bluuebunny/crossref_metadata_2025 huggingface dataset:
Matrix Metalloproteinase-3 Differences in Oral and Skin Fibroblasts
Authors: McKeown S.T.W. , Barnes J.J. , Hyland P.L. , Lundy F.T. , Fray M.J. , Irwin C.R.
Published: January 2009

While skin wounds heal by scarring, wounds of oral mucosa show privileged healing with minimal scar formation. Our hypothesis was that phenotypic differences between oral and skin fibroblasts underlie these differences in healing. The aims of this study were to compare MMP-3 expression by oral and skin fibroblasts and investigate a role for MMP-3 in mediating collagen gel contraction. Oral fibroblasts induced significantly greater gel contraction than did paired skin cells. Inhibition of MMP activity significantly inhibited gel contraction by both cell types. Specific inhibition of MMP-3 activity reduced gel contraction by oral, but not skin, fibroblasts. Oral fibroblasts produced significantly higher levels of MMP-3 than did skin fibroblasts at all levels studied. TGF-β1 and -β3 isoforms stimulated MMP-3 expression at mRNA, protein, and activity levels by both fibroblast populations. Results suggest that increased MMP-3 production by oral fibroblasts may underlie the differences in wound-healing outcome seen in skin and oral mucosa.
Hard Tissue Formation in Subcutaneously Transplanted Rat Dental Pulp
Authors: Hosoya A. , Nakamura H. , Ninomiya T. , Hoshi K. , Yoshiba K. , Yoshiba N. , Takahashi M. , Okabe T. , Sahara N. , Yamada H. , Kasahara E. , Ozawa H.
Published: January 2009

While dental pulp appears to be able to form mineralized matrices that do not always resemble dentin, the precise characteristics of the hard tissue and the mechanism of its induction remain unknown. Therefore, we evaluated hard tissue induced by transplantation of pulp into subcutaneous tissue. Seven days after transplantation, initial hard tissue was formed at the inner periphery of the pulp. After 14 days, this hard tissue expanded inwardly. Mineralized matrix was immunopositive for osteocalcin, osteopontin, and bone sialoprotein, but negative for dentin sialoprotein. Transplantation of GFP-labeled pulp into wild-type rats showed these formative cells to have been derived from the transplant. TEM observation revealed apatite crystals within necrotic cells and matrix vesicles at the initial stage of calcification. These results indicate that pulp cells possess the ability to form a bone- or cementum-like matrix. Calcification of the matrix may occur in necrotic cells and matrix vesicles, followed by collagenous calcification.
Orofacial Pain in Cancer: Part II—Clinical Perspectives and Management
Authors: Epstein J.B. , Elad S. , Eliav E. , Jurevic R. , Benoliel R.
Published: January 2009

Cancer-associated pain is extremely common and is associated with significant physical and psychological suffering. Unfortunately, pain associated with cancer or its treatment is frequently under-treated, probably due to several factors, including phobia of opioids, under-reporting by patients, and under-diagnosis by healthcare workers. The most common etiology of cancer pain is local tumor invasion (primary or metastatic), involving inflammatory and neuropathic mechanisms; these have been reviewed in Part I. As malignant disease advances, pain usually becomes more frequent and more intense. Additional expressions of orofacial cancer pain include distant tumor effects, involving paraneoplastic mechanisms. Pain secondary to cancer therapy varies with the treatment modalities used: Chemo-radiotherapy protocols are typically associated with painful mucositis and neurotoxicity. Surgical therapies often result in nerve and tissue damage, leading, in the long term, to myofascial and neuropathic pain syndromes. In the present article, we review the clinical presentation of cancer-associated orofacial pain at various stages: initial diagnosis, during therapy (chemo-, radiotherapy, surgery), and in the post-therapy period. As a presenting symptom of orofacial cancer, pain is often of low intensity and diagnostically unreliable. Diagnosis, treatment, and prevention of pain in cancer require knowledge of the presenting characteristics, factors, and mechanisms involved.
Effect of Load Deflection on Corrosion Behavior of NiTi Wire
Authors: Liu I.H. , Lee T.M. , Chang C.Y. , Liu C.K.
Published: January 2009

For dental orthodontic applications, NiTi wires are used under bending conditions in the oral environment for a long period. The purpose of this study was to investigate the effect of bending stress on the corrosion of NiTi wires using potentiodynamic and potentiostatic tests in artificial saliva. The results indicated that bending stress induces a higher corrosion rate of NiTi wires in passive regions. It is suggested that the passive oxide film of specimens would be damaged under bending conditions. Auger electron spectroscopic analysis showed a lower thickness of passive films on stressed NiTi wires compared with unstressed specimens in the passive region. By scanning electron microscopy, localized corrosion was observed on stressed Sentalloy specimens after a potentiodynamic test at pH 2. In conclusion, this study indicated that bending stress changed the corrosion properties and surface characteristics of NiTi wires in a simulated intra-oral environment.
IL-10 Gene Transfer Attenuates P. gingivalis-induced Inflammation
Authors: Houri-Haddad Y. , Soskolne W.A. , Halabi A. , Shapira L.
Published: January 2009

