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2009 Research Forum Poster Session Abstracts

Abstracts for presentations at the 95th AAP Annual Meeting in Boston

Basic Research
Clinical Research

The Research Forum provides a platform for clinical and basic research to be presented by those in the field of periodontics. The posters of the 16 finalists below will be on display during the Annual Meeting in Exhibit Hall A of the Boston Convention & Exhibition Center on Sunday, September 13, and Monday, September 14, from 10:00 am - 6:00 pm. Authors will be present Monday from 10:00 am to 12:00 noon to answer questions. A panel of judges will award one cash prize in Basic Science and one prize in Clinical Science. Our thanks to The Natural Dentist for sponsoring the Research Forum Poster Session.

All abstracts that will be on display at the Annual Meeting can also be accessed using the AAP's Abstract Viewer.

NOTE: You may click on any photo below to see an enlarged version.

BASIC RESEARCH ABSTRACTS

Infection of Periodontal Bacteria Accelerates Progression of Abdominal Aortic Aneurysms with Altered Expression of MMPS and TIMPS

Category: Basic Research
Primary Author: Norio Aoyama, Tokyo Medical and Dental University, Tokyo, Japan
Secondary Authors: Dr. Jun-ichi Suzuki, University of Tokyo, Tokyo, Japan, Drs. Dongqing Wang, Masahito Ogawa, Yasuo Takeuchi, Mitsuaki Isobe, Yuichi Izumi, Tokyo Medical and Dental University, Tokyo, Japan
Financial Support: None
Background: Over the past decade, death caused by abdominal aortic aneurysm (AAA) in older persons has increased. Inflammation appears to play a key role in AAA development, however, the mechanism of AAA progression has not been clarified. Several researchers have reported that periodontopathic bacteria were detected in the aortic walls and it seems to increase the risk of AAA. A number of researchers have reported that periodontal bacteria are associated with several systemic diseases. The purpose of this study was to examine the effects of Porphyromonas gingivalis (Pg), one of the major periodontopathic bacteria, on AAA development.
Methods: Two weeks before AAA induction, heat-killed Pg was injected into the chamber that had been implanted subcutaneously in advance. AAA was produced by periaortic application of 0.25M CaCl2. Mice were inoculated with live Pg (n = 6) or PBS (control) (n = 6) once per week into the chamber. Four weeks after application of CaCl2, the diameter of the abdominal aorta was measured. The mice were sacrificed to obtain samples for histopathological and immunohistochemical analysis. The presence of live Pg in the chamber fluid was analyzed and the anti-Pg IgG levels of mice were examined. Plasma samples were collected and levels of matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinase (TIMP)-1 were analyzed using enzyme-linked immunosorbent assay (ELISA).
Results: The aortic diameter of Pg-challenged mice increased significantly (90 ± 14%) compared to vehicle control mice (47 ± 29%) (p < 0.05). Pg was detected in samples of the Pg-challenged mice. Histopathological analysis showed that the elastic degradation was greater in the Pg-challenged mice than control. Additionally, enhanced MMP-9 expression was observed immunohistochemically in the aorta layer. Anti-Pg IgG levels of mice were higher in the Pg-challenged group (2.10 ± 0.82-fold increase than the native) than in the control group (1.15 ± 0.15-fold increase than the native). The level of MMP-9 in the plasma samples of Pg-challenged mice (81.3 ± 33.1 ng/ml) was higher than the vehicle control mice (32.7 ± 18.1 ng/ml) by ELISA. The level of TIMP-1 in the plasma samples of Pg-challenged mice (1.92 ± 0.24 ng/ml) was also higher than the vehicle control mice (1.04 ± 0.14 ng/ml).
Conclusions: These findings demonstrate that Pg can promote the development of experimental AAA with the altered expression of MMPs and TIMPs. The treatment of periodontitis may be a critical factor in the prevention of AAA.

Radiographic Bone Evaluation in Corticotomy-Assisted Tooth Movement Using MicroCT

Category: Basic Research
Primary Author: Soulafa S. Baloul, Boston University, Boston, MA
Secondary Authors: Drs. Elise F. Morgan, Louis C. Gerstenfeld, Roberto S. Carvalho, Thomas E. Van Dyke, Alpdogan Kantarci, Boston University, Boston, MA
Financial Support: USPHS Grant :DE16191
Background: Corticotomy-facilitated tooth movement induces bone changes adjacent to the surgically injured cortical bone allowing rapid tooth movement.
Objective: To evaluate alveolar bone changes in response to tooth movement with or without corticotomy using MicroCT-analysis.
Methods: Seventy-two CRL-CD male rats were included as corticotomy alone (CORT); tooth-movement alone (TM); and “combined” therapy (CTM). Tooth-movement was performed on the first molar utilizing a 25-gram Sentalloy spring secured to a micro-screw palatal to the incisors. Active tooth movement (tooth movement phase) was observed for a period of 42-days. Appliances were removed and animals were followed-up for an additional 42-days (follow-up phase). Animals were sacrificed at 0, 7, 14, 21, 28, 42, 49, 56, 62, and 84 days. Maxillae were removed, stripped and fixed in formaldehyde. MicroCT-imaging was performed at 36µ voxel; samples were binarized using the same parameters for filter and threshold. Bone volume (BV), bone volume fraction represented by bone volume/total volume (BV/TV), bone mineral content (BMC), and average mineral density of hydroxyapatite (BMD) were calculated. Statistical analysis was performed using ANOVA with LSD post-hoc test.
Results: During the active tooth movement, amount and rate of tooth movement were higher in the CTM group at 7 days compared to the TM group (p= 0.04). CTM group showed a steady increase in amount of tooth movement up to 21 days. BV decreased significantly in the CTM group by 14 days (p=0.016) and by 21 days in the TM group compared to the baseline (p=0.013). BV was restored to baseline levels by 42 days in both CTM and TM groups. BV/TV decreased significantly at both 7 days (p=0.010 vs. baseline) and 14 days (p=0.039), and was restored to its baseline levels by 28 days in the CTM group. BMC decreased at 7 days (p=0.056) and further decreased by 14 days (p=0.015) in CTM group. In the TM group, BMC decreased and was significantly lower than baseline by 21 days (p=0.015). BMC was restored to baseline levels by 42 days in both CTM and TM groups. During the follow-up phase, both TM and CTM groups showed changes in both the distance and rate of the tooth movement at 49 days. This was a loss of space gained by the tooth movement in the TM group while there was a further space opening in the CTM group (p=0.09). BV decreased significantly compared to the 42-day (p=0.03, p=0.016; respectively), BMC decreased significantly at 49 days compared to 42 days in both CTM and TM groups (p=0.026, p=0.024; respectively).
Conclusions: Corticotomy combined with tooth-movement led to increased amount of tooth movement and at a faster rate with decrease in bone volume, bone volume fraction, and bone mass during the initial 7 days of orthodontic treatment. All variables were restored to baseline levels by 56 days.

