Barrier Membranes Used for Ridge Augmentation- Is There an Optimal Pore Size

J Oral Maxillofac Surg67:1218-1225, 2009

*

ger

An

Ala

Bir

SurBarrier Membranes Used for RidgeAugmentation: Is There an

Optimal Pore Size?Rajesh Gutta, BDS, MS,* Robert A. Baker, DVM,

Alfred A. Bartolucci, PhD, and Patrick J. Louis, DDS, MD

Purpose: To identify the optimal pore size of barrier membranes for successful alveolar ridge recon-struction procedures, to determine if cortical perforations have any effect on bone regeneration, and toreiterate that bone graft containment is an important parameter for successful regeneration.

Materials and Methods: This was a prospective, randomized, controlled study performed on hounddogs. Corticocancellous tibial bone grafting was performed to the lateral border of the mandible andprotected with barrier membranes (meshes). The experiment analyzed three different pore sized meshes,compared with controls without the mesh. Two meshes (macroporous and microporous) were made oftitanium, and one was a resorbable mesh. Meshes were preformed into the shape of a cube with one faceopen. Each side of the cube measured approximately 10 mm. Cubes were open-faced on one side, tofacilitate packing of the graft material. The dogs received bilateral ramus grafts. Cortical perforationswere created on the left ramus of all the dogs and compared with the right side, which did not haveperforations. The dogs were randomly divided into 3 groups and sacrificed at intervals of 1, 2, and 4months. Before sacrifice, all dogs received 2 doses of tetracycline as a marker for new bone formation.Histomorphometry was performed by using Bioquant image-analysis software. Areas of new bone andsoft tissue were measured. The rate of mineral apposition was also calculated. All values obtained viahistomorphometry were statistically analyzed with a t test.

Results: Thirty-one experimental sites were evaluated. The amount of new bone growth into themacroporous mesh was significantly higher than in the other groups. The mean area of new boneformation in large and small meshes was 66.26 13.78 mm2 and 52.82 24.75 mm2, respectively. Inthe resorbable mesh group, the mean area of new bone formed was 46.76 21.22 mm2. The amountof new bone formed in the control group was 29.80 9.35 mm2. There was no significant difference inamount of bone formation between left and right sides (P .3172). Resorbable meshes had significantsoft tissue ingrowth (23.47 mm2) compared with macroporous mesh (16.96 mm2) and microporousmesh (22.29 mm2). Controls had the least amount of soft tissue ingrowth (9.41 mm2). Mineral appositionrate was found to be higher in the resorbable group (2.41 m/day), and the rate was lowest (1.09m/day) in the large pore mesh group.

Conclusion: Macroporous membranes facilitated greater bone regeneration compared with micro-porous and resorbable membranes. Macroporous mesh also prevented significant soft tissue in-growth compared with other meshes. Containment of a bone graft is the most critical parameter insuccessful bone regeneration. Cortical perforations did not have any effect on the quantity ofregenerated bone. Further research should be directed toward identifying a critical pore size andmanufacturing a reliable mesh that would prevent excessive soft tissue ingrowth in ridge augmen-tation procedures. 2009 American Association of Oral and Maxillofacial SurgeonsJ Oral Maxillofac Surg 67:1218-1225, 2009

Assistant Professor, Department of Oral and Maxillofacial Sur-

y, University of Texas Health Science Center at San Antonio, San

tonio, TX.

Senior Veterinarian, Animal Resources Program, University of

bama at Birmingham, Birmingham, AL.

Professor, Department of Biostatistics, University of Alabama at

mingham, Birmingham, AL.

Professor and Director, Department of Oral and Maxillofacial

gery, University of Alabama at Birmingham, Birmingham, AL.

