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2007 Research Forum Oral Session Abstracts

Abstracts for twelve presentations at the 93rd AAP Annual Meeting in Washington, DC.

Research contributor names, credentials, training institutions abstract content and abstract titles are listed below as provided by submitting author. In the list of authors for each abstract, an asterisk (*) indicates the presenting author at the Annual Meeting session on Sunday, October 28, from 2:00 to 5:00 p.m.

Platform Shifting and the Reality of Crestal Bone
Bone Response Between Platform Switched Implants Placed With an Inter-Implant Distance of 4 and 3 mm

Healing After Tooth Extraction and Immediate Implant Installation With and Without Open A Flap

Tissue Engineered Cultured Periosteum Sheets Combined with Platelet-Rich Plasma and Porous Hydroxyapatite in Regenerating Human Periodontal Infrabony Osseous Defects

Retention of "hopeless" teeth and its effect on the adjacent proximal bone following periodontal surgery

Promotional Training in Periodontology

Neutrophil Formylpeptide Receptor SNP 348T>C in Subjects with Aggressive Periodontitis

Actinobacillus Actinomycetemcomitans Mimics TLRVYK Peptides in Beta-2 Glycoprotein I

Periodontitis is an Independent Predictor for Elevated Serum CRP Levels in Solid Organ

Are “Periodontal Derived” Stem Cells Multipotent Adult Progenitor Cells?

Periodontal Regeneration by Application of Human Periodontal Cell Sheet in an Athymic Rat Model

Platform Shifting and the Reality of Crestal Bone

David L. Cochran* DDS, MS, PhD, University of Texas Health Science Center at San Antonio; Ronald E. Jung, University of Zurich, Switzerland; Frank L. Higginbottom, University of Texas Health Science Center at San Antoni;, Archie A. Jones, University of Texas Health Science Center at San Antonio; Marco Wieland, Institute Straumann AG, Basel, Switzerland

Background: Platform shifting is a concept that has been of great interest recently. Most reports describe radiographs and measure marginal bone levels over time. These studies suggest that there is less bone loss compared to butt-joint connections with external hex attachments used in the past. The aim of this study was to radiographically and histologically evaluate crestal bone changes around experimental implants with an internal fitting abutment.
Methods: Experimental implants with an abutment that fit inside the implant leaving a ledge on the implant at the implant-abutment interface were placed either submucosally or transmucosally at three different levels relative to the alveolar crest. Sixty of these two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. Within each side of the jaw, six implants were placed randomly at three distinct levels relative to the alveolar crest. Twelve weeks later, sixty gold crowns were cemented. Radiographs were obtained from all implant sites following implant placement, crown insertion, and monthly for six months after loading. Histological specimens were performed after six months.
Results: Radiographic analyses revealed minimal bone loss as well as a slight increase in bone level for implants placed at the level of the crest or implants placed one millimeter above the crest. The greatest bone loss occurred around implants placed one millimeter below the bone crest. No significant differences occurred in marginal bone loss and level of the bone to implant contact between implants placed submucosally compared to those implants placed transmucosally. Histological analyses revealed the first bone to implant contact below the implant abutment interface and, as usually observed in this model, that the bone level was more apical on the buccal aspect compared to the mesial, distal, and lingual aspect.
Conclusion: The results indicated that an implant with non-matching implant-abutment diameters demonstrated minimal crestal bone loss. Relative to the literature, the amount of bone loss observed falls between the bone loss traditionally found around implants with butt-joint connections with external hex attachments (the most bone loss) and implants that do not have an interface at the alveolar crest (one piece implants, the least bone loss). No significant differences were found between submucosally placed or transmucosally placed implants. Greater bone loss is observed when the implants were placed below the alveolar crest. Importantly, cross-sectional evaluation of implants after healing does not allow the clinician to know the amount of bone change that has occurred since the time of implant placement. This can be critical in esthetic sites.

