Biomedical subjects

S Ebisu

Publications and source records attributed to S Ebisu.

At least 19 recordsLinked to original sources

PubMed2006

Fatigue behavior of resin composites in aqueous environments.

OBJECTIVES: Interaction between mechanical and chemical fatigue of resin composites was investigated. METHODS: Fatigue fracture resistance of composites after (1) water immersion and under (2) dry and (3) aqueous conditions was analyzed using a fatigue crack propagation test. The characteristics of fatigue crack propagation were expressed as the correlation between the fatigue crack growth rate (da/dN) and stress intensity factor range (DeltaK) and by the fatigue crack growth threshold (DeltaKth). Following the fatigue test, a fractographic examination was performed by scanning electron microscopy. RESULTS: Contrary to common perception, fatigue crack propagation was retarded under aqueous conditions but accelerated after water immersion. In addition, fatigue cracks detoured around inorganic macro-fillers, but penetrated organic fillers. SIGNIFICANCE: It was concluded that the inverse effects of water on fatigue resistance of composites are dependent on the experimental conditions. Moreover, inorganic macro-fillers were shown to be functional in retarding fatigue cracks in composites.

Composite Resins↗

PubMed2006

Prevalence of root caries in a selected population of older adults in Japan.

In this study, the prevalence of root caries in a sample of Japanese elders was investigated along with various aetiological factors. Two hundred and eighty-seven independently living elderly people over the age of 60 years were examined for the prevalence of active, inactive, and filled root lesions as well as the number of teeth. General health, oral status and brushing habits were surveyed, and salivary flow was determined in terms of flow rate and subjective feeling of dry mouth during eating. About 39% of the subjects had one or more decayed roots and 53.3% had at least one decayed or filled lesion. Root caries was seen most frequently on canine teeth followed by the first premolar. The number of decayed or filled lesions increased with increasing number of residual teeth (Kruskal-Wallis test, P = 0.033), however, there was no association between the proportion of teeth with root decay and the number of teeth. For subjects with 20 or more teeth, the number of decayed roots is likely to be lower in subjects who reported brushing frequently (P = 0.058), and higher in subjects with low salivary flow (P = 0.059) or subjective feeling of dry mouth (P = 0.052) (Chi-squared). The presence of decayed lesions is likely to be related to dry mouth (P = 0.057, odds ratio 3.13) and brushing frequency (P = 0.088, odds ratio 1.76) (Multiple logistic regression analysis). The results indicate a high frequency of root surface caries in this Japanese community-dwelling older population. Oral hygiene status and low salivary flow or perceived dry mouth were potential risk factors for disease.

Age Distribution↗

PubMed2005

Influence of explorer tip diameter in identifying restoration margin discrepancies.

OBJECTIVES: Evaluations of the marginal adaptation of restorations in clinical trials rely on subjective assessments by evaluators. The purpose of the present study was to assess the use of dental explorers with different tip diameters to detect simulated marginal discrepancies. METHODS: Using three devices simulating vertical steps, horizontal gaps, and the combination of vertical and horizontal discrepancies and explorers with five different tip diameters, 10 experienced dental faculty members were asked to identify discrepancies at the boundary between Alfa (replacement unnecessarily) and Bravo (replacement questionable) ratings, according to modified United States Public Health Service criteria. RESULTS: A significant correlation was found between the tip diameters of the explorers and the Alfa/Bravo boundaries for the horizontal gaps, but not for the vertical steps. CONCLUSION: It was concluded that the tip diameter of dental explorers had no significant effect on the detection of vertical steps, but had a significant effect on the detection of horizontal gaps. The diagnosis of restoration marginal discrepancies and the rating of marginal adaptation in clinical trials may subsequently be found to be best achieved using techniques other than the probing of restoration margins.

Dental Instruments↗

PubMed2005

Ammonium hexafluorosilicate increased acid resistance of bovine enamel and dentine.

