bluuebunny/crossref_metadata_2025 huggingface dataset:
Isocyanato- and Methacryloxysilanes Promote Bis-GMA Adhesion to Titanium
Authors: Matinlinna J.P. , Lassila L.V.J. , Kangasniemi I. , Vallittu P.K.
Published: January 2009

In dentistry, adhesion promotion with 3-methacryloyloxypropyltrimethoxysilane is usually sufficient, but its hydrolytic stability is a continuous concern. The hydrolytic stability of an alternative, 3-isocyanatopropyltriethoxysilane, was compared with that of conventional 3-methacryloyloxypropyltrimethoxysilane. Two silanes, both in 0.1 and 1.0 vol-% in ethanol-water, were evaluated in the attachment of an experimental bis-phenol-A-diglycidyldimethacrylate (Bis-GMA) resin to grit-blasted (with two different systems) titanium. Silane hydrolysis was monitored by FTIR spectrometry. Bis-GMA resin was applied and photo-polymerized on titanium. The specimens were thermocycled (6000 cycles, 5–55°C). Surface analysis was carried out with scanning electron microscopy. Statistical analysis (ANOVA) showed that the highest shear bond was achieved with 0.1% 3-isocyanatopropyltriethoxysilane (12.5 MPa) with silica-coating, and the lowest with 1.0% 3-methacryloyloxypropyltrimethoxysilane (3.4 MPa) with alumina-coating. The silane, its concentration, and the grit-blasting method significantly affected the shear bond strength ( p < 0.05). SEM images indicated cohesive failure of bonding, and, in conclusion, 3-isocyanatopropyltriethoxysilane is a potential coupling agent.
Discontinuous Fiber-reinforced Composites above Critical Length
Authors: Petersen R.C.
Published: January 2009

Micromechanical physics of critical fiber length, describing a minimum filament distance for resin impregnation and stress transfer, has not yet been applied in dental science. As a test of the hypothesis that 9-micron-diameter, 3-mm-long quartz fibers would increase mechanical strength over particulate-filled composites, photocure-resin-pre-impregnated discontinuous reinforcement was incorporated at 35 wt% into 3M Corporation Z100, Kerr Corporation HerculiteXRV, and an experimental photocure paste with increased radiopaque particulate. Fully articulated four-point bend testing per ASTM C 1161-94 for advanced ceramics and Izod impact testing according to a modified unnotched ASTM D 256-00 specification were then performed. All photocure-fiber-reinforced composites demonstrated significant improvements over particulate-filled compounds (p < 0.001) for flexural strength, modulus, work of fracture, strain at maximum load, and Izod toughness, with one exception for the moduli of Z100 and the experimental reinforced paste. The results indicate that inclusion of pre-impregnated fibers above the critical aspect ratio yields major advancements regarding the mechanical properties tested.
Effects of Cyclic Tensile Forces on the Expression of Vascular Endothelial Growth Factor (VEGF) and Macrophage-colony-stimulating Factor (M-CSF) in Murine Osteoblastic MC3T3-E1 Cells
Authors: Motokawa M. , Kaku M. , Tohma Y. , Kawata T. , Fujita T. , Kohno S. , Tsutsui K. , Ohtani J. , Tenjo K. , Shigekawa M. , Kamada H. , Tanne K.
Published: January 2009

It has been reported that vascular endothelial growth factor (VEGF), expressed by osteoblasts, can induce osteoclast recruitment and thus affects bone remodeling. The purpose of this study was to investigate the effects of cyclic tensile forces on the expression of VEGF and macrophage-colony-stimulating factor (M-CSF) in osteoblastic MC3T3-E1 cells. VEGF and M-CSF gene expression and protein concentration were determined by real-time PCR and enzyme-linked immunoassay. The expression of VEGF and M-CSF mRNA in the experimental group was higher than in the control group. The increase in the concentration of VEGF and M-CSF protein in the experimental group was time-dependent. Moreover, gadolinium (an S-A channel inhibitor), but not nifedipine (L-Type Ca2+ channel blocker), treatment reduced the concentration of VEGF and M-CSF mRNA and protein in the experimental groups. These findings suggest that cyclic tensile forces increase the expression of VEGF and M-CSF in osteoblastic MC3T3-E1 cells via a stretch-activated channel (S-A channel).
The Finite Element Method: a Tool to Study Orthodontic Tooth Movement
Authors: Cattaneo P.M. , Dalstra M. , Melsen B.
Published: January 2009

Orthodontic tooth movement is achieved by (re)modeling processes of the alveolar bone, which are triggered by changes in the stress/strain distribution in the periodontium. In the past, the finite element (FE) method has been used to describe the stressed situation within the periodontal ligament (PDL) and surrounding alveolar bone. The present study sought to determine the impact of the modeling process on the outcome from FE analyses and to relate these findings to the current theories on orthodontic tooth movement. In a series of FE analyses simulating teeth subjected to orthodontic loading, the influence of geometry/morphology, material properties, and boundary conditions was evaluated. The accurate description of alveolar bone morphology and the assignment of non-linear mechanical properties for the PDF elements demonstrate that loading of the periodontium cannot be explained in simple terms of compression and tension along the loading direction. Tension in the alveolar bone was far more predominant than compression.
Treponema medium Glycoconjugate Inhibits Activation of Human Gingival Fibroblasts Stimulated with Phenol-Water Extracts of Periodontopathic Bacteria
Authors: Asai Y. , Ohyama Y. , Taiji Y. , Makimura Y. , Tamai R. , Hashimoto M. , Ogawa T.
Published: January 2009