Address correspondence and reprint requests to Dr Gutta:

Department of Oral and Maxillofacial Surgery, MSC 7908, Univer-

sity of Texas Health Science Center, 7703 Floyd Curl Drive, San

Antonio, TX 78229; e-mail: [email protected]

2009 American Association of Oral and Maxillofacial Surgeons

0278-2391/09/6706-0011$36.00/0

doi:10.1016/j.joms.2008.11.022

1218

TrwiprbomeThal19bolosbacaatubraNuvabothesositeofanim

M

stulouthebalyzcowianzo

mmfrotidpointEammpadoHotheran1suanresdomaBioAntiswamoprpepeofPro

Su

vetheha

FIGme

GuMa

GuMa

GUTTA ET AL 1219aditionally, alveolar ridge augmentation is achievedth various graft materials and barrier membranes toevent soft tissue ingrowth. The concept of guidedne regeneration (GBR) has been used in experi-ntal reconstructive surgery since the mid-1950s.e principle of GBR was first described by Hurley etfor the treatment of experimental spinal fusion in59.1 In the 1960s, the healing of defects in longnes and jaws was tested using microporous cellu-e acetate laboratory filters.2-4 Although the value ofrrier membranes was shown to be reliable in verti-l ridge augmentation procedures, little in the liter-re supports the role of pore size of barrier mem-nes in preventing excessive soft tissue ingrowth.merous studies showed a layer of fibrous tissue ofrying thickness adhering to newly regeneratedne.5-8 The specific hypotheses of this study are thatre is an optimal pore size that prevents significantft tissue ingrowth into the graft material or graft, that pore size definitely has an effect on the qualityregenerated bone and predictability of graft intake,d that the presence of cortical perforations has anportant role in the bone regeneration process.

aterials and Methods

This was a prospective, randomized, controlleddy performed on adult hound dogs. Corticocancel-s tibial bone grafting was performed to augmentlateral border of the mandible and protect with

rrier membranes (meshes). The experiment ana-ed 3 different pore sized meshes compared withntrols without mesh. The bone graft was protectedth meshes of varying pore sizes. The macroporousd microporous meshes (Stryker-Leibinger, Kalama-o, MI) had an average pore size of 1.2 mm and 0.6

URE 1. Preformed macroporous, microporous, and resorbableshes.

tta et al. Barrier Membranes for Ridge Augmentation. J Oralxillofac Surg 2009., respectively. The resorbable mesh was madem polylactic acid (70/30 copolymer of poly[L-lac-e-co-D,L-lactide] with a pore size of 1.0 mm (Macro-re, Inc, San Diego, CA). Meshes were preformedo the shape of a cube with one face open (Fig 1).ch side of the cube measured approximately 10. Cubes were open-faced on one side to facilitate

cking of the graft material. Originally 5 adult houndgs were used as experimental subjects in this study.wever, 1 animal died intraoperatively due to anes-tic complications. The remaining 4 animals weredomly divided into 3 groups. Group I consisted ofanimal sacrificed at the end of 1 month after thergical procedure. Groups II and III consisted of 2imals each sacrificed at 2 months and 4 months,pectively. Before sacrifice, all animals received 2ses of tetracycline as a marker for new bone for-tion.9,10 Histomorphometry was performed usingquant image analysis software (Biquant Imagealysis, Nashville, TN). Areas of new bone and softsue were measured. The rate of mineral appositions also calculated. All values obtained with histo-rphometry were statistically analyzed with a t testocedure. All the dogs had the same proceduresrformed under general anesthesia. The study wasrformed according to guidelines of the UniversityAlabama at Birmingham (UAB) Animal Resourcegram.

rgical Technique

BONE-HARVESTING TECHNIQUE

Two surgical teams prepared simultaneously to har-st the tibia and perform the bone graft procedure tomandible. A tibial strut measuring 7 1 cm was

rvested (Fig 2). A small bone graft curette was then

FIGURE 2. Harvesting the tibial bone graft.

tta et al. Barrier Membranes for Ridge Augmentation. J Oralxillofac Surg 2009.

intwamesencopamisal

sioriolat(Fitrapaofpra 0wi

intlaidothethetitabuthemawewesitsamco

weAprin

infexatstaadAftcaremwe

bleabstumefortowitothobeemligbuealinanCitso

FIGma

GuMa

FIGsid

GuMa

1220 BARRIER MEMBRANES FOR RIDGE AUGMENTATIONroduced into the harvest site and cancellous bones harvested. To achieve consistency in the experi-ntal procedure, the right tibia was randomly cho-for graft harvest. The graft was harvested under

pious irrigation with saline and morselized intorticles less than 1 mm in size with the use of a bonell/ronguers. The graft was then stored in normaline until the recipient site was ready for grafting.

