Oral Abstract Session 3

MAXILLOFACIAL RECONSTRUCTIONFriday, October 1, 2004, 12:30 pm–3:30 pm

A Novel Fused Interconnected Scaffoldfor Bone Tissue EngineeringHaru Abukawa, DDS, PhD, Department of Oral andMaxillofacial Surgery, WRN 1201, MGH, 55 FruitStreet, Boston, MA 02114 (Shin M; Vacanti JP; KabanLB; Troulis MJ)

Statement of the Problem: The use of tissue-engi-neered bone would eliminate the problem of donor sitemorbidity when reconstructing the maxillofacial skele-ton. We previously reported in vitro construction of atissue engineered mandibular condyle using a solid poly-DL-lactic-co-glycolic acid (PLGA) scaffold with pore sizefrom 20 to 400 microns. Bone formation occurred onlyon the surface. In order to obtain uniform and completebone penetration, a novel PLGA fused interconnectedscaffold with both large (1 mm to 2 mm in diameter) andsmall pores (20 to 200 microns in diameter) was de-signed. The purpose of this study was to compare thesolid and fused interconnected scaffolds in vitro.

Materials and Methods: PLGA solid scaffolds were fab-ricated in a 20 � 20 � 7 mm mold using solvent-castingparticulate-leaching. Fused interconnected scaffoldswere prepared from PLGA foam squares cut into chipsmeasuring 7 � 7 � 2 mm. The chips were placed in a20 � 20 � 7 mm mold and heated in an oven for 8 hoursat 65° centigrade. This caused the PLGA to melt at thesurface, binding the individual chips together, forming asingle, three-dimensional polymer scaffold with an inter-connected pore structure (“fused interconnected scaf-fold”). Porcine mesenchymal stem cells (pMSCs) wereisolated from minipig (age 6 months; n � 3) iliac crestmarrow. The pMSCs were suspended in medium con-taining osteogenic supplements (OS: 100 nM dexameth-asone, 50 �g/mL ascorbic acid, and 10 mM �-glycero-phosphate) and then diluted to 30 � 106 cells per 35 mLOS medium. The cell suspension was seeded onto PLGAsolid and fused interconnected scaffolds. The seeded scaf-folds were placed in a rotational oxygen-permeable biore-actor system (ROBS) and incubated for 2, 4, and 6 weeks.

Method of Data Analysis: After incubation, scaffolds wereexamined histologically to assess cell and bone penetra-tion. The number of cells in the center of the scaffolds wascounted in 3 areas of the scaffold and averaged (n � 3)using image analysis software (NIH Image 1.62 graphicsprogram; NIH, Bethesda, MD). Bone formation depth wasassessed in 3 areas of the scaffold cultured for 6 weeks andaveraged (n � 3) (Meta Morph version 6.6v4, UniversalImaging Corporation, Downingtown, PA).

Results: At 2, 4, and 6 weeks, the fused interconnected

scaffolds exhibited cell penetration of 116.9, 74.3, and 60.4cells/1.4 mm2, respectively, and cells observed throughoutthe scaffolds. PLGA solid scaffolds exhibited penetration of42.4, 66, and 32.9 cells/1.4 mm2, respectively, at the sametime points. At 6 weeks, bone in the fused interconnectedscaffolds penetrated deeper toward the center (0.45 mm)as compared to the solid scaffolds (0.18 mm).

Conclusion: The novel, PLGA fused interconnected scaf-fold permits deeper cell and bone penetration than do thestandard solid PLGA scaffolds in this in vitro model.

References

Abukawa H, et al: J Oral Maxillofac Surg 61, 2003Abukawa H, et al: J Oral Maxillofac Surg 62, 2004

Funding Source: Hanson Foundation, the Massachusetts General Hos-pital Laboratory for Tissue Engineering and Organ Fabrication, ThericsInc, Department of OMFS Education and Research.

The Reproducibility of Human Platelet-Rich Plasma With Respect to PlateletCounts and Putative Cytokine LevelsBen Davis, DDS, FRCD, 1767 Pryor Street, Halifax,Nova Scotia B3H 4G7, Canada (Rose C; Filiaggi M)

Statement of the Problem: Platelet-rich plasma (PRP) hasbeen advocated as a beneficial adjunct to bone graftingprocedures in the maxillofacial region. Many questionsremain unanswered, however, concerning PRP efficacywhen used in combination with bone grafting. This studysought to establish what range of PRP concentrates andcytokine levels could predictably be obtained from healthyvolunteers using a commercially available automated cen-trifuge designed specifically for the collection of PRP.

Materials and Methods: Twenty-four blood samples werecollected from 15 male and 9 female healthy volunteers. Allsamples (60 mL for females, 55 mL for males) had a 500microliter aliquot removed for determination of baselinecomplete blood counts. A SmartPReP machine (HarvestTechnologies) was used according to the manufacturer’sinstructions to prepare the PRP. Aliquots of platelet-poorplasma (PPP), PRP, and whole blood were run on theCoulter STKS (Coulter Corporation). Eleven PRP samplesunderwent cytokine analysis. Levels of platelet derivedgrowth factor AB (PDGF-AB) were determined using aHuman PDGF-AB Quantikine Colorimetric Sandwich ELISAkit (R&D Systems). Transforming growth factor beta 1(TGF-�1) levels were determined using a Human TGF-�1Colorimetric Sandwich ELISA kit (YesBiotech).