Bone Response Between Platform Switched Implants Placed With an Inter-Implant Distance of 4 and 3 mm: An Experimental Study in Minipigs

Giuseppe Cardaropoli* DDS, PhD, Department of Periodontology and Implant Dentistry, New York Univesity; San-Choon Cho, Department of Periodontology and Implant Dentistry, New York Univesity; Mitch Bloom, Department of Periodontology and Implant Dentistry, New York Univesity; Nick Elian, Department of Periodontology and Implant Dentistry, New York Univesity; Michel Dard, Pre-clinical Research, Institute Straumann, Switzerland; Dennis Tarnow, Department of Periodontology and Implant Dentistry, New York Univesity

Background: An initial bone loss of about 1.5-2.0 mm has been reported for implant systems with a non platform switched connection (Cardaropoli et al. 2003). The bone loss may be greater when two implants are placed adjacent to each other than when an implant is placed next to a natural tooth, especially if the distance between these implants is less than 3.0 mm (Tarnow et al. 2000). Therefore, the aim of this study is to investigate the bone and soft tissue alterations at two adjacent implants with an inter-implant distance of 3 mm and 4 mm.
Methods: In the current experiment 12 minipigs were used. The mandibular premolars and the first molar were extracted. After 3 months of healing implant installation was performed using a template guide. Three experimental platform switching implants with SLActive surfaces (Institute Straumann, Switzerland) were placed in each mandibular quadrant. On one side of the mandible, an inter-implant distance of 3mm was established while on the contralateral side the distance was 4mm. One stage procedure was used with abutment placement at time of surgery utilizing a transmucosal abutment healing cap. Radiographic measurements of the bone levels were done at 0 and after 8 weeks. In addition, clinical measurements of the soft tissue level changes were performed after 4 and 8 weeks of healing. The animals were sacrificed after 2 months of healing.
Results: A mean bone gain of 0.2 mm ± 0.6mm adjacent to the implants was recorded in the 3 mm inter-proximal distance group while a bone gain of 0.2 mm ± 0.3 mm in the 4mm inter-proximal distance group was measured. In both experimental groups the soft tissue levels remained stable over time in both groups. Histological data will be added to this material.
Conclusion: The results of the present study revealed no bone loss and no statistically significant differences in the bone maintenance in the proximal areas between implant/implant units with inter-implant distances of 3mm and 4 mm. This might be attributed to the implant design featuring a platform switch along with no changing of the healing abutments.

Healing After Tooth Extraction and Immediate Implant Installation With and Without Open A Flap: An Experimental Study in the Dog

Giuseppe Cardaropoli* DDS, PhD, Department of Periodontology and Implant Dentistry, New York Univesity; Francesca Monticelli, Department of Dental Materials, Granada University; Raquel Osorio, Department of Dental Materials, Granada University; Manuel Toledano, Department of Dental Materials, Granada University; Peter Thomsen, Department of Biomaterial Goteborg University; Dennis Tarnow, Department of Periodontology and Implant Dentistry, New York Univesity

Background: Experimental and clinical studies showed that marked hard tissue alterations occurred following tooth extraction and implant installation in the socket (Botticelli et al. 2004, Araújo et al. 2005). However, in these experiments open flap approach was performed for implants placements. Several studies suggested that flap elevation might result in alveolar ridge resorption (Wood et al. 1972, Nobuto et al. 2005). The aim of this investigation was to study the healing after tooth extraction and immediate implant installation using flapless technique.
Methods: In the current experiment 8 beagle dogs were used. The mandibular premolars were extracted. In one side of the mandible an immediate implant installation (n=16) (3.3x10 mm Osseospeed ® Astra, Astra Tech, Moldan, Sweden) was performed without opening the flap (test) while in the contralateral side the implants (n=16) were inserted following flap opening (control). After 3 months of healing the animals were sacrificed and the mandible were processed for ground section in buccal lingual direction. Histometric measurements of bone loss and bone implant contact were performed by a blind investigator.
Results: Significant differences were recorded between the experimental groups (p<0.05). A buccal bone loss of 0.6mm was recorded at the test implants while the bone loss at the control implants was 2.11mm. The bone implant contact was of same magnitude in both the experimental groups.
Conclusion: The results of the present study revealed a minimal buccal bone loss when the flap was not open. The insertion of fluoride-modified surface implants did not prevent buccal bone loss.

