bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Monomer/Additive Release and Variability in Cytotoxicity of Light-curing Glass-ionomer Cements and Compomers
Authors: Geurtsen W. , Spahl W. , Leyhausen G.
Published: January 2009

In previous studies, light-cured glass-ionomer cements have been shown to evoke cytotoxic reactions. It was the purpose of this investigation (a) to determine the nature of the ingredients released into an aqueous medium from 2 light-cured glass-ionomer cements (GICs) and 3 compomers ; (b) to evaluate the cytotoxicity of these extracts; and (c) to correlate the extent of the cytotoxic effects with eluted substances. Specimens of 2 light-cured GICs and 3 compomers were prepared and extracted in distilled water or cell culture medium for 24 hrs (surface-liquid ratio 42.4 mm2/mL). The aqueous eluates were analyzed by gas chromatography/mass spectrometry (GC/MS). The relative amounts of the components released from various products were compared by means of an internal caffeine standard [%CF]. For evaluation of cytotoxic effects, permanent 3T3 fibroblasts were incubated with medium extracts for 24 hrs. In addition, the ED50 concentration of the photoinitiator diphenyliodoniumchloride (DPICI) was determined. In all extracts, several water-elutable organic substances were found: (Co)monomers (especially HEMA and ethylene glycol compounds), additives (e.g., camphorquinone and diphenyliodoniumchloride), and decomposition products. The extracts of 3 products inhibited cell growth only moderately, whereas the light-cured GIC Vitrebond and the compomer Dyract Cem revealed severe cytotoxic effects. Vitrebond liberated the initiator DPICI, whereas Dyract Cem segregated a relatively high quantity [2966 %CF] of the comonomer TEGDMA in comparison with the other products. The present data show that TEGDMA and DPICI may be regarded as the prime causes for cytotoxic reactions evoked by the investigated light-cured glass-ionomer cements or compomers. Therefore, leaching of these substances should be minimized or prevented.
Signal Transduction Pathways Involved in the Synergistic Stimulation of Prostaglandin Production by Interleukin-1β and Tumor Necrosis Factor a in Human Gingival Fibroblasts
Authors: Yucel-Lindberg T. , Nilsson S. , Modéer T.
Published: January 2009

Accumulating evidence indicates that prostaglandins play an important role in the pathogenesis of periodontal disease. In this study, the effects and interactions between IL-1β and TNFa on prostaglandin production and its regulation were investigated. The cytokines IL-1β and TNFa stimulated prostaglandin E2 (PGE2) and prostacyclin (PGI2) production in gingival fibroblasts. Simultaneous treatment of the cells with IL-1β and TNFa resulted in a synergistic stimulation of PGE2 and PGI2formation. IL-1β and, to a lesser extent, TNFa stimulated the release of 3H-arachidonic acid (3H-AA), and simultaneous addition of IL-1β and TNFa further increased the release of 3H-AA from pre-labeled gingival fibroblasts. Furthermore, IL-1β and, to a lesser extent, TNFa induced the expression of cyclooxygenase-2 (COX-2) mRNA. Simultaneous addition of IL-1β and TNFa synergistically enhanced COX-2 mRNA levels, accompanied by a corresponding stimulation of PGE2 synthesis. Neither IL-1β, TNFa, nor the combination of these two cytokines affected COX-1 mRNA levels. PMA, known to activate protein kinase C (PKC), enhanced the stimulatory effect of IL-1β, TNFa, and the combination on COX-2 mRNA levels accompanied by a corresponding increase in PGE2 production. The phospholipase A2 (PLA2) inhibitor, BPB, and the PKC inhibitor, BIS, reduced PGE2 production, whereas dexamethasone, indomethacin, and NS-398 completely abolished PGE2 production induced by IL-1β, TNFa, and the combination. The study indicates that the synergistic stimulation of prostaglandin production by IL-1β, and TNFa is mediated partly at the level of COX-2 and partly at the level of PLA2 and that PKC is involved in the signal transduction of the synergy between the two cytokines. The synergy between IL-1β and TNFa may play an important role in the inflammatory processes in gingival tissue in vivo.
Construction and Characterization of Human Salivary Histatin-5 Multimers
Authors: Situ H. , Tsai H. , Bobek L.A.
Published: January 2009

Human salivary histatin-5 (Hsn-5), a 24-amino acid polypeptide, is a potent candidacidal molecule. In this study, we have explored the following two hypotheses: More potent Hsn molecules may be achieved by duplication of the functional domain of Hsn-5 (C16, residues 9-24 of Hsn-5), and Hsn may act like other cationic peptides which aggregate and form channels across the target membrane. A PCR-based gene splicing by overlap extension (SOE) method was used to construct the DNA fragments encoding the following fusion molecules: Hsn-5-Hsn-5, Hsn-5—C16, and C16—C16. These constructs were expressed in E. coli, the proteins produced were purified, and their anticandidal activities as well as secondary structures were determined. Contrary to our hypotheses, results showed that none of the multimers possessed increased candidacidal activity. Specifically, C16—C16 and Hsn-5—C16 displayed candidacidal activity comparable with that of Hsn-5, while Hsn-5-Hsn-5 possessed significantly decreased candidacidal activity, yet all molecules retained an a-helical structure in a hydrophobic environment. Additionally, the circular dichroism data showed that Hsn-5 in an a-helical conformation does not aggregate in a hydrophobic environment, not even at 14- to 18-fold its physiological concentration. Our results suggest that the development of enhanced Hsn-5 molecules may not be achieved by duplication of its functional domain, and that Hsns may not act like other antimicrobial cationic peptides which aggregate and form channels across the target membrane.
Ceramic Whisker Reinforcement of Dental Resin Composites
Authors: Xu H.H.K. , Martin T.A. , Antonucci J.M. , Eichmiller EC
Published: January 2009