Oral treponemes are well-known as causative agents of periodontal diseases; however, the details have not been fully clarified. Here, we examined the effects of Treponema medium glycoconjugate on the activation of human gingival fibroblasts using phenol-water extracts from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum subsp. nucleatum, and Actinobacillus actinomycetemcomitans. The phenol-water extracts activated human gingival fibroblasts to mediate IL-8 production, as well as IL-8 mRNA expression, phosphorylation of p38 mitogen-activated protein kinase, and expression of intercellular adhesion molecule-1. T. medium glycoconjugate exhibited no activation of human gingival fibroblasts, while phenol-water extract-induced activation of human gingival fibroblasts was clearly inhibited by T. medium glycoconjugate. Furthermore, binding of biotinylated phenol-water extracts to CD14 in the presence of LPS-binding protein was blocked with T. medium glycoconjugate. These results suggest that T. medium glycoconjugate has an inhibitory effect on host cell activation by periodontopathic bacteria caused by binding to CD14- and LPS-binding protein.
Fetal Jaw Movement Affects Condylar Cartilage Development
Authors: Habib H. , Hatta T. , Udagawa J. , Zhang L. , Yoshimura Y. , Otani H.
Published: January 2009

Using a mouse exo utero system to examine the effects of fetal jaw movement on the development of condylar cartilage, we assessed the effects of restraint of the animals’ mouths from opening, by suture, at embryonic day (E)15.5. We hypothesized that pre-natal jaw movement is an important mechanical factor in endochondral bone formation of the mandibular condyle. Condylar cartilage was reduced in size, and the bone-cartilage margin was ill-defined in the sutured group at E18.5. Volume, total number of cells, and number of 5-bromo-2′-deoxyuridine-positive cells in the mesenchymal zone were lower in the sutured group than in the non-sutured group at E16.5 and E18.5. Hypertrophic chondrocytes were larger, whereas fewer apoptotic chondrocytes and osteoclasts were observed in the hypertrophic zone in the sutured group at E18.5. Analysis of our data revealed that restricted fetal TMJ movement influences the process of endochondral bone formation of condylar cartilage.
Gene Expression during Palate Fusion in vivo and in vitro
Authors: Pungchanchaikul P. , Gelbier M. , Ferretti P. , Bloch-Zupan A.
Published: January 2009

Failure of secondary palate fusion during embryogenesis is a cause of cleft palate. Disappearance of the medial epithelial seam (MES) is required to allow merging of the mesenchyme from both palatal shelves. This involves complex changes of the medial edge epithelial (MEE) cells and surrounding structures that are controlled by several genes whose spatio-temporal expression is tightly regulated. We have carried out morphological analyses and used a semi-quantitative RT-PCR technique to evaluate whether morphological changes and modulation in the expression of putative key genes, such as twist, snail, and E-cadherin, during the fusion process in palate organ culture parallel those observed in vivo, and show that this is indeed the case. We also show, using the organotypic model of palate fusion, that the down-regulation of the transcription factor snail that occurs with the progression of palate development is not dependent on fusion of the palatal shelves. Abbreviations: dsg1, desmoglein1; EMT, epithelial-mesenchymal transition; MEE, medial edge epithelium; MES, medial epithelial seam; RT-PCR, reverse-transcriptase polymerase chain-reaction.
Rotary Culture Enhances Pre-osteoblast Aggregation and Mineralization
Authors: Facer S.R. , Zaharias R.S. , Andracki M.E. , Lafoon J. , Hunter S.K. , Schneider G.B.
Published: January 2009

Three-dimensional environments have been shown to enhance cell aggregation and osteoblast differentiation. Thus, we hypothesized that three-dimensional (3D) growth environments would enhance the mineralization rate of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. The objective of this study was to investigate the potential use of rotary cell culture systems (RCCS) as a means to enhance the osteogenic potential of pre-osteoblast cells. HEPM cells were cultured in a RCCS to create 3D enviroments. Tissue culture plastic (2D) cultures served as our control. 3D environments promoted three-dimensional aggregate formations. Increased calcium and phosphorus deposition was significantly enhanced three- to 18-fold (P < 0.001) in 3D cultures as compared with 2D environments. 3D cultures mineralized in 1 wk as compared with the 2D cultures, which took 4 wks, a decrease in time of nearly 75%. In conclusion, our studies demonstrated that 3D environments enhanced osteoblast cell aggregation and mineralization.
Effect of Mandibular Position on Upper Airway Collapsibility and Resistance
Authors: Inazawa T. , Ayuse T. , Kurata S. , Okayasu I. , Sakamoto E. , Oi K. , Schneider H. , Schwartz A.R.
Published: January 2009

It has been proposed that advancement of the mandible is a useful method for decreasing upper airway collapsibility. We carried out this study to test the hypothesis that mandibular advancement induces changes in upper airway patency during midazolam sedation. To explore its effect, we examined upper airway pressure-flow relationships in each of 4 conditions of mouth position in normal, healthy subjects (n = 9). In the neutral position, Pcrit ( i.e., critical closing pressure, an index of upper airway collapsibility) was −4.2 cm H2O, and upstream resistance (Rua) was 21.2 cm H2O/L/sec. In the centric occlusal position, Pcrit was −7.1 cm H2O, and Rua was 16.6 cm H2O/L/sec. In the incisor position, Pcrit was significantly reduced to −10.7 cm H2O, and Rua was significantly reduced to 14.0 cm H2O/L/sec. Mandibular advancement significantly decreased Pcrit to −13.3 cm H2O, but did not significantly influence Rua (22.1 cm H2O/L/sec). We conclude that the mandibular incisors’ position improved airway patency and decreased resistance during midazolam sedation.
Novel Bacterial Phylotypes in Endodontic Infections
Authors: Siqueira J.F. , Rôças I.N. , Cunha C.D. , Rosado A.S.
Published: January 2009