Although diamine silver fluoride (AgF: (NH3)2AgF) stains teeth black, it is known as a very effective agent to prevent the dental caries progress. In order to find another fluoride that has a similar anticariogenic effect without changing tooth color, we prepared ammonium hexafluorosilicate (SiF: (NH4)2SiF6), in which the silver of AgF is replaced with silicon. In this study, the anticariogenic effect of SiF was evaluated using bovine teeth. Fluoride solutions, SiF, AgF, acidulated phosphate fluoride (APF), and sodium fluoride (NaF), were applied to bovine enamel and dentine blocks, and the depth of demineralization was measured after exposure to a demineralizing solution for 24 h. Also, fluoride was applied to a simulated dentine caries specimen to evaluate the caries progress-preventing ability. For the dentine specimens, mineral loss (Delta Z) was also measured with microradiography. We found that SiF treated enamel showed better acid resistance than specimens treated with NaF or APF. AgF treated enamel also showed similar acid resistance, but was stained black. SiF and AgF treated caries-affected dentine showed reduced demineralization when exposed to a demineralization solution for 24 h. Mineral loss (Delta Z) was reduced to 85% and 75%, respectively. Although the acid resistance of the SiF treated teeth was inferior to that of the AgF treated teeth, we consider that SiF has good potential as anticariogenic agent, since it increased acid resistance without changing tooth color.

Acids↗

PubMed2005

Inhibition of root caries progression by an antibacterial adhesive.

A dentin primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) has been shown to penetrate and kill the bacteria in artificially demineralized dentin. We hypothesized that an experimental adhesive system, which incorporates the MDPB-containing primer, would be effective in inhibiting the progression of root caries in vitro. Artificial caries lesions were prepared by either an acid-gel or a Streptococcus mutans culture technique on the roots of extracted human teeth. The progression of these lesions after the application of the experimental or proprietary adhesive system was examined. Further demineralization was completely prevented by the experimental adhesive system, while lesions managed with the proprietary materials showed limited ability to inhibit further demineralization. We conclude that the experimental adhesive system can inhibit the progression of root-surface caries in vitro, through a combination of its antimicrobial activity and sealing of the demineralized dentin.

Acetone↗

PubMed2004

In vitro estrogenicity of resin composites.

Previously, we have reported that sealants incorporating bisphenol A dimethacrylate showed estrogenicity by a reporter gene assay. This study tested the hypothesis that commercial composites, which contain various monomers and additives, exhibit estrogenic activity in vitro. The estrogenic activities of eluates obtained from 24 composites and 18 chemicals identified from the composites tested were examined with the use of the reporter gene assay. Among the 24 composites, 6 products were estrogenic, and among the 18 constituents, 1 photostabilizer, 2-hydroxy-4-methoxy-benzophenone (HMBP), 1 photoinitiator, 2,2-dimethoxy-2-phenyl-acetophenone (DMPA), and 1 inhibitor, 2,6-di-tert-butyl-p-cresol (BHT) had significant estrogenic activity. The concentration of HMBP in 4 estrogenic eluates was greater than the minimum concentration required for estrogenicity, and DMPA was found at a higher level than the minimum estrogenic concentration in the remaining 2 estrogenic specimens. These results suggest that the observed estrogenic activity of 6 composites is associated with the elution of either HMBP or DMPA.

Acetophenones↗

PubMed2004

Influence of resin monomers on growth of oral streptococci.

Ethyleneglycol dimethacrylate monomers have been previously reported to stimulate the growth of certain caries-associated bacteria on the basis of turbidity measurements. To elucidate the detail of this effect, we examined the influence of resin monomers on the growth of Streptococcus sobrinus and Streptococcus sanguis by determination of bacterial numbers (colony-forming units), morphological observation, and chemical analysis. Although the absorbance values in the stationary phase of bacterial suspension were increased in the presence of ethyleneglycol monomers, no significant differences were observed for bacterial numbers throughout the incubation period. Scanning electron microscopy observation revealed the formation of sparse vesicular material surrounding bacterial cells when incubated with ethyleneglycol monomers, and these products were proved to be resin polymers. The results demonstrate that the apparent biomass increase during incubation with ethyleneglycol monomers is due not to promotion of bacterial multiplication, but to the polymerization of resin monomers to form vesicular structures attached to cells.

