Periodontics

Guided osteogenesis using synthetic membranes andalloplastic materials: A pilot study

Büket Aybar, DDS, PhDVOmer Gunhan, MD, PhD /̂Levent Bilgiç, MD, PhDWusuf Emes, DDS'

Objective: The aim ot this study was to develop an experimental model for the assessment of bone aug-mentation, and in doing so, compare the use ot ß-tricaldum ptiosphate (TCP) bone gratts in combinationwith Gore-Tex augmentation material (GTAtVI) and GTAM without TCP. Method and materials: Calwanalsites in eight Sprague Dawley rats were prepared for bone augmentation. Graft materials and Hermannstainless steel bone pins were used for localized bone augmentation. Specimens were subjected tomacroscopic and histological evaluation at the sixth week. Results: Bone formation was significantlyhigher in the group with the graft support. Conclusion: TCP bone grafts used in conjunction with support-ing pins may contribute to successful bone regeneration by osseoconduction and by maintaining tbe mem-brane-created space. At tbe sixth week, guided bone regeneration utilizing Gore-Tex augmentation mater-ial and TCP bone grafts resulted in tbe fcrmation cf viable new bone. (Quintessence int 2003;34:117-122)

Key words: bcne pins, Gore-Tex augmentation material, guided bone regeneration, tent pole technique

CLINICAL RELEVANCE: Insufficient bone volume in thealveolar ridges as a result of early tootfi loss can causeproblems during tbe placement of denfal implants.Guided bone regeneration is one of tbe meüiods for ob-taining bigber bone volume at the implantation sites. Tbisstudy demonstrates tfie usage of nonresorbable mem-branes and an alloplastic graft material in conjunctionwitb titanium microscrews for guided bone regeneration.

Tbe early loss of teetb due to trauma or advancedperiodontitis often leads to deformities of the alve-

olar bone. These deformities can lead to complicafionsin attempts for the restoration of related areas. In re-cent years there has been an increase in the number ofstudies focusing on the augmentation of tbese atropbicridges either before or at the time of implantsurgery.'-'

•Research Assistant, Faculty of Dentistry, Department of Oral Surgery,Istanbul University, Istanbul, Turkey.

'Professor, Department cf Pathology, Gulhane Military Acaderry ofMedicine, Ankara, Turkey.

sAssodate Professor. Istanbul University, Faculty of Medicine, Dépannentof Pathology, Istanbul University, Istanbul, Turkey.

Reprint requests: Dr Büket Aybar, Dr Esat 151k Cad. 90/13. Moda/Kadikóy,Istanbul.Turkey 81300. E-mail: buketaybar@hotmail.com

The technique of guided bone regeneration (GBR)was evolved to augment atrophie or damaged ridges.̂GBR employs a physical barrier to selectively allownew bone growtb into the space created between thebarrier and the existing bone.^' The techniques havebeen developed to restore tbe defected bone with ei-ther simultaneous or staged approaches. The successof these techniques is directly related to the ability ofthe barrier to prevent the surrounding connective tis-sue to repopulate the deiect and to maintain the spacebetween the barrier and the bone.^

It has been sbowTi that an expanded polytetrafluo-roethylene (PTFE) membrane can be used to improvetbe healing of botb patbologic and experimentally cre-ated defects.^ Graft materials such as ß-tricaiciumphosphate in combination with membranes enhancesuccess of tbe treatment of bone defects.̂

The expanded PTFE membrane creates a secludedspace in which the blood clot is protected from me-cbanJcal injuries and from the colonization of cells de-riving from tbe surrounding connective tissues. As aresuh, only cells from the bone can populate tbe bloodclot.« Space provision for bone regeneration is one oftbe main problems in GTR procedures, as it definesthe maximum volume of bone, which can be regener-ated.'^"" It has been clinically proven that the fewerthe residual bony walls, the more difficult it is to avoidsoft tissue and membrane collapse. Various filling ma-terials have been experimented witb and proposed for

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Fixationscrew

MembraneSupporting screw

Fig 1 Schematic presentaiion of tfie sagittal section of ifie ratcalvarium.

the creation and maintenance of space and for preven-tion of a collapse of both the flap and the barriermembrane into the defect or the augtnentation site.'^"

It has been clinically experienced that empty spacesbecome rapidly obliterated by a blood clot containingboth nonbone-forming and bone-forming cells afterthe surgical procedure.**

The aim of this study was to evaluate histopatho-logically the use of ß-tricalcium phosphate in conjunc-tion with stainless steel microscrews and Gore-Texaugmentation material (GTAM, WL Gore) for local-ized ridge augmentation.

