1990Buser_Regeneration and Enlargment of Jaw Bone Using Guided Tissue Regeneration

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Regeneration and enlargement of jaw boneusing guided tissue regenerationBuser 0, Bragger U, Lang NP, Nyman S. Regeneration and enlarge-ment of jaw bone using guided tissue regeneration.Clin Oral Impl Res 1990: 1: 22-32.The purpose of this study was to present the surgical procedures and theclinical results of guided tissue regeneration (GTR) treatment aimed atregenerating local jaw bone in situations where the anatomy of the ridgedid not allow the placement of dental implants. 12 patients were se-lected for ridge enlargement or bony defect regeneration. A combinedsplit- and full-thickness flap was raised in areas designated for subse-quent implant placement. Following perforation of the cortical bone tocreate a bleeding bone surface, a PTFE membrane was adjusted to thesurgical site in such a way that a secluded space was created betweenthe membrane and the subjacent bone surface in order to increase thewidth of the ridge or to regenerate bony defects present. Completetension-free closure of the soft tissue flap was emphasized. Following ahealing period of 6 to 10 months, reopening procedures were performedand the gain of bone dimension was assessed. In 9 patients with 12 po-tential implant sites, a sufficient bone volume was obtained to allowsubsequent implant placement. The gain of new bone formation variedbetween 1.5 and 5.5 mm. In 3 patients, acute infections developedwhich necessitated early removal of the membranes and no bone regen-eration could be achieved. The results of the study indicate that thebiological principle of GTR is highly predictable for ridge enlargementor defect regeneration under the prerequisite of a complication-freehealing.

In the past 10 years, the replacement of missingteeth using dental implants has become a predict-able treatment modality for totally and partiallyedentulous patients. At present, the anchorage ofendosseous implants with intimate bone-to-im-plant contact is preferred (Branemark et al. 1985,Schroeder 1990). To obtain this type of implantanchorage, a sufficient volume of healthy bonemust be available. Consideration has to be givennot only to the quality of the bone tissue and thevertical bone height, but also to the oro-facial bonewidth. Based on clinical experience, it has beensuggested that a bone wall of at least 1 mm shouldbe present on the oral and facial aspects of theimplant in order to achieve good long-term prog-nosis (Lekholm et al. 1986). For cases where thepresurgical evaluation reveals an insufficientheight or width of the jaw bone at desired implantlocations and/or the presence of a localized bonedefect in the actual ridge, several surgical tech-niques have been described in the literature toregenerate such bone defects or to increase thevolume of bone using grafts (Streckbein & Woltge1987, Khoury 1987) or bone substitutes such as2 2

D . B use r, U . B ra gg er, N . P .L an g a ndS .NymanU niv ers ity o f B ern e, S ch oo l o f D en ta l M e dic in e,Bern/Switzer land

K ey w ord s: b on e re ge ne ra tio n - d en ta l irn pla nts -g uid ed tis su e re ge ne ra tio n - rid ge e nla rg em en tD an ie l B us er, D ep artm e nt o f O ra l S urg ery , S ch oo lo f D e nta l M e di ci ne , F re ib u rg stra ss e 7 , C H 3 0 10Bern/Switzer landA cc ep te d fo r p ub lic atio n 6 S ep te m be r 1 99 0

hydroxyapatite (Osborn 1985, Nentwig & Kniha1986).The principle of "guided tissue regeneration"(GTR) using a membrane technique was initiallydeveloped to regenerate the attachment apparatusaround natural teeth with advanced loss of perio-dontal tissue (for review, see Nyman et al. (1989.This principle was later applied in a series of exper-imental studies for the regeneration of bone tissuein different types of jaw bone defects as well asaround dental implants (Dahlin et al. 1988.1989a,b, Seibert & Nyman 1990. Becker et al.1990). In these studies, a membrane barrier wasplaced over the defect and closely adapted to thebone surface surrounding the defect. Hereby, asecluded space was created between the bone de-fect and the inner surface of the membrane intowhich cells originating from bone tissue could mi-grate without interference of other competingtypes of tissue cells.In conjunction with the placement of dental im-plants, there are at least 2 different applications ofGTR: (1) for ridge regeneration or ridge enlarge-ment, and subsequent placement of a dental im-