Resin composites currently available are not suitable for use as large stress-bearing posterior restorations involving cusps due to their tendencies toward excessive fracture and wear. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to reinforce dental resins with ceramic single-crystalline whiskers of elongated shapes that possess extremely high strength. A novel method was developed that consisted of fusing silicate glass particles onto the surfaces of individual whiskers for a two-fold benefit: (1) to facilitate silanization regardless of whisker composition; and (2) to enhance whisker retention in the matrix by providing rougher whisker surfaces. Silicon nitride whiskers, with an average diameter of 0.4 μm and length of 5 μm, were coated by the fusion of silica particles 0.04 μm in size to the whisker surface at temperatures ranging from 650°C to 1000°C. The coated whiskers were silanized and manually blended with resins by spatulation. Flexural, fracture toughness, and indentation tests were carried out for evaluation of the properties of the whisker-reinforced composites in comparison with conventional composites. A two-fold increase in strength and toughness was achieved in the whisker-reinforced composite, together with a substantially enhanced resistance to contact damage and microcracking. The highest flexural strength (195 ± 8 MPa) and fracture toughness (2.1 ± 0.3 MPa · m1/2 ) occurred in a composite reinforced with a whisker-silica mixture at whisker:silica mass ratio of 2:1 fused at 800°C. To conclude, the strength, toughness, and contact damage resistance of dental resin composites can be substantially improved by reinforcement with fillers of ceramic whiskers fused with silica glass particles.
Attrition, Eruption, and the Periodontium
Authors: Newman H.N.
Published: January 2009

Features of natural masticatory function, of physiological attrition, both occlusal and approximal, and of continuing tooth eruption in adult life need to be borne in mind in considering how the chronic inflammatory periodontal diseases and dental caries have become so widespread. Evidence is reviewed showing that teeth continue to erupt in adulthood, that natural masticatory function prevented plaque accumulation at the approximal risk site of onset of both CIPDs and caries, that epithelial attachment to cementum may be physiological, and that periodontal attachment studies must be age-related.
Extracts of Actinobacillus actinomycetemcomitans Induce Apoptotic Cell Death in Human Osteoblastic MG63 Cells
Authors: Morimoto Y. , Morimoto H. , Murata T. , Kobayashi S. , Ohba T. , Haneji T.
Published: January 2009

Whether an extracellular component of periodontal-disease-causing bacteria induces apoptotic cell death in bone-related cells is unknown. To study the effects on osteoblasts of extracts obtained from sonicated Actinobacillus actinomycetemcomitans and Prevotella intermedia, we cultured human osteoblastic cell lines MG63 and Saos-2 cells and mouse osteoblastic cell line MC3T3-E1 cells in the presence of such extracts. The addition of the extracts from Actinobacillus actinomycetemcomitans induced cell death in MG63 cells in a dose- and time-dependent fashion over the concentration range of 0.1 to 10 μg/mL. By contrast, the extracts from Prevotella intermedia did not induce cell death in these cells, even in the presence of 10 μg/mL protein. By using the Hoechst 33342 staining technique, we observed marked nuclear condensation and fragmentation of chromatin in MG63 cells treated with the extracts of Actinobacillus actinomycetemcomitans. DNA ladder formation, a hallmark of apoptosis, also was detected in MG63 cells treated with extracts from Actinobacillus actinomycetemcomitans. In MG63 cells, DNA ladder formation was dose-dependent, with a maximal effect at a concentration of 10 μg/mL, and time-dependent, from 12 to 48 hrs. However, the extracts from Prevotella intermedia did not induce DNA fragmentation in MG63, Saos-2, or MC3T3-E1 cells. The extracts from Actinobacillus actinomycetemcomitans did not induce cell death and DNA fragmentation in Saos-2 and MC3T3-E1 cells. Sonicated extracts of Actinobacillus actinomycetemcomitans that had been treated with heat and trypsin did not induce DNA ladder formation in MG63 cells, suggesting that the apoptosis-inducing factors are proteinaceous. Cycloheximide prevented the Actinobacillus actinomycetemcomitans-induced DNA ladder formation in MG63 cells in a dose-dependent fashion, suggesting that new gene transcription and protein synthesis are regulated for Actinobacillus actinomycetemcomitans-induced apoptosis in MG63 cells. Our results indicate that apoptosis in alveolar bone cells induced by Actinobacillus actinomycetemcomitans plays an important role in periodontal diseases.
Cumulative Correlations of Lysozyme, Lactoferrin, Peroxidase, S-IgA, Amylase, and Total Protein Concentrations with Adherence of Oral Viridans Streptococci to Microplates Coated with Human Saliva
Authors: Rudney J.D. , Hickey K.L. , Ji Z.
Published: January 2009