BONE-GRAFTING TECHNIQUE

An extraoral approach with a submandibular inci-n was used bilaterally in all the animals. A subpe-steal dissection was then performed to expose theeral aspect of the body and ramus of the mandibleg 3). Similar exposure was performed on the con-lateral site. Four sites of regeneration were pre-red on each side along the lateral body and ramusthe mandible. On the left side, the cortex along theoposed site of graft placement was perforated with.8-mm round carbide bur under copious irrigationth normal saline (Fig 4).The harvested particulate graft was then packedo the preformed mesh cubes. Meshes were over-d along the lateral border of the mandible. This wasne such that the open end of the mesh cube facedlateral cortex of the mandible. Each mesh wasn secured with approximately 1.1-mm-diameternium screws of a depth sufficient to pierce theccal cortex, but not pierce the lingual cortex. Forcontrol site, an equivalent amount of bone graftterial was used as in the mesh cubes. Control sitesre not covered by a barrier membrane. Once graftsre secured, the wound was closed and the oppo-e side was addressed. The site preparation was thee, except that no holes were drilled through the

rtex of the ramus. The mesh cubes with bone graft

URE 3. Extraoral approach to the body and ramus of thendible.

tta et al. Barrier Membranes for Ridge Augmentation. J Oralxillofac Surg 2009.re secured in a similar fashion as described above.Penrose drain was inserted into the surgical site toevent wound seroma. The wound was then closedlayers.The dogs were monitored daily for signs of woundection, dehiscence of the surgical wound, or graftposure. Before sacrifice, they received tetracyclinea dose of 25 mg/kg as a marker for appropriateining of regenerated bone. A total of 2 doses wasministered with a 2-week interval between doses.er animals were successfully euthanized, the surgi-l sites were re-entered. Meshes were identified andoved en bloc, using a surgical drill. Specimensre stored in formalin solution for analysis.

HISTOLOGY

Eight specimens were harvested from each mandi-for a total of 31 specimens. In group I, the resorb-

le mesh on the left side was excluded from thedy due to improper surgical technique. All speci-ns were trimmed and fixed in 10% neutral bufferedmalin for 1 month. All specimens were subjectedtissue processing, dehydration, and infiltrationth methyl methacrylate (MMA) solution, accordingthe standard operating procedure of the UAB Or-paedic Research Laboratory, and subsequently em-dded in methylmethacrylate. All specimens withbedding mixture were placed under ultravioletht for 48 hours to allow for polymerization. Accal-lingual midline section was obtained fromch specimen using an Exakt macrosaw. Each mid-e section was then ground to 80 to 100 m, usingExakt grinder (Exakt Technologies Inc, Oklahomay, OK). Then sections were stained with Sander-ns bone stain (Surgipath Inc, Richmond, IL).

URE 4. Cortical perforations to the external cortex on the lefte of the subjects.


incwiofabma

ImTNsecThtotca

Re

sta

of13theforwiwa

insig

FIGpor

GuMa

FIGpor

GuMa

FIGabl

GuMa

FIGsite

GuMa

GUTTA ET AL 1221HISTOMORPHOMETRY

A region of interest was selected within the meshluding the area between the pores for subgroupsth small mesh and large mesh. Four random regionsinterest were selected for subgroups with resorb-le mesh and no mesh. Each region was approxi-tely 10 mm from the border of the compact bone.Histomorphometry was performed using Bioquantage Analysis Software (R&M Biometrics, Nashville,). With this software, a 2-dimensional histologiction displays profiles of 3-dimensional structures.ree measurements were made: total tissue area,al bone area, and soft tissue area. Software thenlculated indices.

URE 5. Microsection revealing bone formation with macro-ous mesh.


URE 6. Microsection revealing bone formation with micro-ous mesh.

tta et al. Barrier Membranes for Ridge Augmentation. J Oralxillofac Surg 2009.sults

All values obtained with histomorphometry weretistically analyzed with a t test.

BONE GROWTH

Mean areas of new bone formation for the groupsmacroporous and microporous mesh were 66.26.78 mm2 and 52.82 24.75 mm2, respectively. Ingroup without mesh, the amount of new bone

med was 29.80 21.22 mm2, and in the groupth resorbable mesh, the area of new bone formeds 46.76 9.35 mm2 (Figs 5-8).Among the 4 groups analyzed, new bone formationthe group with macroporous titanium mesh wasnificantly higher than in the other groups. This was

URE 7. Microsection revealing bone formation with resorb-e mesh.