plant; (2) for covering an already installed implantwith a peri-implant bony defect. The potential ofthe GTR procedure for both types of applicationwas demonstrated in a previous case report (Ny-man et al. 1990).The purpose of the present article is to describethe surgical procedures and the results of thismembrane technique for the first application, i.e.,in situations, where the local anatomy of the jawbone did not allow a direct placement of a dentalimplant.Ma t eria l a n d m e th o dsAmong the patients referred to the University ofBerne, School of Dental Medicine for implantplacement. 12 patients (6 female and 6 male) wereincluded in the study. They were partially edentu-lous and presented with single tooth gaps, ex-tended edentulous gaps, or distal extension basesituations (Table 1). The presurgical evaluationdisclosed an anatomy of the local bone which didnot allow the placement of TTl implants. * Depend-ing on the clinical status, the principle of GTR wasused for 2 different purposes: (1) in 10 patients forridge enlargement; these patients had a sufficientvertical bone height but a width of the jaw bone ofless than 5.5 mm which is the minimal requirementfor the placement of ITI implants (Buser et a!.1990); (2) for defect regeneration in 2 patients witha sufficient width and height of the jaw bone, butwith a bony defect present apical to the crest whichdid not allow the placement of an ITI implant.The surgical procedures were performed by oneof the authors (D.B.). The patients were given anantibiotic prophylaxis for 48 h (amoxicillin 750 mggiven orally 2 h preoperatively, and every 6 hpostoperatively). In addition, the patients weregiven an anti sialagogue (0.5 mg atropine intra-muscularly) 30 min before surgery to reduce sali-

Guided bone tissue regenerationvary flow. A sedative premedication (5 mg Nidazo-lam intramuscularly) was additionally used foranxious patients.In the first 2 treated patients. crest incisions withdivergent relieving incisions were used to elevatemucoperiosteal flaps orally and buccally. Due tocomplications observed in the first patient (seeTable 2). the incision technique was modified, andsplit- and full-thickness flap techniques were usedfor the following 10 patients. In the maxilla. thesupraperiosteal incision was carried out on the pal-atal aspect of the jaw (Fig. la) with a subsequentmucosal flap elevation and incision of the perios-teum on top of the crest. Thereafter, the flap in itsfull thickness was extended onto the buccal aspectusing divergent relieving incisions. In the man-dible. the supraperiosteal incision was carried outon the buccal aspect of the jaw, followed by thesame surgical procedure on the lingual aspect asdescribed (Fig. 2a).Following elevation of the flaps. the bone ridgewas carefully examined (Fig. 2b) and desired im-plant locations were determined. Since all patientsin the present study had a sufficient vertical boneheight, only the oro-facial bone width at theselocations was measured to the nearest quarter of amillimeter using a caliper. If present in the bone,foreign body materials such as filling material frompreviously performed root canal treatment (Figs.3a, 4a) were removed. When present, the corticalbone was perforated with a small round bur inorder to create a bleeding bone surface and toopen the cancellous bone (Figs. 2c, 3a). Subse-quently, an experimental PTFE membrane** wastrimmed with a pair of scissors and applied to thesurgical site. The membrane was styled with a 3-4mm extension over the bone margins of the defect* Institut Straumann AG. Waldenburg. Switzerland.** W. L. Gore & Associates. Flagstaff AZ. USA.

Tab le 1. P erson al d ata a nd loca l s ta tus o f a ll 12 p atie nts tre ated w ith G TR fo r de fe ct reg ene ra tion o r ridg e e nla rge men tP a tie n t S ex A ge A rch Loca l s ta tus S ite ls ) P urp o se o f s u rge ryno . I years )1 24 m ax sing le to o th gap 13 r id g e e n la rg em en t2 18 m ax sing le to o th gap 22 ridge en la rgem en t3 m 29 m ax sing le to o th gap 22 r id g e e n la rg em en t4 m 45 m ax sing le to o th gap 21 r id g e e n la rg em en t5 f 29 m ax doub le to o th gap 11 ,21 ridge en la rgem en t6 m 31 m ax sing le to o th gap 12 ridge en la rgem en t7 f 45 m ax trip le to o th gap 13 ,12 r id g e e n la rg em en t8 f 3 5 m and d is ta l e x tens io n 34 ,36 d e fe c t r e ge n e ra ti on9 m 27 man d d is ta l e x te n s io n 36 ridge en la rgem en t1 0 m 39 m ax s ing le to o th gap 14 r id g e e n la rg em en t1 1 f 54 man d d i st al e x te n s io n 35 ,3 6 ridge en la rgem en t12 m 44 m and s ing le to o th gap 46 defe c t regene ra tion