Evaluation of rhBMP-2 Implant Coating Techniques on Local Bone Formation and Osseointegration. A Study in the Supraalveolar Peri-Implant Defect Model.

Category: Basic Research
Primary Author: John Decker, U.S. Army Advanced Education Program in Periodontics, Fort Gordon, GA
Secondary Authors: Drs. Jaebum Lee, Susin Cristiano, Giuseppe Polimeni, Carlo A. Cortella, Ulf M. Wikesjö, Medical College of Georgia, Augusta, GA, Dr. Michael D. Rohrer, University of Minnesota, Minneapolis, MN, Dr. Jan Hall, Nobel Biocare AB, Göteborg, Sweden, Dr. John M. Wozney, Wyeth Research, Cambridge, MA
Financial Support: None
Background: Implant dentistry is undergoing a paradigm shift. Esthetic, and early restoration and loading demands challenge the conventional use of oral implants. The goal for this research is to develop an oral implant that may make bone augmentation procedures obsolete. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a potent osteoinductive biologic mediator. rhBMP-2 coated implants have the potential to correct bone deficient areas without additional bone replacement or regenerative procedures (Hall et al. 2007, Wikesjö et al. 2008). This study focused on evaluation of rhBMP-2 implant coating techniques on local bone formation and osseointegration.
Methods: Supraalveolar peri-implant defects in 12 male, adult, Hound Labrador mongrel dogs were used. The animals received 10-mm titanium porous oxide surface (TiUnite) implants coated in their most coronal aspect with rhBMP-2 (C; 30µg rhBMP-2/implant) or coated following soak-load of the entire implant in an rhBMP-2 solution (S; 30µg rhBMP-2/implant). Implants were subsequently dried in ambient air (A) or vacuum dried (V). Six animals received CA and CV implants randomized to contralateral jaw quadrants (3 implants/jaw quadrant) and 6 animals similarly received SA and SV implants. The animals were euthanized at 8 weeks for histometric evaluation.
Results: No significant differences in new bone formation, density or bone-implant contact were observed. Bone formation averaged (±SE) 3.4±0.2, 3.2±0.5, 3.5±0.4, and 3.6±0.3mm for implant groups CA, CV, SA and SV, respectively. Corresponding bone density estimates averaged 38.0±3.8%, 46.7±5.8%, 34.4±5.6% and 31.6±4.4%, while bone-implant contact estimates averaged 25.0±3.8%, 28.0±5.6%, 31.2±3.3%, and 36.9± 3.4%. In contrast, peri-implant remodeling in resident bone was significantly influenced by the coating protocol. Distinct remodeling zones were observed at soak-load implants irrespective of drying technique. Peri-implant bone density averaged 74.7±3.8% and 72.2±2.1% for CA and CV vs. 50.8±4.1% and 60.6±4.7% for SA and SV implants (p<0.05), while bone-implant contact averaged 70.1±6.7% and 70.7±6.1% for CA and CV vs. 43.3± 3.9% and 47.2± 6.0% for SA and SV implants (p<0.05).
Conclusions: Local application of rhBMP-2 appears a viable technology to produce rhBMP-2 coated implants in support of local bone formation and osseointegration obviating resident bone remodeling.

Results (means ± SE) of the histometric recordings for rhBMP-2 induced resident bone remodeling.

Influence of Intravenous Bisphosphonates on the Healing of Extraction Sockets in Rats. A Histologic and Histometric Study.

