Histologic Evaluation of Autogenous Connective Tissue and Acellular Dermal Matrix Grafts in Humans

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Successful coverage of exposedroots for esthetic as well as func-tional reasons has been the objec-

tive of various mucogingival procedures.This has been performed through lateral1

or coronal2-4 repositioning of the adjacentattached gingiva via a pedicle flap, coro-nal advancement of previously placedgingival grafts,5,6 gingival grafts placeddirectly over the root surface,7 and gin-gival grafting performed in conjunctionwith flap advancement for submersion.8,9

When adequate adjacent gingiva exists,repositioning of it over the denuded rootsurface provides the most esthetic result;however, adequate gingiva does notalways exist in adjacent locations. Forthis reason, grafting of gingiva from aremote location is often required to aug-ment the area. Traditionally, this aug-mentation of the gingival complex at thetime of root coverage has been per-formed with autogenous connective tis-sue (CT) harvested from the palate oredentulous ridge. However, this necessi-tates a donor surgical site which not onlymay be a source of discomfort, but thepalate may simply not provide an ade-quate amount of connective tissue forthe proposed procedure. It is for thesereasons that dentists have looked to non-autogenous substitutes for palatal tissue.

For several years in burn repair andplastic surgery, surgeons have used anacellular dermal matrix (ADM) as a sub-stitute for autogenous connective tissue.Additionally, ADM has been used bydentists as a substitute for palatal con-nective tissue in gingival augmentation.

* Department of Surgical Specialties, University of Nebraska Medical Center, College ofDentistry, Lincoln, NE and private practice, Kingwood, TX.

† Department of Surgical Specialties, University of Nebraska Medical Center, College ofDentistry.

‡ Department of Periodontics, Baylor College of Dentistry, Texas A&M University System,Dallas, TX.

Histologic Evaluation of AutogenousConnective Tissue and Acellular DermalMatrix Grafts in HumansLewis C. Cummings,* Wayne B. Kaldahl,† and Edward P. Allen‡

Background: The clinical success of root coverage with auto-genous connective tissue (CT) or acellular dermal matrix (ADM)has been well documented. However, limited histological resultsof CT grafts have been reported, and a case report of a humanblock section has been published documenting an ADM graft.The purpose of this study is to document the histological resultsof CT grafts, ADM grafts, and coronally advanced flaps to coverdenuded roots in humans.

Methods: This study included four patients previously treat-ment planned for extractions of three or more anterior teeth.Three teeth in each patient were selected and randomly desig-nated to receive either a CT or ADM graft beneath a coronallyadvanced flap (tests) or coronally advanced flap alone (con-trol). Six months postoperatively block section extractions wereperformed and the teeth processed for histologic evaluation withhematoxylin-eosin and Verhoeff’s stains.

Results: Histologically, both the CT and ADM were well incor-porated within the recipient tissues. New fibroblasts, vascularelements, and collagen were present throughout the ADM, whileretention of the transplanted elastic fibers was apparent. Noeffect on the keratinization or connective tissue organization ofthe overlying alveolar mucosa was evident with either graft. Forboth materials, areas of cemental deposition were present withinthe root notches, the alveolar bone was essentially unaffected,and the attachments to the root surfaces were similar.

Conclusion: Although CT and ADM have a slightly differenthistological appearance, both can successfully be used to coverdenuded roots with similar attachments and no adverse healing.J Periodontol 2005;76:178-186.

KEY WORDSGingival recession/surgery; gingival recession/therapy; grafts,acellular dermal matrix; grafts, connective tissue; tooth root;wound healing.