Redundancy refers to the observation that many salivary proteins exhibit similar properties in vitro. It is possible that bacterial adherence to salivary pellicle occurs as a cumulative effect of multiple proteins. This study determined the joint and individual contributions of salivary amylase, S-IgA, lysozyme, salivary peroxidase, lactoferrin, and total protein concentrations to adherence by oral viridans streptococci in microplates coated with whole saliva from 123 persons. Strains used were: Streptococcus gordonii Blackburn, 10558, Streptococcus mitis 10712, 903, Streptococcus oralis 10557, 9811, and Streptococcus sanguis 10556, 13379. Rabbit antibody against 13379 was used for the detection of adherence. This antibody cross-reacted with all strains. Absorbance was standardized against saliva pooled from five donors. All saliva samples had been previously assayed for amylase, lactoferrin, lysozyme, secretory IgA, peroxidase, and total protein. Adherence scores for all strains except 13379 were significantly and positively correlated. Salivas binding high or low levels of one strain tended to bind others correspondingly. Multiple regression indicated significant contributions to 10558 adherence from total protein and lactoferrin (positive), and peroxidase and lysozyme (negative). Similar results were obtained for Blackburn and 903. Significant individual correlations were seen for 9811 and total protein (positive), 10557 and peroxidase (negative), and 13379 and lactoferrin (negative). Salivas with high adherence scores contained significantly more protein and lactoferrin, and significantly less peroxidase, than salivas with low adherence scores. These findings support the hypothesis that multiple proteins contribute to the adherence of streptococcal strains in vivo.
The Optimum Time to Initiate Habitual Xylitol Gum-chewing for Obtaining Long-term Caries Prevention
Authors: Hujoel P.P. , Mäkinen K.K. , Bennett C.A. , Isotupa K.P. , Isokangas P.J. , Allen P. , Makinen P.-L.
Published: January 2009

Habitual xylitol gum-chewing may have a long-term preventive effect by reducing the caries risk for several years after the habitual chewing has ended. The goal of this report was (1) to determine if sorbitol and sorbitol/xylitol mixtures provide a long-term benefit, and (2) to determine which teeth benefit most from two-year habitual gum-chewing-those erupting before, during, or after habitual gum-chewing. Children, on average 6 years old, chewed gums sweetened with xylitol, sorbitol, or xylitol/sorbitol mixtures. There was a "no-gum" control group. Five years after the two-year program of habitual gum-chewing ended, 288 children were re-examined. Compared with the no-gum group, sorbitol gums had no significant long-term effect (relative risk [RR], 0.65; 95% confidence interval [c.i.], 0.39 to 1.07; p < 0.18). Xylitol gum and, to a lesser extent, xylitol/sorbitol gum had a long-term preventive effect. During the 5 years after habitual gum-chewing ended, xylitol gums reduced the caries risk 59% (RR, 0.41; 95% c.i., 0.23 to 0.75; p < 0.0034). Xylitol-sorbitol gums reduced the caries risk 44% (RR, 0.56; 95% c.i., 0.36 to 0.89; p < 0.02). The long-term caries risk reduction associated with xylitol strongly depended on when teeth erupted (p < 0.02). Teeth that erupted after 1 year of gum-chewing or after the two-year habitual gum use ended had long-term caries risk reductions of 93% (p < 0.0054) and 88% (p < 0.0004), respectively. Teeth that erupted before the gum-chewing started had no significant long-term prevention (p < 0.30). We concluded that for long-term caries-preventive effects to be maximized, habitual xylitol gum-chewing should be started at least one year before permanent teeth erupt.
Intracellular Interleukin-1α Production in Human Gingival Fibroblasts is Differentially Regulated by Various Cytokines
Authors: Kobayashi M. , Okada N. , Okamatsu Y. , Mugikura K. , Nishihara T. , Hanazawa S. , Kitano S. , Hasegawa K.
Published: January 2009

Interleukin-1 (IL-1) may play a critical role in immune and inflammatory responses in inflamed gingiva, and it is synthesized by a wide variety of host cells. In this study, we examined the regulatory effects of various cytokines on bioactive membrane IL-1 and intracellular IL-1α production in cultured human gingival fibroblasts (HGF). Recombinant human (rh) IL-lp stimulated membrane IL-1 activity, which was mainly attributed to IL-la. rhIL-1β and rh tumor necrosis factor (TNF)-a stimulated HGF to produce intracellular IL-la, whereas rh interleukin-6 (IL-6), rh interleukin-4 (IL-4), and rh interferon (IFN)-γ did not do so. Intracellular IL-la production induced by rhIL-1β or rhTNF-a may be partially related to protein kinase C (PKC) activation, because rhIL-1β or rhTNF-a-induced intracellular IL-la production was stimulated by pre-treatment with 12- o-tetradecanoylphorbol 13-acetate (TPA), a PKC activator, but was suppressed by the pre-treatment with 1-(5-isoquinoline-sulfonyl) -2-methylpiperazine dihydrochloride (H-7), which is a PKC inhibitor. rhIL-4 inhibited rhIL-1β- or rhTNF-a-induced intracellular IL-la production, but rhIL-6 had no effect on this production. Pre-treatment with rh IFN-γ remarkably enhanced intracellular IL-la production induced by subsequent treatment with rhIL-1β or rhTNF-a. Simultaneous treatment with rhIFN-γ and rhIL-1β inhibited rhIL-1β-induced intracellular IL-la production, but co-treatment with rhIFN-γ and rhTNF-a enhanced rhTNF-a-induced intracellular IL-la production. These results suggest that in inflamed gingiva, pro-inflammatory cytokines such as IL-1β and TNF-a may induce bioactive intracellular IL-la production in human gingival fibroblasts and that this production can be differentially modulated by T-cell-derived cytokines such as IFN-γ or IL-4.
Effects of Dentin Depth and Cavity Configuration on Bond Strength
Authors: Yoshikawa T. , Sano H. , Burrow M.F. , Tagami J. , Pashley D.H.
Published: January 2009