Category: Basic Research
Primary Author: Flavia Furlaneto, Sao Paulo State University, Sao Paulo, Brazil
Secondary Authors: Drs. Maria H. Nagata, Michel R. Messora, Cristina A. Silva, Tetuo Okamoto, Stephen E. Fucini, Natália Pola, Michyele C. Sbrana, Luis A. Esper, Alvaro F. Bosco, Sao Paulo State University, Sao Paulo, Brazil
Financial Support: None
Background: The bisphosphonate zoledronic acid has been widely used in the treatment of patients that presents cancers with bone metastasis. Recently, a significant incidence of osteonecrosis of the jaws in patients with a history of intravenous bisphosphonate therapy has been reported and is associated most commonly with tooth extraction. Therefore, researches are required to elucidate the existing correlation between bisphosphonates and osteonecrosis because of the increasing use of these drugs and also because of the morbidity of the patients affected. The purpose of this study was to evaluate the influence of the intravenous bisphosphonate Zometa® 4 mg (zoledronic acid) on the healing of extraction sockets in rats.
Methods: 40 rats were divided into 2 groups: a) C (control) and b) ZA (zoledronic acid). During 6 months, the animals of Groups C and ZA received, once every 4 weeks, intravenous injections of saline solution (0,002 ml/g) and zoledronic acid (0,002 ml/g), respectively. After 6 months, the maxillary right incisor of each animal was extracted. Each group was sub-divided into 2 sub-groups for euthanasia at either 7 or 28 days post-operative (n=10). The blocks obtained were fixed in 10% neutral formalin for 48 hours, decalcified in 18% ethylediaminetetraacetic acid solution and embedded in paraffin. Serial sections 6 μm thick were cut in a longitudinal direction. The sections were stained with either hematoxylin and eosin or Masson’s Trichrome for analysis by light microscopy. Histologic and histometric analyses were performed. New bone formation was quantified as a percentage of the total area of the extraction socket. These data were transformed into arccosine for statistical analysis (ANOVA, Tukey, p < 0.05).
Results: In Group C, well developed trabecular bone was observed in the apical and middle portions of the extraction sockets at 28 days post-operative. In the same period of observation, well organized and thick bone trabeculae were observed throughout the extraction sockets of Group ZA. No statistically significant differences in relation to the amount of bone formation were found between Groups C and ZA at 7 days (15.91% ± 5.58 and 17.17% ± 5.82, respectively) and at 28 days (58.27% ± 15.41 and 70.22% ± 11.43, respectively) post-operative.
Conclusions: Within the limits of this study, it can be concluded that the intravenous zoledronic acid did not influence the healing of extraction sockets in rats.

Effects of Nicotine on Innate Immunity of Gingival Epithelial Cells

Category: Basic Research
Primary Author: Yoichiro Kashiwagi, Osaka University Graduate School of Dentistry, Osaka, Japan
Secondary Authors: Drs. Manabu Yanagita, Yuko Kojima, Ryohei Kobayashi, Satoru Yamada, Masahiro Kitamura, Shinya Murakami, Osaka University Graduate School of Dentistry, Osaka, Japan
Financial Support: None
Background: Smoking is one of risk factors of periodontal diseases. A major component of tobacco is nicotine. Some reports have indicated that nicotine regulates the TNF-α production from macrophages after LPS stimulation via nicotinic acetylcholine receptors (nAChR) signaling. However, effects of nicotine on innate immunity of human gingival epithelial cells (HGEC) have not been fully investigated. In this study we investigated whether nicotine regulates productions of IL-8 and anti-microbial peptide, human β-defensin2 (hBD2) by HGEC.
Methods: Human gingival tissue specimens were obtained from patients during periodontal surgical therapy after receiving informed consent. The collected specimens were treated with 0.4% dispase∥. The epithelial layers were then peeled off, cut into small sections, and incubated in 0.05% trypsin-0.53mM EDTA solution. The isolated cells were cultured in keratinocyte-specific growth media (Humedia-KG2: Kurabo, Osaka, Japan) and used as HGEC. A line of HGEC was transfected with the simian virus 40 (SV40) T antigen gene using calcium phosphate. The established cell line was named Epi-4.
Epi-4 was cultured with or without nicotine (10-8~10-3μM) in the presence or absence of recombinant IL-1β (10ng/ml), TNF-α (10ng/ml) and IFN-γ (50ng/ml) for 12h or 24h, and then the mRNAs were extracted and purified. Messenger RNA expressions of nAChRs, IL-8 and hBD2 mRNA expression were examined by RT-PCR or quantitative realtime PCR. Epi-4 was cultured for 24h or 48h in the same condition described above, and the culture supernatants were then collected. The concentrations of IL-8 and hBD2 in the supernatants were analyzed by ELISA. The effects of antagonists of nAChR, such as d-tubocurarine (non-specific nAChR) and α-bungarotoxin (specific α7 nAChR), on IL-8 and hBD2 productions were also examined by ELISA.
Results: Messenger RNA of several nAChRs such as α2, α3, α4, α5, α6, α7, α9, β1, β2 and β4 were expressed in Epi-4. Expressions of IL-8 and hBD2 by Epi-4 were synergistically increased by nicotine and inflammatory cytokines, IL-1β/ TNF-α/ IFN-γ. The antagonists of nAChR inhibited productions of IL-8 and hBD2 which were induced by nicotine and inflammatory cytokines.
Conclusions: These data indicate that nicotine up-regulates the expressions of IL-8 and hBD2 of HGEC, and may play an important role to modulate immuno-functions of HGEC via nAChR.

Periodontal Wound Healing / Regeneration Following Application of RHGDF-5 in Supraalveolar Periodontal Defects. A Histological Study in the Dog.