URE 8. Microsection revealing minimal bone formation in thewithout any containment.


folthepesigboTasid19pe51bo.31

gropomeinsensoofticwigro

latclimithe/megrolowpo

Di

onbratattheporepbesu10higten

FIGbon

GuMa

T BETW

Mesh

Ma 004NoRe 828Mi 175

Gu xillofa

1222 BARRIER MEMBRANES FOR RIDGE AUGMENTATIONlowed by the group with microporous mesh andn the resorbable mesh group. However, as ex-cted, the group without mesh failed to show anynificant bone formation. The statistical difference inne formation between each group is represented inble 1. The mean amount of bone formation on thee that received cortical perforations was 46.79 .17 mm2. On the side that did not receive corticalrforations, the mean amount of bone formation was.32 25 mm2. There was no difference in amount ofne formation between the left and right sides (P 72).

SOFT TISSUE INGROWTH

The resorbable mesh had significant soft tissue in-wth (23.47 22.22 mm2) compared with macro-rous mesh (16.96 8.02 mm2) and microporoussh (22.29 16.50 mm2). The statistical differencesoft tissue formation between each group is repre-ted in Table 2. Controls had the least amount of

ft tissue ingrowth (9.41 4.82 mm2). The amountsoft tissue ingrowth into the mesh was not statis-ally different between the right and the left sides (P.2301). The amount of bone growth comparedth soft tissue ingrowth was statistically higher in allups combined (P .0043).

URE 9. Tetracycline-stained histological section revealing newe formation with macroporous mesh.


able 1. STATISTICAL DIFFERENCE IN BONE FORMATION

Macroporous Mesh No

croporous mesh .0mesh .0004

sorbable mesh .0480 .0croporous mesh .1512 .0

tta et al. Barrier Membranes for Ridge Augmentation. J Oral MaMINERAL APPOSITION RATE

The rate of mineral apposition (MAR) was calcu-ed by dividing the distance between the 2 tetracy-ne markers by the time interval between their ad-nistrations. The MAR was observed to be higher inresorbable mesh group, with a mean value of 2.41

day, followed by the group with microporoussh, which corresponded to 2.25 /day. In theup without mesh, the MAR was 2.2 /day. Theest value was noted in the group with macro-

rous mesh, at 1.09 /day (Figs 9-12).

scussion

Reports in the literature on the effect of pore sizefibrous tissue ingrowth into porous barrier mem-nes are remarkably few. In subcutaneous implan-ion experiments in rats, Salvatore et al examinedsoft tissue response to polyurethane sponges in 6

re sizes ranging from 280 m to 3.2 mm.11 Theyorted that implants with the smallest pore sizecame rapidly filled with collagen and vascular tis-e. Chvapil et al suggested that pores in excess of0 m are required for the rapid penetration ofhly vascular connective tissue, and small poresd to become filled with more avascular tissue.12

URE 10. Tetracycline-stained histological section revealingbone formation with microporous mesh.


EEN GROUPS AS NOTED BY P-VALUE

Resorbable Mesh Microporous Mesh

.0480 .1512

.0828 .0175.5250

.5250

c Surg 2009.FIGnew

GuMa

TamemsizBamabatis

bowitenwigrothenocaofwalarampo

intshingreqboocstuforformmisizbo

MAthial.formiinc

terrespaaftingimingtisbobobyintstrevisreathaexdeoththi

titawidisofsigmegro

FIGnew

GuMa

FIGnew

GuMa

GUTTA ET AL 1223ylor and Smith tested 2 types of porous methyl-thacrylate implants with average pore sizes of 42and 361 m.13 They found that the smaller pore

e was inadequate for penetrations of capillaries.sed on our search, there is no information in thexillofacial literature on the optimal pore size ofrrier membranes for prevention of excessive softsue ingrowth.In this study, there was an increased quantity ofne formation in the large pore mesh comparedth the small pore mesh. This finding was consis-t with Bobyn et al, who reported that implantsth a large pore size initially had greater in-wth.14 At the end of the 52 weeks of their study,y concluded that the difference in pore size hasinfluence on the healing response and on clini-