During polymerization of resin composites, shrinkage stresses compete with resin-dentin bonds in a manner that can cause failure of the bond, depending upon the configuration of the cavity, its depth, and the restorative technique. The hypothesis tested in this study was that the effect of cavity configuration (C) and remaining dentin thickness (RDT) influence resin bond strength to the dentin of Class I cavity floors. The occlusal enamel was ground to expose a flat superficial dentin surface as a control (superficial dentin, C-factor = 1) in human extracted third molars. Cavities 3 mm long x 4 mm wide were prepared to a depth 2 mm below the ground dentin surfaces (deep dentin within cavity floor, C-factor = 3). To assess the relationship between C-factor and RDT, we removed the walls of cavities, making a deep flat surface for bonding (deep dentin, C-factor = 1). The teeth were restored with either Clearfil Liner Bond II (LB II), One-Step (OS), or Super-Bond D Liner (DL), followed by Clearfil Photo Posterior resin composite. After 24 hrs' storage in water, the teeth were sectioned vertically into 3 or 4 slabs (0.7 mm thick) and trimmed for the micro-tensile bond test so that we could determine the strength of the resin bonds to the pulpal floor. All groups gave high bond strengths to superficial dentin, but OS and DL gave significantly lower bond strengths to flat deep dentin when the C-factor was 1. When the C-factor was increased to 3 by the creation of a three-dimensional cavity preparation, the bond strengths of all materials fell (range, 21 to 35%), but the difference was significant (p < 0.05) only with DL. SEM observations of failure patterns showed that specimens with high bond strengths tended to exhibit cohesive failures within the hybrid layer, while specimens exhibiting low bond strengths showed failures at the top of the hybrid layer. Some adhesives do not bond well to deep dentin, making them more susceptible to polymerization shrinkage stress that develops in cavities with high C-factors.
Keratin 19 Downregulation by Oral Squamous Cell Carcinoma Lines Increases Invasive Potential
Authors: Crowe D.L. , Milo G.E. , Shuler C.E.
Published: January 2009

Squamous cell carcinoma (SCC) of the head and neck is the sixth most frequent cancer worldwide. The survival rate is among the lowest of the major cancers and has not improved significantly in the past two decades. Extensive local invasion and regional lymph node metastasis are, in large part, responsible for the poor clinical outcome of these tumors. Keratin intermediate filaments are the most abundant cytoskeletal proteins in SCCs and regulate the migration of normal and transformed epithelial cells. Previous studies have shown that expression of the 40-kDa keratin K19 is dysregulated in SCCs arising from oral epithelium. Immunohistochemical experiments demonstrated that, while normal epithelium and dysplastic lesions expressed abundant K19 protein, invasive SCCs exhibited a patchy or negative staining pattern. We subsequently determined that K19 expression was consistently downregulated in seven SCC lines compared with normal epithelium. We therefore wanted to determine if K19 downregulation affected the invasive phenotype of these cells. We found that SCC lines which do not express K19 are significantly more invasive in vitro than those which retain expression of this gene. Stable expression of the K19 cDNA in K19 negative cell lines altered cell morphology and intercellular adhesiveness, and significantly decreased the number of cells able to migrate through a reconstituted basement membrane. Reduced invasiveness was not due to decreased metalloproteinase activity in the K19-expressing clones. We conclude that K19 overexpression in oral SCCs decreases their invasive potential by diminishing migratory capability.
Genetic Linkage of the Dentinogenesis Imperfecta Type III Locus to Chromosome 4q
Authors: MacDougall M. , Jeffords L.G. , Gu T.T. , Knight C.B. , Frei G. , Reus B.E. , Otterud B. , Leppert M. , Leach R.J.
Published: January 2009

Dentinogenesis imperfecta type III (DGI-III) is an autosomal-dominant disorder of dentin formation which appears in a tri-racial southern Maryland population known as the "Brandywine isolate". This disease has suggestive evidence of linkage to the long arm of human chromosome 4 (LOD score of 2.0) in a family presenting with both juvenile periodontitis and DGI-III. The purpose of this study was to screen a family presenting with only DGI-III to determine if this locus was indeed on chromosome 4q. Furthermore, we wanted to determine if DGI-III co-localized with dentinogenesis imperfecta type II (DGI-II), which has been localized to 4q21-q23. Therefore, a large kindred from the Brandywine isolate was identified, oral examination performed, and blood samples collected from 21 family members. DNA from this family was genotyped with 6 highly polymorphic markers that span the DGI-II critical region of chromosome 4q. Analysis of the data yielded a maximum two-point LOD score of 4.87 with a marker for the dentin matrix protein 1 (DMP1) locus, a gene contained in the critical region for DGI-II. Our results demonstrated that the DGI-III locus is on human chromosome 4q21 within a 6.6 cM region that overlaps the DGI-II critical region. These results are consistent with the hypothesis that DGI-II is either an allelic variant of DGI-III or the result of mutations in two tightly linked genes.
Effect of Moist vs. Dry Bonding to Normal vs. Caries-affected Dentin with Scotchbond Multi-Purpose Plus
Authors: Nakajima M. , Sano H. , Zheng L. , Tagami J. , Pashley D.H.
Published: January 2009