Category: Basic Research
Primary Author: David Kwon, U.S. Army Advanced Education Program in Periodontics, Ft. Gordon, GA
Secondary Authors: Drs. Frederick Bisch, Robert Herold, U.S. Army Advanced Education Program in Periodontics, Ft. Gordon, GA, Drs. Samuel Herberg, PatriziaBastone, Scil Technology GmbH, Martinsried, Germany, Dr. Nancy Rodriguez, Medical College of Georgia, Augusta, GA, Drs. Cristiano Susin, Ulf Wikesjö, Medical College of Georgia School of Dentistry, Augusta, GA
Financial Support: None
Background: As the periodontium encompasses several tissues, it remains a challenge to develop technologies that fulfill requirements including biocompatibility, porosity (space-provision), bioadhesion (wound-stability), and uneventful biodegradation to achieve a balanced support of periodontal wound healing/regeneration. The objective of this study was to evaluate the effect of a novel moldable recombinant human GDF-5 (rhGDF-5) formulation intended for onlay indications on periodontal wound healing/regeneration.
Methods: Bilateral, critical-size, 6-mm, supraalveolar, periodontal defects were created in 5 adult Hound Labrador mongrel dogs. The animals received the moldable rhGDF-5 formulation [rhGDF-5 in a bioresorbable Poly(lactic-co-glycolic acid)/ β-tricalciumphosphate (β-TCP) composite carrier] or carrier-control in contralateral jaw quadrants. The rhGDF-5 and carrier-control formulations were molded around the teeth to the shape of the original alveolar process and allowed to set. The gingival flaps were advanced; flap margins being adapted 3-4 mm coronal to the teeth, and sutured. The animals were euthanized at 8 weeks postsurgery when block biopsies were collected for histometric analysis.
Results: Healing was generally uneventful. A few sites exhibited minor exposures. One control and one site receiving the rhGDF-5 formulation (in separate animals) exhibited more extensive wound dehiscences. The rhGDF-5 and control constructs were easy to apply and provided adequate structural integrity to support the mucoperiosteal flaps in this challenging onlay model. Limited residual β-TCP particles were observed at 8 weeks for both rhGDF-5 and control sites. Treatment with the moldable rhGDF-5 formulation showed significantly greater cementum (2.3±0.4mm) and bone formation (2.9±0.7mm), but also ankylosis (0.5±0.2mm) compared to the carrier control (p<0.05).
Conclusions: Within limitations of study, the results suggest that the moldable rhGDF-5 formulation appears a promising candidate technology in support of periodontal wound healing/regeneration. Additional evaluation under conditions for optimal wound healing including variations in rhGDF-5 dosage and release kinetics to optimize the moldable rhGDF-5 formulation will precede clinical evaluation.

supraalveolar critical-size periodontal defect

Defect with rhGDF-5 in the moldable carrier (PLGA/β-TCP) or the equivalent amount of the carrier control was placed for each supraalveolar defect site.

8-week healing observation

A Newly Developed Honeycomb Pored Film as a 3D Scaffold for Periodontal Regeneration

Category: Basic Research
Primary Author: Hidetoshi Shimauchi, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan
Secondary Authors: Drs. Nagayoshi Iwama, Hiroshi Ishihata, Yoshihisa Murakami, Eiji Nemoto, Tohoku University Graduate School of Dentistry, Sendai, Miyagi, Japan, Drs. Masaru Tanaka, Masatsugu Shimomura, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Miyagi, Japan
Financial Support: None
Background: Three-dimensional (3D) porous scaffolds fabricated from biodegradable polymers have been applied for the tissue regeneration therapy as temporary cell matrices, as well as expecting topographical control of cellular functions. However, the technology of scaffold-based tissue engineering has not been developed and introduced for periodontal regeneration. A newly developed honeycomb film has a horizontal micropore network that can be modified intercellar spaces by changing the distribution of equalized porous sizes at a micron order. To explore the possibility of honeycomb film as a cell-interactive 3D scaffold, we cultured periodontal ligament (PDL) cells on the fabricated films and investigated the behaviors of the cultured cells in vitro.
Methods: Self-organized honeycomb films from poly(ε-caprolactone)(PCL) and amphiphilic polymer were prepared with highly regular porous structure by using humid atmospheric casting method. Fibroblast-like cells were obtained from periodontal membranes of extracted human molar teeth, and were used as PDL cells. PDL cells were culture on the honeycomb films with various pore sizes (5, 10 and 15 µm) for 4 hours (hr) and up to 42 days (d). The plane film of PCL substrate without pores was used as controls. The architecture of cultured cells was morphologically analyzed by fluorescence confocal laser scanning microscopy.
Results: Under both culture conditions, PDL cells proliferated in a sheet-like configuration after the confluent till the end of culture (28 and 42 d). However, PDL cells cultured on the honeycomb film extended the pseudopodiums of cell bodies and attached to the pillars in the structure throughout the culture period (4 hr to 42 d). And spindle-shaped cells were appeared after 24 hr, suggesting the start of self-organization behavior. A certain numbers of cells penetrated into the honeycomb structural lumen through the osculum of 10 and 15 µm (Fig.1), and the multi-layered sheet-like organized cells were carried out adhesions with cross linking to the honeycomb substrate on 28 and 42 d. PDL cells penetrated into the film shaped dendritic processes into pores with an active formation of actin filaments (Fig.2). On the PCL flat film, adhered PDL cells maintained a flat shape till 24 hr, and a spindle shape was appeared after 72 hr. The adhesion between cells and flat film tended to be vulnerable with observing exfoliated cells from the substrate on 28 and 42d.
Conclusions: Our results indicated that PDL cells were strongly adhered on the honeycomb film and quickly started multi-layered and self-organization as compared to the flat film. Furthermore, an appearance of unordinary-shaped PDL cells with dendritic processes into pores also suggested the microtopographic modification of cell differentiation by a pillar-structure. The honeycomb film may be a useful 3D biomaterial scaffold for the periodontal tissue regeneration. This study was supported in part by Grant-in-Aid from JSPS (No. 2039052, HS).