Acrylates↗

PubMed2004

Effects of cyclosporin-A-induced immunosuppression on periapical lesions in rats.

Cyclosporin A (CsA) might induce immune response alterations in periapical lesions and modify bone remodeling. This study determined the changes that occur in the periapical lesions of rats during CsA administration and after CsA withdrawal. After the induction of periapical lesions, the animals were treated with CsA (0-20 mg/kg/day) for 4 wks. Lesion volumes were measured by computed tomography. Histological observations and immunohistochemical evaluations were performed with anti-CD3 and anti-CD25 antibodies. CsA administration reduced lesion volumes, and the lesions significantly expanded after CsA withdrawal. CsA inhibited the proliferation and activation of T-cells at lesion sites. The effects of CsA on T-cells were dose-dependent up to 10 mg/kg/day, after which no significant difference was evident. These results suggest that CsA inhibits periapical destruction by interfering with T-cell function in periapical lesions.

Alveolar Process↗

PubMed2004

Localization of Porphyromonas gingivalis-carrying fimbriae in situ in human periodontal pockets.

Fimbriae, which are involved in adherence, constitute an important pathogenic factor of Porphyromonas gingivalis. In vivo, however, the distribution of P. gingivalis-carrying fimbriae is unknown. The localization of P. gingivalis-carrying fimbriae was examined in situ. From 19 patients with severe periodontitis and P. gingivalis, we obtained 20 teeth with periodontal tissue attached, with and without immunolocalized fimbriae. Eleven teeth were subjected to light microscopy, 9 to electron microscopy. In 6 of the 11 samples examined, we detected positive reactions with an anti-P. gingivalis-fimbriae serum, located in the cementum-attached plaque area in the deep pocket zones. In the so-called 'plaque-free zones', P. gingivalis-carrying fimbriae were immunocytochemically observed to reside in contact with the dental cuticle in 6 of the 9 samples examined. These findings suggest that P. gingivalis-carrying fimbriae are strongly related to adherence to the root surface at the bottoms of human periodontal pockets.

Aged↗

PubMed2002

An antibody to VacA of Helicobacter pylori in cerebrospinal fluid from patients with Guillain-Barre syndrome.

OBJECTIVE: To detect antibodies to recombinant vacuolating cytotoxin (r-VacA) of Helicobacter pylori in cerebrospinal fluid (CSF) from patients with Guillain-Barre syndrome (GBS). METHODS: CSF samples from 13 patients with GBS (electrophysiologically classified as eight acute inflammatory demyelinating polyradiculoneuropathy (AIDP), four acute motor axonal neuropathy (AMAN), and one unexcitable nerve conduction) and eight disease control patients were studied. The r-VacA protein was separated by SDS/PAGE, and Western blot analysis was carried out. RESULTS: Six of the 13 patients with GBS had a specific IgG antibody to VacA of H pylori, which was confirmed by absorption experiments using r-VacA. Every patient with positive CSF anti-r-VacA IgG had AIDP. CONCLUSION: The sequence homology previously found between VacA and human (Na(+)+K(+))-ATPase A subunit suggests that antibodies to VacA involve ion channels in abaxonal Schwann cell plasmalemma resulting in demyelination in some patients with GBS.

Adult↗

PubMed2001

High-level production of recombinant chicken interferon-gamma by Brevibacillus choshinensis.