Recent research in dentin bonding demonstrated the superiority of moist bonding over dry bonding on normal dentin, but it is unclear if this technique is also superior in bonding to caries-affected dentin. The purpose of this study was to evaluate the SEM appearance and bond strength of Scotchbond Multi-Purpose Plus (SMPP) to normal vs. caries-affected dentin bonded under moist vs. dry conditions, with and without polyalkenoic acid in the primer. Extracted carious human third molars were ground down by means of 600-grit SiC paper until the carious dentin no longer stained with caries detector solution. The flat surfaces were then primed, bonded, and built up with resin composite. After soaking in water for 1 day, the teeth were serially sectioned vertically into 5 or 6 slabs 0.7 mm thick. The bonded caries-affected areas were isolated by means of an ultrafine diamond bur to create an hourglass configuration with a cross-sectional area of 0.9 mm2. Bonded normal dentin was isolated the same way. Each specimen was attached to a Bencor device and tested in tension to failure. SMPP bonds to dry, normal dentin were only half as strong (21 ± 10 MPa, x ± SD) as those made to moist, normal dentin (42 ± 9 MPa, p < 0.01). There was no significant difference between bonds made to normal vs. caries-affected dentin by means of the moist technique (42 ± 9 vs. 48 ± 4 MPa, respectively). Removal of the polyalkenoic acid from the primer lowered (p < 0.05) the bond strength of SMPP to caries-affected dentin (38 ± 8 MPa). The benefits of moist bonding extend to caries-affected dentin. The polyalkenoic acid in the SMPP primer contributes to the high bond strength that can be achieved to caries-affected dentin.
Longevity of Extensive Class II Open-sandwich Restorations with a Resin-modified Glass-ionomer Cement
Authors: van Dijken J.W.V. , Kieri C. , Carlén M.
Published: January 2009

Several new techniques have been introduced for use in the esthetic restoration of posterior cavities to substitute for the presumed toxicity of amalgam. Composite-laminated glass-ionomer cement restorations, the sandwich technique, have been recommended for caries-risk patients. Clinical evaluation of the use of conventional glass-ionomer cements in the open-sandwich restoration has shown a high failure rate. The aim of this study was to evaluate the durability and cariostatic effect of a modified open-sandwich restoration utilizing a resin-modified glass-ionomer cement (RMGIC) in large cavities. The materials consisted of 274 mostly extensive Class II Vitremer/Zl00 restorations performed by four dentists in 168 adults. Six experimental groups were investigated. In four groups a thick and in two groups a thin layer of cement was placed. Cavity conditioning before application of the RMGIC self-etching primer was done in 3 groups with polyacrylic acid and in one group with maleic acid; in two groups, only water rinsing was performed. The restorations were evaluated at baseline and after 6, 12, 24, and 36 months according to modified USPHS criteria (van Dijken, 1986). After 3 years, 239 restorations were evaluated. Twelve (5%) were estimated as non-acceptable. Two were replaced, and seven were repaired with resin composite. Tooth fractures were observed in 2.5%. Slight erosion of the RMGIC part was seen in 4%, and in one case operative treatment was indicated. Post-operative sensitivity was reported for 9 teeth. Forty-three percent of the patients were considered as caries-risk patients. Only one restoration showed secondary caries. The three-year results indicated that the modified open-sandwich restoration is an appropriate alternative to amalgam including extensive restorations.
92K-GL (MMP-9) and 72K-GL (MMP-2) are Produced in vivo by Human Oral Squamous Cell Carcinomas and can Enhance FIB-CL (MMP-1) Activity in vitro
Authors: Pickett K.L. , Harber G.J. , DeCarlo A.A. , Louis P. , Shaneyfelt S. , Windsor L.J. , Bodden M.K.
Published: January 2009

Previous studies have shown a correlation between the production of certain matrix metalloproteinases (MMPs), especially the gelatinases, by malignant tumors and the progression of these cancers as they invade and metastasize through the extracellular matrix and basement membranes. However, very few of these studies examined this relationship in human oral cancer in vivo, and none addressed the issue of how combinations of the MMPs may further enhance tumor progression. To determine which MMPs are produced in vivo by human oral cancers, we used specific anti-human-MMP antibodies and immunocytochemistry (ICC) methods to examine oral cancer tissue specimens from 20 surgery patients. The ICC data indicated that 72-kDa (72K-GL) and 92-kDa gelatinases (92K-GL) were produced in vivo by discreet clusters of tumor cells and by stromal fibroblasts, vascular endothelial cells (72K-GL), and PMNs (92K-GL). Some stromal fibroblasts near the tumors also appeared to produce fibroblast-type collagenase (FIB-CL), a finding confirmed by Western blot analysis of media conditioned by oral tumor explant cultures. ICC results indicated that 5 of the 20 tumors coincidentally produced all three MMPs. To examine how the two gelatinases and FIB-CL may interact in vitro to degrade fibrillar type I collagen, a major structural component of the extracellular matrix, we used a modified FIB-CL activity assay. Combinations of the gelatinases and FIB-CL were incubated with a 3H-collagen substrate, with the results compared with the combination of stromelysin-1 (SL-1, a superactivator of FIB-CL) and FIB-CL. 92K-GL caused a nine-fold increase in collagenase activity, equivalent to SL-1, while 72K-GL produced a four-fold increase. These results indicate that human oral cancers produce 92K-GL, 72K-GL, and FIB-CL in vivo and that the gelatinases and FIB-CL cooperate to enhance collagen degradation greatly in vitro.
Structure/Function Analysis of Human Cystatin SN and Comparison of the Cysteine Proteinase Inhibitory Profiles of Human Cystatins C and SN
Authors: Hiltkel T.R. , Lee T.-C. , Bobekl L.A.
Published: January 2009