Fig. 1 Vertical slice of honecomb film culturing PDL cells (Blue: nucleus, Green: actin filaments)

Fig. 2 PDL cells extended dendritic processes into pores

Chronic Periodontitis and the Incidence of Head and Neck Cancers

Category: Basic Research
Primary Author: Mine Tezal, State University of New York, Buffalo, NY
Secondary Authors: Drs. Maureen A. Sullivan, Andrew Hyland, Daniel Stoler, Mary E. Reid, James R. Marshall, Thom Loree, Mihai Merzianu, Roswell Park Cancer Institute, Buffalo, NY, Drs. Jean Wactawski-Wende, Frank A. Scannapieco, State University of New York, Buffalo, NY
Financial Support: None
Background: Substantial evidence supports an association between chronic infections/inflammation and cancer in several organs. We conducted the present study to assess the association between chronic periodontitis history and head and neck cancers.
Methods: The study population consisted of new patients at the department of Dentistry and Maxillofacial Prosthetics, Roswell Park Cancer Institute between 1999 and 2005. Cases consisted of all patients diagnosed with primary head and neck squamous cell carcinoma (HNSCC). Controls were all patients seen during the same time period but negative for malignancy. Patients aged <21 years, edentulous, immunocompromised and those with history of cancer were excluded. Periodontitis was measured by alveolar bone loss (ABL) from panoramic radiographs. ABL was measured in millimeters (mm) at mesial and distal sites of all natural teeth using an operator-interactive program on digitized radiographic images by one trained periodontist blind to cancer status.
Results: A total of 473 patients (266 cases and 207 controls) were included in the study. Each millimeter of ABL was associated with >4 fold increased risk of HNSCC (OR=4.36, 95% CI=3.16-6.01) after adjustment for age, gender, race/ethnicity, marital status, smoking, alcohol use, and missing teeth. The strength of the association was greatest in the oral cavity (OR=4.52, 95% CI=3.03-6.75), followed by oropharynx (OR=3.64, 95% CI=2.54-5.22) and larynx (OR=2.72, 95% CI=1.78-4.16). There was a significant interaction between smoking status and ABL (p=0.03). The association between ABL and HNSCC was weaker in current smokers (OR=2.85, 95% CI=1.85-4.40) compared to former (OR=7.59, 95% CI=3.51-16.42) and never (OR=5.96, 95% CI=3.04-11.68) smokers. Alcohol consumption was not a significant effect modifier (p=0.474). The strength of the ABL-HNSCC association was similar in drinkers (OR=4.45, 95% CI=2.70-7.34) and in nondrinkers (OR=4.31, 95% CI=2.82-6.58).
Conclusions: Chronic periodontitis is independently associated with HNSCC incidence, and smoking modifies this association. These results have important implications for prevention, diagnosis and treatment of HNSCC.

CLINICAL RESEARCH ABSTRACTS

Supracrestal Gingival Tissue Dimension. Preliminary Results Following Crown Lengthening Procedures in Humans.

Category: Clinical Research
Primary Author: Ramzi V. Abou Arraj, School of Dentistry at the Lebanese University, Hadath, Mount Lebanon, Lebanon
Secondary Authors: Drs. Meera Allam, Fatme Mouchref-Hamasni, Zeina Majzoub, School of Dentistry at the Lebanese University, Hadath, Mount Lebanon, Lebanon
Financial Support: None
Background: Crown lengthening has been generally performed applying the concept of the biologic width (BW) which stems from an early histologic study in cadavers (mean of 2.04 mm). Considerable variations in BW dimension between individuals, teeth, and surfaces of the same tooth were reported in more recent publications. The height of supracrestal gingival tissues (SGT) (including the BW plus the sulcus depth) has been recently theorized as a genetically determined dimension that re-establishes itself postsurgically and was proposed as a more representative dimension to apply in crown lengthening surgery as it accounts for the variability of sulcular depth. The aims of this study were to: 1) compare the pre- and 24-week postsurgical height of SGT; 2) assess the stability of crown height extension over time; and 3) evaluate the effect of buccal gingival thickness (TBT) on SGT dimension.
Methods: Twenty adult patients requiring crown lengthening were included in the study. Surgical crown lengthening was performed at 33 teeth and the patients were re-evaluated up to 24 weeks. The following parameters were recorded using a customized stent for measurement reproducibility: stent-gingival margin (SGM) (baseline, right after surgery, 6 weeks, 12 weeks, and 24 weeks); and stent-bone crest (SBC) (baseline, post-osseous resection, and 24 weeks). SGT was calculated by subtracting SGM from SBC. TBT was measured transgingivally prior to flap reflection and at 24 weeks through the mid-buccal gingiva until bone contact. The paired t-test was used to compare baseline and 24-week postoperative values of SGT separately for buccal, lingual/palatal and interproximal sites. Friedman’s test was applied to detect changes in SGM from right after surgery till 24 weeks. The relationship between SGT and TBT was analyzed using Pearson’s correlation.
Results: There were no statistically significant differences between SGT at baseline and at 24 weeks for any of the 4 tooth sides, nor for the average overall SGT (P>0.05). When crown extension height was assessed, statistically significant differences were found between SGM right after surgery and SGM at 24 weeks for the mesial and distal sides (P<0.001) in contrast to the buccal and lingual/palatal sides where such differences were not detected (P=0.63 and 0.64 respectively). Overall SGT dimension correlated positively with TBT at baseline (r=0.39; P=0.001) and at 24 weeks (r=0.38; P=0.006).
Conclusions: The preliminary results of this investigation suggest the following: 1) presurgical SGT dimension can be used as a guideline measurement in crown lengthening as it is re-established apically with a similar apico-coronal dimension 24 weeks postoperatively; 2) over time, crown height extension is more significantly reduced at the interproximal aspects than at the buccal and lingual/palatal surfaces, suggesting greater postsurgical tissue rebound interproximally; and 3) greater SGT heights are associated with thicker gingival morphotypes.