IL-10 is an anti-inflammatory cytokine secreted by stimulated Th2 lymphocytes that can down-regulate inflammatory responses to bacterial challenge. We hypothesized that local delivery of IL-10 using gene-transfer will down-regulate inflammatory responses. We examined the effect of IL-10 plasmid injection on the local cytokine response. Two weeks after the implantation of chambers, either IL-10 plasmid or vector was injected into the mice. Four days later, they were challenged with an intra-chamber injection of P. gingivalis. The intra-chamber levels of IL-10, IFNγ, TNFα, and IL-1β were evaluated after 2 and 24 hrs. The results showed that local IL-10 gene delivery elevated the levels of IL-10 at both time periods. It attenuated the levels of IFNγ (656 ± 154 to 218 ± 144 pg/mL) and TNFα (23 ± 2.0 to 12.5 ± 2.9 ng/mL) at 2 hrs, and of IL-1β (21.5 ± 5.7 to 12.4 ± 3.0 ng/mL) at 24 hrs. The results suggest the possibility of modulating the local inflammatory response to P. gingivalis by direct IL-10 gene transfer.
The Effect of NIDCR R25 Grant Support on the Curriculum and Culture of a Research Non-intensive Dental School
Authors: Iacopino A.M. , Pryor M.E. , Taft T.B. , Lynch D.P.
Published: January 2009

Our objective was to evaluate changes in curriculum and culture within a research non-intensive dental school after implementation of programs supported by the NIH-NIDCR R25 Oral Health Research Curriculum Grant. We designed new curricular elements to foster an appreciation of research/discovery, an interest in academic/research careers, and application of biomedical/clinical advances to patient care. Funding was utilized to develop, implement, and assess a dedicated curricular track of continuous student research/scholarly activity throughout the four years of dental education. This track represented mandatory hours of didactic time exposing students to topics not traditionally included in dental curricula. Additionally, students were provided with customized flexible schedules to participate in elective “hands-on” mentored research/scholarly experiences at local, national, and international sites, including linkages to certificate, MS, and PhD programs. Funding was also used to support a wide array of faculty development activities that provided skill sets required to deliver integrated biomedical/clinical content, research-oriented evidence-based approaches to dental education, and translational case-based teaching methods emphasizing the application of new science/technologies to patient care. We measured changes in student, faculty, and institutional profiles/attitudes using traditional benchmarks, surveys, and focus groups. Comparisons were made between baseline data prior to R25 program initiation and data collected after years 3–4 of program implementation. Significant increases were demonstrated in: (1) student participation in research/scholarship, attendance at national meetings, research awards, publication of manuscripts, pursuit of advanced training/degrees, and expressions of interest in academic/research careers; (2) faculty participation in development activities, publication of manuscripts, and mentoring of students; and (3) increased institutional credibility within the university, supportive infrastructure for research/scholarship, and cultural expectations for academic excellence. Thus, we believe that the R25 programming changed the culture of our dental school, creating a supportive environment for research/scholarship, increasing academic productivity, and altering the attitudes of faculty/students.
The VicRK System of Streptococcus mutans Responds to Oxidative Stress
Authors: Deng D.M. , Liu M.J. , ten Cate J.M. , Crielaard W.
Published: January 2009

In Streptococcus mutans, virulence and cariogenicity may be modulated via the two-component regulatory system VicRK. Environmental signals, sensed by VicK, inducing this modulation are still unclear, however, and were investigated in the present study. We found that VicRK displays homology with protein-domains that, in other bacteria, are involved in redox-sensing. After constructing a VicRK-promoter GFP-reporter strain, we showed increased fluorescence intensity under oxidative stress. Potential interference of alternative signals and experimental conditions on GFP expression was excluded by the use of negative and positive control strains. Finally, we constructed a clean vicK knockout mutant, which proved to be more sensitive to H2O2 than the wild-type. In conclusion, this study showed that the VicRK system responds to and protects against oxidative stress. As a result, a link between oxidative/redox stress and the cariogenic nature of S. mutans can be hypothesized.
Intermittent Force Induces High RANKL Expression in Human Periodontal Ligament Cells
Authors: Nakao K. , Goto T. , Gunjigake K.K. , Konoo T. , Kobayashi S. , Yamaguchi K.
Published: January 2009

Intermittent compressive force stimulates bone resorption in orthodontic treatment. This study examined the molecular mechanism in human periodontal ligament (PDL) cells stimulated by an intermittent force. PDL cells were subjected to compressive force (2.0 or 5.0 g/cm2) for 2–4 days. Continuous or intermittent force was applied all day or for 8 hrs per day, respectively. At days 3 and 4, cell damage was less with intermittent force than with continuous force. At day 4, RANKL and IL-1β expressions were greater with intermittent force than with continuous force. An IL-1 receptor antagonist inhibited the compressive force-induced RANKL expression. These findings indicate that IL-1β is an autocrine factor regulating compressive force-induced RANKL expression in PDL cells, and that intermittent force can effectively induce RANKL in PDL cells with less cell damage.
Porphyromonas gingivalis Dihydroceramides Induce Apoptosis in Endothelial Cells
Authors: Zahlten J. , Riep B. , Nichols F.C. , Walter C. , Schmeck B. , Bernimoulin J.-P. , Hippenstiel S.
Published: January 2009

