the international journal of periodontics & restorative...

The International Journal of Periodontics & Restorative Dentistry

Since the acceptance of dentalimplants as a valid treatment modal-ity for the completely1,2 or partially3,4

edentulous patient, bone graftinghas been proposed, either be-fore5–15 or simultaneously with16–19

the placement of dental implants,so that implants may be placed inpatients lacking adequate bone vol-ume. While xenografts,15,20–25 allo-plastic bone grafts,26,27 and allo-grafts13,14,28,29 have been proposedand studied for alveolar ridge aug-mentation, the use of autogenousbone remains the gold standard forbone augmentation procedures.

Autogenous bone graft has beenused as a block,5,7–12,18,19 in particu-late form,13,30–32 or in combinations ofblock and particulate forms.15,33

When autogenous bone graft is usedin particulate form, various tech-niques have been applied to securethe graft material at the recipient site.Nonresorbable membrane barri-ers7,29–33 and titanium mesh34–37 havebeen proposed as securing devicesfor particulate bone graft. Block graftscan be secured at the recipient sitewith fixation screws5,8–12,15,33 or dental implants.16–19

Autogenous block grafts, incomparison to particulate bone mar-row, have been associated with

Periklis Proussaefs, DDS, MS*Jaime Lozada, DDS**

This study presents a clinical, radiographic, laboratory, and histologic/histomor-phometric analysis of the use of mandibular block autografts for vertical alveolarridge augmentation. Twelve patients were included in the study. The autogenousblock autografts were fixated at the recipient sites with screws, and a mixture ofautogenous bone marrow and inorganic bovine mineral (Bio-Oss) was used at theperiphery. At re-entry surgery, all the grafts appeared well incorporated at therecipient sites. Radiographic measurements revealed an average of 5.75 ± 1.29mm vertical ridge augmentation at 1 month after surgery and 4.75 ± 1.29 mm at4 to 6 months after surgery. This indicated 17.4% resorption. Laboratory volumet-ric measurements revealed an average of 0.84 ± 0.34 mL of alveolar ridge aug-mentation 1 month after surgery and 0.71 ± 0.28 mL at 6 months postoperatively.The resorption rate according to the laboratory volumetric measurements was15.5%. Linear laboratory measurements revealed 5.92 ± 1.38 mm of verticalridge augmentation 1 month postoperatively and 4.08 ± 1.01 mm at 4 to 6months after surgery. Histologic evaluation of the block autografts indicated signsof active remodeling activity in 10 of the 12 specimens. In one case the blockgraft became exposed and infected, and in another case the block autograftbecame dislodged during implant placement surgery. Histomorphometric analy-sis of the peripheral particulate bone indicated bone present at 33.99% ± 8.82%of the graft surface, while 42.43% ± 11.06% of the area was occupied by fibroustissue and 23.89% ± 9.12% was made up of residual Bio-Oss particles. ResidualBio-Oss particles were in tight contact with newly formed bone along 58.57% ±15.22% of their perimeter. (Int J Periodontics Restorative Dent 2005;25:351–363.)

*Assistant Professor, Graduate Program in Implant Dentistry, Loma LindaUniversity, Loma Linda, California; and Private Practice limited toImplant and Prosthetic Dentistry, Encino, California.

**Professor and Director, Graduate Program in Implant Dentistry, LomaLinda University, Loma Linda, California.

Correspondence to: Dr Periklis Proussaefs, Loma Linda University,School of Dentistry, Graduate Program in Implant Dentistry, LomaLinda, CA 92350. Fax: (909) 558-4803. E-mail: [email protected]

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Volume 25, Number 4, 2005

The Use of Intraorally HarvestedAutogenous Block Grafts for VerticalAlveolar Ridge Augmentation: A Human Study

reduced osteogenic activity38 andslow revascularization.39,40 Regardingthe source of the autogenous bone,both extraoral6,8,16,17,19,35 and intra-oral5,7–13,15,18,31–34 donor sites havebeen proposed. Several studieshave demonstrated that intraorallyharvested intramembraneous bonegrafts, in comparison to extraorallyharvested endochondral bonegrafts, demonstrate less resorp-tion,41–44 enhanced revasculariza-tion,42 and better incorporation atthe donor site.43

The current study provides clin-ical, radiographic, laboratory, andhistologic/histomorphometric analy-ses of the use of mandibular block

autografts for vertical alveolar ridgeaugmentation when a mixture ofparticulate bone marrow and inor-ganic bovine mineral was used atthe periphery of the block autograft.