Although molecular studies have revealed potential oral pathogens among the phyla Spirochaetes and Deferribacteres, their occurrence in endodontic infections has not been consistently investigated. In this study, we devised a nested PCR-DGGE approach to survey samples from infected root canals for the presence of members of these two phyla, and to examine their diversity. The primers used also amplified DNA from Atopobium species. Eight of 10 cases showed bands representative of the target bacterial groups. DGGE profiles revealed a mean number of 6.5 intense and faint bands. No single band occurred in all profiles. Sequences from intense bands excised from the gel showed similarities to species/phylotypes of all target groups— Flexistipes species ( Deferribacteres phylum), uncharacterized spirochetes, and Atopobium species. Analysis of these data indicates that uncultivated Spirochaetes and Deferribacteres phylotypes are frequent members of the endodontic microbiota and may be potential pathogens involved with the etiology of periradicular diseases.
In vivo Cross-sectional Area of Human Jaw Muscles Varies with Section Location and Jaw Position
Authors: Goto T.K. , Yahagi M. , Nakamura Y. , Tokumori K. , Langenbach G.E.J. , Yoshiura K.
Published: January 2009

Muscle cross-sectional area (CSA) is used as a measure for maximum muscle force. This CSA is commonly determined at one location within the muscle and for one jaw position. The purpose of this study was to establish a method to standardize the analysis of the CSA of the masticatory muscles in vivo, and to compare the CSAs along their entire length for two different jaw positions (opened and closed). The CSAs in the planes perpendicular to the long axes of the masseter, medial, and lateral pterygoid muscles were measured in ten normal young adult subjects by magnetic resonance imaging. Our results showed large differences among the muscles and a non-uniform change in CSA after jaw-opening. The method enables the CSA measurement to be standardized in vivo, and allows for a correct comparison of CSAs in different skull morphologies.
Transglutaminase Crosslinking of SIBLING Proteins in Teeth
Authors: Kaartinen M.T. , Sun W. , Kaipatur N. , McKee M.D.
Published: January 2009

Transglutaminase 2 (TG2), a protein-crosslinking enzyme, participates in extracellular matrix maturation and cell adhesion in cartilage and bone. We hypothesized that TG2 has similar roles in teeth. A TG activity assay and immunoblotting of rat tooth extracts showed TG activity and the presence of high-molecular-weight forms of the SIBLING (Small Integrin-Binding LIgand N-linked Glycoprotein) proteins: dentin matrix protein 1 (DMP1), dentin phosphoprotein (DPP), and bone sialoprotein (BSP). DMP1 and BSP, each containing both glutamine and lysine residues critical for crosslink formation, readily formed polymers in vitro when incubated with TG2. The ability of glutamine-lacking DPP to form polymers in vitro and in vivo demonstrates that it could act as a lysine donor for crosslinking, potentially having protein crosslinking partner(s) in teeth. Consistent with a role in cell adhesion, the TG2 isoform was co-localized by immunohistochemistry with its substrates at cell-matrix adhesion sites, including along odontoblast tubules (DMP1 and DPP), in the pericellular matrix of cementocytes (DMP1), and in predentin (BSP).
Suppression of Stress-induced nNOS Expression in the Rat Hypothalamus by Biting
Authors: Hori N. , Lee M.-C. , Sasaguri K. , Ishii H. , Kamei M. , Kimoto K. , Toyoda M. , Sato S.
Published: January 2009

Nitric oxide (•NO) modulates the activity of the endocrine system in the behavioral response to stress. The purpose of this study was to investigate the effect of restraining the body of an animal on expression of neuronal nitric oxide synthase (nNOS) in the paraventricular nucleus (PVN) of the hypothalamus, and the inhibitory effect of para-masticatory activity on restraint-induced nNOS expression. We observed an increase in nNOS mRNA expression and nNOS-positive neurons in the rat hypothalamus after 30 or 60 min of restraint. Biting on a wooden stick during bodily restraint decreased nNOS mRNA expression in the hypothalamus. In addition, the number of nNOS-positive neurons was significantly reduced in the PVN of the hypothalamus. These observations clearly suggest a possible anti-stress effect of the masticatory activity of biting, and this mechanism might be unconsciously in operation during exposure to psychological stressors.
Cleavage of PDGF Receptor on Periodontal Ligament Cells by Elastase
Authors: Nemoto E. , Kanaya S. , Minamibuchi M. , Shimauchi H.
Published: January 2009

Human leukocyte elastase, a neutrophil serine protease, is considered to be a potential immunoregulatory protease. Since the PDGF receptor (PDGFR) on periodontal ligament (PDL) cells is a crucial element for various functions, such as wound healing in periodontal tissue, we investigated the effect of elastase on the expression of PDGFR on PDL cells by flow cytometry and Western blotting. We found that PDGFR-α disappeared with an increasing dose of elastase, and PDGFR-β was degraded into several fragments. Elastase degraded both receptors on fixed cells, indicating that the degradation resulted from direct proteolysis on the cell surface. Elastase also then disturbed the phosphorylation of ERK1/2, JNK/SARK, and p38, triggered by PDGF-AA and PDGF-BB, suggesting that elastase inhibited PDGFR-dependent cell activation in PDL cells. These results suggest that elastase may modulate the PDGF-mediated activity of PDL cells during periodontal wound healing.
PTH(1-34) Affects Osteoprotegerin Production in Human PDL Cells in vitro
Authors: Lossdörfer S. , Götz W. , Jäger A.
Published: January 2009