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dFig. 1. (a) Single-tooth gap, patient no. 3. Supraperiosteal incision on the palatal aspect of the jaw for the combined split- andfull-thickness flap technique. (b) Primary closure with matress and interrupted sutues. (c) Digital subtraction image of standardizedradiographs obtained 8 months apart. Bright areas at the crestal region demonstrate increase in bone density. (d) Color conversionof image from Fig. Ic, No change-areas are depicted in green. increase in density (grey levels > 128) are depicted in blue.

on both aspects of the ridge to achieve a closeadaptation of the membrane to the bone (Fig. 3b).Any periosteum present on these bone marginswas carefully removed. In patients with need forridge enlargement, the membrane was appropri-ately placed to create a space underneath themembrane in order to increase the width of theridge. Tn 3 patients (nos. 7, to, 11), mini-corticalscrews" were used to support the membrane like a2 4

tent pole in order to secure the created space un-derneath the membrane in its proper dimension(Fig. 2c). Furthermore, small pieces of Collagen-Fleeces" were applied to stabilize the blood clot inthe space underneath the membrane. Hereby, thecollagen was completely soaked in blood. In the 2

* Pentaharrn AG, Basel/Switzerland.



patients with a bony defect within the jaw bone,the membrane was placed onto the bone surface toallow solely for regeneration of the defect withoutextension of the width of the ridge. Adjacent tothe approximal aspects of neighbouring teeth, asmall zone of crestal bone was left uncovered (Fig.4b). If the membranes could not be sufficientlystabilized, mini-cortical srews were additionallyused to affix the membrane to the bone (Fig. 2d).Prior to suturing, the periosteum was carefullyslashed at the base of the flap to achieve a tension-free wound closure. The closure was carried outwith interrupted and matress sutures (Figs. lb,2e).Temporary removable partial dentures were ad-justed to avoid any contact with the wound area.In addition, the patients were instructed neither tochew nor to brush in the treated area for approxi-mately 2 weeks. Chemical plaque control withchlorhexidine-digluconate solution (0.1%, 10 ml3 x 1 min/day) was instituted for the same period.The sutures were removed 10-14 days after sur-gery. Further recalls were scheduled once a weekuntil the soft tissue healing was completed. Sub-sequently, the patients were recalled once every 2months for clinical and radiographic evaluation.Periapical radiographs were obtained using acrylicbite blocks and long-cone technique in order tostandardize the image geometry for digital sub-traction radiography (for review, see Bragger(1988.From a pair of standardized radiographs dig-itized pictures were taken using a commercialblack and white CCD camera (Hitachi Ci-20 PM,734 x 580 pixels, specially adapted for pictureprocessing) and a frame grabber hardware card(Matrox MVP/AT) in a microcomputer (Compac-386/20). Ideally, a digital subtraction image from asite where absolutely no change in density hasoccurred would show a perfect cancellation of thestructures. An average grey level value of 128 (themiddle of the digitizer grey level range set by soft-ware) would show up at each pixel. Areas withgrey levels 128 increase in den-sity (appearing bright against the background of128). The digital subtraction images were also dis-played and evaluated after color conversion (Brag-ger & PasquaJi 1989). The color conversion re-sulted in subtraction images in which the range ofgrey levels between 115 and 141 appeared green(representing no change in bone density), greylevels from 0 to 115 appeared brown (representingloss in density) and grey levels from 141 to 255appeared blue (representing increase in density).In case of infection or a dehiscence of the mu-

Guided bone tissue regenerationcosa, the membrane was removed and healing al-lowed to continue without membrane. Prior to apossible reopening surgery, the width of the bonewas evaluated in these patients with a bone map-ping procedure using a fine needle and a rubberstop (Tetsch 1984). If this evaluation showed abone width of less than 5 mm, no subsequent reo-pening surgery was carried out for ethic reasons. Inthe patients with a complication-free healing, themembrane was left in situ for a healing period of6-10 months. At this time, a reopening procedurewas performed (Table 2). In patients with ridgeenlargement, the oro-facial width of the ridge wasmeasured at the same locations as at the time ofreconstructive surgery. Subsequently. ITI implantswere placed, if the dimensions of the regeneratedbone were sufficient.