Methods and materials

Patient selection

Twelve consecutively treated sub-jects (5 men and 7 women with amean age of 60.15 years; range 51 to71) participated in this study (Table 1).The subjects required vertical alveo-lar ridge augmentation before theplacement of dental implants (Fig 1).

In all the cases, an autogenous blockgraft harvested intraorally from eitherthe chin (Fig 2) or the ascendingramus area was used for grafting.The bone grafting procedures wereperformed during the period May1998 to September 2001. Treatmentwas performed by graduate studentsat the Center for Prosthodontics andImplant Dentistry at Loma LindaUniversity (LLU). All subjects weretreated by residents of the GraduateProgram in Implant Dentistry andsigned the corresponding informedconsent, which had been approvedby the Institutional Review Board atLoma Linda University, to have abiopsy taken during implant surgery.

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Table 1 Patient distribution

Healing FixationRecipient Donor period Implants screws

Patient no. Age Sex site site (months) (N) (N)

1 63 F 18-20 (35-37) Ramus 8 2 12 67 M 12-13 (24-25) Ramus 5 3 13 59 M 3-5 (14-16) Ramus 14 3 14 56 F 29-30 (45-46) Ramus 7 2 25 54 M 19-21 (34-36) Chin 6 2 16 71 F 18-21 (34-37) Ramus 4 2 27 71 F 21-23 (32-34) Ramus 5 2 18 51 M 28-30 (44-46) Chin 4 N/A* 19 68 F 18-20 (35-37) Ramus 5 N/A* 210 67 F 18-20 (35-37) Ramus 6 2 211 63 M 19 (36) Chin 9 1 112 67 F 28-30 (44-46) Ramus 5 2 2Average 60.15 N/A N/A N/A 6.5 N/A N/ASD 7.34 N/A N/A N/A 2.81 N/A N/ARange 51–71 N/A N/A N/A 4–14 N/A N/A

Tooth numbers are listed as Universal (FDI).*The block graft was dislodged during implant placement surgery.

Surgical protocol

At the time of bone grafting proce-dure or implant placement, the sub-jects were permitted to chooseeither local anesthesia (LA) only, LAwith oral sedation (Halcion, 0.25 mg,Greenstone Ltd), or LA with intra-venous sedation.

Full-thickness labiobuccal and linguopalatal flaps were reflected atthe recipient site (Fig 3). The donorsite was either the chin area (threepatients) or the ascending ramus area(nine patients) (Table 1). Harvesting ofthe bone graft was performedaccording to the standard proceduredescribed elsewhere.5,10 Briefly, forthe chin donor site, a vestibular inci-sion was made at least 2 mm beyondthe mucogingival junction. A full-thickness flap was reflected; 4 to 5mm of periosteum were left intact atthe most coronal part of the surgical

site. The bone that would be har-vested was defined 5 mm below theapex of the mandibular anterior teeth,5 mm mesial to the mental foramen,and 5 mm above the inferior borderof the mandible (Fig 2). A fissure burand a chisel were used to remove ablock autograft. Collagen hemostaticagent was placed at the donor site(Avitene; Alcon Pharmaceuticals) andthe area was sutured.