l consequences. In the present study, the amountbone growth between smaller pore size meshess not significant statistically (P .5250). Simi-ly, there was no statistical difference in theount of bone growth between small and largere sized meshes (P .1512).Several other investigators studied bone ingrowtho systems with different pore sizes.15-17 Theyowed that a pore size of 100 m allows bonerowth, but a pore size greater than 150 m isuired for osteon formation. Studies on the rate ofne ingrowth mentioned that bone ingrowth wouldcur if a pore size was greater than 50 m.18 Thesedies indicated that the optimum pore size requiredbone ingrowth remains undefined. But for osteonmation, the pore size should be greater than 150. An interesting finding in our study involves theneral apposition rate in the mesh with large poree. Although this group had a greater amount ofne formation compared with other groups, the

URE 11. Tetracycline-stained histological section revealingbone formation with resorbable mesh.

tta et al. Barrier Membranes for Ridge Augmentation. J Oralxillofac Surg 2009.R was only 1.09 m. Based on this observation,s finding is consistent with the study of Bobyn et14 There might have been faster ingrowth of bone-ming cells into the mesh with large pore size. Theneral apposition might have been slower due toreased surface area through the large pores.Micromovement between bone and implanted ma-ial was also shown to prevent bony ingrowth andult in the development of fibrous tissue membrane,rticularly if this occurs during the healing processer implantation.18-21 During the initial 3-week heal-period there should be minimal stress on the

planted barrier membrane, to prevent any fibrousrowth. With sufficient initial stability, the earlysue infiltrate through the pores will differentiate tone by either direct bone formation or appositionalne growth from adjacent bone. This was describedSpector, based on observations of tissue ingrowtho porous polymer systems.22 Pilliar et al demon-ated that bone can form within porous implantsen with limited initial movement, provided the sitesufficiently vascular and that no local inflammatoryctions occur. The extent of this movement is lessn 150 m.23 In contrast to the above studies, withcellent blood supply to the maxillofacial region andspite using rigid fixation for the titanium mesh orer membranes, there are reports associated withck fibrous tissue beneath the membrane.7,24,25

In this study, meshes had been secured well with anium screw. Also, the extraoral approach helpsth stability during masticatory function. Anothertinct advantage with this approach is the absencemesh exposure. As reported in the literature, anificant amount of soft tissue ingrowth into thesh was also noted. The amount of soft tissue in-wth was greater in the resorbable mesh group.

URE 12. Tetracycline-stained histological section revealingbone formation in the site without any mesh.


Homaos

pecuinforrepAnfroindnetheanThticfortwwi

bualwthiregSimthethiSimhuforforboexsuexprblostabrainsmerea

ening

ThtenturprprmepeprSomerepthitharemlaytisThtheevif lboeff

regabveothcripreffFuingmegro

Re1.

T TION

Mesh

Ma 985NoRe 673Mi 818

Gu xillofa

1224 BARRIER MEMBRANES FOR RIDGE AUGMENTATIONwever, in the group without mesh, the bone graftterial was significantly displaced underneath peri-teal flaps.Another area of controversy is the need for corticalrforation during guided bone regeneration for vas-lar supply. One study advocated that perforationsthe cortical bone of the mandible provide accessbone-forming cells from the bone marrow, toopulate the space created by the membrane.26

other study noted that bone formation took placem a noninjured cortical bone surface. That studyicated that perforations are not prerequisites forw bone formation.27 In this study, the left side ofmandible received 0.8-mm cortical perforations,

d the right side did not receive any perforations.e results of this study support the theory that cor-al perforations are not necessary for new bonemation. There was no statistical difference be-een amount of bone formed in the left comparedth the right side.Many studies used membranes to regenerate bone,t qualitative and quantitative measurements are notays recorded. Very few studies reported on theckness of soft tissue ingrowth after guided boneeneration. Becker et al, Jovanovic and Nevins, andion et al reported that the soft tissue layer undermembrane and overlying the regenerated bone is