Porphyromonas gingivalis dihydroceramides are found in extracts of calculus-contaminated root surfaces, diseased gingival tissue, and atherosclerotic plaques. These ceramides have been shown to promote inflammatory secretory responses in gingival fibroblasts. Little is known about their effects on the vascular system. We tested the hypothesis that P. gingivalis lipids induce apoptosis of human endothelial cells, and investigated the effects of extracted and purified P. gingivalis lipids on human umbilical vein endothelial cells. P. gingivalis phosphoglycerol dihydroceramides induced apoptosis, but not necrosis, in endothelial cells. Early apoptotic cells showed exposure of phosphatidylserine on the cell surface, followed by the cleavage of procaspases 3, 6, and 9. The release of apoptosis-inducing factor was increased, suggesting mitochondrial involvement. Different caspase inhibitors and cAMP elevation blocked DNA fragmentation. Moreover, N-acetylcysteine significantly reduced apoptosis, suggesting a role for reactive oxygen species in this process. Analysis of these data indicates that dihydroceramides may be important virulence factors of P. gingivalis.
Randomized Controlled Trial of a One-minute Intervention Changing Oral Self-care Behavior
Authors: Sniehotta F.F. , Araújo Soares V. , Dombrowski S.U.
Published: January 2009

Non-compliance with oral self-care recommendations, despite education and motivation, is a major problem in preventive dentistry. Forming concrete if-then action plans has been successful in changing self-care behavior in other areas of preventive medicine. This is the first trial to test the effects of a brief planning intervention on interdental hygiene behavior. Two hundred thirty-nine participants received a packet of floss, information, and a flossing guide. They were randomly assigned to a control or an intervention group. The intervention took 1.16 minutes and consisted of forming a concrete plan of where, when, and how to floss. Baseline measures and two-week and two-month follow-ups included self-report, residual floss, and theory of planned behavior variables. The intervention significantly affected flossing in that group at two-week and two-month follow-ups, as compared with the control group. This study provides evidence for the effects of a concise intervention on oral self-care behavior.
Time to Survival for the Restoration of the Shortened Lower Dental Arch
Authors: Thomason J.M. , Moynihan P.J. , Steen N. , Jepson N.J.A.
Published: January 2009

Removable partial dentures may adversely affect remaining tissues and have a low prevalence of use. This randomized controlled trial was designed to compare the time to survival of cantilever resin-bonded fixed partial dentures and conventional removable partial dentures to restore shortened lower dental arches. We randomly allocated 25 male and 35 female patients (median age, 67 years) to fixed or removable partial denture groups of 30 persons, matched for age and sex. Survival of the prostheses was assessed, based on listed criteria, at each review or when problems arose. Although the removable partial denture group required rather more maintenance visits, the difference in survival rates was not statistically significant (hazard ratio = 0.59, with 95% CI 0.27, 1.29). In the absence of significant differences in five-year survival, the reported advantages of fixed partial dentures, including reduced maintenance frequency, offer positive support for the use of resin-bonded fixed partial dentures.
Saliva: a Dynamic Proteome
Authors: Helmerhorst E.J. , Oppenheim F.G.
Published: January 2009

The proteome of whole saliva, in contrast to that of serum, is highly susceptible to a variety of physiological and biochemical processes. First, salivary protein secretion is under neurologic control, with protein output being dependent on the stimulus. Second, extensive salivary protein modifications occur in the oral environment, where a plethora of host- and bacteria-derived enzymes act on proteins emanating from the glandular ducts. Salivary protein biosynthesis starts with the transcription and translation of salivary protein genes in the glands, followed by post-translational processing involving protein glycosylation, phosphorylation, and proteolysis. This gives rise to salivary proteins occurring in families, consisting of structurally closely related family members. Once glandular secretions enter the non-sterile oral environment, proteins are subjected to additional and continuous protein modifications, leading to extensive proteolytic cleavage, partial deglycosylation, and protein-protein complex formation. All these protein modifications occur in a dynamic environment dictated by the continuous supply of newly synthesized proteins and removal by swallowing. Understanding the proteome of whole saliva in an environment of continuous turnover will be a prerequisite to gain insight into the physiological and pathological processes relevant to oral health, and be crucial for the identification of meaningful biomarkers for oral disease.
Photodynamic Therapy in Dentistry
Authors: Konopka K. , Goslinski T.
Published: January 2009

Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemo-therapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly: the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis (PDD) of the malignant transformation of oral lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. Photodynamic antimicrobial chemotherapy (PACT) has been efficacious in the treatment of bacterial, fungal, parasitic, and viral infections. The absence of genotoxic and mutagenic effects of PDT is an important factor for long-term safety during treatment. PDT also represents a novel therapeutic approach in the management of oral biofilms. Disruption of plaque structure has important consequences for homeostasis within the biofilm. Studies are now leading toward selective photosensitizers, since killing the entire flora leaves patients open to opportunistic infections. Dentists deal with oral infections on a regular basis. The oral cavity is especially suitable for PACT, because it is relatively accessible to illumination.
Risk-Benefit Balance in the Use of Fluoride among Young Children
Authors: Do L.G. , Spencer A.J.
Published: January 2009