For the ramus area, after admin-istering block anesthesia for the infe-rior alveolar canal, a crestal incisionwas made distal to either of themandibular third molar areas. Theincision followed the direction of theramus, and a vertical releasing inci-sion was placed distal to the thirdmolar areas and to the ramus area.Full-thickness buccolingual flapswere reflected. Under copious irri-gation and with a fissure bur, a blockgraft was harvested. A bone chisel

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was used to detach the block auto-graft. In the chin area, the donor sitereceived collagen hemostatic agentand was then sutured. For bothdonor sites, additional bone marrowwas harvested with a curette andwas used in conjunction with inor-ganic bovine mineral (Bio-Oss,Geistlich Pharmaceuticals) aroundthe block autograft.15,33

The recipient site was perfo-rated to induce bleeding and pro-mote incorporation of the graft.45,46

The block autograft was then fixatedat the recipient site with one or twofixation screws (Fig 3), and an addi-tional mixture of autogenous bonemarrow and Bio-Oss was placed atthe periphery of the site. Periostealfenestration47,48 was performedalong the labiobuccal flap to enableprimary closure. The recipient areawas then sutured without the use ofany barrier membrane.

Fig 1 Preoperative clinical view. A verticalalveolar defect is observed indicating aneed for vertical ridge augmentation beforeimplant placement can be attempted.

Fig 2 A monocortical block autograft isharvested from the chin area.

Fig 3 The monocortical block autograftis secured at the recipient site with a fixa-tion screw.

Two weeks after the bone graftsurgery, the sutures were removed.One subject (#9) received a remov-able provisional prosthesis 2 weeksafter bone grafting. The remainingsubjects did not receive any provi-sional prosthesis during the entirehealing period.

Four to 8 months were allowedfor the bone graft to heal before theplacement of the implants (Fig 4,Table 1). One subject (#3) receivedimplants 14 months after the bonegrafting procedure, because she wasunable to return earlier for personalreasons. During implant surgery, full-thickness labiobuccal and palatolin-gual flaps were reflected (Fig 5) andthe fixation screws were removed.Hydroxyapatite-coated root-formimplants (Steri-Oss; Nobel Biocare)were placed using a surgical stent(Fig 6). All patients were treatment-planned to receive an implant-sup-ported screw-retained fixed partialdenture. A biopsy specimen wastaken from the grafted area duringimplant placement. A 2-mm internal-diameter trephine bur (ACE Surgical

Supply) was used as the first drill dur-ing the osteotomy preparation forimplant placement. The area withthe more pronounced preoperativebone deficiency was selected for thebiopsy. This biopsy specimen wastaken through the autogenous blockautograft.15 The specimens werefixed in 10% buffered formalin.

Radiographic evaluation

Measurements for the vertical boneaugmentation were made by evalu-ating the preoperative, 1-month post-operative, and 4- to 6-month post-operative periapical radiographs (Figs7a to 7c). A panoramic radiographwas taken in all cases immediatelyafter bone grafting surgery. No peri-apical radiographs were taken imme-diately after bone grafting to avoidstretching of the tissue, especially incases where the posterior mandiblewas the recipient site. All measure-ments were made by one investiga-tor (PP) under 10� magnification.49

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Laboratory evaluation

The volume and linear assessment ofthe vertical alveolar ridge augmen-tation were made with a techniquedeveloped at the Graduate Programin Implant Dentistry at LLU.50 Briefly,impressions were made around thegrafted area with a custom traymade from photopolymerizedacrylic resin (Triad; DentsplyInternational) by using irreversiblehydrocolloid as impression material(Coe Alginate; GC America). Theimpressions were made preopera-tively and 1 and 6 months after bonegrafting. The impressions werepoured with Type m dental stone(Microstone; Whip-Mix).

An impression was made fromthe postoperative stone casts withthe custom tray and silicone (Lab-putty; Coltene/Whaledent). Poly-vinylsiloxane bite registration mate-rial (Exabite II NDS; GC America)was then loaded in the tray, whichwas then placed on the preoperativestone cast, and the bite registrationmaterial was allowed to polymerize.

Fig 4 Lateral view at 3 months after bonegrafting.

Fig 5 Nine months after bone grafting,the block autograft and the peripheral par-ticulate bone graft have been well incor-porated into the recipient site.