The Effect of Photodynamic Therapy on Periodontal Status and Glycemic Control of Diabetic Patients

Category: Clinical Research
Primary Author: Shatha O. Bamashmous, King Abdulaziz University, Jeddah, Saudi Arabia
Secondary Authors: Drs. Mohammad S. Al-Zahrani, Ahmed A. Alhassani, Mossad M. Al-Sherbini, King Abdulaziz University, Jeddah , Saudi Arabia
Financial Support: None
Background: Periodontitis is a major cause of tooth loss among adults. Several studies have shown a possible impact of periodontal infection on individual's systemic condition including poor glycemic control of diabetic patients. Recently, photodynamic therapy was used successfully to treat periodontal infection. Photodynamic therapy is a light disinfection technique that provides a broad spectrum antimicrobial efficacy with no local or systemic side effects. The objective of this study is to examine the effect of adjunctive use of photodynamic therapy on periodontal status and glycemic control of diabetic patients affected with periodontitis.
Methods: Forty-five patients with type 2 diabetes and moderate to severe chronic periodontitis were selected and randomly assigned to one of the following three treatment modalities (15 subjects each): group A, scaling and root planing only; group B, scaling and root planing plus systemic doxycycline; and group C, scaling and root planing plus photodynamic therapy. Plaque index, probing depth, clinical attachment level, fasting blood glucose level and glycated hemoglobin (HbA1c) were recorded at baseline and at 3 months after periodontal treatment. Descriptive statistics, paired t-test and ANOVA were used for data analysis.
Results: Statistically significant difference in the mean probing depth, plaque deposit and bleeding on probing were found between baseline and 12-week post-treatment for all the three groups. No significant differences in previous parameters were detected between the three groups. Only group B, showed a significant reduction in mean HbA1c level, after treatment.
Conclusions: No added benefit of photodynamic therapy on clinical periodontal parameters and glycemic control of diabetics were found. Non-surgical periodontal treatment plus doxycycline, however, showed an improvement in the glycemic control of diabetic patients.

Periodontal Variables, Hemodialysis Status and Serum IL-6 Levels

Category: Clinical Research
Primary Author: Eric Choundury, Periodontology, University of Connecticut Health Center, Farmington, CT
Secondary Authors: Drs. Anna Dongari-Bagtzoglou and Effie Ioannidou, UCHC, Farmington, CT, Dr. Andre Kaplan, School of Medicine, Farmington, CT
Financial Support: None
Background: Chronic kidney disease is characterized by a state of chronic inflammation that has been associated with high mortality rates. Factors related to hemodialysis and low kidney function lead to low urinary IL-6 excretion and trigger increased cytokine response. The role of periodontitis on the serum cytokine levels has been a conflicting topic. The aims of this pilot investigation were to assess the periodontal status of chronic kidney disease (CKD) subjects and explore the interaction effect between chronic periodontitis and hemodialysis (HD) status on serum IL-6 in CKD subjects.
Methods: 20 CKD subjects, including 9 hemodialysis (HD) and 11 pre-dialysis patients (stage 2-4 CKD) were recruited, using the following criteria: 1. more that 15 teeth, 2. no periodontal treatment within the past 6 months, 3. absence of systemic infection and 4. no use of systemic antibiotics within the last month. All subjects received a full-mouth periodontal examination including clinical attachment levels (CAL), pocket depths (PD), bleeding on probing (BOP) and plaque scores (PS). Blood samples were collected for quantification of serum IL-6. Chronic periodontitis was defined by the presence of at least one tooth site with PD≥4mm and mean BOP≥10% in all sites. Subject hemodialysis status was treated as a categorical variable (“yes/no” dialysis). In the statistical analyses, all variables were tested for normality. When a continuous variable was not normally distributed it was treated with logarithmic transformation to achieve normality. Serum IL-6 levels were transformed to satisfy this criterion. Continuous variables were compared with two independent samples t-test. Univariate analysis of variance was used to assess the impact of concurrent periodontal and HD status on serum IL-6 levels.
Results: The prevalence of chronic periodontitis and diabetes was 64.7% and 37.2%, respectively, in this population. The mean age was 63.5±12.1, mean serum IL-6 was 19.60±13.0pg/ml. The mean creatinine level in the pre-dialysis subjects was 2.7±2.2mg/dl. When comparing subjects with periodontitis vs. subjects without periodontitis, we found that serum IL-6 levels were significantly elevated (p=0.01) in subjects with periodontitis. Additionally, a univariate analysis of variance was conducted to explore the between periodontal variables, dialysis status and IL-6 levels in this population. Using serum IL-6 as a dependent variable, the effect of diabetic status or age was not significant. However, mean periodontal pocket depths and dialysis status had a small effect but the interaction between the two had a significant effect on serum IL-6 (p=0.001).
Conclusions: CKD subjects with periodontitis had higher serum IL-6 levels compared to subjects without periodontitis. Moreover, when combining periodontal and dialysis status appeared to have a statistically significant effect in predicting serum IL-6 levels.