Since periodontal ligament (PDL) cells exhibit several osteoblastic traits, we hypothesized that human PDL cells will respond to hormonal stimulation in an osteoblast-like manner. Confluent and pre-confluent PDL cells from six patients were challenged with PTH(1-34). Cell number, ALP, osteocalcin, osteoprotegerin, and RANKL expression were determined. Intermittent PTH(1-34) treatment of confluent PDL cells caused a significant increase in proliferation, whereas differentiation and osteoprotegerin production decreased significantly. In pre-confluent PDL cells, this treatment regimen induced a biphasic decrease in proliferation, but a biphasic increase in differentiation and osteoprotegerin production. Continuous PTH(1-34) exposure enhanced proliferation but inhibited osteocalcin production in confluent cells and stimulated osteoprotegerin production in pre-confluent PDL cells. RANKL was hardly detectable and unaffected by PTH(1-34) treatment. These results indicate that human PDL cells respond to PTH(1-34) in an osteoblast-like manner, and that the PTH(1-34) effect depends on the maturation state of the cells and on the mode of administration.
Regulatory T-cells Infiltrate Periodontal Disease Tissues
Authors: Nakajima T. , Ueki-Maruyama K. , Oda T. , Ohsawa Y. , Ito H. , Seymour G.J. , Yamazaki K.
Published: January 2009

CD4+CD25+ regulatory T (Tr) cells are critical in regulating the immune response and thereby play an important role in the defense against infection and control of autoimmune diseases. Our previous studies demonstrated the involvement of autoimmune responses in periodontitis. The aim of this study was to identify CD4+CD25+ Tr cells in periodontitis tissues and compare them with those in gingivitis tissues. Immunohistological analysis of CD4, CD25, and CTLA-4 and the gene expression analysis of FOXP3, TGF-β1, and IL-10 on gingival biopsies revealed the presence of CD4+CD25+ Tr cells in all tissues. In periodontitis, the percentage of CD4+CD25+ Tr cells increased with increasing proportions of B-cells relative to T-cells. FOXP3, a characteristic marker for CD4+CD25+ Tr cells, TGF-β1 and IL-10 were expressed more highly in periodontitis compared with gingivitis. These findings suggest that CD4+CD25+ Tr cells and possibly other regulatory T-cell populations do exist and may play regulatory roles in periodontal diseases.
The Adaptive Remodeling of Condylar Cartilage— A Transition from Chondrogenesis to Osteogenesis
Authors: Shen G. , Darendeliler M. Ali
Published: January 2009

Mandibular condylar cartilage is categorized as articular cartilage but markedly distinguishes itself in many biological aspects, such as its embryonic origin, ontogenetic development, post-natal growth mode, and histological structures. The most marked uniqueness of condylar cartilage lies in its capability of adaptive remodeling in response to external stimuli during or after natural growth. The adaptation of condylar cartilage to mandibular forward positioning constitutes the fundamental rationale for orthodontic functional therapy, which partially contributes to the correction of jaw discrepancies by achieving mandibular growth modification. The adaptive remodeling of condylar cartilage proceeds with the biomolecular pathway initiating from chondrogenesis and finalizing with osteogenesis. During condylar adaptation, chondrogenesis is activated when the external stimuli, e.g., condylar repositioning, generate the differentiation of mesenchymal cells in the articular layer of cartilage into chondrocytes, which proliferate and then progressively mature into hypertrophic cells. The expression of regulatory growth factors, which govern and control phenotypic conversions of chondrocytes during chondrogenesis, increases during adaptive remodeling to enhance the transition from chondrogenesis into osteogenesis, a process in which hypertrophic chondrocytes and matrices degrade and are replaced by bone. The transition is also sustained by increased neovascularization, which brings in osteoblasts that finally result in new bone formation beneath the degraded cartilage.
Smokeless Tobacco and Severe Active Periodontal Disease, NHANES III
Authors: Fisher M.A. , Taylor G.W. , Tilashalski K.R.
Published: January 2009

Whereas smoking is a major risk factor for periodontal disease, the role of smokeless tobacco is unclear. The purpose of this US population-based study of 12,932 adults participating in the Third National Health and Nutrition Examination Survey was to evaluate the association between smokeless tobacco use and severe active periodontal disease. Univariable and multivariable logistic regression modeling quantified the associations between tobacco use and severe active periodontal disease. All adults and never-smokers who currently used smokeless tobacco were twice as likely to have severe active periodontal disease at any site [respective odds ratios (ORAdj) and 95% confidence intervals: ORAdj = 2.1; 1.2–3.7 and ORAdj = 2.1; 1.0–4.4] or restricted to any interproximal site [respective ORAdj = 2.1; 1.0–4.2 and ORAdj = 2.3; 0.9–6.3], simultaneously adjusted for smoking, age, race, gender, diabetes, and having a dental visit in the past year. These results indicate that smokeless tobacco may also be an important risk factor for severe active periodontal disease.
Tuftelin, Mutans Streptococci, and Dental Caries Susceptibility
Authors: Slayton R. L. , Cooper M.E. , Marazita M.L.
Published: January 2009

The purpose of this study was to identify genetic factors that contribute to dental caries susceptibility, either alone or in combination with environmental factors. Dental examinations were performed and buccal swab samples collected from 3- to 5-year-old children with at least 4 surfaces of decay, or with no evidence of decay. SNP assays for each of 6 candidate genes were performed for all cases and controls. Chi-square analysis and regression analysis were used for the evaluation of individual gene effects, environmental effects, and gene-environment interactions. There were no significant associations between single candidate genes and caries susceptibility. Levels of S. mutans were positively and Lactobacilli were negatively associated with caries. Regression analysis revealed a significant interaction between tuftelin and S. mutans, with 26.8% of the variation in dmfs explained by the interaction. Future research will focus on the identification of these additional factors and the development of functional assays so that these interactions can be better understood.
Efficacy of Silver Diamine Fluoride for Caries Reduction in Primary Teeth and First Permanent Molars of Schoolchildren: 36-month Clinical Trial
Authors: Llodra J.C. , Rodriguez A. , Ferrer B. , Menardia V. , Ramos T. , Morato M.
Published: January 2009