Fig 6 After the fixation screw is removed,one threaded hydroxyapatite-coatedimplant is placed.

The bite registration material wasthen removed from the tray and theexcess material was trimmed. Theweight of the material was assessed,and by considering the specialweight provided by the manufac-turer, it was possible to calculate thevolume of alveolar ridge augmenta-tion. In addition, linear measure-ments were made by evaluating thevertical height of the bite registrationmaterial. Linear measurements weremade with a caliper (Derby DentalSupply). Linear measurements weremade at the location where preop-erative clinical and radiographicevaluation revealed the maximumbone deficiency. This method forlaboratory evaluation of alveolarridge resorption has been utilized inprevious studies.51,52

Histologic processing

The specimens were fixed in 10%buffered formalin, dehydrated inalcohol, and embedded in special-ized resin (Technovit 7200 VLC;

izontal lines (each two pixels wide),one by one, on a vertically orientedimage selected for analysis. In thisstudy, the lines were spaced 50 pix-els apart in the object plane, andthe first line was placed randomly atthe top of the image. Keyboardentries and cursor clicks recordedthe lengths of the line segments thatcrossed the various types of tissue(bone, soft tissue, or residual bonegraft particles). Intersections of lineswith residual bone graft particleswere recorded as contacting bone orsoft tissue, depending on the type oftissue at the interface.15 For eachhistologic specimen, one or twoimages were analyzed (dependingon the size of the specimen).

Percent composition of thespecimen was given by the ratio ofthe sum of the lengths of line seg-ments falling on a given component(bone, soft tissue, or graft particles)to the total length of lines analyzed.The percent of residual xenograftsurface occupied by bone was givenby the ratio of the number of lineintersections with bone-particle

Kulzer). Initial midaxial sections of200 µm were made by means of thecutting-grinding system (EXACTMedical Technologies). The sectionswere then ground to 40 to 50 µmand were stained with Stevenel’sblue and Van Gieson’s picro-fuchsinfor light microscopy.51,52

Histomorphometric evaluation

Histomorphometric evaluation wasperformed by one investigator (PP)by using a computer-assisted linearanalysis program (Ribbon) devel-oped at LLU.53 The histomorphom-etry was performed for the speci-mens where part of the peripheralparticulate bone graft (mixture ofautogenous bone marrow and Bio-Oss) was harvested during thebiopsy procedure. Because thebiopsy was taken through the blockgraft, three specimens representedonly the block autograft, with noperipheral particulate bone graft.

The Ribbon program uses aseries of systematically spaced hor-

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Figs 7a to 7c Periapical radiographs demonstrating the site (a) preoperatively, (b) 9 months after bone grafting, and (c) 6 months afterimplant loading.

interfaces to the total number ofgraft-xenograft surface intersections.

All histomorphometric analysiswas performed by capturing imagesunder 2� magnification (OlympusMicroscope, Model BH-2; McBainInstruments).

Results

Clinical evaluation

Exposure of the block graft duringhealing was observed in three of the10 cases (Table 2). In two situations(#2 and #4) the exposure occurred 3months after bone grafting, while inone case (patient #9) the exposureoccurred 2 weeks after surgery. Inthat case and 3 weeks after the expo-sure, the exposed part of the blockgraft revealed clinical signs of necro-sis (discoloration, odor, soft consis-tency when examined with anexplorer). The clinically necrotic part

was removed with a curette. Twomonths after the bone graft surgery,a new surgical procedure was per-formed in this case to attempt pri-mary closure of the block graft.Despite the new surgical interven-tion, the block graft was re-exposed2 weeks later. The necrotic bone graftwas completely removed 5 monthsafter the initial grafting surgery.