Resul tsThe results of the present study are listed in Tables2 and 3. In 3 patients (nos. 1, 4, 6), an acuteinfection in the membrane site developed with pusflow 3-4 months following surgery. In 2 of them,foreign body materials from previously performedroot canal fillings were initially present in the jawbone. Following the membrane removal and a fur-ther healing period of around 3 months, the bonemapping procedure in all 3 patients revealed aninsufficient width of the bone, and hence no reo-pening surgery was performed for ethical reasons.In the remaining 9 patients with 13 potentialimplant sites, a reopening surgery was performed.In 7 of them with a complication-free healing pe-riod (Fig. 4c), the membranes were still in place,whereas in 2 patients the membranes had beenremoved earlier due to a dehiscence of the mu-cosa. One dehiscence (no. to) developed in thefirst postoperative week, probably caused by anunusual edema, and the second one (no. 11) be-came apparent in the area of the former mesio-buccal relieving incision (Fig. 2f) about 3 monthsfollowing reconstructive surgery. During mem-brane removal in this patient, a soft tissue similarto granulation tissue was found underneath themembrane. This tissue was left in place and theflap was readapted with interrupted sutures. Inboth cases with a dehiscence, a fast and complica-tion-free healing of the mucosa was seen followingthe membrane removal (Fig. 2g).During the reopening surgery, no clinical signsof inflammation around the membranes werefound and the membranes were firmly attached tothe newly formed tissue underneath (Fig. 3e). Themembranes were removed and the newly regener-ated ridge was carefully examined. The clinical

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Fig. 2. (a) Distal extension base in the mandible, patient no. 11. Supraperiosteal incision on the buccal aspect of the jaw withsubsequent supra periosteal preparation of the flap. (b) Status following flap elevation shows an insufficient ridge for implantplacement in regia 35, 36. (c) Removal of granulation tissue from the former extraction socket in regia 36, perforation of thecortical bone with a round bur and placement of2 mini-screws for support of the membrane. (d) Placement of a membrane creatinga space in order to increase the width of the ridge. The membrane is secured by an additional mini-screw mesio-buccally. (e)Wound closure with matress and interrupted sutures. (f) Small dehiscence at the mesio-buccal relieving incision 3 months followingsurgery. (g) Clinical status 3 months following membrane removal. (h) Intra-operative status at the time of implant placement, 9months following reconstructive surgery. The bone width measured 6.0 mm in regia 35, 36. (i) Undccalcified histologic section.The coronal portion of the removed bone core reveals regular bone tissue (light-green staining, original magnification 6.5x). (j)The enlarged bone ridge allowed the placement of 2 ITl hollow-screw implants.26



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Fig. 3. (a) Single-tooth gap in regio 22, patient no. 2. Bonedefect following removal of retained root filling material andperforation of the cortical bone. Initial ridge measured 3.0 mmin width. (b) Placement of a membrane with a wide extensionin its apical part in order to achieve a close contact to the bonesurface. (c) Status at the time of reopening procedure, follow-ing a complication-free healing period of 10months. The mem-brane is firmly attached to the newly formed tissue under-neath. (d) Clinical status following membrane removal. Thewidth of the ridge had increased from 3.0 mm to 7.0 mm. (e)Periapical radiograph following placement of an IT! hollow-cylinder implant.



a

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estatus revealed in all sites a hard tissue which hadthe appearance of normal bone (Fig. 3d), also inthe 2 cases, where the membrane had been re-moved earlier. In these particular 2 patients, the"granulation tissue" seen at the time of membraneremoval, was now calcified and had the appear-ance of normal bone (Fig. 2h). The increase inwidth of the bone was also apparent with an in-crease of density in the obtained periapical ra-diographs (Figs. lc, d). The measurements madein 7 patients with ridge enlargement, revealed in 9of 10 sites a sufficient bone width of at least 5.5