METHOD AND MATERIALS

Eight mature male Sprague-Dawley rats with a meanage of 5 months were used. Animal selection, manage-ment and surgical protocol were planned according toour standard laboratory protocol approved for thisstudy by the Institutional Animal Care and UseCommittee, Istanbul University. Animals were sedatedwith an intraperitoneal injection of a solution consist-ing of 12 mg of Ketavet (ketamine hydrochloride;Parneli) and 10 mg of rompun (xylene hydrochloride,Bayer). The scalp was then prepared with 1% aqueouschlorhexidine solution. A midline sagittal incision wasmade extending from the occipital to the frontal re-gion. The skin and the periosteum were elevated. Asmall hole was created at the surgical site using theHermann bur (Whaledent) for the Herman titaniummicroscrews. Using a low speed handpiece, holes weredrilled into the bone at the sites selected for the sup-porting and fixation microscrews. Extreme care wasexercised in order to avoid injury to the underlyingdura and brain. The titanium microscrews were in-serted by hand to a depth of approximately 0.3 mm.

The surfaces of the osseous tissues were decorticatedusing a small round bur (2-mm diameter) at 600 toSOO rpm. Oval e-PTFE augmentation material(GTAM, WL Gore) membranes were selected andplaced on the operated regions. They then were fixedby fixation microscrews of 0.2-mm diameter. By thismethod, the supporting screws created a space be-tween the membrane and the bone (Fig 1). In group 1(n = 8), tricalcium phosphate (Cerasorb, Curasan)granules were packed under the membrane, coveringthe supporting screw. In group 2 (n = 8), only Gore-Tex augmentation material membranes without TCPwere placed on the supporting screws acting as a tentpole for the membrane.

At the end of 6 weeks the animals were sacrificed,and the expeñtnental sites were removed and fixed byimmersion in 4% buffered formalin. Specimens weresubsequently decalcified by immersion in Iiristensen'sSolution (Sodium Formate-Formic Acid) (SFFA,Aldrich) and oriented for processing. After tissue pro-cessing, specimens were embedded into the 5- to ô-ymthick paraffin sections and stained with hematoxylinand eosin (H & E) solution. They were subsequently as-sessed histologically by light microscope. Following his-tologie assessment, the prepared slides were submittedfor histomorphometric analysis in order to obtain dis-tinct newly formed bone area measurements. The newhone formation in the (2.5 x 10) x25 magnificationarea was measured by a 2.5 objective microscope. Usingtransmitted white light, an array of monochrome imageswas acquired on computer platform using KS400 ver-sion 3.0 (ic/Windows release 3.0) image analysis pro-gram. The results were recorded on Excel spreadsheet.

RESULTS

Macroscopic observations

Prior to sacrifice at six weeks, the closed surgical sitein each animal was examined. Healing of the surgicalwounds was found to be complete in all cases with noevidence of wound breakdown, infection, bleeding, orirritation to the animals. After sacrifice, no evidence ofovert subdural or intracranial hemorrhage or infectionwas detected. The GTAM membrane remained in itsinitial position over the pin throughout the experimen-tal period.

Histopattiologicai observations

Gore-Tex augmentation material group. In the con-trol group sections with only Gore-Tex augmentationmaterial, there was loose connective tissue over the

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Fig 2 In the control group: Cortical part ot the calvarium stiowingweak new bone formation under ttie Gore-Tex membrane andloose connective tissue. (Hematoxyhn-eosm stain; original magni-fication x25; m = membrane; nfb = newly tormed tjone; c = cal-vafium,)

Fig 3 In me exper'rr]e,n;al g'oup; Cortical caivarial bone and nevibone formation immigrating into Ihe graft material under ttie Gore-Tex membrane. [Hematoxylin-eosin stain; original magnificationx25; g = graft material: m = membrane; nfb = newly formedbone; c = calvarium.l

bone. Gore membrane was visible over the connectivetissue. Bone stirface was smooth with minimal superfi-cial bone formation and there were thin strips of os-teoid material and remodeling (Fig 2),

Gore-Tex augmentation material in conjunctionwith ß-tricaicium phosphate group. In the experi-mental sections of Gore-Tex augmentation materialand ß-tricalcium phosphate, groups of porous graftmateriai were seen over the bone. Bone tissue wasfound to immigrate into the graft material as a resultof bone formation. In these areas, graft particles com-pletely surrounded by the hone were also observed. Insome areas new bone formation was found to reachhalf the gap of the graft material. There were prolifer-ated osteoblasts over the new bone tissue. Other areashad thin fibrillar loose connective tissue around thegraft material- In some areas small newly formed boneareas in the middle of the graft material with no con-nection to the cortical bone were seen (Fig 3),

Histomorphometry

The sites with the highest amount of new bone forma-tion in the sections selected for histomorphometricanalysis are shown in Figs 4 to 6, The mean values ofthe new-bone formation area measurements are 0,41± 0,12 mm- for the experimental group and 0,06 ±

0,02 mm- for the control group (P < ,0001), The statis-tical analysis was performed using the Mann-WhitneyU test to assess the significance of the difterences he-tween the groups. The P < ,0001 was considered to bestatistically significant

DiSCUSSiON

This study demonstrated the significance of space pro-vision for regeneration of alveolar bony defects in im-plant therapy. Recently, Sigurdsson et aP tested theconcept of space provision in supporting bone growthutilizing a reinforced e-PTFE barrier and proiided abiologic rationale for enhanced hone and cementtmiregeneration in periodonta) defects.