During re-entry surgery forimplant placement, all block graftsappeared to be fixated at the recip-ient site. However, during osteotomypreparation for implant placement,two of the block grafts (#8 and #9)became dislodged. In one clinicalsituation (#8) short implants were uti-lized, while in the other situation (#9)the area was scheduled for re-graft-ing. For patient #9, repeated graftexposure had resulted in necrosis ofthe autograft. All block grafts hadtype 1 or 2 bone quality.54 No com-plications occurred at the donor site,except in one patient (#5), where

dehiscence of the incision was seen3 weeks after surgery.

The peripheral particulate bonegraft (mixture of autogenous bonemarrow and Bio-Oss) appeared wellincorporated at the recipient site.The Bio-Oss particles were firmlyattached to the newly formed bone.Primary stability was achieved duringthe placement of all implants.

Radiographic evaluation

Radiographic measurementsrevealed that 5.75 ± 1.29 mm of ver-tical ridge augmentation (range 5 to9 mm) was achieved 1 month aftersurgery and 4.75 ± 1.29 mm (range4 to 8 mm) of augmentation wasachieved 4 to 6 months after surgery(Table 3). The resorption rate accord-ing to the radiographic measure-ments was 17.4%.

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Table 2 Clinical assessment

Patient no. Bone quality of graft54 Complications at donor site Complications at recipient site (before implant placement)

1 2 None None2 1 Persistent pain Exposure 1 � 3 mm3 1 Persistent pain None4 2 None Exposure 2 � 4 mm5 1 Dehiscence of incision line None6 1 None None7 1 None None8 N/A* None None9 N/A* None Exposure 4 � 7 mm10 1 None None11 1 None None12 1 None None

In all cases, the Bio-Oss appeared to be well-incorporated at the recipient sites.*The block graft was dislodged during implant placement.

Laboratory evaluation

Laboratory volumetric measure-ments revealed that a mean of 0.84± 0.34 mL (range 0.52 to 1.82 mL) ofridge augmentation was achieved 1month postoperatively, and a meanof 0.71 ± 0.28 mL of augmentationwas seen 6 months after surgery(range 0.48 to 1.53 mL) (Table 4).These measurements dictated15.5% resorption by 6 months afterthe bone grafting. Linear measure-ments revealed that 1 month afterthe grafting, 5.92 ± 1.38 mm (range4 to 9 mm) of vertical ridge aug-mentation, and 4.08 ± 1.01 mm(range 3 to 6 mm) of augmentationwas achieved by 6 months aftersurgery (Table 5).

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Table 3 Radiographic assessment (periapicalradiographs) of vertical ridge augmentation (mm)

Patient no. 1 mo 4 to 6 mo

1 7 62 9 83 5 44 5 45 5 46 7 67 6 58 5 49 5 410 5 411 5 412 5 4Mean 5.75 4.75SD 1.29 1.29Range 5–9 4–8

Table 4 Laboratory volumetric measurements (mL)

Patient no. 1 mo 6 mo

1 0.55 0.492 1.82 1.533 0.94 0.804 0.60 0.535 0.79 0.736 0.75 0.617 0.77 0.568 0.73 0.639 0.81 0.6710 1.03 0.7711 0.52 0.4812 0.78 0.69Mean 0.84 0.71SD 0.34 0.28Range 0.52–1.82 0.48–1.53

Table 5 Linear laboratory measurements(vertical augmentation, in mm)

Patient no. 1 mo 4 to 6 mo

1 8 62 9 63 5 34 5 35 6 36 6 57 6 58 5 39 4 310 6 411 6 412 5 4Mean 5.92 4.08SD 1.38 1.01Range 4–9 3–6

Histologic evaluation

The specimens from the block graftspresented a solid core composedalmost entirely of cortical bone (Fig8). In all but one patient (#9), blockgrafts demonstrated histologic signsof remodeling activity. In the situa-tion (#8) where the block autograftbecame dislodged during implantsurgery, the block autograftappeared to have signs of vitalityand remodeling activity. Polarizedmicroscopy emphasized the remod-eling pattern (Fig 9). In a specimenof grafting procedure, obtained from

patient #9, areas of necrosis wereseen close to the coronal aspect ofthe block graft (toward the exposedsurface).