We hypothesized that the six-monthly application of silver diamine fluoride (SDF) can arrest the development of caries in the deciduous dentition of six-year-old schoolchildren and prevent caries in their first permanent molars. A prospective controlled clinical trial was conducted on the efficacy of a 38% SDF solution for caries reduction. Four hundred and twenty-five six-year-old children were divided into two groups: One group received SDF solution in primary canines and molars and first permanent molars every 6 mos for 36 mos. The second group served as controls. The 36-month follow-up was completed by 373 children. The mean number of new decayed surfaces appearing in primary teeth during the study was 0.29 in the SDF group vs. 1.43 in controls. The mean of new decayed surfaces in first permanent molars was 0.37 in the SDF group vs. 1.06 in controls. The SDF solution was found to be effective for caries reduction in primary teeth and first permanent molars in schoolchildren.
Oxygen Inhibition in Dental Resins
Authors: Gauthier M.A. , Stangel I. , Ellis T.H. , Zhu X.X.
Published: January 2009

Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a concern when thin layers of resin are being polymerized, or in circumstances where conventional means of eliminating inhibition are inappropriate. In this study, we tested the hypothesis that viscosity, filler content, and polymerization temperature modify oxygen diffusion in the resin or the reactivity of radical species, and affect the degree of conversion near the surface. Confocal Raman micro-spectroscopy was used to measure monomer conversion from the surface to the bulk of cured resins. Increased viscosity was shown to limit oxygen diffusion and increase conversion near the surface, without necessarily modifying the depth of inhibition. The filler material was shown to increase, simultaneously, oxygen diffusivity and the viscosity of the resin, which have opposite effects on conversion. Polymerization at a temperature above ~ 110°C was shown to eliminate oxygen inhibition.
Chlorhexidine Arrests Subclinical Degradation of Dentin Hybrid Layers in vivo
Authors: Hebling J. , Pashley D.H. , Tjäderhane L. , Tay F.R.
Published: January 2009

The recent paradigm that endogenous collagenolytic and gelatinolytic activities derived from acid-etched dentin result in degradation of hybrid layers requires in vivo validation. This study tested the null hypothesis that there is no difference between the degradation of dentin bonded with an etch-and-rinse adhesive and that in conjunction with chlorhexidine, an MMP inhibitor, applied after phosphoric-acid-etching. Contralateral pairs of bonded Class I restorations in primary molars of clinical subjects were retrieved after a six-month period of intra-oral functioning and processed for transmission electron microscopy. Hybrid layers from the chlorhexidine-treated teeth exhibited normal structural integrity of the collagen network. Conversely, abnormal hybrid layers were seen in the control teeth, with progressive disintegration of the fibrillar network, to the extent that it was beyond detection by collagen staining. Self-destruction of collagen matrices occurs rapidly in resin-infiltrated dentin in vivo and may be arrested with the use of chlorhexidine as an MMP inhibitor.
Distraction Osteogenesis May Promote Periodontal Bone Regeneration
Authors: Faber J. , Azevedo R.B. , Báo S.N.
Published: January 2009

Distraction osteogenesis has numerous applications in the treatment of conditions affecting the dentofacial complex, from midface advancement to orthodontic tooth movement produced by transversal distraction of the periodontal ligament. The purpose of this study was to test the hypothesis that periodontium can be consistently distracted toward the tooth crown to promote periodontal bone regeneration. After the surgical production of periodontal defects in maxillary canines of 5 mongrel dogs, periodontal bone distraction was performed. Light microscopy was used for histopathological and morphometric analysis. Periodontal bone regeneration occurred in all animals. Periodontal bone regeneration in the distraction sites (Mean ± SD: 5.45 ± 2.01 mm) differed from that in control sites (0.008 ± 0.67 mm; p < 0.0001). Periodontal bone distraction resulted in periodontal bone regeneration. This finding may establish periodontal bone distraction as a new treatment alternative for periodontal defects.
Effect of NOS Inhibitor on Cytokine and COX2 Expression in Rat Pulpitis
Authors: Kawashima N. , Nakano-Kawanishi H. , Suzuki N. , Takagi M. , Suda H.
Published: January 2009

Various kinds of chemical mediators are synthesized in the course of pulpitis; thus, control of their production would assist in inducing a reduction in pulpal inflammation. We hypothesized that nitric oxide (NO) would be an important mediator of pulpal inflammation. Pulpal inflammation was induced by the application of LPS in rat incisor pulp, and inducible nitric oxide synthase (iNOS) expression was evaluated by reverse-transcription/polymerase chain-reaction and immunohistochemical staining. After LPS application, iNOS mRNA was first detected after 3 hrs, peaked at 6 hrs, and decreased thereafter. iNOS-positive cells were macrophages and neutrophils. An NOS inhibitor caused drastic decreases in the expression of pro-inflammatory cytokines and COX2 mRNA, which was highly induced in the LPS-induced pulpitis. These results indicate that NO synthesis is related to the initiation of mediator production, and that its down-regulation should contribute to the prevention of pro-inflammatory mediator synthesis. Abbreviations: ANOVA, analysis of variance; COX2, cyclo-oxygenase 2; EDTA, ethylenediaminetetraacetic acid; iNOS, inducible nitric oxide synthase; IL, interleukin; L-NAME, NG-nitro L-arginine methyl ester; LPS, lipopolysaccharide; NO, nitric oxide; NOS, nitric oxide synthases; PG, prostaglandin; RT-PCR, reverse-transcription/polymerase chain-reaction; TNFα, tumor necrosis factor alpha.
Fiber-type Composition of the Human Jaw Muscles—(Part 1) Origin and Functional Significance of Fiber-type Diversity
Authors: Korfage J.A.M , Koolstra J.H. , Langenbach G.E.J. , van Eijden T.M.G.J.
Published: January 2009