Tissue Engineered Cultured Periosteum Sheets Combined with Platelet-Rich Plasma and Porous Hydroxyapatite in Regenerating Human Periodontal Infrabony Osseous Defects

Kanoko Yamamiya* DDS, Niigata University Graduate School of Medical and Dental Sciences; Kazuhiro Okuda, Niigata University Graduate School of Medical and Dental Sciences; Tomoyuki Kawase, University Graduate School of Medical and Dental Sciences; Ken-ichiro Hata, Japan Tissue Engineering Co., Ltd.; Larry F. Wolff, University of Minnesota; Hiromasa Yoshie, Niigata University Graduate School of Medical and Dental Sciences

Background: Our laboratory has shown that treatment of infrabony osseous defects with a combination of platelet-rich plasma (PRP) and porous hydroxyapatite (HA) compared to HA, led to a more favorable clinical result. Furthermore, Mizuno and co-workers demonstrated that cultured periosteum (CP) sheets, utilized in grafting Class III furcation defects in dogs, resulted in newly formed osseous tissue in furcations. Based on these results, we compared CP sheets combined with PRP and HA with only PRP and HA in the treatment of human infrabony defects.
Methods: Twenty-six infrabony defects in 26 healthy subjects with chronic periodontitis were included in this study. Subjects were randomly assigned to either the test (n=13) or control (n=13) study groups. Cells from periosteum specimens were harvested from the mandible of each subject and cultured for 6 weeks until CP sheets formed. In the test group, the PRP and HA granule mixture was placed into the osseous defects and covered with CP sheets. In the control group only a combination of PRP and HA was placed. Surgical flaps were repositioned to their presurgical level and sutured to insure primary closure. Clinical and radiographic measurements were determined at baseline and at six months. Data between baseline and 6 months was statistically evaluated with the Wilcoxon signed-rank matched pair test or the Mann-Whitney U-test.
Results: The gingival index and bleeding scores in both study groups demonstrated a significant decrease at 6 months when compared to baseline (p<0.05). Between group comparisons at baseline indicated clinical parameters demonstrated no statistically significant differences (p>0.05). When compared to baseline, the 6-month results indicated that both treatment modalities resulted in a significantly (p<0.01) favorable change in clinical parameters. At 6 months, the test group, when compared to the control group, had significantly less mean CAL loss (4.3 versus 5.5 mm; p<0.05), less mean infrabony defect depth (0.5 versus 1.7 mm; p<0.01) and greater mean vertical attachment gain (79.1 versus 56.4 %; p<0.05).
Conclusion: A combination of CP sheets, PRP and HA graft or PRP plus HA graft treatment led to significant clinical improvement. However, the added benefits of CP sheets together with the combination of PRP and HA treatment are not only of statistical but also of clinical significance. A factor contributing to these favorable clinical results would be the presence of osteogenic cells in the CP sheets which provided greater regeneration potential. In support of these results, a previous study by Mizuno and coworkers using canine CP sheets demonstrated alkaline phosphatase activity, which is associated with bone regeneration, increased in CP sheets and Type I and II collagen, osteocalcin, osteonectin and osteopontin, all markers of osteoblastic cell activity, were positive immunohistochemically in CP sheets. In addition, CP sheets functioned as a barrier membrane, further increasing regeneration.

Retention of "hopeless" teeth and its effect on the adjacent proximal bone following periodontal surgery

Eli E. Machtei* DMD, Rambam Medical Center and Faculty of Medicine – Technion; Ilan Hirsch, Rambam Medical Center