Scientific Relevance of Study Design of Articles Published in Journal of Periodontology

Category: Clinical Research
Primary Author: Satheesh Elangovan, Harvard School of Dental Medicine, Boston, MA
Secondary Authors: Drs. Veerasathpurush Allareddy, Andrea Shah, Chin-Yu Lin, Min Kyeong Lee, Sivabalan Vasudavan, Nadeem Y. Karimbux, Harvard School of Dental Medicine, Boston, MA
Financial Support: None
Background: Meta analysis along with systematic reviews occupies the highest echelon along the continuum of hierarchy of evidence in the scientific community. We hypothesize that meta analysis and systematic reviews are cited more often compared to other study designs in Periodontology literature published in the journal of Periodontology. The objective of this study is to examine the association between different study designs and the scientific relevance of articles published in the Journal of Periodontology in 2005.
Methods: All the research articles published in the Journal of Periodontology during the year 2005 excluding editorial comments, letters to editor, commentaries, innovations in periodontology, and articles published in the 11th supplementary issue were included in the study. The number of times an article was cited in the first 24 months (obtained from the Web of Science – Science Citation Index) since its publication was used to assess the scientific importance of the study. The published articles were classified as either meta analysis / review article, randomized controlled trial, clinical trial (not randomized), animal study, case series, case report, or miscellaneous study designs. The association between study design and citation count was examined by Kruskal Wallis test and multiple post-hoc testings were performed by the Man-Whiteny U test. We alsoexamined the association between other confounding variables (including number of authors, number of references used in the published article, geographic region, and funding source) and citation counts using non-parametric statistical methods. Since the number of citations is count data and the data was widely dispersed, we used a multivariable negative binomial regression model to examine the simultaneous association between all independent variables and citation counts. All statistical tests were two-sided.
Results: A total of 271 articles were reviewed, which included 10 meta analysis / review articles, 33 randomized controlled trials, 13 clinical trials (excluding randomized clinical trials), 61 animal studies, 15 case series, 23 case reports, and 116 miscellaneous study designs (including observational studies, cross-sectional studies, and retrospective studies). With regards to the number of citations received, meta analysis / review articles were associated with the highest number of citations when compared to case reports (p <0.0001), randomized controlled trials (p=0.008), animal studies (p<0.0001), and miscellaneous study designs (p=0.001) even after adjusting for confounding factors.
Conclusions: Among various study designs, meta analysis and review articles are more likely to be cited in the first 24 months since publication. Our study underscores the importance of publishing more meta analyses and review articles for quicker dissemination of research findings.

Marginal Periosteal Pedicle Graft- A Novel Autogenous Guided Tissue Membrane for Treating Localized Intrabony Defects.

Category: Clinical Research
Primary Author: Ahmed Y. Gamal, al Azhar Universty, Cairo, Cairo, Egypt
Secondary Authors: Jason M. Mailhot, Marquette University School of Dentistry, Milwaukee, WI
Financial Support: None
Background: The use of periosteal tissues as an autogenous guided tissue membrane could compensate for the deficient progenitor cells and osteogenic factors required for regeneration within periodontal defects. In addition, second surgery that is required to get a donor tissue for free grafting may be eliminated by using a pedicle periosteal flap and harvesting the periostium from the same site of the periodontal defect. This will reduce patient post operative discomfort and time consumption for harvesting palatal donor tissue. The use of pedicle periosteum was also suggested to provide adequate nutrition that minimizing the possibilities of flap partial or complete necrosis. In an attempt to evaluate the type of healing following the use of vascularized periostium as an autogenous guided tissue membrane, this study was designed to clinically and histologically evaluate the use of marginal periosteal pedicle flap for treating interproximal intrabony periodontal defects and compare outcomes with open flap debridement.
Methods: Fifteen patients with severe chronic periodontitis participated in this prospective, controlled, blind trial. Five of the selected patients have at least contralateral teeth diagnosed as hopeless for periodontal reasons and designated for extraction. Each paired periodontal defect were subjected to either marginal periosteal pedicle flap (MPP test group)or open flap debridement (OFD control group). MPP was performed by harvesting a marginal periosteal strip from the facial periosteum adjacent to the defect which was then rotated to cover the interproximal defect. Defects of both groups were then clinically evaluated for 9 months. Nine months following therapy at reentry, samples of the newly formed tissue were harvested from all test and control sites. Hopeless teeth of test and control samples were extracted for histologic evaluation of root surfaces exposed to the pocket environment.
Results: At nine months, the experimental MPP treated group resulted in a significant improvement in PD reduction, CAL gain and intrabony defect reduction when compared to that of the control (p<0.01). Histologic evaluation of test samples revealed coarse fibred woven bone filling the defects 9 months following therapy in a three out of the 10 examined test newly formed tissue samples. Apical root notches of such samples showed homogenous layer of cementum like tissue deposition. Five of the test samples appeared with no any cemental like tissue deposition within the notch in spite of defect bony fill, some areas of root resorption is suggestive of bony ankylosis. Most of the tissues harvested from the control OFD treated sites revealed inflammatory cells infiltrate of varying extent and red blood corpuscles being entrapped in a fibrin meshwork.
Conclusions: Placement of a vascularized marginal periosteal pedicle graft as a barrier membrane significantly improved clinical and histologic parameters of deep periodontal intrabony defects.

Mean defect characteristics of both experimental (MPP) and control (OFD) groups expressed in mm ± SD during different observation periods.

Comparative Analysis of Peri-Implant Bone Level Based on Microthread Location: A 1 Year Prospective Study.