Cystatins are reversible, competitive inhibitors of cysteine proteinases. Their inhibitory profiles, as well as their affinities for target enzymes, vary with different cysteine proteinases. Human cystatin C and salivary cystatin SN are 120-and 121-amino-acid (a.a.) proteins, respectively, and both contain 2 disulfide bonds. In this study, we examined the structure/function relationship of cystatin SN with respect to the inhibition of papain, with particular emphasis on the role of cystatin SN's cysteine residues, and addressed the inhibitory profiles of these two human cystatins on several cysteine proteinases (papain, clostripain, and calpain II). The full-length recombinant cystatin C and cystatin SN, and cystatin SN variants (C-truncated [C-tr; a.a. 1-102], A56-60 deletion, cysteine 74 → serine [C74S], cys 84 → serine [C84S], cysteine 98 → serine [C98S], and cysteine 118 → serine [C118S]) were cloned, expressed, and produced in the pET30(b) and pGEX2T Escherichia coli expression systems. All recombinant proteins were tested for the inhibition of papain, and the full-length proteins were also tested for the inhibition of clostripain and calpain II. The secondary structures of the cystatins were also determined and compared. The results showed that the full-length cystatin C and cystatin SN, and the cystatin SN variants C98S and C118S inhibited the activity of papain. However, cystatin SN C-tr and A56-60 variants exhibited no inhibitory activity toward papain, while the cystatin SN variants C74S and C84S exhibited slight inhibition at higher concentrations. These results suggested that in the inhibition of papain by cystatin SN, the first disulfide loop is more important than the second. In addition, cystatin C, but not cystatin SN, inhibited calpain II, while neither cystatin inhibited clostripain, and these results, in conjunction with those from other studies, indicated that cystatin C is a broader-spectrum inhibitor of cysteine proteinases than cystatin SN.
Biodegradation of Commercial Dental Composites by Cholesterol Esterase
Authors: Santerre J.P. , Shajii L. , Tsang H.
Published: January 2009

The research literature suggests that current dental polymeric composites are not chemically inert at the material/biological interface. Several studies have investigated the process of "biodegradation" on dental composites in the presence of enzymes, by monitoring changes in weight loss and surface hardness properties. However, it is hypothesized that these methods can provide an erroneous measure of biochemically induced degradation, since they are less sensitive to molecular events and lack the ability to provide chemical information. Knowledge of the latter is important because it relates to the biological significance of biodegradation, i.e., the identification and quantification of released compounds that may be capable of influencing cell, bacteria, or enzyme function. It was the objective of this study to compare three methods (weight loss, surface micro-hardness, and liquid chromatography combined with mass spectrometry) for their ability to measure the effect of enzyme-induced biodegradation on three commercial composite resin materials. The enzyme was cholesterol esterase, and the composites were Silux Plus XL, Z100 A2 (3M), and TPH XL (L.D. Caulk). Biodegradation was readily detected by liquid chromatography, and its sensitivity was shown to be substantially greater than that of weight loss or surface hardness measurements, although surface hardness measurements did show some agreement with liquid chromatography data. The data also indicated that the levels and distribution of released degradation products can vary substantially from one product to the next, and that this merits further investigation if the potential impact of different commercial restorative materials on cell and bacteria function is to be assessed.
A Within-subject Comparison of Mandibular Long-bar and Hybrid Implant-supported Prostheses: Evaluation of Masticatory Function
Authors: Tang L. , Lund J.P. , Taché R. , Clokie C.M.L. , Feine J.S.
Published: January 2009

Sixteen edentulous subjects participated in a within-subject crossover clinical trial to test the hypotheses that a long-bar overdenture attached to 4 implants gives greater patient satisfaction and masticatory efficiency than a two-implant hybrid overdenture. All subjects were given a new maxillary conventional denture. Ten received mandibular long-bar overdentures first and six the hybrid overdentures. Two months later, psychometric assessments and functional tests were repeated 3 times at one-week intervals. The mandibular prosthesis was then changed, and recordings were repeated after another 2 months. Mandibular movements and electromyographic activity of jaw muscles were recorded while subjects chewed standard-sized pieces of 5 foods: bread, cheese, apple, sausage, and carrot. Measurements included masticatory time, cleaning time (the time between the end of mastication and the last swallow), and duration and amplitude of masticatory cycles and phases. Multilevel analyses were performed. No significant differences in masticatory time were found between prostheses for any test food. However, cleaning time for carrot [estimated mean of difference (A) ± SE: 1.6 sec ± 0.7] and bread (A = 1.0 sec ± 0.4) was slightly but significantly longer for subjects wearing long-bar overdentures. Cycle duration was longer with the long-bar overdenture only for subjects chewing carrot. The opening phase was shorter and the closing phase longer with the long-bar overdenture for almost all test foods. Vertical amplitude was significantly less with the long-bar overdenture for cheese (A = -2.6 mm ± 1.1), apple (A = -2.6 mm ± 1.0), and sausage (A = -2.9 mm ± 1.3). These results suggest that mastication with the 2 prostheses is equally efficient, although clearance of some foods from the mouth is longer with the long-bar overdentures. They also indicate that patients adapt their masticatory movements to the characteristics of different prostheses.
Co-increase of Nerve Fibers and HLA-DRand/or Factor-XIIIa-expressing Dendritic Cells in Dentinal Caries-affected Regions of the Human Dental Pulp: An Immunohistochemical Study
Authors: Sakurai K. , Okiji T. , Suda H.
Published: January 2009