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J Periodontol • February 2005 Cummings, Kaldahl, Allen

A small number of clinical studies report the use ofADM in periodontal surgical procedures. Harrisreported a comparative clinical study of root cover-age obtained with ADM versus CT.10 No clinically orstatistically significant differences between the twomaterials in root coverage were obtained, and probingdepth reduction and increase in keratinized tissue wereidentified. At 3 months postoperatively, a punch biopsyof the grafted area was obtained that revealed elastinfibers. He stated that the presence of these fibersimplied that the ADM was being incorporated into thehost tissue.10 Randomized controlled clinical studieshave also confirmed the effectiveness of ADM for rootcoverage.11-15

Although the clinical aspects of various techniquesof autogenous CT grafts and ADM grafts for root cov-erage have been well documented in the literature,6-16

only a few studies16-23 in humans have evaluated thecellular events at a histologic level. All of these havebeen case reports on one to four teeth. The reportedtissue interfaces between the autogenous CT graftsand the roots have varied with different specimens. Apredominately long junctional epithelium between thegraft and root was found in some specimens,17,18 whilea long connective tissue adhesion without fiber insertioninto new cementum was identified in others.17,19-22 Avery small amount of new bone with cementum depo-sition has also been reported.17,20

A single case report has been published documen-ting the histologic healing of the tooth to tissue inter-face of the ADM when used as a submerged graft.23

It was reported, based on the histologic appearance ofthe ADM 4 months postoperatively, that the apical por-tion of the graft had been resorbed and replaced byhost tissue, while the coronal portion of ADM that wasstill present as identified by elastic fiber presence didnot show revitalization or revascularization.

This study was undertaken to expand the limitedhuman histologic data available in the literaturedescribing wound healing outcomes with autogenousCT grafts and ADM grafts. The primary purpose wasto assess histologically the periodontal response ofautogenous CT grafts and ADM grafts for the coverageof denuded root surfaces via human block sectionbiopsies in each of four patients.

MATERIALS AND METHODSPatients who were treatment planned for the extractionof three or more anterior teeth by the University ofNebraska Medical Center (UNMC), College of Dentis-try, Department of Adult Restorative Dentistry, werescreened for participation in this study. Patients wereselected based on the condition of their remaining den-tition and their medical histories. The patients were ingood overall health with no conditions that would affectexpected healing outcomes or any other medical his-

tory that precluded conventional periodontal surgery.All procedures and medications were approved by theUNMC Institutional Review Board and informed con-sents were obtained from each patient prior to the startof the study.

Four patients (two women, two men; age range 36to 60 years) participated in this study. Upon initialexamination, the patient’s age, gender, social historyand habits (tobacco usage), medical history, and med-ications were noted. All patients smoked at least onepack of cigarettes daily. Scaling and root planing wasthen performed on all teeth to reduce gingival inflam-mation. The patients were instructed in mechanicalplaque control and use of a 0.12% chlorhexidine rinse.Surgical treatment began approximately 4 weeks fol-lowing initial therapy.

Surgical ProcedureThree vital anterior teeth, previously treatment plannedfor extraction, were randomly selected by a third partyto receive grafting with either autogenous connectivetissue (CT), acellular dermal matrix (ADM),§ or nograft (C). Recession defects on the chosen teeth rangedfrom 3 to 6 mm.

Following local anesthesia, the study roots wereplaned, burnished with 24% ethylenediaminetetra-acetate (EDTA),� and rinsed thoroughly.11 A standardintrasulcular or scalloped submarginal incision wasthen performed on the buccal aspects of the test andcontrol teeth and connected to horizontal incisions inthe interproximal areas. Vertical incisions were madeat the mesial and distal extent of the horizontal inci-sions as necessary for access and subsequent coro-nal advancement of the facial flap. Following this, asplit-thickness facial flap was elevated by means ofsharp dissection as close to the periosteum as possi-ble. After reflection, a notch was placed in the buccalroot surface with a 1/4 round bur at the level of thefacial osseous crest.