This study aimed to evaluate the risk-benefit balance of several fluoride exposures. Fluoride exposure history of randomly selected children was collected for calculation of exposure to fluoridated water, toothpaste, and other fluoride sources. We evaluated the risk-benefit balance of fluoride exposure by comparing dental fluorosis on maxillary central incisors, recorded at the time of the study with the use of the Thylstrup and Fejerskov Index, and deciduous caries experience, recorded at age six years, of the same group of South Australian children who were from 8 to 13 years old in 2002–03. Population Attributable Risk for fluorosis and Population Prevented Fraction for caries were estimated. Fluorosis prevalence was found to be 11.3%; caries prevalence, 32.3%; mean dmfs, 1.57 (SD 3.3). Exposure to fluoridated water was positively associated with fluorosis, but was negatively associated with caries. Using 1000-ppm-F toothpaste (compared with 400- to 550-ppm-F toothpaste) and eating/licking toothpaste were associated with higher risk of fluorosis without additional benefit in caries protection. Evaluation of the risk-benefit balance of fluoride exposure provides evidence to assist in the formulation of appropriate guidelines for fluoride use.
Origin of Interfacial Droplets with One-step Adhesives
Authors: Van Landuyt K.L. , Snauwaert J. , De Munck J. , Coutinho E. , Poitevin A. , Yoshida Y. , Suzuki K. , Lambrechts P. , Van Meerbeek B.
Published: January 2009

Contemporary one-step self-etch adhesives are often documented with interfacial droplets. The objective of this study was to research the origin of these droplets. Two HEMA-rich and one HEMA-free adhesive were applied to enamel and dentin, with the lining composite either immediately cured or cured only after 20 min. All one-step adhesives exhibited droplets at the interface; however, the droplets had two different origins. With the HEMA-free adhesives, droplets were located throughout the adhesive layer and were stable in number over time. With the HEMA-rich adhesives, the droplets were observed exclusively at the adhesive resin/composite interface, and their number increased significantly when the composite was delay-cured. Only the latter droplets caused a significant drop in bond strength after delayed curing. While the droplets in the HEMA-free one-step adhesives should be ascribed to phase separation, those observed with HEMA-rich adhesives resulted from water absorption from dentin through osmosis.
Influence of Contamination on Zirconia Ceramic Bonding
Authors: Yang B. , Wolfart S. , Scharnberg M. , Ludwig K. , Adelung R. , Kern M.
Published: January 2009

The removal of contaminants prior to the bonding of ceramics is critical for the clinical success of a long-term durable resin bond. This study tested the null hypotheses that there are no contaminants on the zirconia ceramic surface left after try-in simulation, and there are no influences of contamination and cleaning methods on zirconia ceramic bonding durability with 10-methacryloyloxy-decyl dihydrogenphosphate-containing composite resins. After saliva immersion and the use of a silicone disclosing agent, airborne-particle-abraded ceramic specimens were cleaned with acetone, 36% phosphoric acid, additional airborne-particle abrasion, or only water spray. Chemical analyses of specimen surfaces were performed by x-ray photoelectron spectroscopy. The influences of contamination and cleaning methods on ceramic bond durability were examined by tensile testing after 3 or 150 days’ water storage with 37,500 thermal cycles. Contamination, existing after try-in simulation as confirmed by chemical analysis, significantly reduced zirconia ceramic-resin bonds. Airborne-particle abrasion may be the most effective cleaning method.
A Mutation in the Enamelin Gene in a Mouse Model
Authors: Seedorf H. , Klaften M. , Eke F. , Fuchs H. , Seedorf U. , Hrabe de Angelis M.
Published: January 2009

Amelogenesis imperfecta is an inherited disorder affecting tooth enamel formation. We previously isolated a mouse strain with an amelogenesis imperfecta phenotype (ATE1 mice) from a dominant ethylnitrosourea screen and mapped the disease-causing defect to a 9-cM region of mouse chromosome 5. In the current study, we tested the hypothesis that there is a mutation in enamelin (ENAM) or ameloblastin (AMBN), both of which are located wihin the linkage region, by sequencing these two candidate genes. Analysis of our data shows that the amelogenesis imperfecta phenotype is linked to a C > T transition in exon 8 of the enamelin gene. The mutation predicts a C826T transition, which is present in the enamelin transcript and changes the glutamine (Gln) codon at position 176 into a premature stop codon (Gln176X). Conversely, no mutation could be detected in the ameloblastin gene. These results define the ATE1 mice as a model for local hypoplastic autosomal-dominant amelogenesis imperfecta (AIH2), which is caused by enamelin truncation mutations in humans.
Accumulation of Topical Naproxen by Cultured Oral Epithelium
Authors: Fitzgerald R.R. , Walters J.D.
Published: January 2009

Topically administered non-steroidal anti-inflammatory drugs (NSAIDs) inhibit periodontal bone loss, but little is known about the mechanism by which they penetrate oral epithelium. Active transporters could potentially play a role in this process. In this study, we used a cell line derived from oral epithelium to investigate a role for transporters and to characterize conditions that enhance epithelial penetration. Using fluorescence to monitor uptake, we demonstrated that SCC-25 cell monolayers transport naproxen with a Michaelis constant (Km) and maximum velocity (Vmax) of 164 μg/mL and 0.94 ng/min/μg protein, respectively. At steady state, the intra-cellular/extracellular concentration ratio was 3.4. Naproxen accumulation was more efficient at acidic pH than under neutral or alkaline conditions. Small proportions of glycerol, Pluronic F-127, and glucosylceramide enhanced naproxen entry. The individual and combined effects of glycerol and Pluronic F-127 were of lesser magnitude than those obtained with glucosylceramide or at pH 6.3. Thus, SCC-25 cells possess transporters for naproxen.
Autoimmunity to deltaNp63alpha in Chronic Ulcerative Stomatitis
Authors: Solomon L.W. , Neiders M.E. , Zwick M.G. , Kirkwood K.L. , Kumar V.
Published: January 2009