n and rarely exceeds 1 mm in thickness.7,24,25

ion et al, in a clinical and histological study inmans, demonstrated that the use of titanium-rein-ced expanded polytetrafluoroethylene membranesvertical ridge augmentation resulted in incompletene regeneration under the membrane.7 Histologicamination showed a layer of loose connective tis-e about 2.1 mm in mean thickness. Some possibleplanations for the incomplete new bone formationoposed by the authors were: 1) shrinkage of theod clot under the membrane during the initialge of healing; 2) entrapment of air under the mem-ne; 3) micromovement of the membrane; and 4)ufficient healing period. In this study, all speci-ns had incomplete bone formation, and all thesons cited above might have played a role.An important observation in our study involves thevelope of bone formed around the mesh. This find-is noted in most of the nonresorbable meshes.

able 2. STATISTICAL DIFFERENCE IN SOFT-TISSUE FORMA

Macroporous Mesh No

croporous mesh .2mesh .2985

sorbable mesh .3853 .0croporous mesh .4613 .0

tta et al. Barrier Membranes for Ridge Augmentation. J Oral Mais is a supportive finding and is consistent with thet-pole effect, as reported extensively in the litera-e. However, a layer of soft tissue ingrowth wasesent between the mesh and the graft material. Atesent it is not known if the soft tissue beneath thembrane undergoes mineralization if left for a longriod, or if the presence of a membrane barrier is aerequisite for the completion of mineralization.me studies reported the soft tissue underneath thembrane to be a periosteum-like tissue, and othersorted it to be fibrous tissue.5,7,8 The vascularity ofs tissue has been variable. Some authors suggestedt this tissue should be left in place after membraneoval.28 Others propose eliminating this soft tissue

er to expose the new bone.6,29 In this study, softsue was fibrous in nature, with very few capillaries.is does not support earlier theories that reportedsoft tissue to be periosteum-like. There is no

idence in this study for mineralization of the tissueeft longer, because there is an incomplete layer ofne formed over the mesh based on the tent-poleect.Macroporous membranes facilitated greater boneeneration compared with microporous and resorb-le membranes. The macroporous mesh also pre-nted significant soft tissue ingrowth compared wither meshes. Containment of a bone graft is the mosttical issue in successful bone regeneration. Theesence of cortical perforations did not have anyect on the quality or quantity of regenerated bone.rther research should be directed toward identify-a critical pore size and manufacturing a reliablesh that would prevent excessive soft tissue in-wth in ridge augmentation procedures.

ferencesHurley L, Stinchfield F, Bassett A, Lyon W: The role of softtissues in osteogenesis. An experimental study of canine spinefusions. J Bone Joint Surg [Am] 41A:1243, 1959Boyne PJ: Regeneration of alveolar bone beneath celluloseacetate filter implants. J Dent Res 43:827, 1964Boyne P, Mikels T: Restoration of alveolar ridges by intraman-dibular transposition osseous grafting. J Oral Surg 26:569, 1968Boyne P: Restoration of osseous defects in maxillofacial casu-alties. J Am Dent Assoc 78:767, 1969Buser D, Dula K, Belser U, et al: Localized ridge augmentationusing guided bone regeneration. II. Surgical procedure in themandible. Int J Periodont Restor Dent 15:10, 1995

BETWEEN GROUPS AS NOTED BY P-VALUE

Resorbable Mesh Microporous Mesh

.3853 .4613

.0673 .0818.8737

.8737

c Surg 2009.2.

3.

4.

5.

6. Mattout P, Mattout C: Conditions for success in guided boneregeneration: Retrospective study on 376 implant sites. J Peri-odontol 71:1904, 2000

7. Simion M, Trisi P, Piattelli A: Vertical ridge augmentation usinga membrane technique associated with osseointegrated im-plants. Int J Periodont Restor Dent 14:496, 1994

8. Simion M, Jovanovic S, Trisi P, et al: Vertical ridge augmenta-tion around dental implants using a membrane technique andautogenous bone or allografts in humans. Int J Periodont RestorDent 18:8, 1998

9. Elkin SL, Vedi S, Bord S, Garrahan NJ, Hodson ME, CompstonJE: Histomorphometric analysis of bone biopsies from the iliaccrest of adults with cystic fibrosis. Am J Respir Crit Care Med166:1470, 2002