For the CT tooth, a conventional autogenous con-nective tissue graft was obtained from the patient’spalate. Following harvesting, the connective tissue wastrimmed to fit the defect and sutured into place using6.0 chromic gut sutures. For the ADM tooth, an acel-lular dermal matrix was prepared following the man-ufacturer’s guidelines and trimmed to fit the area. Eachmatrix specimen was oriented with the basement mem-brane adjacent to the root surface16 and sutured intoplace with 6.0 chromic gut sutures in a sling fashionaround the root. The control tooth received the sameflap reflection procedure with no subsequent graftplacement. Following graft stabilization (none with con-trol), the reflected gingival flaps were then coronally

§ AlloDerm, LifeCell, Branchburg, NJ.� PrefGel, Straumann Biologics Division, Waltham, MA (formerly Biora

Pharmaceuticals, Chicago, IL).

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Connective Tissue and Dermal Matrix Grafts Volume 76 • Number 2

advanced to cover the graft/defect and sutured using5.0 polyglactin sutures.

Postoperatively, the patients were prescribedazithromycin 500 mg the day of surgery and 250 mgper day on days 2 through 524 and ibuprofen 600 mgevery 6 hours for postoperative inflammation and paincontrol. Sutures were removed 10 to 14 days follow-ing the initial surgical procedures. The patients thenreturned weekly for supragingival deplaquing for 4weeks and monthly thereafter.

Block SectionsAfter a 6-month healing period, block section biop-sies of the experimental teeth were performed using amodification of the technique originally presented byKohler and Ramfjord.25 The extracted specimensincluded a small portion of the labial gingiva, graftedmaterial (not on controls), underlying alveolar process,and the entire tooth. At the same appointment, adja-cent non-study teeth treatment planned for removalwere elevated and extracted in the traditional manner.

Following removal, each specimen was immediatelyassigned a numerical code for identification as topatient, location, and procedure. Specimens were fixedin 10% formalin for a minimum of 72 hours prior todecalcification. Following a 10-day decalcificationperiod in 5% formic acid, the specimens were pro-cessed and embedded in paraffin. They were seriallysectioned longitudinally at 7 µm and every tenth sec-tion was stained with hematoxylin and eosin (H&E)and the following section with Verhoeff’s solution26 toidentify the presence or absence of elastin.

Histologic AnalysisEach stained specimen was evaluated under a lightmicroscope¶ at varying magnifications to determine ori-entation. After initial evaluation, each stained sectionwas magnified and photographed using a digital camerabody# with the images then recorded and transferred toan image analysis software package** to perform allnecessary linear measurements. The software and mea-surements were calibrated using additional digital imagesfrom the same camera and light microscope of a stagemicrometer at corresponding magnifications.

From each H&E stained slide, histometric mea-surements were recorded for the length of the sulcularepithelium, length of the junctional epithelium, lengthof the connective tissue attachment coronal to theosseous crest, length from the apical edge of the notchto the osseous crest, and gingival thickness at the levelof the notch’s apical edge.

Analysis of each section was carried out under thelight microscope at varying magnifications to recordinformation pertaining to the overall structure and com-position of the tissues. Notes were made identifyingthe type of overlying epithelium, nature and orienta-

tion of the underlying connective tissue, presence ofelastin, location of inflammatory infiltrate, osseouscrest response (apposition or resorption), root surfaceresponse, and apposition of cementum.

RESULTSControl SpecimensThe control teeth presented with similar histologicfindings in relation to overall structure, with slight inter-subject variations. Para-keratinized epithelium coveredthe gingiva and extended slightly apical past the muco-gingival junction with non-keratinized epitheliumextending beyond that covering the alveolar mucosa.The sulcular epithelium (mean 0.62 ± 0.35 mm) andjunctional epithelial attachment (mean 1.6 ± 0.48 mm)on the roots were apparent (Fig. 1).

The underlying connective tissue of the gingiva haddense collagen throughout. Coronal to the osseous crestcorresponding to the connective tissue attachment zone(mean 0.54 ± 0.31 mm), the collagen fibers were in aparallel arrangement with the root. Apically, within themucosa, the collagen fibers were more loosely arrangedand the elastin identified with the Verhoeff’s stain wasrandomly dispersed throughout and spilled over slightlycoronal to the mucogingival junction into the area ofthe more densely arranged fibers of the gingiva. Otherthan this small area of fraternization, no other signifi-cant elastin fibers could be identified in the area fromthe muco-gingival junction to the free-gingival margin.The periosteum was identified overlying the labialosseous surface beneath the mucosa but blended withthe dense collagen of the gingiva.