Regarding the peripheral par-ticulate bone graft, a mixture ofbone, connective tissue, and resid-ual Bio-Oss particles was observed(Fig 10). In the majority of thecases, the Bio-Oss particlesappeared to be in close contactwith bone (Figs 11 and 12). Nosigns of resorption or active inflam-matory process were identified inany of the specimens.

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Histomorphometric evaluation

Histomorphometric analysis of thespecimens from which peripheralparticulate bone graft was harvestedrevealed bone in 33.99% ± 8.82% ofthe area (range 16% to 45%), soft tis-sue in 42.43% ± 11.06% of the spec-imen area (range 24% to 57%), andresidual Bio-Oss particles in 23.89%± 9.12% of the surface (range 8% to41%) (Table 6). The surface of theresidual Bio-Oss particles was in con-tact with bone at 58.57% ± 15.22%(range 42% to 79%) of the total sur-face of all particles.

Fig 8 (top left) Histologic overview of aspecimen representing a block graft (origi-nal magnification �2.5).

Fig 9 (top center) Under polarizedmicroscopy, the remodeling activity of theautogenous mandibular block autograft isemphasized (original magnification �4).

Fig 10 (top right) Histologic overview ofthe particulate peripheral bone graft (origi-nal magnification �4).

Fig 11 At a higher magnification, Bio-Oss particles (black arrows) appear to be“amalgamated” within the surroundingnewly formed bone (white arrows) (originalmagnification �20).

Fig 12 Intimate contact between resid-ual Bio-Oss particles (black arrows) andperipheral bone (white arrows) is apparent(original magnification �20).

Discussion

The present study provided histo-logic evidence in humans re-garding the potential of mandibularblock autografts to maintain theirvitality after bone grafting.Corticocancellous block grafts havebeen associated with a reduced rateof revascularization.39,40 Enneking etal40 reported that in cortical boneautografts, most of the interior ofsuch grafts was never revascularizedor replaced by viable bone. As aresult, they are prone to infection,and if infected they may neverrecover. Burchardt55 used the term“creeping substitution” to describethe dynamic reconstructive and heal-ing process of bone transplantation.He reported that cortical bone trans-plants are not penetrated by bloodvessels until the sixth day after trans-

ity to maintain their vitality by thetime exposure occurred.

In the literature there is a scarcityof human histologic evidence of thepotential of intramembranousmandibular block grafts to heal anddemonstrate signs of vitality. Shirotaet al,6 in a study that included threecases with block autografts, signs ofdevitalized bone tissue were seen inthe block grafts. Urbani et al,12 infive clinical cases, demonstratedsigns of vitality of the bone trans-plants. Matsumoto et al56 demon-strated the potential of mandibularblock autografts to maintain theirvitality. In that study, in which biopsyspecimens were taken from 10patients, mandibular autograftsappeared to have enhanced remod-eling activity and vascularity as com-pared to extraorally harvested endo-chondral bone grafts. Proussaefs etal15,33 have demonstrated in humansthe potential of mandibular blockautografts to maintain their vitality.Similar observations (histologic evi-dence of vital bone graft) have alsobeen made in an animal study46 inwhich intramembranous bone graftwas utilized as a block.

The radiographic and laboratoryvolumetric measurements in the cur-rent study demonstrated similarresorption rates (17.4% and 15.5%,respectively). This is in agreementwith other investigators. Misch et al5

reported 0% to 25% resorption,while Raghoebar et al9 reported 5%to 20% resorption with mandibularautogenous bone grafts. Proussaefset al15 reported 17% resorption at 4to 6 months after bone graftingwhen the ascending ramus was used

plantation and that the revascular-ization process may take twice aslong as when particulate bone mar-row is transplanted. According to hisstudy, cancellous bone autograftswere completely repaired, but in thecortical admixtures, both necroticand viable bone were oftenobserved. In this study, mandibularblock autografts that were exposedafter 3 months (patients #2 and #4)maintained their vitality. The blockautograft that was exposed 2 weeksafter bone grafting (patient #9)became necrotic. Within the limita-tions of the restricted number ofcases, it could be suggested thatearly exposure may result in graftnecrosis, potentially because thegraft has not obtained adequate vas-cularity to maintain its vitality. Withlate exposures, block autograftsseemed to have adequate vascular-