Chronic ulcerative stomatitis (CUS) is a recently described mucocutaneous condition in which patients experience chronic, painful, ulcerative lesions of the oral mucosa. CUS is diagnosed by immunofluorescence studies that demonstrate antinuclear antibodies. These autoantibodies are specific for a protein, deltaNp63alpha, which is normally expressed in basal cell nuclei of stratified squamous epithelia. The purpose of this study was to characterize the autoimmune response in CUS. Protein antigens were produced by in vitro transcription/translation of polymerase chain-reaction (PCR)-amplified cDNAs. We used immunoblotting and immunoprecipitation experiments with serum from CUS patients to examine the (1) antibody isotype, (2) immunogenic functional domains of the deltaNp63alpha antigen, and (3) cross-reactivity with homologous p53, p73, and p63 proteins. Results demonstrate CUS patient antibodies to deltaNp63alpha, and 52% of cases have circulating IgA isotype antibodies. The N-terminal and DNA-binding domains are the immunodominant regions, and antibody cross-reactivity with p53, p63, and p73 isoforms is limited.
Jaw Clenching: Muscle and Joint Forces, Optimization Strategies
Authors: Schindler H.J. , Rues S. , Türp J.C. , Schweizerhof K. , Lenz J.
Published: January 2009

Realistic masticatory muscle and temporomandibular joint forces generated during bilateral jaw clenching are largely unknown. To determine which clenching directions load masticatory muscles and temporomandibular joints most heavily, we investigated muscle and joint forces based on feedback-controlled electromyograms of all jaw muscles, lines of action, geometrical data from the skull, and physiological cross-sectional areas acquired from the same individuals. To identify possible motor control strategies, we applied objective functions. The medial pterygoid turned out to be the most heavily loaded muscle for all bite directions. Biting with accentuated horizontal force components provoked the highest loading within the medial and lateral pterygoids. The largest joint forces were also found for these bite directions. Conversely, the lowest joint forces were detected during vertical biting. Additionally, joint forces with a clear posterior orientation were found. Optimization strategies with the elastic energy as objective function revealed the best fit with the calculated results.
Depression as a Risk Factor for Denture Dissatisfaction
Authors: John M.T. , Micheelis W. , Steele J.G.
Published: January 2009

Depression is associated with impaired health outcomes. This study investigated whether there is a significant association between depression and dissatisfaction with dentures in older adults. In a population-based study (1180 adults aged 65–74 yrs), depression was measured by an abbreviated Geriatric Depression Scale. Denture dissatisfaction was assessed with a five-point Likert-type question ("very dissatisfied" to "very satisfied"). The depression-denture dissatisfaction association was analyzed with simple (dissatisfied vs. not dissatisfied outcome) and ordinal logistic regression (based on outcome’s full range). For each unit increase on the 15-point depression scale, the probability of denture dissatisfaction increased by 24% [95% confidence interval, 15–34%, P < 0.001 (simple logistic regression)] and the probability for higher levels on the five-point dissatisfaction scale increased by 16% [95% CI, 11–22%, P < 0.001 (ordinal logistic regression)], adjusted for potential confounding variables. The likely causal association in older adults has major implications for the evaluation of treatment effects and the demand for prosthodontic therapy.
Inorganic Polyphosphate: a Possible Stimulant of Bone Formation
Authors: Hacchou Y. , Uematsu T. , Ueda O. , Usui Y. , Uematsu S. , Takahashi M. , Uchihashi T. , Kawazoe Y. , Shiba T. , Kurihara S. , Yamaoka M. , Furusawa K.
Published: January 2009

Inorganic polyphosphates [Poly(P)] are often distributed in osteoblasts. We undertook the present study to verify the hypothesis that Poly(P) stimulates osteoblasts and facilitates bone formation. The osteoblast-like cell line MC 3T3-E1 was cultured with Poly(P), and gene expression and potential mineralization were evaluated by reverse-transcription polymerase chain-reaction. Alkaline phosphatase activity, von Kossa staining, and resorption pit formation analyses were also determined. The potential role of Poly(P) in bone formation was assessed in a rat alveolar bone regeneration model. Poly(P) induced osteopontin, osteocalcin, collagen 1α, and osteoprotegerin expression and increased alkaline phosphatase activity in MC 3T3-E1 cells. Dentin slice pit formation decreased with mouse osteoblast and bone marrow macrophage co-cultivation in the presence of Poly(P). Promotion of alveolar bone regeneration was observed locally in Poly(P)-treated rats. These findings suggest that Poly(P) plays a role in osteoblastic differentiation, activation, and bone mineralization. Thus, local poly(P) delivery may have a therapeutic benefit in periodontal disease.
The Birth of the Most Important 18th Century Dental Text: Pierre Fauchard’s Le Chirurgien Dentist
Authors: Spielman Andrew I.
Published: January 2009