¶ Nikon Labophot, Nikon Instrument Group Inc., Melville, NY.# Nikon D1, Nikon Corporation, Tokyo, Japan.** Sigma Scan Pro Image Analysis 5.0, SPSS Science, Chicago, IL.

Figure 1.Control specimen demonstrating osseous crest (B), connective tissueattachment (CT), and junctional epithelial attachment ( JE) to rootsurface (original magnification ×20; H&E).

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A small inflammatory infiltrate was identified con-fined within the connective tissues adjacent to the sul-cular and junctional epithelium. The alveolar crest wasidentified just apical to the root notch (mean 0.43 ±0.22 mm) with no active resorption, and two of the fourspecimens demonstrated crestal apposition. Addition-ally, no root resorption or cemental deposition wasnoted along the root surfaces coronal to the osseouscrest (Fig. 1).

Autogenous Connective Tissue SpecimensIn the CT-grafted specimens, parakeratinized epithe-lium covered the gingiva and extended slightly apicalpast the mucogingival junction, with non-keratinizedepithelium extending apically beyond that covering thealveolar mucosa. The sulcular epithelium (mean 0.57 ±0.19 mm) and junctional epithelial (mean 0.97 ± 0.44mm) attachment on the roots were similar to the con-trols (Fig. 2A).

The organization of the underlying connective tissuein the area coronal to the osseous crest, although some-what disorganized, was generally arranged parallel to theroot surface (mean 1.04 ± 0.63 mm). Relative to the con-trols, an apparently increased bucco-lingual thickness ofcollagen fibers was noted in the areas of previous graftplacement. Differences between the connective tissue ofthe graft and overlying gingiva could not be ascertained.In the apical portion, the loose collagen arrangement ofthe overlying alveolar mucosa demarcated it from theunderlying dense collagen of the CT graft (Fig. 2B). Adja-cent to the alveolus, the grafted collagen fibers appearedwell incorporated with the periosteal surface. Addition-ally, adipose tissue was apparent in the area that receivedthe autogenous palatal grafts in two specimens (Fig. 3).

In the Verhoeff’s stained (VH) sections, elastin wasrandomly dispersed throughout the loosely arrangedcollagen fibers of the alveolar mucosa overlying theapical portion of the dense collagen of the graft, witha slight spill-over coronal to the muco-gingival junc-tion into the gingiva overlying the coronal aspect of thegraft. Otherwise, elastin was not seen in the dense col-lagen of the overlying gingiva or any portion of thegraft except where some elastin was identified adjacentto the adipose tissue in one specimen (Fig. 3).

As no gross inflammatory reaction was taking place,the inflammatory infiltrate was predominately locatedwithin the connective tissues adjacent to the sulcularepithelium. The alveolar crest was identified slightlyapical to the root notch (mean 0.39 ± 0.08 mm), withone specimen demonstrating apposition and two spec-imens presenting with cemental deposition within theroot notch (Fig. 3).

Acellular Dermal Matrix Graft SpecimensSome organizational variability was also noted be-tween the specimens that received the ADM grafts.

Figure 2.a) Connective tissue specimen demonstrating osseous crest (B),connective tissue attachment (CT), junctional epithelial attachment (JE),and cemental deposition (C) within the root notch (original magnification×20; H&E). b) Connective tissue specimen demonstrating mucosaltissue (M) overlying dense grafted connective tissue (C) and osseouscrest (B) (original magnification ×40; H&E).

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The overlying epithelium of the gingiva and mucosaas well as the sulcular epithelium (mean 0.47 ±0.19 mm) and junctional epithelium (mean 1.17 ±0.67 mm) were similar to the autogenous CT-graftedsections (Fig. 4).