There is controversy regarding the use of human al-lograft material in conjimction with guided bone regen-eration materials. Most reports on the efftcacjf of thesematerials are devoid of measurable data and are largelybased upon clinical impression. Buser et al" exclusivelyutilized autogenous bone grafts in guided bone regener-ation, and cited inconclusive results regarding the os-seoconductive and osseoinductive effect of allograft ma-terial. In a dog study. Becker at aF found poor resultsutilizing human decalcified freeze-dried bone (DFDB)as a xenograft, Howex'er, the results of that study may

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Fig 4 Minimal osteoid pro-duction over the cortical boneand schematic presentationof measured area were seenin the control group. On theschematic presentation, grayarea shows corticai bone;biack area shows newiylormed bone. (Hematoxyiin-eosih staih; original magniti-cation X25, ntb = newiyformed bohe.]

Figs 5 and 6 Histopathoiogicappearahces of the experi-mental groups and schematicpresentations of new bone for-mations on the surface of thecaivariai cortical bone immi-grating and surrounding to thegratt materials. On theschematic presentation, grayarea shows corticai bone;black area shows newlyformed bone. (iHematoxylin-eosin stain; origmai magnitica-tion x25: ntb = newiy formedbone, g = graft material.)

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not be applicable to humans. Many clinicians have re-ported good results in humans when utilizing DFDB al-lografts with guided bone regeneration,^'''"'

Supporting and fixation pins may play a crucialrole in bone regeneration in GBR," with regard tomaintenance of the membrane-created space. In thisprotected environment, blood cLot formation and or-ganization occurs. Several authors have noted that,to achieve primary closure, especially at immediateextraction sockets, tbe tension plaeed by tbe flap cancause a partial or complete collapse of tbe mem-brane, thereby eliminating the membrane-createdspace,^""" Schenk et al'^ histomorphologically evalu-ated tbe secluded space under barrier membranestwo months after GBR in surgically created defects indogs, and determined that the volume was reduced inthe standard barriers compared to reinforced mem-branes. In a different study, Becker et aP successfullyused absorbable ortbopedic pins as tent poles to pre-vent the e-PTFE barrier membranes from collapsinginto localized alveolar ridge defects. The three de-feets were completely filled with new bone and en-dosseous implants were placed. The biopsies takenfrom each of the augmented sites demonstrated newbone formation.

In the study by Buser et al" the fixation pins alsoplayed an important role in stabilization of tbe mem-brane during clot formation and subsequent healing. Itis postulated that membrane stability is very importantfor wound healing in GBR procedures.^"'« A stablemembrane may be a necessity for achieving a success-ftil result with GBR,

Schenk et al'« evaluated tbe healing of bone inGBR and determined tbat, once initiated, bone forma-tion follows a programmed series of maturation stepssimilar to tbat of normal hone development. The his-tologie results of tbis paper revealed an ingrowtb ofnew hone into the space created by supporting micro-screws, DFDB allograft, and a membrane. This pro-gressively matured over a 9-month period, with an in-crease in bone density from the 6-montb period,Landsberg et aP^ have shown remnants of DFDB allo-graft in contact with newly formed woven bone for upto 12 months in histologie sections, Doblin et al' sug-gests that DFDB in conjunction with supporting pinsmay contribute to successful bone regeneration eitherby osteoinduction or osteoconduction. This is pro-vided by maintaining the membrane-created spaceduring the eaily events in wound healing. At 9 monthsGBR utilizing Gore-Tex augmentation material mem-branes and DFDB allografts resulted in the formationof dense viabîe bone.

It can be assumed that GBR can be used in condi-tions in which higher bone regeneration is wanted.The autbors of the current study believe that the func-

tion of GBR can be improved by tbe usage of tbe tentpole tecbnique. Altbougb the results were better in tbemembrane in conjunction with alloplastic graft mater-ial group, the autbors believe tbat tbe space provisionplays tbe most important part in hone regeneration.

CONCLUSIONS

1, Guided bone regeneration used in conjunction witbsupporting microscrews may contribute to success-ful bone regeneration by osseoconduction and bymaintaining the membrane-created space duringtbe early events of wound healing,

2. At the sixth week, GBR-utilizing-Gore-Tex aug-mentation material membranes and TCP-bone-aî-loplast resulted in tbe formation of viable newbone.