Pierre Fauchard (1678–1761) is considered the father of modern dentistry. His seminal book, Le Chirurgien Dentiste, ou Traité des Dents (1728), is the discipline’s first complete work. During the five years preceding its publication (1723–1728), Pierre Fauchard sought the opinions, contributions, and “ approbation” (approval) of 19 of his colleagues: six physicians, 12 surgeons, and one dentist. The first and most important contributor to the manuscript was Jean Devaux, surgeon and mentor to Fauchard. The next six reviewers were illustrious physicians and scientists of the time: Philippe Hecquet, Jean-Claude Adrien Helvetius, Jean Baptiste Silva, Antoine DeJussieu, Raymond Jacob Finot, and Antoine Benignus Winslow. The subsequent 12 reviewers were all sworn-surgeons (certified by St. Côme), including a lone dentist, Laudumiey, surgeon-dentist to His Majesty, Philip V, King of Spain. Fauchard knew that for dentistry to be regarded as a learned profession, and perhaps for Fauchard to be recognized as its leader, he needed the support and approval of the establishment before publishing his book. This is an account of how he attained this endorsement.
VEGF: an Essential Mediator of Both Angiogenesis and Endochondral Ossification
Authors: Dai J. , Rabie A.B.M.
Published: January 2009

During bone growth, development, and remodeling, angiogenesis as well as osteogenesis are closely associated processes, sharing some essential mediators. Vascular endothelial growth factor (VEGF) was initially recognized as the best-characterized endothelial-specific growth factor, which increased vascular permeability and angiogenesis, and it is now apparent that this cytokine regulates multiple biological functions in the endochondral ossification of mandibular condylar growth, as well as long bone formation. The complexity of VEGF biology is paralleled by the emerging complexity of interactions between VEGF ligands and their receptors. This narrative review summarizes the family of VEGF-related molecules, including 7 mammalian members, namely, VEGF, placenta growth factor (PLGF), and VEGF-B, -C, -D, -E, and -F. The biological functions of VEGF are mediated by at least 3 corresponding receptors: VEGFR-1/Flt-1, VEGFR-2/Flk-1, VEGFR-3/Flt-4 and 2 co-receptors of neuropilin (NRP) and heparan sulfate proteoglycans (HSPGs). Current findings on endochondral ossification are also discussed, with emphasis on VEGF-A action in osteoblasts, chondroblasts, and chondroclasts/osteoclasts and regulatory mechanisms involving oxygen tension, and some growth factors and hormones. Furthermore, the therapeutic implications of recombinant VEGF-A protein therapy and VEGF-A gene therapy are evaluated. Abbreviations used: VEGF, Vascular endothelial growth factor; PLGF, placenta growth factor; NRP, neuropilin; HSPGs, heparan sulfate proteoglycans; FGF, fibroblast growth factor; TGF, transforming growth factor; HGF, hepatocyte growth factor; TNF, tumor necrosis factor; ECM, extracellular matrix; RTKs, receptor tyrosine kinases; ERK, extracellular signal kinases; HIF, hypoxia-inducible factor
Effects of Dentin Characteristics on Interfacial Nanoleakage
Authors: Yuan Y. , Shimada Y. , Ichinose S. , Sadr A. , Tagami J.
Published: January 2009

Water emanating from dentinal tubules during air-drying and light-curing of adhesives leads to entrapment of droplets at the resin-dentin interface and contributes to nanoleakage. This study tested the null hypothesis that characteristics of substrate dentin and type of adhesive used for bonding would not affect the occurrence of nanoleakage. Three self-etch adhesives were used to bond to 4 types of dentin with different characteristics in 12 groups. After silver challenge, nanoleakage percentage was measured within the hybrid layer of each sample. The deep dentin cut perpendicular to tubules always showed a significantly higher nanoleakage percentage compared with that of the other 3 types of dentin. The percentages of nanoleakage within the hybrid layers were not statistically different among adhesives. However, when bonding to deep perpendicular dentin, both all-in-one adhesives revealed more distinct nanoleakage within the adhesive layer compared with that achieved with Clearfil SE Bond, a two-step self-etch adhesive. The results did not support the null hypothesis.
Effects of Hydrogen Peroxide on Human Dentin Structure
Authors: Jiang T. , Ma X. , Wang Y. , Zhu Z. , Tong H. , Hu J.
Published: January 2009

It has been hypothesized that hydrogen peroxide (H2O2) bleaching may cause destruction of dentin by a mechanism of protein oxidation. However, to our knowledge, there has been no direct chemical evidence to validate this viewpoint. To investigate the effects of H2O2 on the structure of human dentin, we used Fourier transform infrared spectroscopy (FTIR) and attenuated total reflection (ATR) spectroscopy. Human intact dentin specimens were treated either with 30% H2O2 or Hanks’ balanced salt solution (HBSS). Significant differences were observed in ATR spectra parameters. Additionally, demineralized dentin specimens were also tested. They were completely dissolved in the H2O2, but remained intact in the 0.1 N HCl and HBSS. The results suggested that H2O2 attacked both the organic and mineral components of dentin. Destruction of the organic components was mainly because of the oxidizing ability of H2O2, while changes in the mineral components were probably due to its acidity.
Craniofacial Morphology in Myostatin-deficient Mice
Authors: Vecchione L. , Byron C. , Cooper G.M. , Barbano T. , Hamrick M.W. , Sciote J.J. , Mooney M.P.
Published: January 2009