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Table 6 Histomorphometric analysis of particulate bone grafts

Fibrous Bone/residualPatient no. Bone % tissue % Bio-Oss % particles contact %

2 32 43 25 793 30 52 18 444 29 47 24 485 16 53 31 426 35 57 8 447 35 24 41 5410 45 30 25 7111 43 36 21 7812 41 40 19 67Average 33.99 42.43 23.89 58.57SD 8.82 11.06 9.12 15.22Range 16–45 24–57 8–41 42–79

For patients 1, 8, and 9, no particulate bone was harvested.

as the donor site. However, Widmarket al11 reported 25% resorption ofthe graft material during implantplacement and 60% at the time ofabutment connection. Althoughintramembranous mandibular bonegrafts have been shown to have areduced resorption rate versus extra-orally harvested bone grafts,41–44 it isunknown whether the resorptionprocess is continuous. Some clini-cians have reported that the resorp-tion of the bone graft slows afterimplant placement.57 Furtherresearch is required before defini-tive conclusions can be made.

In patient #8 of this study, theblock autograft became dislodgedduring osteotomy for implant place-ment. No previous complication hadbeen observed in that patient, andthe block autograft appeared wellattached at the recipient site afterflap reflection. Nevertheless, DeCarvalho et al46 have shown thepresence of a connective tissue layerbetween a mandibular block graftand the recipient bony site. Thislayer of connective tissue may offerreduced resistance to dislodgementof the block graft during implant sitepreparation. It has been recom-mended that the block graft be heldfirmly with two fingers by the sur-geon during implant osteotomy pro-cedure.15 In the patient (#8) in whomthe block graft was dislodged, 4months of healing time were allowedbefore implant surgery. Further heal-ing might have resulted in a firmerattachment of the graft to the recip-ient site. Certainly, studies of morecases are needed before definitiveconclusions can be made.

In the present study, no mem-brane barriers were utilized.Nonresorbable membrane barriershave been used to mechanically pro-tect and isolate the graft mater-ial.7,29–31 However, nonresorbablemembrane barriers have been asso-ciated with infection upon expo-sure,7,32 incomplete healing,29,30 andthe presence of a connective tissuelayer between the membrane andthe newly formed bone.29–31

Raghoebar et al9 reported that whenautogenous mandibular bone graftis used, a nonresorbable membranebarrier may not be needed becauseof the minimal resorption and highrate of revascularization of theintramembranous particulate bonegraft. Proussaefs et al15,33 haveshown that when particulate bonegraft (mixture of autogenous boneand Bio-Oss) is placed around ablock autograft, newly formed bonecan be created without the use ofany barrier above the graft material.In the technique presented here, theassumption was made that the blockgraft would provide mechanical sup-port for the surrounding particulatebone graft and no membrane barrierwould be necessary.

In the presented technique, theparticulate bone graft that wasplaced at the periphery of the blockwas a mixture of autogenous bonemarrow and inorganic bovine min-eral (Bio-Oss). The use of Bio-Osshas been well documented as aninlay bone graft for sinus graftingprocedures.58,59 On the other hand,little is known about the use of thismaterial as an onlay bone graft.While bone formation has been

shown around and in tight contactwith Bio-Oss particles at four-walldefects,21,23 no bone formation wasseen when Bio-Oss was used as anonlay graft material.20 In the currentstudy, the Bio-Oss particles weremixed with autogenous bone mar-row, which contains abundant bonecells38 to provide the necessaryosteogenic potential to the graftmaterial. Young et al25 demon-strated that when Bio-Oss is usedalone as a graft material, connectivetissue will result, while when mixedwith autogenous bone graft as afiller, newly formed bone will formthat will be in close contact with theresidual Bio-Oss particles. Proussaefset al15,33,36 have demonstrated boneformation around and in contact withBio-Oss particles when used aroundblock autografts15,33 or under a tita-nium mesh.36