This is the first of two articles on the fiber-type composition of the human jaw muscles. The present article discusses the origin of fiber-type composition and its consequences. This discussion is presented in the context of the requirements for functional performance and adaptation that are imposed upon the jaw muscles. The human masticatory system must perform a much larger variety of motor tasks than the average limb or trunk motor system. An important advantage of fiber-type diversity, as observed in the jaw muscles, is that it optimizes the required function while minimizing energy use. The capacity for adaptation is reflected by the large variability in fiber-type composition among muscle groups, individual muscles, and muscle regions. Adaptive changes are related, for example, to the amount of daily activation and/or stretch of fibers. Generally, the number of slow, fatigue-resistant fibers is relatively large in muscles and muscle regions that are subjected to considerable activity and/or stretch.
Environmental and Heritable Factors in the Etiology of Oral Diseases—A Population-based Study of Swedish Twins
Authors: Mucci L.A. , Björkman L. , Douglass C.W. , Pedersen N.L.
Published: January 2009

A population-based twin study is a useful design for quantification of the effects of genes and environmental factors in disease etiology. We used data from 10,000 Swedish twin pairs to quantify genetic and environmental contributions to tooth loss and periodontal health. Oral health information was obtained from telephone interviews. Structural equation models measured the relative importance of genetic and environmental factors. Genetic factors contributed to 14% of variation in tooth loss among women, and 39% among men. Non-shared environmental factors accounted for one-quarter of risk; environmental factors shared by twins comprised the remainder. Heritability estimates of periodontal disease were 39% and 33% for women and men, respectively, while non-shared environmental factors accounted for the remaining variation. Heritability for both conditions varied as a function of age and smoking status. Analysis of data from this large, population-based study demonstrates a moderate role of genetic factors in oral diseases, and suggests potential gene-environment interactions.
Polymorphisms in PTCH1 Affect the Risk of Ameloblastoma
Authors: Kawabata T. , Takahashi K. , Sugai M. , Murashima-Suginami A. , Ando S. , Shimizu A. , Kosugi S. , Sato T. , Nishida M. , Murakami K. , Iizuka T.
Published: January 2009

Ameloblastoma is the most common odontogenic tumor, but the genetic nature of the changes in the tumor cells has been unclear. Mutations of CTNNB1 or PTCH1 are observed in many human tumors. Both CTNNB1 and PTCH1 are important in tooth development and are expressed in ameloblastoma. The aim of this study was to investigate whether genetic alterations of CTNNB1 and PTCH1 are present in ameloblastoma. We investigated 14 cases of ameloblastoma. The polymorphisms found in the ameloblastoma patients were further examined in a subsequent case-control study. We found a CTNNB1 mutation in one case of plexiform-type ameloblastoma. CGG triplet repeat-number polymorphism (CGG7/CGG8) in the 5′-untranslated region of PTCH1 was observed. The proportion of CGG8 alleles was significantly higher in the ameloblastoma group. The results of this study indicate a possible relationship between the CGG8 allele in PTCH1 and the risk for ameloblastoma.
Colloidal β-Tricalcium Phosphate Prepared by Discharge in a Modified Body Fluid Facilitates Synthesis of Collagen Composites
Authors: Shibata Y. , Yamamoto H. , Miyazaki Takashi
Published: January 2009

The development of hydroxyapatite/collagen composites that are naturally synthesized and need no additional treatment is required for use in bone repair. Since reducing the diameter can increase the specific surface area of calcium phosphate particles that can conjugate collagen molecules, we expected colloidal calcium phosphates of submicron diameter obtained by discharge to be effective in formulating these composites. Additionally, since biodegradable β-tricalcium phosphate has better osteoconductivity than hydroxyapatite, this study aimed to investigate the synthesis of colloidal hydroxyapatite and β-tricalcium phosphate/collagen composites. Collagen molecules were tightly polymerized in the β-tricalcium phosphate/collagen composite by catalysis of the generated -P-O-P- polyphosphate chain. Bonding strength between collagen NH+ amino groups and -P-O-P-, and cross-linking of the Ca++-RCOO− in the collagen were increased compared with those in the hydroxyapatite/collagen composite. These chemical reactions due to colloidal β-tricalcium phosphate might play a key role in the synthesis of collagen composites.
Fluorosis: A New Model and New Insights
Authors: Bartlett J.D. , Dwyer S.E. , Beniash E. , Skobe Z. , Payne-Ferreira T.L.
Published: January 2009

Fluoride is an effective agent for the prevention of dental caries. However, the mechanism of how excessive fluoride exposure causes fluorosis remains uncertain. Zebrafish ( Danio rerio) exhibit periodic tooth replacement throughout their lives, thereby providing continuous access to teeth at developmental stages susceptible to fluoride exposure. Zebrafish teeth do not contain true enamel, but consist of a hard enameloid surface. Therefore, we asked whether zebrafish could be used as a model organism for the study of dental fluorosis. Scanning electron microscopy of fluoride-treated teeth demonstrated that the enameloid was pitted and rough, and FTIR analysis demonstrated that the teeth also contained a significantly higher organic content when compared with untreated controls. Furthermore, we demonstrate for the first time that decreased expression of an important signaling molecule (Alk8) in tooth development may contribute to the observed fluorotic phenotype, and that increased cell apoptosis may also play a role in the mechanism of fluorosis.
CSF-1 Regulation of Osteoclastogenesis for Tooth Eruption
Authors: Wise G.E. , Yao S. , Odgren P.R. , Pan F.
Published: January 2009