Background: Clinical wisdom often suggests that retention of periodontally "hopeless" may accelerate the destruction of the adjacent periodontium. Nonetheless, the long-term effect of hopeless teeth on the adjacent alveolar bone has seldom been studied. Therefore the purpose of this study was to examine the effect of retaining "hopeless" teeth on the adjacent alveolar bone following periodontal surgery.
Methods: This was a retrospective comparative long-term study of patients in the department of periodontology at the Rambam medical center. Teeth were considered "hopeless" if they had lost 70% or more bone height at either of the proximal surfaces as evident in periapical radiographs. The minimal follow-up period was ≥24 months post surgery. All patients have completed periodontal therapy including SRP and periodontal surgery at these sites. Consequently, 93 patients with 110 "hopeless" teeth were included in this study. Cases were sorted into two groups: Retained—57 ‘hopeless’ teeth (50 patients) that were maintained; Extracted—53 "hopeless" teeth (43 patients) that were removed at surgery. All radiographs were digitized and measurements of radiographic bone distance (RBD) were performed using computerized software.
Results: Mean follow up was 4.40 years±0.23 SD. For the retained "hopeless" teeth there was a mean bone gain of 0.82 mm from baseline (7.18±0.35mm) to final examination (6.45±0.41mm, p=0.0061). Likewise, post-op percentage RBD of the retained "hopeless" teeth showed a statistically significant improvement from baseline (57.46±1.5%) to final examination (52.32±2.03%, p=0.0032). Teeth adjacent to "hopeless" tooth had slight radiographic bone gain post-op which was greater in the extracted group. However, it was significant only for the distal neighboring teeth (1.50% versus 11.36% respectively; p=0.0119).
Conclusion: Over the last decades, dental implants have become a common treatment alternative for periodontally compromised teeth. Many clinicians tend to prefer nowadays to extract hopeless teeth and replacing them with dental implants. The results of the present study and more recent report on the survival rate of these teeth, would therefore invite a revision of this trend in favor of conserving and maintaining questionable and ‘hopeless’ teeth. In summary, within the limitations of the study, it appears that long-term preservation of ‘hopeless’ teeth following periodontal surgery is an attainable goal with no detrimental effect on the neighboring teeth.

Promotional Training in Periodontology

Russell A. Dylla* DDS, University of Minnesota; James E. Hinrichs, DDS, MS, University of Minnesota

Background: The American Academy of Periodontology recommends building a positive relationship with pre-doctoral dental students and promoting a career in Periodontics. The use of a combined didactic and clinical periodontal honors course to encourage dental students to seek a career in Periodontology has not been previously reported. The aim of this study was to determine if the availability of a pre-doctoral periodontal honors course could increase the quantity and quality of dental students who apply to an Advanced Education Program in Periodontology (AEPP).
Methods: Twenty-four senior dental students were offered an elective course in Periodontology between 2003-2006 that provided hands-on experience in surgical and implant procedures completed on dentiforms and euthanized dogs. Control groups were individuals who graduated prior to the initiation of the honors course (1999-2002) and non participating classmates of honor students (2003-2006). Exit and follow-up surveys were completed by the 24 course participants. Outcomes included demographics, area of practice according to ADA specialties, professional interests, and influence of honors course on career choice and practice abilities. Odds ratio with a 95% confidence interval (CI) limits and probability of pursuing an AEPP was calculated. Mean GPA for course participants and applicants to AEPP were calculated and plotted via linear regression.
Results: Only 2 of 626 non-course graduates (1999-2006) enrolled in an AEPP, while 5 of 24 course graduates enrolled in an AEPP with a mean GPA of 3.58(+0.16sd) on a 4.0 scale. Odds ratio for an honors student to enroll in an AEPP was 82.1 (95% CI of 450.4-15.0) versus 1.09 for non-enrollees. Mean GPA for the honor students was 3.61(+0.18sd) with a steady increase from 2003 to 2006 (3.51 to 3.71, respectively)(r2=0.24). Mean class rank of course enrollees was 16.1(+11.2sd). Students’ interest in an AEPP after the honors course was 8.00 on a 1-10 scale (1=none;10=major), while influence on career path was 8.13. Ninety-six percent reported high satisfaction with the honors course and 42% enrolled in another advanced education program, 21% into an AEPP.
Conclusion: Data from this investigation indicates a periodontal honors course that provides both didactic and hands-on experiences can promote dental students in the top quartile of the class to enroll in an Advanced Education Program in Periodontology and select a career in Periodontics. Enhancement of this course and distribution of the course methods to other dental schools has the potential to improve the quantity and quality of the applicant pool to Advanced Education Programs in Periodontology as well as to enhance the ability of dental students to provide periodontal care.