A newly developed laboratorymeasuring technique was used inthis study to calculate the volume ofthe augmented alveolar ridge and toprovide linear measurements of theaugmented sites. This technique hasbeen shown to be reproducible andaccurate.50 However, in this studythe impressions were made preop-eratively and postoperatively, andincluded measurements of the softtissue as well. This imposes a limita-tion in the presented data; animpression made during the surgeryfrom the bony defect would offermore valuable results.

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Conclusions

Mandibular block autografts canmaintain their vitality when used forvertical alveolar ridge augmentation.An average of 4.75 ± 1.29 mm ofvertical ridge augmentation can beexpected, with 17.4% resorption at4 to 6 months after bone grafting.Late graft exposure does not neces-sarily result in graft necrosis, whileearly exposure will probably result incompromised healing and partial ortotal graft necrosis. Inorganic bovinemineral (Bio-Oss) can be used at theperiphery of the block graft whenmixed with autogenous bone mar-row. This mixture results in an aver-age of 33.99% bone formation.

Acknowledgments

The authors would like to acknowledgeSammy Noumbissi, DDS, and MiguelEstrella, DDS, for their contribution. Theyare also thankful to Michael Rohrer, DDS,MS, for the histologic analysis of the speci-mens and Hari Prasad, BS, MDT, for his tech-nical assistance during the histologic pro-cessing. They are thankful to Nobel Biocarefor covering part of the expense for histo-logic analysis, Osteomed for providing thefixation screws, and ACE Surgical Supply forproviding the trephine burs.

10. Misch CM. Comparison of intraoral donorsites for onlay grafting prior to implantplacement. Int J Oral Maxillofac Implants1997;12:767–776.

11. Widmark G, Andersson B, Ivanoff CJ.Mandibular bone graft in the anteriormaxilla for single-tooth implants.Presentation of surgical method. Int JOral Maxillofac Surg 1997;26:106–109.

12. Urbani G, Lombardo G, Santi E, TarnowD. Localized ridge augmentation withchin grafts and resorbable pins: Casereports. Int J Periodontics RestorativeDent 1998;18:363–375.

13. Nevins M, Mellonig JT, Clem DS, ReiserGM, Buser DA. Implants in regeneratedbone: Long-term survival. Int J PeriodonticsRestorative Dent 1998;18:35–45.

14. Simion M, Jovanovic SA, Trisi P, ScaranoA, Piattelli A. Vertical ridge augmenta-tion around dental implants using a mem-brane technique and autogenous bone orallografts in humans. Int J PeriodonticsRestorative Dent 1998;18:9–23.

15. Proussaefs P, Lozada JL, Kleinman A,Rohrer M. The use of ramus autogenousblock grafts for vertical alveolar ridge aug-mentation and implant placement: A pilotstudy. Int J Oral Maxillofac Implants2002;17:238–248.

16. Breine U, Brånemark P-I. Reconstructionof alveolar jaw bone. Scand J PlastReconstr Surg 1980;14:23–48.

17. Adell R, Lekholm U, Grondahl K,Brånemark P-I, Lindstrom J, Jacobsson M.Reconstruction of severely resorbededentulous maxillae using osseointe-grated fixtures in immediate autogenousbone grafts. Int J Oral Maxillofac Implants1990;5:233–246.

18. Jensen J, Sindet-Pedersen S.Autogenous mandibular bone grafts andosseointegrated implants for reconstruc-tion of the severely atrophied maxilla: Apreliminary report. J Oral Maxillofac Surg1991;49:1277–1287.

19. Isaksson S, Alberius P. Maxillary alveolarridge augmentation with onlay bone-grafts and immediate endosseousimplants. J Craniomaxillofac Surg1992;20:2–7.

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