GDF-8 (myostatin) is a negative growth regulator of skeletal muscle, and myostatin-deficient mice are hypermuscular. Muscle size and force production are thought to influence growth of the craniofacial skeleton. To test this relationship, we compared masticatory muscle size and craniofacial dimensions in myostatin-deficient and wild-type CD-1 control mice. Myostatin-deficient mice had significantly (p < 0.01) greater body (by 18%) and masseter muscle weight (by 83%), compared with wild-type controls. Significant differences (p < 0.05) were noted for cranial vault length, maxillary length, mandibular body length, and mandibular shape index. Significant correlations were noted between masseter muscle weight and mandibular body length (r = 0.68; p < 0.01), cranial vault length (r = −0.57; p < 0.05), and the mandibular shape index (r = −0.56; p < 0.05). Masticatory hypermuscularity resulted in significantly altered craniofacial morphology, probably through altered biomechanical stress. These findings emphasize the important role that masticatory muscle function plays in the ontogeny of the cranial vault, the maxilla, and, most notably, the mandible.
Inhibition of Trigeminal Respiratory Activity by Suckling
Authors: Koizumi H. , Nomura K. , Ishihama K. , Yamanishi T. , Enomoto A. , Kogo M.
Published: January 2009

The trigeminal motor system is involved in many rhythmic oral-motor behaviors, such as suckling, mastication, swallowing, and breathing. Despite the obvious importance of functional coordination among these rhythmic activities, the system is not well-understood. In the present study, we examined the hypothesis that an interaction between suckling and breathing exists in the brainstem, by studying the respiratory activity in trigeminal motoneurons (TMNs) during fictive suckling using a neonatal rat in vitro brainstem preparation. The results showed that fictive suckling, which was neurochemically induced by bath application of N-methyl-D,L-aspartate and bicuculline-methiodide, or by local micro-injection of the same drugs to the trigeminal motor nucleus, inhibited the inspiratory activities in both respiration TMNs and respiratory rhythm-generating neurons. Under patch-clamp recording, fictive suckling caused membrane potential hyperpolarization of respiration TMNs. We conclude that the brainstem preparation contains an inhibitory circuit for respiratory activity in the trigeminal motor system via the rhythm-generating network for suckling. Abbreviations: BIC, bicuculline methiodide; GABA, gamma aminobutyric acid; NMA, N-methyl-D,L-aspartate; NMDA, N-methyl-D-aspartate; and TMN, trigeminal motoneuron.
Histamine Amplifies Immune Response of Gingival Fibroblasts
Authors: Minami T. , Kuroishi T. , Ozawa A. , Shimauchi H. , Endo Y. , Sugawara S.
Published: January 2009

Histamine is an important mediator in immune responses, but it is unclear whether periodontal tissues express histamine receptors and are able to respond to histamine. We hypothesized that histamine, inflammatory cytokines, and bacterial components released in inflamed periodontal tissues may be synergistically involved in periodontitis. The present study showed that human gingival fibroblasts mainly express histamine receptor H1R, and responded to histamine to produce interleukin (IL)-8. Stimulation of gingival fibroblasts with tumor necrosis factor-α, IL-1α, and lipopolysaccharide markedly induced IL-8 production, and the IL-8 production was synergistically augmented in the presence of or pre-treatment with histamine. Selective inhibitors of mitogen-activated protein kinases (MAPKs), nuclear factor (NF)-κB, and phospholipase C (PLC) significantly inhibited the synergistic effect. These results indicate that histamine induces IL-8 production from gingival fibroblasts through H1R, and synergistically augments the inflammatory stimuli by amplification of the MAPK and NF-κB through H1R-linked PLC. Abbreviations used: HDC, histidine decarboxylase; LPS, lipopolysaccharide; IL, interleukin; TNF, tumor necrosis factor; HR, histamine receptor; PLC, phospholipase C; MAPK, mitogen-activated protein kinase; NF, nuclear factor; ERK, extracellular signal-related kinase; JNK, c-Jun N-terminal kinase; R, receptor; TLR, Toll-like receptor; α-MEM, alpha-minimum essential medium; FCS, fetal calf serum; RT-PCR, reverse-transcriptase polymerase chain-reaction; ELISA, enzyme-linked immunosorbent assay; SD, standard deviation; LDH, lactate dehydrogenase.
Dentin Matrix Protein 1 (DMP1): New and Important Roles for Biomineralization and Phosphate Homeostasis
Authors: Qin C. , D’Souza R. , Feng J.Q.
Published: January 2009

Previously, non-collagenous matrix proteins, such as DMP1, were viewed with little biological interest. The last decade of research has increased our understanding of DMP1, as it is now widely recognized that this protein is expressed in non-mineralized tissues, as well as in cancerous lesions. Protein chemistry studies have shown that the full length of DMP1, as a precursor, is cleaved into two distinct forms: the C-terminal and N-terminal fragments. Functional studies have demonstrated that DMP1 is essential in the maturation of odontoblasts and osteoblasts, as well as in mineralization via local and systemic mechanisms. The identification of DMP1 mutations in humans has led to the discovery of a novel disease: autosomal-recessive hypophosphatemic rickets. Furthermore, the regulation of phosphate homeostasis by DMP1 through FGF23, a newly identified hormone that is released from bone and targeted in the kidneys, sets a new direction for research that associates biomineralization with phosphate regulation.
Efficacy of Antibiotic Prophylactic Regimens for the Prevention of Bacterial Endocarditis of Oral Origin
Authors: Carmona I. Tomás , Diz Dios P. , Scully C.
Published: January 2009