Method of Data Analysis: All quantitative measure-ments were described using summary statistics. Scatter-

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plots and Spearman rank correlation coefficient wereused to identify relationships between 1) platelet countsin whole blood and PRP, and 2) growth factor levels andplatelet counts. Student’s t tests were also performed toidentify any differences in test groups.

Results: Analysis of PRP samples showed an averageplatelet increase of 396%. Significant variation did exist,however, with platelet counts ranging from 363 � 109

cells/L to 1,900 � 109 cells/L. Females did appear to pro-duce a more concentrated PRP product, but this was notstatistically significant. An association was demonstratedbetween the volunteer’s whole blood platelet count andthat of the PRP. A high degree of variability was also notedwhen examining the results of the initial cytokine releaselevels of PRP and PPP. Although variability did exist, rela-tive cytokine increases in PRP compared to PPP were 151%for TGF-�1 and 415% for PDGF-AB. No correlation wasnoted between growth factor levels and platelet counts.

Conclusion: These initial results demonstrate in-creases in both platelet counts and cytokine levels. Ofconcern, however, was the significant variation in theselevels among PRP samples obtained from healthy volun-teers using a commercially available device.

References

Marx RE, Carlson ER, Eichstaedt RM, et al: Platelet rich plasma:Growth factor enhancement for bone grafts. Oral Surg Oral Med OralPathol Oral Radiol Endod 85:638, 1998

Weibrich G, Kleis WK, Hafner G: Growth factor levels in the plateletrich plasma produced by 2 different methods: Curasan-type PRP kitversus PCCS PRP system. Int J Oral Maxillofac Implants 17:184, 2002

Is There a Role for ReconstructiveTechniques to Prevent PeriodontalDefects After Third Molar Surgery?Thomas B. Dodson, DMD, MPH, Massachusetts GeneralHospital, 55 Fruit Street, Warren 1201, Boston, MA 02114

Statement of the Problem: Most studies assessing therole of therapeutic intervention to prevent periodontalpocketing on the mandibular second molar (M2) follow-ing third molar (M3) extraction fail to demonstrate treat-ment benefit. We hypothesize, however, the existenceof a high-risk cohort who may benefit from reconstruc-tive procedures to prevent M2 periodontal defects afterM3 removal. The specific aim of this study was to answerthe following question: Among patients at high risk forM2 periodontal defects after M3 removal, does activetreatment, ie, demineralized bone powder (DBP) graft-ing or guided tissue regeneration (GTR) therapy, at thetime of extraction, when compared to no treatment,alter the risk of postextraction M2 periodontal defects?

Materials and Methods: We used a prospective cohortstudy design and a sample composed of subjects at highrisk for developing M2 periodontal defects after M3 extrac-tion, ie, age greater than or equal to 26 years, preexisting

periodontal defects defined as attachment level (AL)greater than or equal to 3 mm, and mesioangular or hori-zontal M3 impaction. The predictor variable was treatmentstatus of the M3 extraction site. The M3 extraction siteswere reconstructed with DBP, bioresorbable GTR therapy,or no treatment. The outcome variable was ALs measuredat the M2 distobuccal line angle preoperatively and 26weeks after extraction.

Method of Data Analysis: Appropriate uni-, bi-, andmultivariate statistics were computed and statistical sig-nificance was set at a P � .05.

Results: The cohort was composed of 12 subjects con-tributing 18 high-risk M3s. There were no statistically sig-nificant differences in the distribution of the tooth-specificstudy variables among the three groups (P � .46), ie, DBP-or GTR-treated or control M3s. Preoperatively, the ALsranged from a mean of 5.4 mm (GTR-treated M3s) to 6.8mm (control M3s) to 7.6 mm (DBP-treated M3s). The pre-operative ALs were not statistically different among thethree groups (P � .43). Twenty-six weeks after M3 re-moval, the ALs for GTR-treated (3.0 � 1.2 mm), DBP-treated (1.4 � 0.5 mm), and control (3.8 � 0.9) M3 siteswere statistically significantly different (P � .002). Tukeypost-hoc comparisons revealed a statistically significant dif-ference between control and DBP ALs (P � .001). GTR-treated and DBP-treated ALs comparisons were also signif-icantly different (P � .037). There was no statistically sig-nificant difference in ALs between control and GTR-treatedM3s (P � .35). Three M3 sites (16.6%) in 3 subjects (25%)had postoperative inflammatory complications.

Conclusion: The results of this study suggest that sub-jects at high risk for developing M2 periodontal defectsafter M3 removal may benefit from the use of DBP placedat the time of M3 extraction to enhance periodontalhealing. Future studies addressing the role of reconstruc-tive procedures in enhancing M3 extraction site healingshould be limited to subjects considered high risk forpostextraction M2 alveolar bone defects.

References

Dodson TB: Bone allograft versus guided tissue regeneration toreconstruct third molar extraction sites: A randomized clinical trial.J Oral Maxillofac Surg 61:49, 2003 (suppl)

Pecora G, Celleti R, Davapanah M, et al: The effects of guided tissueregeneration on healing after impacted mandibular third-molar surgery:1-Year results. Int J Periodont Restorative Dent 13:397, 1993Funding Source: Oral and Maxillofacial Surgery Research Foundation.

Direct Digital Panoramic Radiology and2-D Reconstructions of Cone BeamComputed Tomography in Localizationof the Inferior Alveolar Canal andMaxillary Floor of Sinus forIntraosseous Dental ImplantsDouglas K. Doran, DMD, PO Box V-12, Palo Alto, CA94304 (Hollender LG; Peck J; Girod S)

Oral Abstract Session 3: Maxillofacial Reconstruction

AAOMS • 2004 37