Neutrophil Formylpeptide Receptor SNP 348T>C in Subjects with Aggressive Periodontitis

Pooja Maney* BDS, MPH, Ohio State University; John D. Walters, Ohio State University

Background: Formylpeptide receptors (FPR) are important for neutrophil chemotaxis towards periodontopathic bacteria. This receptor is highly polymorphic. Studies have reported associations of single nucleotide polymorphisms (SNPs) with aggressive periodontitis (AP). We previously reported findings on association of synonymous FPR SNP 348T>C with AP in African Americans. We extended these findings to a larger subject population and conducted neutrophil chemotaxis studies to determine whether AP neutrophils exhibit an impaired chemotactic response to formylpeptides.
Methods: African-American AP subjects (n=25) and healthy controls (n=20) were recruited under IRB supervision. Genomic DNA was isolated from peripheral blood. PCR amplification and sequencing was used to detect polymorphism 348T>C. A ~350bp fragment of the FPR promoter region was amplified and sequenced to look for SNPs. Neutrophils from AP subjects (n=7) and controls (n=13) were isolated by ficoll-hypaque centrifugation and dextran sedimentation. Chemotaxis was assayed for 30 min at 37° C with a modified Boyden chamber, using 10nM N-formyl-Met-Leu-Phe as the chemoattractant.
Results: The 348T variant was over-represented in the AP group with a frequency of 38% as compared to the control group in which the frequency was 17.5%; the difference was significant (P=0.038). AP subjects exhibited a neutrophil chemotactic response that was lower than that observed in controls (P=0.049). Approximately 60% of the subjects showed reduced chemotactic activity. Random migration was similar in AP and control subjects. We found one SNP at position –60 in the amplified fragment of the promoter region, the frequency of which was similar in both AP subjects and controls.
Conclusion: Our findings suggest that individuals with the 348T variant have an increased risk of developing AP. Neutrophils from AP subjects exhibit impaired chemotaxis to formylpeptides relative to healthy controls. Although the 348T>C polymorphism is synonymous, it could be linked to other polymorphisms in the FPR promoter region. This type of linkage has been observed in the human α2 adrenergic receptor gene and is associated with reduced receptor expression. Our further studies are focused on looking for other SNPs in the promoter region that could be associated with the 348T>C SNP and reduced FPR receptor expression. Supported by R21 DE017178.

Actinobacillus Actinomycetemcomitans Mimics TLRVYK Peptides in Beta-2 Glycoprotein I

Toshiyuki Nagasawa* DDS, PhD, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University; Dongging Wang, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University; YiWen Chen, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University; Hiroaki Kobayashi, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University; Yasuo Takeuchi, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University; Yuichi Izumi, Periodontology, Department of Hard Tissue Engineering, Graduate School, Tokyo Medical and Dental University

Background: Beta-2 glycoprotein I (b2GPI) is an important molecule to suppress coagulation, and antibodies against TLRVYK peptides on b2GPI are related to thrombosis. Schenkein et al. reported that P gingivalis have homologous peptide sequences with TLRVYK peptides, and periodontitis patients had increased antibody against b2GPI-dependent cardiolipin antibody. Aactinomycetemcomitans (A. a) has homologous sequences (SIRVYK) with TLRVYK peptides. Aim of the present study was to investigate the antibody response against SIRVYK peptides in periodontitis patients.
Methods: Serum and plaque samples were obtained from 74 periodontitis patients and 20 healthy subjects. Presence of A.a in the plaque samples was determined using specific primers for A. a 16s ribosomal RNA and polymerase chain reaction. Antibody titers against SIRVYK or TLRVYK peptides were determined using ELISA. Rabbits were immunized with TLRVYK peptides, and anti-TLRVYK peptide antibody was affinity purified using TLRVYK peptide coupling column.
Results: Periodontitis patients had higher serum IgG antibody against SIRVYK peptides compared with healthy subjects. Subjects with A.actinomycetemcomitans had significantly higher anti-SIRVYK antibody than subjects without A. actinomycetemcomitans. Rabbit anti-TLRVYK antibody cross-reacted with SIRVYK antibody.
Conclusion: Reaction of anti-TLRVYK antibody with SIRVYK peptide suggested the molecular mimicry between beta-2 glycoprotein 1 and A.actinomycetemcomitans. Present study suggested that infection with A.actinomycetemcomitans might elicit anti-SIRVYK IgG antibodies and modify the anti-TLRVYK antibody responses in periodontits patients.