Neuro-immune interaction has been suggested to play some modulatory role in the immunodefense of the dentin/pulp complex. In this study, we performed a simultaneous immunohistochemical observation of neural elements and pulpal dendritic cells (PDCs) on human carious teeth, to obtain morphological evidence for neuro-immune interaction in response to dentinal tubule-derived carious stimuli. Human third molars bearing a pulp-exposure-free caries lesion were studied. Immunoperoxidase staining was performed with anti-HLA-DR, anti-coagulation factor XIIIa, and anti-CD14 as PDC markers, and anti-low-affinity nerve growth factor receptor (NGFR), anti-protein gene products 9.5, and anti-calcitonin gene-related peptide as nerve markers. The carious teeth usually exhibited localized accumulation of both PDCs and nerve fibers immunoreactive to each marker, in the para-odontoblastic region corresponding to the pulpal end of carious dentinal tubules. Semi-quantitative digital densitometry revealed that pixel numbers corresponding to factor-XIIIa- and NGFRimmunoreactivity were significantly higher in the carious regions than those in the non-carious regions of the same teeth as well as those in the corresponding regions of intact teeth. Classification of specimens with respect to caries depth showed that the co-increase was most apparent in teeth with superficial caries. The increase of PDCs was less pronounced in carious teeth with reparative dentin. These findings suggest that both pulpal nerves and PDCs respond promptly and actively to dentinal tubule-derived carious stimuli. The synchronized accumulation of the two structures suggests an increased opportunity for neuro-immune interaction that may be of significance in the modulation of pathological processes in the dental pulp.
Autocrine Regulation of Osteoclast Formation and Bone Resorption by IL-1α and TNFα
Authors: Tani-Ishii N. , Tsunoda A. , Teranaka T. , Umemoto T.
Published: January 2009

Bone resorption is regulated by the cytokines within marrow cells that mediate osteoclast formation and activation. IL-1 and TNF induce bone resorption by stimulating the production of osteoclast-like multinucleated cells and by increasing the bone-resorbing activity of formed osteoclasts. This study was designed to detect IL-1 and TNF in osteoclasts in vitro and to determine whether these cytokines up-regulate osteoclast differentiation and bone resorption. The production of IL-1α, -β, and TNFa, β in osteoclasts was examined immunohistochemically and by in situ hybridization. In the co-culture of C57BL/6N mouse bone marrow and MC3T3-G2/PA6 cells, a colony of osteoclasts formed, and IL-1α and TNFa were detected. However, IL-1β and TNF β were not detected. To investigate the role of IL-1α and TNFα from osteoclasts, we enumerated TRAP-positive cells and measured the resorption pit areas in the presence of antibodies against IL-1α and TNFα. The addition of antibodies against IL-1α and TNFα to the co-culture system decreased the number of TRAP-positive colonies at seven days after incubation (anti-IL-1α, 25.0 ± 2.3%; anti-TNFα, 41.7 ± 3.7%; anti-IL-1α + anti-TNFα, 40.5 ± 1.3%; and control, 100%), and the ratio of mononuclear to multinuclear cells had changed (anti-IL-1α, 90:10; anti-TNFα, 75:25; anti-IL-1α+ anti-TNFα, 88:12; and control, 60:40). The total pit areas per dentin slice also decreased with the addition of antibodies (anti-IL-1α, 28,828; anti-TNFα, 49,249; anti-IL-1α + anti-TNFα, 30,685; and control, 303,139 mm2). These results suggest that local production of IL-la and TNFα by osteoclasts is an important mechanism for regulating the osteoclast differentiation and bone resorptive process.
Recombinant Human Bone Morphogenetic Protein-2 Stimulates Osteoblastic Differentiation in Cells Isolated from Human Periodontal Ligament
Authors: Kobayashi M. , Takiguchi T. , Suzuki R. , Yamaguchi A. , Deguchi K. , Shionome M. , Miyazawa Y. , Nishihara T. , Nagumo M. , Hasegawa K.
Published: January 2009

Periodontal ligament cells may play an important role in the successful regeneration of the periodontium. We investigated the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2), one of the most potent growth factors that stimulates osteoblast differentiation and bone formation, on cell growth and osteoblastic differentiation in human periodontal ligament cells (HPLC) isolated from four adult patients. rhBMP-2 induced no significant changes in cell growth in any of the HPLCs. rhBMP-2 at concentrations over 50 ng/mL significantly stimulated alkaline phosphatase (ALPase) activity and parathyroid hormone (PTH)-dependent 3', 5'-cyclic adenosine monophosphate accumulation, which are early markers of osteoblast differentiation, in the HPLCs. rhBMP-2 (500 ng/mL) also slightly enhanced the level of PTH/PTH-related peptide receptor mRNA expression in these cells. While interleukin-1β enhanced ALPase activity stimulated with rhBMP-2, tumor necrosis factor-a inhibited the rhBMP-2-stimulated activity. Interleukin-6 induced no significant changes in ALPase activity stimulated with rhBMP-2. Although HPLCs, whether treated with rhBMP-2 or not, could not produce measurable amounts of osteocalcin, which is a marker of more mature osteoblasts, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] induced osteocalcin mRNA expression and protein synthesis in these cells. rhBMP-2 inhibited 1,25(OH)2D3-induced osteocalcin synthesis in HPLCs at both the mRNA and protein levels. These results suggest that rhBMP-2 provides an anabolic effect on periodontal regeneration by stimulation of osteoblastic differentiation in human periodontal ligament cells, and that this stimulatory effect is differentially modulated by inflammatory cytokines during the course of periodontal regeneration.
Saliva, Salivary Micro-organisms, and Oral Health in the Home-dwelling Old Elderly-A Five-year Longitudinal Study
Authors: Narhi T.O. , Kurki N. , Ainamo A.
Published: January 2009