Within the gingiva, the collagen fibers of the host’soverlying connective tissue and those of the underlyingarea corresponding to the grafted ADM were similarlydense and incorporated such that it was difficult to dif-ferentiate the two with standard H&E (Fig. 4). Adjacentto the tooth and coronal to the osseous crest, beneaththe graft, dense collagen was generally arranged par-allel to the root surface (mean 1.13 ± 0.47). In one

specimen, connective tissue fibers were identifiedinserting perpendicularly into the root surface in anarea of cementum presumably incompletely planedduring the initial surgical procedure, located coronal tothe root notch (Fig. 5).

As with the autogenous connective tissue samples,a significantly increased bucco-lingual thickness ofcollagen fibers was noted in the areas of previous graftplacement with complete incorporation of the trans-plant. The area containing the ADM appeared as adense band of collagenous tissue closely approximat-ing the underlying periosteum and continuing apically.Fibroblasts and small vessels were noted populating thegrafted area in its entirety.

Figure 3.Connective tissue specimen with adipose tissue (A), elastin (E), andcemental deposition (C) within the root notch (original magnification×100;VH).

Figure 4.Acellular dermal matrix specimen demonstrating osseous crest (B),connective tissue attachment (CT), junctional epithelial attachment (JE),and cemental deposition within the root notch (C) (originalmagnification ×20; H&E).

Figure 5.Acellular dermal matrix specimen demonstrating connective tissueinsertion into residual cementum (C) overlying the root surface (R)(original magnification ×400; H&E).

Figure 6.Acellular dermal matrix specimen demonstrating osseous crest (B),elastin (E), and connective tissue layer void of elastin (*) (originalmagnification ×20;VH).

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Staining with Verhoeff’s solution revealed an abun-dance of elastin contained within the band of denselyarranged collagen fibers associated with the ADM graft.Elastin presumably associated with the ADM extendedin many sections, from just below the free gingival mar-gin to the apical extent of the biopsy specimen (Fig. 6).In the area coronal to the osseous crest adjacent to thetooth, a layer of dense connective tissue with no elastinfibers was identified between the elastin containingportion of the graft and the root (Fig. 6). In the apicalportion of the specimens, the mucosa overlying theADM graft with its loosely arranged collagen also hadloosely arranged elastin that extended coronal to andslightly beyond the muco-gingival junction into theoverlying denser collagen of the gingiva. The graftedADM had a greater quantity of elastin than the over-lying connective tissue of the mucosa and the colla-gen arrangement of the ADM appeared denser thanthat of the adjacent mucosa. This distinct difference inthe organization of elastin and collagen fibers alloweda differentiation of the graft from the overlying gingi-val and mucosal tissues (Fig. 7).

Again, no gross inflammatory reaction was seen, andthe inflammatory infiltrate was predominately locatedwithin the connective tissues adjacent to the sulcularepithelium. The osseous crest was slightly apical to theroot notch (mean 0.58 ± 0.34 mm), and two specimenspresented with minimal apposition of bone. Addition-ally, cemental deposition was identified within the rootnotch in two specimens (Fig. 4).

DISCUSSIONADM is acellular, nonimmunogenic cadaveric humandermis.27 It has a polarity by which one side of thematerial has a basal lamina for epithelial cell migra-tion, and the other side, an underlying porous dermalmatrix, which allows in-growth of fibroblasts and angio-genic cells.28 This material has been used extensivelyin medicine for lip augmentation,29 facial augmenta-tion,30 dural replacement,31 and burn repair.32

Histologically, prior to implantation, ADM has thesame appearance as normal dermis, without the cel-lular or vascular components. The distinguishing com-ponent of ADM, when compared histologically tohuman gingival tissue, is its abundance of elastin.Although elastin is present in the oral mucosal tissues,it is not present in gingiva. The primary method ofdetermining the fate of ADM following oral implanta-tion has been by staining biopsy samples to identifyelastin contained within the tissues with stains such asVerhoeff’s solution. Microscopically, the presence ofelastin allows for easy determination of graft presenceor absence, as well as incorporation within the surround-ing tissues.