Guided bone tissue regeneration

b

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Fig. 4. (a) Periapical radiograph of a single tooth gap in region46, patient no. 12. Note the insufficient bone regeneration ofthe former extraction socket and the presence of foreign bodymaterial distally (arrow). (b) Clinical status following mem-brane placement. Note the small zone of uncovered crestalbone close to the neighboring teeth (arrows). (c) Status 9months following surgery. Healing without complications.(d) Periapical radiograph 9 months following surgery revealsthe regeneration of the bone defect. (e) Periapical radiographfollowing placement of an ITI hollow-screw implant.

mm (Table 3). One membrane, placed in a patientwith a double tooth gap (no. 5), was obviouslypushed into contact with the bone surface by thesoft tissue cover during healing in one of the sites,hereby preventing ridge enlargement in this area.In the patients with successful ridge enlargement, again of bone width varying between l.5 mm and5.5 mm was obtained (Table 3).In both cases with defect regeneration (nos. 8,12; Table 1), the previous defects present withinthe bone were fined with newly formed bone. Thebone regeneration was also visible radiographically

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Buser et .al.T ab le 2 . P os to pe ra tiv e w o un d h ea lin g w ith d ate o f m em bra ne rem ov al a nd d ate o f re op en in g s urg eryPat ient Sitetsl Reconstructive Postopera tive Membrane Reopeningno. surge ry w ound hea ling removal su rgery1 13 Nov 88 abscess M ar 892 22 Dec 88 no complica tion Oct 89 Oct 893 22 Apr 89 no complica tion Jan 90 Jan 904 21 May 89 abscess Sep 895 11 ,21 May 89 no complica tion Jan 90 Jan 906 12 May 89 abscess Oct 897 13 ,12 May 89 no complica tion Jan 90 Jan 908 34,36 Jun 89 no complica tion Jan 90 Jan 909 36 Jul89 no complica tion Apr 90 Ap r 9010 14 Jul 89 deh iscence Nov 89 Jan 9011 35,36 Jul89 deh iscence Jan 90 Ap r 9012 46 Jul89 no complica tion Apr 90 Apr 90

with an increase of bone density in the surgicalsites (Fig. 4d).The clinical evaluation in patient no. 3 demon-strated an increase in width of the alveolar crest of5.5 mm. In accordance with the clinical results,digital subtraction radiography demonstratedclearly an increase in density at the crestal region(bright areas in Fig. Ic, blue areas in Fig. l d),when the radiographs obtained eight months apartwere analyzed.In conjunction with the reopening procedures at

the termination of the healing period, the bonecavities for implant placement were prepared usinga trephine mill. With this technique, the coronalportion of the central bone core could be gainedfor histologic analysis using undelcacified sections(Schroeder 1990). These specimens showed in allcases bone tissue with regular structure (Fig. 2i).Finally, a total number of 11 implants could beplaced in 8 patients (Figs. 2j, 3e, 4e), i.e., 3 im-plants in 2 patients with defect regeneration and 8implants in 6 patients with ridge enlargement.Discuss ionIn surgery aimed at regenerating periodontal tis-sues, lost as a result of periodontal disease, a newconcept has been developed which was termed"guided tissue regeneration" (for review, see Ny-man et al. (1989)). This new principle is based onthe hypothesis that the different types of cellswhich surround the surgical wound proliferate intothe wound area, hereby determining the outcomeof the healing process. By the placement of barriermembranes, preference can be given to those cellsto repopulate the wound which have the potentialto regenerate the desired type of tissue. At thesame time, cells which may negatively interferewith adequate regeneration can be excluded fromproliferation into the wound. A further prereq-30

uisite for successful GTR is the creation of a suffi-cient space allowing the formation of the desiredtype of tissue.In the present study, the principle of GTR wasapplied to regenerate tissues outside the perio-dontium, namely bone tissue in conjunction withthe placement of dental implants. In all instanceswith uneventful healing, a sufficient bone volumewas provided by the GTR procedure to allow forsubsequent implant placement. This is in fullagreement with previously published applicationsof this biological principle for bone regeneration inexperimental animals (Dahlin et al. 1988, 1989a, b,Seibert & Nyman 1990, Becker et al. 1990) and inhumans (Lazzara 1989, Nyman et al. 1990). Inaddition, the histological samples, obtained fromthe implant bed preparations, documented a newlyregenerated bone tissue of normal structure andmorphology.In the present material, a few complications oc-curred during healing. In 3 patients, the de vel-