The dental follicle regulates the alveolar bone resorption needed for tooth eruption. In the rat first mandibular molar, a decrease in the expression of osteoprotegerin (OPG) in the dental follicle at day 3 enables the osteoclastogenesis needed for eruption to occur. Because colony-stimulating factor-1 (CSF-1) is maximally expressed in the dental follicle at day 3, it was hypothesized that CSF-1 down-regulates OPG gene expression in the dental follicle in vivo. To test this, we compared the expression of OPG in osteopetrotic toothless ( tl/tl) rats deficient in CSF-1 with expression in their normal littermates for given ages. OPG gene expression was found to be higher in the dental follicle of the tl/tl mutants than in normals. Transfecting short interfering RNA specific for CSF-1 mRNA into dental follicle cells resulted in an up-regulation of OPG expression. Thus, these studies support our hypothesis that the down-regulation of OPG needed for tooth eruption is mediated by CSF-1.
Isolation and Expression of FIP-2 in Wounded Pulp of the Rat
Authors: Oyama M. , Myokai F. , Ohira T. , Shiomi N. , Yamashiro K. , Arai H. , Nishimura F. , Takashiba S.
Published: January 2009

Pulpal wound healing followed by cavity preparation may involve reactionary or reparative dentinogenesis in relation to the cavity position; however, little is known about the molecular responses. We aimed to isolate and analyze genes induced or suppressed in the wounded pulp to identify molecular processes involved in the pulp responses to injury. Twenty-three cDNAs were isolated by cDNA subtraction between healthy and wounded pulp of rats. By library screening, we identified rat 14.7K-interacting protein (rFIP)-2A and B genes homologous to human FIP-2, being involved in regulating membrane trafficking and cellular morphogenesis. RT-PCR analysis showed induction for only rFIP-2B in the wounded pulp. In situ hybridization analysis revealed that both rFIP-2s were expressed strongly in condensing mesenchymal cells of the palatal process and surrounding Meckel’s cartilage, but not in intramembranous chondrogenic cells. Thus, up-regulated rFIP-2B expression may play a role in regulating membrane trafficking or cellular morphogenesis of these embryonic and wounded pulpal cells.
Bupivacaine Induces ApoptosisviaROS in the Schwann Cell Line
Authors: Park C.J. , Park S.A. , Yoon T.G. , Lee S.J. , Yum K.W. , Kim H.J.
Published: January 2009

Local anesthetics have been generally accepted as being safe. However, recent clinical trials and basic studies have provided strong evidence for the neurotoxicity of local anesthetics, especially through apoptosis. We hypothesized that local anesthetics cause neural complications through Schwann cell apoptosis. Among local anesthetics tested on the Schwann cell line, RT4-D6P2T, bupivacaine significantly induced cell death, measured by the methyl tetrazolium (MTT) assay, in a dose- (LD50= 476 μM) and time-dependent manner. The bupivacaine-induced generation of reactive oxygen species (ROS), which was initiated within 5 hrs and preceded the activation of caspase-3 and poly ADP-ribose polymerase (PARP) degradation, was suggested to trigger apoptosis, exhibited by Hoechst 33258 nuclear staining and DNA fragmentation. Furthermore, concomitant block of ROS by anti-oxidants significantly inhibited bupivacaine-induced apoptosis. Among the local anesthetics for peripheral neural blocks, bupivacaine induced apoptosis in the Schwann cell line, which may be associated with ROS production.
Validation of Self-reported Periodontal Disease: A Systematic Review
Authors: Blicher B. , Joshipura K. , Eke P.
Published: January 2009

Self-report is an efficient and accepted means of assessing many population characteristics, risk factors, and diseases, but has rarely been used for periodontal disease (chronic periodontitis). The availability of valid self-reported measures of periodontal disease would facilitate epidemiologic studies on a much larger scale, allow for integration of new studies of periodontal disease within large ongoing studies, and facilitate lower-cost population surveillance of periodontitis. Several studies have been conducted to validate self-reported measures for periodontal disease, but results have been inconsistent. In this report, we conducted a systematic review of the validation studies. We reviewed the 16 studies that assessed the validity of self-reported periodontal and gingivitis measures against clinical gold standards. Seven of the studies included self-reported measures specific to gingivitis, four included measures only for periodontitis, and five included both gingivitis and periodontal measures. Three of the studies used a self-assessment method where they provided the patient with a detailed manual for performing a self-exam. The remaining 13 studies asked participants to self-report symptoms, presence of periodontal disease itself, or their recollection of a dental health professional diagnosing them or providing treatment for periodontal disease. The review indicates that some measures showed promise, but results varied across populations and self-reported measures. One example of a good measure is, “Has any dentist/hygienist told you that you have deep pockets?”, which had a sensitivity of 55%, a specificity of 90%, positive predictive value of 77%, and negative predictive value of 75% against clinical pocket depth. Higher validity could be potentially obtained by the use of combinations of several self-reported questions and other predictors of periodontal disease.
Heterogeneity of IgG Glycosylation in Adult Periodontal Disease
Authors: Novak J. , Tomana M. , Shah G.R. , Brown R. , Mestecky J.
Published: January 2009