In the present study, four patients contributed 12 teeththat were removed via block sections for histologic eval-uation. The difficulty in obtaining histology from humanblock sections is evidenced by the small number ofpublished reports. For a researcher to obtain an intacttooth with the overlying tissue interface, it must eitherbe previously deemed hopeless and treatment plannedfor extraction or happen by chance. Therefore, patientschosen to participate in prospective studies that willlead to eventual extraction of the teeth have a terminaldentition. Many of the test teeth had generalized hori-zontal bone loss leaving them with Miller Class III andmore so Class IV type of facial defects. Unfortunately,these patients also traditionally have poor oral hygieneand motivation which is less than ideal for tissue graft-ing. The suboptimal gingival health of the participantsduring the recruitment period for this study wasimproved with thorough scaling and root planing priorto the surgical therapy. It was discovered that thoroughcleaning and a small monetary incentive were inade-quate to induce the patients to maintain the level of oralhygiene one would expect of a typical patient receiv-ing a soft tissue grafting procedure for root coverage.Additionally, all participants were smokers, each smok-ing more than one pack of cigarettes per day. Obvi-ously these case types and conditions were not optimaland the clinical results were less than desired in theamount of root coverage obtained compared to thatexpected in normal clinical situations.33,34

Upon reflection of the overlying gingiva at the timeof surgery, a reference notch was made into the rootsurface of each study tooth with a 1/4 round bur on ahigh-speed hand piece to create a landmark at the

Figure 7.Acellular dermal matrix specimen demonstrating mucosal tissue (M)overlying the area of graft placement (ADM) and osseous crest (B)(original magnification ×40;VH).

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level of the osseous crest. Upon histologic evaluation,some variability in the distance measured from thenotch to the osseous crest was present (mean 0.39 to0.58 mm). The osseous crest in some specimens hadsigns of bone apposition. It has been documented thatlabial osseous plate resorption occurs following surgi-cal exposure that subsequently can be followed bysome regeneration of lost crest by bone apposition.35

This may also explain some of the small amounts ofnew bone reported in the literature following autoge-nous connective tissue grafts.17,20,23 It is interestingto note that although there were interpatient variationsin the distance from the base of the notch to theosseous crest, intrapatient variations were minimal be-tween the three study teeth. This leads to the assump-tion that the distance identified from the notch to thecrest is likely a combination of placement variationand overall host wound healing. Due to the minimalintrapatient variation, this distance is not likely anadverse healing response generated by a specific graftmaterial.

The only noteworthy cemental deposition along theroot surface was within the notch of the previouslymentioned CT and ADM specimens. Similar findings ofcemental deposition have been reported by otherauthors histologically evaluating autogenous connectivetissue grafts.17,18,20 The collagen fibers of the con-nective tissue attachment were identified running par-allel to the root surface, which also has been reportedfor CT grafts.17,19-21 It is interesting to note that adi-pose tissue was present in two specimens in the areaof the grafted palatal connective tissue. Other authorshave reported similar findings with autogenous con-nective tissue grafts.20,36 The origin of this tissue isobviously the submucosal layer of the patient’s palatalvault, which is known to contain adipose tissue.37

Although the graft incorporated well with the adjacenttissues, the significance of the adipose tissue isunknown but does not appear to affect the clinicalresult.

In one ADM specimen, within the connective tissueadjacent to the root, a small area of junctional epithe-lium was present. This orientation of a “window” ofepithelium within an area of connective tissue adhe-sion to the root surface was not unexpected as it hasbeen previously reported.38