High scores of chair-side salivary microbial tests have been found to be related to an increased prevalence and incidence of coronal and root caries. Many elderly face an increased risk of the growth of oral microbes, and previous studies have reported high salivary microbial counts in elderly populations. The aim of this follow-up study was to compare, at five-year intervals, stimulated salivary flow rates with the numbers of selected salivary micro-organisms (mutans streptococci, lactobacilli, and yeasts) in a group of home-dwelling elderly in Helsinki. A further aim was to study the influence of baseline microbial counts on five-year root caries increments and rates of tooth loss. The baseline study population was comprised of 270 subjects who were all participants in the population-based Helsinki Aging Study. Salivary flow rates and microbial conditions were determined as part of their dental examination at the Institute of Dentistry, University of Helsinki, in 1990-1991. Of these subjects, 110 underwent a follow-up examination in 1995-1996. Commercially available kits (Dentocult SM strip mutans® for mutans streptococci, Dentocult LB® for lactobacilli, and Oricult N® for yeasts) were used for the enumeration of micro-organisms, after the collection of paraffin-wax-stimulated whole saliva. The stimulated whole saliva flow rates of the subjects were significantly lower at the follow-up than at baseline (paired t test, difference -0.16 mL/min; p < 0.05), whereas buffer capacity was higher (paired t test, difference 0.19 on a three-unit scale; p < 0.05). Apart from lower salivary lactobacilli counts at follow-up (paired t test, difference -0.44 CFUs/mL of saliva; p < 0.001), no changes were found in salivary microbial levels. Salivary microbial counts were clearly associated with the subjects' dentition types: More denture-wearers had high microbial counts than persons with natural dentitions. None of the salivary factors correlated with the root caries incidence or the number of teeth lost during the five-year follow-up.
Variations in Dental Anxiety among Middle-aged and Elderly Women in Sweden: A Longitudinal Study between 1968 and 1996
Authors: Hägglin C. , Berggren U. , Hakeberg M. , Hallstrom T. , Bengtsson C.
Published: January 2009

Cross-sectional studies have shown that older individuals are significantly less dentally anxious than younger ones. However, research has not been able to show if this is a cohort effect or an effect of fear declining with age. If it is a cohort effect, dental anxiety among the elderly may pose a greater-than-expected problem for the providers of dental services. With the exception of longitudinal studies in children and a three-year follow-up on adults, no truly longitudinal epidemiological studies concerning dental anxiety have been performed. The aim of this project was to investigate how dental anxiety changes with aging. In a longitudinal population study of women in Goteborg, Sweden, starting in 1968, 1462 women aged 38 to 54 participated. A representative subsample of 778 women took part in a psychiatric examination where an investigation of dental anxiety was included. The same questions were also included when these women were re-examined in 1974,1992, and 1996. Three hundred seventy-five women were still eligible for investigation in 1996. In 1968-69, 48 (12.8%) of the participating women assessed themselves as "very afraid" or "terrified" when visiting the dentist, and in 1996 the frequency was 21 (5.6%) among the same women. In 1968-69, 180 women (48%) reported no dental anxiety when visiting the dentist, and 28 years later the frequency was 230 (61%). In the three youngest age groups, dental anxiety decreased significantly (p < 0.001) over the 28-year period. Older compared with younger women reported significantly less dental anxiety, and this was an age effect rather than a cohort effect. Thus, this longitudinal study supported the hypothesis that dental fear, like many other general and specific phobias, declines with age.
Smoothness of Human Jaw Movement during Chewing
Authors: Yashiro K. , Yamauchi T. , Fujii M. , Takada K.
Published: January 2009

Human limb movements are successfully modeled based on the assumption that the central nervous system controls the movements by maximizing movement smoothness. Movement smoothness is quantified by means of a time integral of squared jerk (jerk-cost), where jerk is defined as the rate of change in acceleration. This study was performed to investigate whether the control of human masticatory vertical jaw movements can also be explained by a minimum-jerk (maximum-smoothness) model. Based on the assumption that minimum-jerk models account for vertical jaw-opening and -closing movements during chewing, the actual time profile of the movement trajectory was simulated by the model. The simulated jerk-costs and peak velocities were compared with those obtained by actual measurements of jaw movements during chewing. Jerk-costs and peak velocities of the jaw movements during chewing were significantly correlated with those predicted by minimum-jerk models (P < 0.0001, r between 0.596 and 0.799). The minimum-jerk models predicted closing movement trajectories more accurately than opening movement trajectories (jaw opening, root-mean-square error = 1.19 mm; jaw closing, 0.52 mm, t = 4.375, P < 0.0001). The results indicated that the vertical jaw movement control during chewing was represented by the minimum-jerk control model and that the vertical jaw-closing movement is smoother than the opening movement during gum-chewing.
Blood Circulation as Source for Osteopontin in Acellular Extrinsic Fiber Cementum and Other Mineralizing Tissues
Authors: VandenBos T. , Bronckers A.L.J.J. , Goldberg H.A. , Beertsen W.
Published: January 2009

Osteopontin (OPN) is one of the major non-collagenous proteins in root cementum and other mineralized tissues. Although most of this mineral-seeking protein is thought to be produced by local tissue cells, some of it might enter the mineralizing matrix from the blood. To test this hypothesis, we followed the distribution of a single dose of purified porcine or rat 1251-labeled OPN injected i.v. in rats, in mineralizing and non-mineralizing tissues and in subcutaneously implanted collagenous implants. The animals were killed 30 or 48 hrs after injection. Tissues (calvaria, tibia, lower and upper jaws) were harvested and processed for radioautography and biochemical analysis. Tissues as well as calcifying collagenous implants proved to have taken up radiolabel. In EDTA extracts of long bones, the majority of the radiolabel was demonstrated to be associated with intact OPN. The iodinated protein was also found in the acellular extrinsic fiber cementum (acellular cementum) layer investing the continuously growing incisors, in laminae limitantes, cement lines, and in forming bone near the mineralization front. Further, the label was present in the circumpulpal dentin of the incisors, and some of it appeared to have been incorporated into developing enamel. It is concluded that OPN in acellular cementum and other mineralizing tissues may-at least partially-originate from sources outside the direct environment following its transportation via serum.