Periodontal disease is a chronic inflammatory disease of bacterial etiology. In many other chronic inflammatory diseases, IgG glycans are galactose-deficient and thus capable of complement activation through the lectin pathway. In this study, we examined whether IgG in serum and gingival crevicular fluid, and IgG locally produced by plasma cells in gingiva of periodontal disease patients, display altered glycosylation. We developed a lectin-ELISA to measure levels of galactose-deficient IgG in the fluids and immunofluorescence staining to detect galactose-deficient IgG-producing cells in gingiva. Our results indicated higher levels of galactose-deficient IgG in sera and gingival crevicular fluid from periodontal disease patients, compared with levels in healthy controls. Furthermore, gingivae from periodontal disease patients exhibited infiltration of IgG-producing plasma cells; many of them contained galactose-deficient IgG in the cytoplasm. Analysis of our data suggests that IgG secreted by B-cells was aberrantly glycosylated, which resulted in the production of pro-inflammatory galactose-deficient IgG.
Early Responses of Periodontal Ligament Cells to Mechanical Stimulus in vivo
Authors: Kawarizadeh A. , Bourauel C. , Götz W. , Jäger A.
Published: January 2009

Previous studies have indicated that human periodontal ligament cells undergo osteoblastic differentiation via the ERK pathway under mechanical stress in vitro. This study aimed to verify this principle in vivo. The right upper first molars of 25 anesthetized rats were loaded with constant forces of 0.1 N for up to 8 hrs. The untreated contralateral side served as a control. Paraffin-embedded sections were analyzed by immunohistochemistry for proliferating cell nuclear antigen (PCNA), runt-related transcription factor 2 (Runx2/Cbfa1), and phosphorylated extracellular signal-regulated kinases 1/2 (pERK1/2). In selected areas under tension, the proportions of Runx2-positive and pERK1/2-positive cells increased within 8 hrs of loading, whereas these proportions in selected areas under pressure were significantly lower than those in control teeth. Moreover, there were no significant changes in the number of PCNA-positive cells. Thus, mechanical stimulus up-regulates Runx2, and this regulation may be achieved via the ERK pathway.
Prevalence and Trends in Periodontitis in the USA: from the NHANES III to the NHANES, 1988 to 2000
Authors: Borrell L.N. , Burt B.A. , Taylor G.W.
Published: January 2009

Trends in periodontal diseases in the USA have been documented for years. However, the results have been mixed, mostly due to different periodontal assessment protocols. This study examined change in the prevalence of periodontitis between the NHANES III and the NHANES 1999–2000, and differences in the prevalence of periodontitis among racial/ethnic groups in the USA. Analysis was limited to non-Hispanic black, non-Hispanic white, and Mexican-American adults aged 18+ yrs in the NHANES III (n = 12,088) or the NHANES 1999–2000 (n = 3214). The prevalences of periodontitis for the NHANES III and the NHANES 1999–2000 were 7.3% and 4.2%, respectively. In multivariable analyses, blacks were 1.88 times (95%CI: 1.42, 2.50) more likely to have periodontitis than whites surveyed in the NHANES III. However, the odds of periodontitis for blacks and Mexican-Americans did not differ from those for whites surveyed in the NHANES 1999–2000. Our findings indicate that the prevalence of periodontitis has decreased between the NHANES III and the NHANES 1999–2000 for all racial/ethnic groups in the USA.
Dental Caries Experience: A Two-generation Study
Authors: Bedos C. , Brodeur J.-M. , Arpin S. , Nicolau B.
Published: January 2009

The life-course framework stresses the importance of social, psychosocial, and biological factors in early life on the development of later disease. From this perspective, the association between edentulousness of mothers and their children’s caries risk has not been studied. Therefore, a sample of 6303 mother-child pairs was randomly selected in Quebec (Canada). Mothers (6039 dentate and 264 edentulous) completed a self-administered questionnaire, and their children, aged 5 to 9 years, were clinically examined. Bivariate analyses and multiple logistic regressions showed that edentulous mothers’ children are more likely to experience caries on both primary [OR = 1.7 (1.3–2.3)] and permanent [OR = 1.4 (1.0–2.0)] dentitions when compared with dentate mothers’ children. These results are independent of socio-economic status, age, gender, and children’s oral-health-related behaviors. Our study is the first to show that edentulous mothers’ children constitute a group at risk of caries. It also highlights the need for a better understanding of the mother-child transmission of risk.
How Does Fluoride Affect Dentin Microhardness and Mineralization?
Authors: Vieira A. , Hancock R. , Dumitriu M. , Schwartz M. , Limeback H. , Grynpas M.
Published: January 2009

Fluoride (F) has been a useful instrument in caries prevention. However, only limted data exist on the effect of its long-term use on dentin mineralization patterns and microhardness. The objective of this study was to evaluate the influence of tooth F concentration ([F]) and dental fluorosis (DF) severity on dentin microhardness and mineralization. We collected 137 teeth in Montreal and Toronto, Canada, and Fortaleza, Brazil, where optimum or suboptimum levels of water F were 0.2 ppm, 1 ppm, and 0.7 ppm, respectively. Teeth were analyzed for DF severity, dentin [F], enamel [F], dentin microhardness, and dentin mineralization. Dentin [F] correlated with DF severity; enamel [F] correlated with dentin microhardness and dentin mineralization; DF severity correlated with dentin microhardness. Genetic factors ( e.g., DF severity) and environmental factors ( e.g., tooth [F]) influenced the mechanical properties (microhardness) of the teeth, while only the environmental factors influenced their material properties ( e.g., mineralization). Fortaleza teeth were harder and less mineralized and presented higher dentin [F] values. Montreal teeth presented lower levels of DF when compared with both Toronto and Fortaleza teeth.