At 6 months the elastin associated with the ADMgraft was present in all of the specimens with completeincorporation of the material into the surrounding tis-sues as determined by the presence of elastin in thesections stained with Verhoeff’s solution. The graft wascomposed of dense collagen possessing fibroblastsand endothelial cells associated with revascularizationby small vessels. This area resembled normal gingi-val tissue and was indistinguishable from the areasthat received autogenous connective tissue grafts on

the H&E slides. This appearance of incorporation andrevascularization extended from just apical to the freegingival margin to the apical extent of the biopsy mar-gin. Additionally, the band of elastin identified was sim-ilar in thickness to that of unimplanted sections of thematrix material processed in the same fashion. This isin contrast to the observations made by Richardsonand Maynard23 in a block section biopsy of an ADMgraft. A maxillary left canine with no initial recessionwas treated with ADM submerged beneath a full-thickness repositioned flap. Following 4 months ofhealing, the tooth with a portion of the overlying peri-odontium was extracted for evaluation. Although theoriginal dimension of the graft was 10 mm in widthapico-coronally, only 2.7 mm of elastic fibers were evi-dent histologically in an apico-coronal direction. Thisarea of elastin was apparent adjacent to the osseouscrest and corresponding root notch. The authors23

stated that the loss of identifying fibers for the ADMimplied that replacement of the matrix by host con-nective tissue and/or sloughing at the cervical marginhad taken place. Fibrous tissue was evident from theapical extent of the junctional epithelium, which mea-sured 0.3 mm, to the most apical portion of the notchidentifying the original osseous crest, with no appar-ent attachment to the root surface. The authors23 pro-posed that this observation would be consistent withconnective tissue apposition. Minimal new bone for-mation was evident in areas with 1.0 mm of priorresorption that had resulted from the surgical trauma,and no new cementum was present. The authors23

placed the graft under a full-thickness mucoperiostealflap, whereas the present study utilized a split-thicknessdesign. Whether such simple alterations of techniquepossibly explain the variances between the two studiesis unknown.

Due to the split-thickness flap design of the initialsurgical procedure, the original periosteum remainedintact overlying the alveolar bone. In all specimens,the portion of the ADM approximating the periostealsurface of the alveolar bone appeared to be bounddown with a density similar to the autogenous CT graftand normal gingival tissue. The outer portion of the ADMapproximating the overlying mucosal flap appearedthoroughly incorporated as well, with inter-digitatingcollagen fibers spanning between the matrix to themore loosely arranged mucosal tissue, not unlike thatseen with the autogenous tissue specimens. The alve-olar mucosa portion of the host flap that was placedover the autogenous CT and ADM grafts maintainedthe histological appearances of alveolar mucosa at6 months, with loosely arranged collagen and elastinfibers and overlying non-keratinized epithelium. Onemight have expected more influence of the graft onthe overlying epithelium in the apical portion since ithas been demonstrated in both animals39 and

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humans40 that characteristics of the epithelium arecontrolled by intrinsic mechanisms inherent to the con-nective tissue. In this study, though, a layer of the alve-olar mucosal connective tissue was present betweenthe epithelium and grafts.

An increase in gingival thickness was noted withthe grafted specimens as compared to the correspond-ing controls. Hence, this thickness is obviously due tothe addition of tissue, whether autogenous CT or ADM,beneath the original gingival flap. This increased thick-ness was not only evident histologically, but clinicallyas well. These findings of a similar increase in thick-ness after grafting with either CT or ADM are in agree-ment with clinical results reported for root coveragegrafting.12,14,41 However, to theorize on the significanceof this increase in gingival thickness was not an aimof this study. Regardless, it has been hypothesized thatan increase in gingival thickness, as obtained with tis-sue grafting, will help prevent future recession inpatients with a thin periodontal phenotype.41,42 Thismay be an important postoperative parameter since themajority of patients presenting with gingival recessionalso have a thin periodontium.

CONCLUSIONSThis study reported the histological wound healingresults 6 months after grafting with autogenous CTand ADM in humans. Both the CT and ADM graftsresulted in the formation of a dense band of collage-nous tissue when placed beneath a coronally advancedgingival and mucosal flap. The gingival attachmentto the root surface was comparable for both the CTand ADM grafts (combination of long junctional epithe-lium and connective tissue adhesion) and the under-lying alveolar bone was essentially unaffected. Thegrafted ADM appeared well incorporated with newfibroblasts, vascular elements, and collagen whileretaining its elastic fibers throughout. Both the CT andADM had no demonstrable effect on keratinization orconnective tissue organization in the areas of overly-ing alveolar mucosa. From these observations it wasapparent that at 6 months postoperatively, the over-all histologic outcomes from human block sectionswere similar between the autogenous CT and ADMgrafts.

