival rate in 45implants, with the 80/20 HA/b-TCP (BCP) material.Lee et al3 used 50/50 HA/b-TCP (BCP) as bonesubstitute in the sinus lift and observed a 98.46%cumulative success rate after a mean period of 12months. Tosta et al13 showed 100% implant survivalrate in 15 patients using BCP. Taken together, ourresult demonstrated BCP is suitable and excellentmaterial for large alveolar defect regeneration andexcellent bone-to-implant contact resulting inosseointegration.

It has been shown that the ratios between HA

and b-TCP significantly affect the resorption rate of

BCP in vivo. The degradation rate of b-TCP is about

3–12 times faster than HA. Therefore, a higher HA

ratio will result in a longer degradation time and

more residual graft particles.14 A ratio about 20/80

HA/b-TCP stimulated earlier and more new bone

formation.14,15 Our observation indicates more new

bone formation with reduced residual matrices in

group B, which is consistent with the above

investigation.11

Although more new bone formation is related to

a higher b-TCP ratio in BCP material, it was not clear

how it will translate into improved BIC. All 3

experimental groups (groups A through C) demon-

strated a high BIC (more than 60%), but without a

statistical difference among different HA/b-TCP

formulations. Albrektsson16 suggested a minimum

of 50% BIC to ensure successful long-term loading

of osseointegrated implants. All 3 groups demon-

strated higher results and therefore meet the

criterion.

CONCLUSION

This preclinical trial provides clinical and histologic

evidence to support 3 formulations of HA/b-TCP to

be efficacious bone substitutes for regenerating

large alveolar ridge defects to receive osseointe-

grated dental implants.

ABBREVIATIONS

b-TCP: beta-tricalcium phosphate

BCP: biphasic calcium phosphate

BIC: bone-to-implant contact

HA: hydroxyapatite

ACKNOWLEDGMENT

This study was sponsored by a grant from Dentium

and Genoss.

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