Category: Clinical Research
Primary Author: Dong-Won Lee, Yonsei University, Seoul, South Korea
Secondary Authors: Drs. Dong-Wook Song, Jung-Joo Kim, Ik-Sang Moon, Yonsei University, Seoul, Korea
Financial Support: None
Background: Hansson (1999) stated that retentive element, such as microthreads at the implant neck, is necessary in order to preserve and maintain peri-implant marginal bone. In a three-year clinical study that compared peri-implant marginal bone loss in microthreaded and non-microthreaded Astra Tech implants, Lee et al. (2007) reported that the presence of microthreads at the implant neck was associated with less peri-implant marginal bone loss. The results of numerous experimental and clinical studies seem to demonstrate that microthreads at the implant neck could help maintaining peri-implant marginal bone. However, previous studies have only focused on the presence or absence of microthreads, and thus could not provide any insight into the effect of the location of the microthreads on peri-implant marginal bone. In a clinical study using implants with different thread locations, Jung et al. (1996) demonstrated that bone loss occurred differently depending on the location of the threads and that peri-implant marginal bone levels stabilized at the first thread. Considering the influence of thread location on peri-implant marginal bone, it could be speculated that the location of microthreads could also have the same effect. The present study was conducted to investigate this relationship.
Methods: Two types of implants were utilized. One with microthreads extending to the top of the implant (Top), and the other with microthreads ends at 0.5mm below the top of the implant (Non-top). Two implants were placed adjacent to each other in the same patient's partially edentulous area. Bone loss around each type of implant was analyzed after one year of functional loading. Wilcoxon's signed-rank test was used to analyze the differences in peri-implant marginal bone loss between the groups.
Results: The average bony change in the Top group was 0.13mm±0.17, and 0.24mm±0.20 in the Non-top group. The difference was statistically significant (p = 0.004).
Conclusions: Less peri-implant bone loss was observed in implants with microthreads extending to the top of the implant neck than in those with microthreads ends at 0.5mm below the top of the fixture. The results of the present study indicate that microthreads act to stabilize peri-implant marginal bone and that their location plays an important role.

Marginal bone loss of Top and Non-top implants
Table

Clinical Evaluation of Tacrolimus-Induced Gingival Overgrowth in the Absence of Calcium Channel Blockers. A Six Months Prospective Study.

Category: Clinical Research
Primary Author: Ricardo T. Sekiguchi, University of São Paulo, São Paulo, Brazil
Secondary Authors: Drs. Caroline G. Paixão, Helio T. Silva , Luciana Saraiva, Claudio M. Pannuti, Roberto F. Lotufo, Giuseppe A. Romito, University of São Paulo, São Paulo, Brazil
Financial Support: None
Background: The aim of this study was to determine the incidence and severity of gingival overgrowth (GO) induced by tacrolimus (Tcr) compared with ciclosporin-A (CsA) in the absence of calcium channel blockers in renal transplant recipients.
Methods: Fifty five subjects (27 Tcr/28 CsA) were evaluated before, 30 days, 90 days and 180 days after kidney transplant surgery. Demographic, periodontal parameters and GO score were recorded for all subjects. In every examination the same data were collected and all the subjects received oral hygiene instructions. Clinical assessment was performed by a single trained and calibrated examiner (ICC=0.967) who was blinded to the patient's drug regime. GO was analyzed by visual examination of the buccal and lingual papillae of the six most anterior teeth of the upper and lower arch. A score ranging from 0 to 5 was attributed to each papilla according to the quantity of GO both in the horizontal and vertical axes. Patients showing a score ≥30 were classified as presenting clinically significant GO. Included in the study were subjects of both genders, older than 18 years, who presented no clinical or radiographic signs of periodontitis. Smokers, diabetics, patients presenting some type of gingival overgrowth during the pre-transplant period and taking any of the following drugs were excluded: nifedipine, diltiazem, verapamil, phenytoin, sodium valproate, azithromycin.
Results: The mean GO score was significantly lower in the Tcr group compared with the CsA group after 30 days (p=0.03), 90 days (p=0.004) and 180 days (p=0.01) of immunosuppressive therapy. At 180 days post-transplant, clinically significant GO was observed in 18% of the CsA group and in 9% of the Tcr group. This difference was not statistically significant (p=0.66).
Conclusions: Despite of the incidence of GO in Tcr group was lower than CsA group, no significant difference in the incidence of clinically GO was observed between both groups up to 180 days of immunosuppressive therapy.

Adjunctive Effects of Anti- Polphyromonas Gingivalis Egg Yolk Antibody with Scaling and Root Planning: A Randomized, Placebo Controlled Clinical Trial.

Category: Clinical Research
Primary Author: Naoyuki Sugano, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
Secondary Authors: Drs. Masatoshi Takane, Naoto Yoshinuma, Koichi Ito, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
Financial Support: None
Background: Gingipains from Porphyromonas gingivalis play a major role in not only bacterial housekeeping but also inactivation of host defenses. We postulated that the inhibition of gingipains using passive immunization may reduce the pathogenic nature of P. gingivalis. In this study, we investigated the effect of anti-P. gingivalis egg yolk antibody against gingipains (IgY-GP) as an adjunct to scaling and root planning in patients with periodontitis.
Methods: This randomized, double blind, placebo controlled parallel study involved 34 adult patients with untreated periodontitis who were randomly assigned to receive either a full-mouth scaling and root planning along with oral administration of IgY-GP or scaling and root planning with placebo. Clinical measurements were recorded at baseline and twelve weeks after therapy. The deepest pocket was selected and samples for microbiological testing were taken to determine the number of P. gingivalis using real-time PCR. Patients got coded study tablet their mouth around without chewing three times a day after meal or blushing. Tablet was containing 50mg IgY-GP or non immunized egg yolk antibody.
Results: There was a significant improvement in mean probing depth in the IgY-GP group at twelve weeks after therapy. Parallel to the clinical changes, IgY-GP administration significantly reduced the number of P. gingivalis in the subgingival plaque from deepest pocket.
Conclusions: The present study showed IgY-GP administration in conjunction with scaling and root planning in periodontitis patients achieved significantly better clinical and microbiological results than placebo group. IgY-GP may an effective immunotherapeutic agent in the treatment of periodontitis.

Effects of IgY-GP on clinical parameters
Table

*P<0.05

Effects of IgY-GP on the subgingival levels of P. gingivalis
Table

*P<0.05