T ab le 3 . P re - a n d p o st op e ra tiv e r id g e w id th in 7 p a tie n ts w ith rid g e e n la rg e -m e nt a nd a re op en in g s urg ery

Pat ient W ound healing S ite pre R W post R W Gain R Wno .2 no c om plica tion 22 3 .00 7.00 4.003 no comp l ic a ti on 22 2.00 7.50 5.505 no c om plica tion 11 4.00 6.00 2.00

21 4.00 4.00 0 .007 no c om plica tion 13 4.00 5.75 1.7512 3 .50 5.75 2 .25

9 no c om plica tion 36 4.00 7.00 3 .0010 dehiscence 14 2.75 6.00 3.2511 dehiscence 35 4.50 6.00 1.50

36 4.50 6.00 1.50p re RW = rid ge w id th a t m em bra ne s urg ery (m rn lp os t RW = rid ge w id th a t re op en in g s urg ery [rn rn ]G a in RW = g ain o f rid ge w id th Irn ml


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opment of abscesses in the surgical area requiredearly removal of the membrane and bone regener-ation could not be achieved. In 2 patients, de-hiscences developed and the membranes were re-moved prematurely. However, complete bone re-generation occurred despite the early membraneremoval, suggesting that the newly formed softtissue found underneath the membranes repre-sented unmineralized bone matrix. In one site ofone patient, no gain in the width of the bone wasobserved due to the fact that the membrane hadbeen pressed into close contact with the underlyingbone surface by the covering soft tissue. This in-cidence clearly demonstrates the importance ofproviding adequate space for regeneration. Forthis purpose, mini-cortical screws were applied incertain instances to function as space holders. It isconceivable, however, that in the future, mem-brane material with adequate stiffness for properspace-holding will be produced. In this respect, thevariation in bone gain found in the present mate-rial, varying from 1.5 to 5.5 mm, was most prob-ably the effect of the space that could be obtainedfrom a technical point of view.The healing period in the present study to secureridge enlargement or defect regeneration was cho-sen to be 6 to 10 months. Obviously these periodswere chosen on the basis of empirism rather thanscientific evidence. Since complete bone regener-ation was also observed in the 2 cases with de-hiscences, where the membranes were removedprematurely, in can be anticipated that the spaceholding effect of the membranes may not be neces-sary for the entire length of a 6 to 10 monthshealing period. On the other hand, the time periodrequired for the mineralization of newly formedjaw bone matrix is not known. Until this mineral-ization period has been determined by controlledstudies, a healing period of at least 6 months mustbe recommended before implant installation.In a previous report, digital subtraction analysisof standardized radiographs, obtained during thehealing phase following GTR procedures in con-junction with implant installation, demonstratedthe increase in density of the periimplant tissues(Nyman et al. 1990). This non-invasive techniquewas also able to detect the increase in bone densityin cases where GTR was applied for ridge enlarge-ment and hence, may represent a helpful diag-nostic technique to document successful or failinghealing of GTR procedures.It is evident from the results of the present studythat the biological principle of GTR is highly pre-dictable for ridge enlargement prior to placementof implants. However, technical factors such asflap design, placement of membranes providingsufficient space for bone regeneration, flap closure

Guided bone tissue regenerationand post-surgical infection control, influence theprognosis to a great degree and must be optimized.In order to achieve complete membrane coverageand tension-free flap closure, a combined split-and full thickness flap technique was used in thepresent study in all but the 2 first patients. Despitethese precautions, dehiscences were observed any-how in 2 patients. This necessitates further im-provements of the surgical technique. Neverthe-less, it should be realized that bone regenerationfor ridge enlargement is obtained by the GTRprocedure and results in the formation of newbone originating from the host's own local bonetissue. From a biologic point of view, this mustcertainly be preferred over various other tissueaugmentation techniques involving the placementof different types of auto- and allografts.AcknowledgementsThis study has been partially supported by theNational Foundation for Scientific Research(Grant No. 32-9302.87) and the Clinical ResearchFoundation (CRF), University of Berne, School ofDental Medicine. The histologic documentationhas been provided by Dr. h.c. H. Stich, Universityof Berne and is highly appreciated. Furthermore,the authors thank Dr. K. Dula and the staff of theDepartment of Oral Surgery, University of Berne,for their assistance and cooperation during thestudy.