ACKNOWLEDGMENTSThe authors would like to thank Phyllis Kumm for thesuperb processing of histological sections and Dr. JohnCasey for guidance and verification of histologic inter-pretation. We also acknowledge Dr. J. Bruce Bavitz andDeborah Dalton for assistance in the study and manu-script preparation. All four individuals are associatedwith the University of Nebraska Medical Center, Collegeof Dentistry, Lincoln, Nebraska. This study was partiallysupported by LifeCell, Branchburg, New Jersey and

BioHorizons, Birmingham, Alabama. Dr. Allen is a con-sultant for BioHorizons.

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sliding flap. Use of free gingival grafts. Odontol Revy 1971;22:37-44.

2. Guinard EA, Caffesse RG. Treatment of localized gingivalrecessions. Part III. Comparison of results obtained with lat-eral sliding and coronally repositioned flaps. J Periodontol1978;49:457-461.

3. Tarnow DP. Semilunar coronally repositioned flap. J ClinPeriodontol 1986;13:182-185.

4. Allen EP, Miller PD Jr. Coronal positioning of existing gin-giva: Short term results in the treatment of shallow mar-ginal tissue recession. J Periodontol 1989;60:316-319.

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6. Matter J. Free gingival graft and coronally repositionedflap. A 2-year follow-up report. J Clin Periodontol 1979;6:437-442.

7. Miller PD Jr. Root coverage using the free soft tissueautograft following citric acid application. III. A success-ful and predictable procedure in areas of deep-wide reces-sion. Int J Periodontics Restorative Dent 1985;5(2):14-37.

8. Raetzke PB. Covering localized areas of root exposureemploying the “envelope” technique. J Periodontol 1985;56:397-402.

9. Langer B, Langer L. Subepithelial connective tissue grafttechnique for root coverage. J Periodontol 1985;56:715-720.

10. Harris R. A comparative study of root coverage obtainedwith an acellular dermal matrix versus a connective tis-sue graft: Results of 107 recession defects in 50 conse-cutively treated patients. Int J Periodontics RestorativeDent 2000;20:51-59.

11. Henderson RD, Greenwell H, Drisko C, et al. Predictablemultiple site root coverage using an acellular dermalmatrix allograft. J Periodontol 2001;72:571-582.

12. Aichelmann-Reidy ME, Yukna RA, Evans GH, Nasr HF,Mayer ET. Clinical evaluation of acellular allograft dermisfor the treatment of human gingival recession. J Perio-dontol 2001;72:998-1005.

13. Novaes AB Jr, Grisi DC, Molina GO, Souza SL, Taba M Jr,Grisi MF. Comparative 6-month clinical study of a subep-ithelial connective tissue graft and acellular dermal matrixgraft for the treatment of gingival recession. J Periodontol2001;72:1477-1484.

14. Paolantonio M, Dolci M, Esposito P, et al. Subpedicleacellular dermal matrix graft and autogenous connectivetissue graft in the treatment of gingival recessions: Acomparative 1-year clinical study. J Periodontol 2002;73:1299-1307.

15. Tal H, Moses O, Zohar R, Meir H, Nemcovsky C. Rootcoverage of advanced gingival recession: A comparativestudy between acellular dermal matrix allograft andsubepithelial connective tissue grafts. J Periodontol 2002;73:1405-1411.

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Correspondence: Dr. Lewis Cummings, 1110 KingwoodDr., Suite 105, Kingwood, TX 77339. Fax: 281/358-6062;e-mail: [email protected].

Accepted for publication May 21, 2004.

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Histologic Evaluation of Autogenous Connective Tissue and Acellular Dermal Matrix Grafts in Humans