ACKNOWLEDGMENT

The auihors thank R.\ Méditai Equipmenl for their support.

REFERENCES

1. Sigurdsson JT, Hardwick R. Boyle CG. Wikesjo EMU,Periodontal repair in dogs: Spaee provision by reinforced e-PTFE membranes enhances bone and cemenlum regenera-tion in large supraalveolar defects, | Periodontol 1994;65:350-356.

2. Beeker W, Becker BE, McQuire M. Localized ridge aug-mentation using absorbable pins and e-PTFE barrier mem-branes, A new sui^ieal technique. Case reports of resorbablepins. Int Ï Periodontics Restorative Dent 1994:14:49-60,

3. Shanaman RH. The use of guided tissue regeneration to fa-cilitate ideal prosthetic placement of implants. Int ]Periodonties Restorative Dent 1992:12:256-265.

4. Buser D, Bragger U. Lang NP Nyinan S, Regeneration andenlargement of jaw bone using guided tissue regeneration.Clin Oral Implants Res 1990;l:22-32.

5. Nevins M, Mellonig |. Enhancement of the damaged eden-tulous ridge to receive dental implants: A combination of al-lograft and the Gore-Tex membrane. Int J PeriodonticsRestorative Dent 1992:12:97-111.

6. Mellonig ]T, Triplett RG. Guided tissue regeneration andendosseous dental implants, Int | Periodonties RestorativeDentl993;15:109-119.

7 Doblin MJ, Salkin ML, Mellado RJ, Freedman LA. A histo-logie evaluation of localized ridge augmentation utilizingDFDBA in combination with e-PTFE membranes and stain-less steel bone pins in humans, Int [ PeriodonticsRestorative Dent 1996:16:121-129,

8 Tinti C Benfenati PS, Polsizzi G, Vertical ridge augmen-tation: What is the limif Int J Periodontics RestorativeDent 1996; 16:221-229.

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9, Buser D, Hoffmann B, Bernard JP, Lussi A, Mettler D,Schenk RK. Evaluation of filling materials in mem-brane-protected bone defects. A comparative histcmorpho-metric study in the mandible of miniature pigs. Clin OralImplants Res 1998;9:]37-150.

10. Dahlin C, Albeerius P, Linde A. Osteopromotion for cranio-plasty, I Neurosurg t991;74:487-491.

11. Nastri LA, Smith CA, Guided osteogenesis using synteticmembranes: An experimental pilot study, J CraniomaxillofacSurgl996;24:163-t67.

12. Schallborn RG, McClain PK. Combined osseous compositegrafting, root conditioning, and guided tissue regeneration.Int I Periodontics Restorative Dent 1988;8:8-31,

13. Simion M, Dahlin C, Trisi P, Piattelli A. Qualitative andquantitative comparative study on different filling materialsused in bone tissue regeneration; A controlled clinical study.Int J Periodontics Restorative Dent 1994;14:198-215.

14. Buser D, Dula K, Belser U, Hirt HP, Hermann B. Locahzedridge augmentation using guided bone regeneration, surgicalprocedure in the maxilla. Int J Periodontics RestorativeDent 1993; 13:29-45.

15. Nevins M, Mellonig J. The advantages of localized ridgeaugmentation prior to implant placement. A staged event.Int) Periodontics Restorative Dent 1994;148:97-111.

16. Landsberg C], Groskoff A, Weinreb M. Clinical and biologicobservations of freeze-dried bone allograff in augmentationprocedures around implants. Int 1 Oral Maxillofac Implants.1994:9:580-591.

17. Dahlin C, Andersson L, Linde A. Bone augmentation at fen-estrated implants by an osteopromotive membrane tech-nique. Clin Oral Implants Res 1990;l:22-30,

18. Schenk R, Buscr D, Hardwick W, Dahlin C. Healing patternof bone regeneration in membrane protected defects: A his-tological study in the canine mandible. Int J PeriodonticsRestorative Dent 1994;14:13-29.

19. Wikesjo U, Nivelus R. Periodontal repair in dogs: Effect ofwound stabilization on healing. J Periodontol 199I);61:719-724.

122 Volume 34, Number 2, 2003

Proceedings of the InternationalConference on Dentin/Pulp

Edited by Tatsuya ¡shikawa, et al

This text presents theproceedings of the4th internationalConference onDentin/PulpComplex, wbichwas held in Chiba,lapan, in 2001.Approximately 160researchers andclinicians from allover [he worldparticipated in themeeting.

Topics explored in ihe text include:• Molecular and genetic aspects of tooth

development• The role of peripheral nerves in the regulation of

ihe function of pulp and dentin• Immunobiology of pulpal/periapical disease• Bioengineering for dentin regeneration• Resin hybridization in the dentin/pulp complex

192 pp (softcover); 281 illus; ISBN 4-87417-733-6;US $50

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