ReferencesBecker. W., Becker. B. . Handlesman. M. Celletti, R.. Och-senbein. C. Hardwick. R. & Langer. B. (1990) Bone forma-tion at dehisced dental implant sites treated with implantaugmentation material: a pilot study in dogs. InternationalJournal of Periodontics and Restorative Dentistrv 10: 93-101.Branemark , P. I.. Zarb. G. A. & Albrektsson, T. (1985)Tissue integrated prostheses. Osseointegration in clinical den-tistry. Chicago: Quintessence Publishing Co.

Bragger. U. (1988) Digital imaging in periodontal radiogra-phy. A review. Journal of Clinical Periodontology 15: 551-557.Bragger. U. & Pasquali. L. (1989) Color conversion of alveo-lar bone density changes in digital subtraction images. Jour-nal of Clinical Periodontology 16: 209-214.Buser. D . . Weber. H. P. & Bragger. U. (1990) The treatmentof partially edentulous patients with ITI hollow-screw im-plants: presurgical evaluation and surgical procedures. In-ternational Journal of Oral and Maxillofacial Implants 5:165-174.Dahlin. C. Linde. A.. Gottlow, J. & Nyman. S. (1988) Heal-ing of bone defects by guided tissue regeneration. Plasticand Reconstructive Surgery 81: 672-676.Dahlin. C., Sennerby, L.. Lekholrn , U .. Linde. A. & Nyman.S. (1989a) Generation of new bone around titanium im-plants using a membrane technique: an experimental studyin rabbits. International Journal of Oral and MaxillofacialImplants 4: 19-25.

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Buser et al.Dahlin. c.. Gottlow, J .. Linde. A. & Nyman. S. (1989b)Healing of maxillary and mandibular bone defects using amembrane technique. Journal of Dental Research 68: 918(abstract # 385).Khoury. F. (1987) Die modifizierte Alveolar-Extensionsplas-tik. Zeitschrift fur Zahniirztliche Implantologie 3: 174-178.Lazzarra, R. J. (1989) Immediate implant placement into ex-traction sites: Surgical and restorative advantages. The In-

ternational Journal of Periodontics & Restorative Dentistry 9:333-343.Lekholm, U . . Adell. R .. Lindhe, J. et al. (1986) Marginaltissue reactions at osseointegrated titanium fixtures. (II) Acrosssectional retrospective study. International Journal ofOral and Maxillofacial Surgery 15: 53-61.Nentwig, G. H. & Kniha. H. (1986) Die Rekonstruktion 10-kaler Alveolarfortsatzrezessionen im Frontzahnbereich mitKalziumphosphatkeramik. Zeitschrift fur Zahniirztliche Im-plantologie 2: 80-85.Nyman. S. Lindhe, J. & Karring, T. (1989) Reattachment-New attachment. In: Lindhe, J., ed. Textbook of clinicalperiodontology, 2nd edition. pp. 450-476. Copenhagen:Munksgaard.

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Nyman, S., Lang, N. P., Buser, D. & Bragger, U. (1990) Boneregeneration adjacent to titanium dental implants usingguided tissue regeneration: a report of two cases. Interna-tional Journal of Oral and Maxillofacial Implants 5: 9-14.Osborn, J. F. (1985) Die Alveolar-Extensionsplastik . Die Quin-tessenz 36: Referat-Nr. 6701.Schroeder, A. (1990) Tissue reactions. In: Schroeder, A.,Sutter, F. & Krekeler, G., eds. Oral implantology. Stuttgart:Georg Thieme Verlag.Seibert, J. & Nyman, S. (1990) Localized ridge augmentationin dogs: a pilot study using membranes and hydroxyapatite.Journal of Periodontology 61: 157-165.Streckbein, R. G. & W61tge, E. (1987) Augmentationsplastikmit tiefgefrorener homologer Spongiosa als praimplanto-logische Massnahme beim Einzelzahnersatz. Zeitschrift furZahniirztliche Implantologie 3: 83.Tetsch, P. (1984) Enossale Implantationen in der Zahnheil-kunde. Miinchen: Carl Hanser Verlag.

1990Buser_Regeneration and Enlargment of Jaw Bone Using Guided Tissue Regeneration

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