Periodontitis is an Independent Predictor for Elevated Serum CRP Levels in Solid Organ

Effie Ioannidou* DDS, MDS, University of Connecticut Health Center; David Hull, Hartford Hospital; Joseph Burleson, University of Connecticut Health Center; Anna Dongari-Bagtzoglou, University of Connecticut Health Center

Background: Inflammation is widely recognized as having a pivotal role in transplant rejection, and several studies have shown that serum C-reactive protein (CRP) levels can identify individuals who are at greater risk for rejection. The purpose of this study was to assess the periodontal status of solid organ transplant recipients, to quantify the levels of serum CRP and to explore a possible association with periodontitis.
Methods: 74 kidney and heart transplant recipients were recruited from Hartford Hospital using the following criteria: 1. clinically stable; 2. at least one year post-transplant; 3. no history of antimicrobial use within the last 4 months; 4. no history of periodontal treatment within the last year. Periodontitis was defined by the presence of at least two sites with probing depth (PD) more than 5mm in two different quadrants. Control subjects (n=37) were age- and sex-matched, systemically healthy, and were randomly selected from Health Center personnel. Subjects received a full mouth periodontal examination including PD, clinical attachment level (CAL), bleeding on probing (BOP) and plaque score (PS) at six sites per tooth. Prior to oral examination blood samples were collected to quantify serum levels of CRP using a high sensitivity immunoassay.
Results: All subjects with periodontitis had significantly higher CRP (p=0.04). In the transplant group, there was a positive association between CRP and missing teeth (r=0.25, p=0.01), % of sites with CAL≥4mm (r=0.24), % of sites with PD≥5mm (r=0.29), and smoking history (r=0.3). In the control group, there was a positive association between CRP and PD (r=0.64), BOP (r=0.5), % of sites with CAL≥4mm (r=0.35) and sites with PD≥5mm (r=0.74). Linear regression in the transplant group using CRP as a dependent variable and % of sites with PD≥5mm as predictor, adjusting for history of rejection, age, gender, immunosuppressant dose, diabetes and smoking history showed that the % of sites with PD≥5mm was a significant independent predictor for elevated CRP.
Conclusion: Subjects with periodontitis have significantly higher serum CRP levels. Percentage of sites with PD more than 5mm is positively associated with high serum CRP levels in solid organ transplant recipients. Moreover, periodontitis is an independent predictor for elevated CRP levels in the same population after adjusting for diabetes, age, gender, smoking history, history of rejection and immunosuppressant dose.

Are “Periodontal Derived” Stem Cells Multipotent Adult Progenitor Cells?

Wolf-Dieter D. Grimm* DDS, MSc, University of Witten; Wolfgang Arnold, University of Witten; Georg Gassmann, University of Witten; Darius Widera, University of Witten; Gabor Varga, SE University, Budapest; Christian Kaltschmidt, University of Bielefeld