10. Parfitt AM, Travers R, Rauch F, Glorieux FH: Structural andcellular changes during bone growth in healthy children. Bone27:487, 2000

11. Salvatore J, Gilmer WJ, Kashgarian M, Barbee W: An experi-mental study of the influence of pore size of implanted poly-urethane sponges upon subsequent tissue formation. Surg Gy-necol Obstet 112:463, 1961

12. Chvapil M, Holusa R, Kliment K, Stoll M: Some chemical andbiological characteristics of a new collagen-polymer com-pound material. J Biomed Mater Res 3:315, 1969

13. Taylor D, Smith F: Porous methyl methacrylate as an implantmaterial. J Biomed Mater Res 6:467, 1972

14. Bobyn J, Stackpool G, Hacking S, et al: Characteristics of boneingrowth and interface mechanics of a new porous tantalumbiomaterial. J Bone Joint Surg [Br] 81:907, 1999

15. Klawitter J, Bagwell J, Weinstein A, Sauer B: An evaluation ofbone growth into porous high density polyethylene. J BiomedMater Res 10:311, 1976

16. Spector M, Flemming W, Kreutner A: Bone growth into poroushigh-density polyethylene. J Biomed Mater Res 10:595, 1976

17. Niles J, Coletti JJ, Wilson C: Biomechanical evaluation of bone-porous material interfaces. J Biomed Mater Res 7:231, 1973

18.

19. Cameron H, Pilliar R, MacNab I: The effect of movement on thebonding of porous metal to bone. J Biomed Mater Res 7:301,1973

20. Ducheyne P, De Meester P, Aernoudt E: Influence of a func-tional dynamic loading on bone ingrowth into surface pores oforthopedic implants. J Biomed Mater Res 11:811, 1977

21. Heck D, Nakajima I, Kelly P, Chao E: The effect of load alter-ation on the biological and biomechanical performance of atitanium fiber-metal segmental prosthesis. J Bone Joint Surg[Am] 68:118, 1986

22. Spector M: Bone ingrowth into porous polymers, in WilliamsDF (ed): Biocompatibility of Orthopedic Implants (vol 2). BocaRaton, FL, CRC Press, 1982, p 55

23. Pilliar R, Cameron H, Welsh R, Binnington A: Radiographic andmorphologic studies of load-bearing porous-surfaced struc-tured implants. Clin Orthop Relat Res 156:249, 1981

24. Becker W, Becker B, McGuire M: Localized ridge augmentationusing absorbable pins and e-PTFE barrier membranes: A newsurgical technique. Case reports. Int J Periodont Restor Dent14:48, 1994

25. Jovanovic S, Nevins M: Bone formation utilizing titanium-rein-forced barrier membranes. Int J Periodont Restor Dent 15:56,1995

26. Buser D, Brgger U, Lang N, Nyman S: Regeneration and en-largement of jaw bone using guided tissue regeneration. ClinOral Implants Res 1:22, 1990

27. Schliephake H, Kracht D: Vertical ridge augmentation usingpolylactic membranes in conjunction with immediate implantsin periodontally compromised extraction sites: An experimen-tal study in dogs. Int J Oral Maxillofac Implants 12:325, 1997

28. Kostopoulos L, Karring T: Augmentation of the rat mandibleusing guided tissue regeneration. Clin Oral Implants Res 5:75,1994

29. Simion M, Trisi P, Maglione M, Piattelli A: A preliminary reporton a method for studying the permeability of expanded poly-

GUTTA ET AL 1225Welsh R, Pilliar R, Macnab I: Surgical implants. The role ofsurface porosity in fixation to bone and acrylic. J Bone JointSurg [Am] 53:963, 1971tetrafluoroethylene membrane to bacteria in vitro: A scanningelectron microscopic and histological study. J Periodontol 65:755, 1994

Barrier Membranes Used for Ridge Augmentation: Is There an Optimal Pore Size?Materials and MethodsSurgical TechniqueBONE-HARVESTING TECHNIQUEBONE-GRAFTING TECHNIQUEHISTOLOGYHISTOMORPHOMETRY

ResultsBONE GROWTHSOFT TISSUE INGROWTHMINERAL APPOSITION RATE

DiscussionReferences

Documents

Barrier Membranes Used for Ridge Augmentation- Is There an Optimal Pore Size