Despite the controversy about the risk of individuals developing bacterial endocarditis of oral origin, numerous Expert Committees in different countries continue to publish prophylactic regimens for the prevention of bacterial endocarditis secondary to dental procedures. In this paper, we analyze the efficacy of antibiotic prophylaxis in the prevention of bacteremia following dental manipulations and in the prevention of bacterial endocarditis (in both animal models and human studies). Antibiotic prophylaxis guidelines remain consensus-based, and there is scientific evidence of the efficacy of amoxicillin in the prevention of bacteremia following dental procedures, although the results reported do not confirm the efficacy of other recommended antibiotics. The majority of studies on experimental models of bacterial endocarditis have verified the efficacy of antibiotics administered after the induction of bacteremia, confirming the efficacy of antibiotic prophylaxis in later stages in the development of bacterial endocarditis. There is no scientific evidence that prophylaxis with penicillin is effective in reducing bacterial endocarditis secondary to dental procedures in patients considered to be "at risk". It has been suggested that there is a high risk of severe allergic reactions secondary to prophylactically administered penicillins, but, in reality, very few cases have been reported in the literature. It has been demonstrated that antibiotic prophylaxis could contribute to the development of bacterial resistance, but only after the administration of several consecutive doses. Future research on bacterial endocarditis prophylactic protocols should involve the re-evaluation of the time and route of administration of antibiotic prophylaxis, and a search for alternative antimicrobials.
Does Psychological Stress Mediate Social Deprivation in Tooth Loss?
Authors: Sanders A.E. , Slade G.D. , Turrell G. , Spencer A.J. , Marcenes W.
Published: January 2009

It is unclear which theoretical dimension of psychological stress affects health status. We hypothesized that both distress and coping mediate the relationship between socio-economic position and tooth loss. Cross-sectional data from 2915 middle-aged adults evaluated retention of < 20 teeth, behaviors, psychological stress, and sociodemographic characteristics. Principal components analysis of the Perceived Stress Scale (PSS) extracted ’distress’ (a = 0.85) and ’coping’ (a =0.83) factors, consistent with theory. Hierarchical entry of explanatory variables into age- and sex-adjusted logistic regression models estimated odds ratios (OR) and 95% confidence intervals [95% CI] for retention of < 20 teeth. Analysis of the separate contributions of distress and coping revealed a significant main effect of coping (OR = 0.7 [95% CI = 0.7–0.8]), but no effect for distress (OR = 1.0 [95% CI = 0.9–1.1]) or for the interaction of coping and distress. Behavior and psychological stress only modestly attenuated socio-economic inequality in retention of < 20 teeth, providing evidence to support a mediating role of coping.
Acidic Proline-rich Protein Db and Caries in Young Children
Authors: Zakhary G.M. , Clark R.M. , Bidichandani S.I. , Owen W.L. , Slayton R.L. , Levine M.
Published: January 2009

Polymorphic, acidic proline-rich proteins (PRPs) in saliva influence the attachment of bacteria associated with caries. Our aims were to detect one of three acidic PRP alleles of the PRH1 locus ( Db) using polymerase chain-reaction (PCR) on genomic DNA, and to determine its association with caries. DNA was obtained from buccal swabs from Caucasian and African-American children, and their caries experience was recorded. PCR primers designed around exon 3 of the PRH1 locus gave a 416-base product representing Db and a 353-base product representing the other two alleles ( Pa or Pif). In Caucasians, Db gene frequency was 14%, similar to Db protein from parotid saliva. In African-Americans, however, it was 37%, 18% lower than Db from parotid saliva (reported previously). Compared with African-Americans, all Caucasians had significantly greater Streptococcus mutans colonization, but only Db-negative Caucasians had significantly more caries. Alleles linked to Db may explain racial differences in caries experience.
Effects of Direct and Indirect Bleach on Dentin Fracture Toughness
Authors: Tam L.E. , Noroozi A.
Published: January 2009

There are concerns that tooth-whitening procedures irreversibly damage tooth structure. We investigated the hypothesis that dental bleaches significantly affect dentin structural integrity. The objective was to evaluate the effects of peroxide bleaches on dentin fracture toughness. Compact test specimens, composed of human dentin, were used (n = 10/group). Bleach (16% or 10% carbamide peroxide or 3% hydrogen peroxide) or control material, containing 0.1% sodium fluoride, was applied directly or indirectly to dentin through enamel (6 hrs/day) for 2 or 8 weeks. Fracture toughness results were analyzed by ANOVA and Fisher’s LSD test (p < 0.05). There were significant decreases in mean fracture toughness after two- and eight-week direct (19–34% and 61–68%, respectively) and indirect (up to 17% and 37%, respectively) bleach application. The in vitro reduction in dentin fracture toughness caused by the application of peroxide bleaches was greater for the direct application method, longer application time, and higher bleach concentration.
Consequences of Viscoelastic Behavior in the Human Temporomandibular Joint Disc
Authors: Koolstra J.H. , van Eijden T.M.G.J.
Published: January 2009

The consequences of the viscoelastic behavior of the temporomandibular joint disc were analyzed in simulated jaw open-close cycles. It was hypothesized that viscoelasticity helps protect the underlying bone, while augmenting the smoothness of articular movements. Simulations were performed with a dynamic model of the masticatory system, incorporating the joints’ cartilaginous structures as Finite Element Models. A non-linear viscoelastic material model was applied for the disc. The apparent stiffness of the disc to principal stress was largest when the jaw was closed, whereas, with the Von Mises’ stress, it appeared largest when the jaw was open. The apparent stiffnesses appeared to be dependent on both the speed of the movements and the presence of a resistance between the teeth. It was concluded that the disc becomes stiffer when load concentrations can be expected. During continued cyclic motion, it softens, which favors smoothness of joint movement at the cost of damage prevention.