Background: Stem cells have been found in human dental tissues. Recently our research group published the highly efficient neural differentiation of periodontium-derived stem cells (PDSCs), isolated via minimal-invasive periodontal surgery (Widera et al. 2007). In the present study, we analyzed the expression pattern of “periodontium-derived stem cells (PDSC) and from human adult dental pulp (DPSC) as control. We investigated the multiline-age differentiation potential of PDSCs into cells of ectodermal and mesodermal lineage.
Methods: Periodontal tissue was isolated during standard surgical therapy under approved local guidelines from 9 patients with periodontal defects.In order to characterize undifferentiated or differentiated PDSCs we analyzed the expression profile using imunocytochem-istry, flow cytometry and RT-PCR analysis. The marker investigated in this study consist of markers specific for neural stem cells (e.g. Nestin), hematopoietic stem cells (e.g. CD133), mesen-chymal stem cells (MSCs), neurons (e.g. beta-III-tubulin) osteogenic precursors and osteoblasts (e.g. ALP). Staining was performed in HE, Azan Gomori, and van Kossa.In order to assess the differentiation capacity of cultured PDSCs, the cells were differ-entiated using protocols designed for neuronal, glial and osteogenic differentiation.
Results: PDSCs could be propagated as 3D spheroids and became substrate adherent. Most of PDSCs were Nestin and Sox2 positive. No expression of hematopoietic stem cell markers CD34 and CD90 was detected. PDSCs showed a typical morphology and histological stem cell pattern. If differentiated into neuronal lineage PDSCs showed neuronal morphology and expressed markers like e.g. NF-M, NF-H and Map-2. Glial differentiation: After 4 days in glial differentiation-medium, a typical glial morphology was observed. Immunocytochistry verified the glial lineage as shown by the high expression of GFAP. Using culture conditions developed for MSC differentiation, PDSCs could also be differentiated into alkaline phosphatase+ osteoblasts showing typical morphology.
Conclusion: Using established methods PDSCs can be efficiently differentiated into multiple lineages as demonstrated by neuronal, glial and osteogenic differentiation. During development neural crest cells generate diverse array of cell types including neurons, glia, bones and all tooth-related cell types. This approach demonstrates multi-lineage differentiation of PDSCs, which suggests their cranial neural crest cell origin. This hypothesis is in general accordance with novel hypotheses postulating that all adult neural stem cells, especially stem cells from alveolar cavity are neural crest derived. (Pierret et al., 2006; Teng et al., 2005). Thus, PDSCs are multipotent stem cells, which can be used as for further experimental studies and as for periodontal regeneration.

Periodontal Regeneration by Application of Human Periodontal Cell Sheet in an Athymic Rat Model

Reiko Yashiro* DDS, Institute of Advanced Biomedical Engineering and Science and Dental University; Mara Gomez Flores, Periodontology, Dept of Hard Tissue Engineeering; Masayuki Yamato, Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University; Teruo Okano, Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University; Isao Ishikawa, Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University

Background: A primary goal in the treatment of periodontal diseases is the regeneration of the mineralized and soft connective tissue components of the periodontium. Current theories suggest the cells from the periodontium have the capacity when appropriately triggered to participate in restoring connective and mineralized tissues. In the present study we apply novel cell culture surfaces with temperature-responsive polymer from which confluent Human Periodontal cells detach as a cell sheet and to evaluate if HPCS is able to reconstruct cementum-periodontal tissue.
Methods: Human periodontal cell sheet (HPCS) were cultured with osteoblastic differentiation medium containing; Dexamethasone, Ascorbic acid and β-Glycerophosphate. After 21 days of culture the effect of HPCS were evaluated in surgically created periodontal fenestration defects into immunodeficient rats, witch were processed for histology and stained with HE & Azan at 10 and 21 days post-operative. We used the buccal surface of the distal root of the first molar to examine the origin of the transplanted HPCS, the sections were stained immunohistochemically with an anti-human mitochondria antibody. The rats were divided in three groups: first, consist of only the defect; second, HPCS cultured without osteoblast differentiation medium as control and third, HPCS cultured with osteoblastic differentiation medium.
Results: Three weeks after transplantation with HPCS cultured with osteoblastic differentiation medium the periodontal defects exhibited with Azan a newly blue stained layer resembling cementum-like tissue and the new attachment of collagen fibers to this newly formed layer. Our data suggest that the seeded HPCS induced cementum-ligament like regeneration on the root surface showing positive staining for anti-human mitochondria, indicating the regeneration potential of periodontal cell sheet engineering when stimulated with osteoblastic differentiation medium.
Conclusion: This study shows that Human Periodontal Cell Sheet contain stems cells that have the potential to generate cementum-ligament like tissue in vivo. Periodontal cell sheet technique might allow that cells obtained from an easily accessible tissue resource and expanded ex-vivo and then detached as a cell sheet might be suitable for transplantation and could be a new therapeutic approach for reconstruction of periodontal tissues destroyed by periodontal disease.

2006 Abstracts | 2005 Abstracts