Cytokines, such as interferon-gamma have been shown to have adjuvant and growth promoting activity in poultry and livestock and have the potential to be used as alternatives to antibiotics. We have developed an efficient system for commercial-scale synthesis of recombinant chicken interferon-gamma (ChIFN-gamma) using Brevibacillus choshinensis as the host for protein production. The ChIFN-gamma expression vector, pNCIFN, was constructed using the novel Escherichia coli-B. choshinensis shuttle vector, pNCMO2. ChIFN-gamma expression was optimized by investigating different culture conditions and different host B. choshinensis mutants. The highest level of production was observed using the B. choshinensis HPD31-MB2 strain grown at 30 degrees C, where ChIFN-gamma was produced at approximately 300-500 mg/L. ChIFN-gamma was also produced as a His-tagged fusion protein by using the pNCHis-IFN expression vector, a derivative of pNCMO2. The protein was constitutively secreted into the culture supernatant and could be partially purified in a single step using a Ni-nitrilotriacetic acid column. This recombinant His-ChIFN-gamma was shown to have the same biological activity as native ChIFN-gamma.

Affinity Labels↗

PubMed2001

Degree of conversion of composites measured by DTA and FTIR.

OBJECTIVE: Differential thermal analysis (DTA) using a split fiber optic light source has been reported to be a convenient method of measuring the degree of conversion (DC) of light-activated composites. The purpose of this study was to compare the results by DTA and Fourier transformation infrared spectroscopy (FTIR), and evaluate the usefulness of the DTA method. METHODS: Experimental 2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl]propane-based composites containing SiO2 filler and various amounts of triethyleneglycol dimethacrylate (TEGDMA) were prepared, and the DC of each composite was determined by DTA or FTIR with 60s irradiation. The DC of three proprietary composites containing hybrid filler or prepolymerized resin filler were also measured by both methods with 20 or 60s irradiation. The results were analyzed by ANOVA and Fisher's protected least significant difference test. RESULTS: By both DTA and FTIR, the DC of experimental composites increased as the proportion of TEGDMA increased, although DTA showed 3-10% greater values (p<0.05) than FTIR. For proprietary composites that contain hybrid filler, the values by DTA were not significantly different from those by FTIR at 20s exposure. Longer irradiation time resulted in greater DC (p<0.05) for both methods, and DTA showed 5-7% greater values than FTIR. However, the DC of the composite containing prepolymerized resin filler was 30% less by FTIR than by DTA, possibly due to the influence of unpolymerized species in the filler. SIGNIFICANCE: The DC values determined by DTA and FTIR showed good agreement for most materials including model composites. In addition, DTA may be more useful than FTIR to measure the DC of composites containing prepolymerized resin filler.

Analysis of Variance↗

PubMed2001

Inhibitory effects of resin composite containing bactericide-immobilized filler on plaque accumulation.

OBJECTIVE: Previously, we have reported that incorporation of the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) was effective in immobilizing bactericide in the resin matrix, and an antibacterial composite without release of the agent could be achieved. In this study, an attempt was made to increase the density of bactericide immobilized in composite, and the inhibitory effects of this modified antibacterial composite on plaque accumulation were determined, focusing on the reliability of the effects and the mechanisms to affect the plaque formation. METHODS: An experimental composite containing immobilized bactericide at 2.83% was prepared by the incorporation of MDPB into a prepolymerized resin filler of control composite, and elution of antibacterial components and inhibition of in vitro plaque accumulation by Streptococcus mutans were determined. The inhibitory effects of the experimental composite on the attachment, glucan synthesis and growth of S. mutans on the surface were also examined in addition to the comparison of surface roughness and hydrophobicity with controls. The results were analyzed using the Student's t-test. RESULTS: The experimental composite had reproducible inhibitory effects against plaque accumulation compared with control (p<0.05), although it showed no elution of unpolymerized MDPB. The plaque-inhibitory effect of the experimental composite was found to depend upon the ability to inhibit the attachment, glucan synthesis, and growth of bacteria on its surface as no significant differences in the surface characteristics were obtained between control and experimental composites (p>0.05). SIGNIFICANCE: It was indicated that the experimental composite containing bactericide-immobilized filler has the possibility to be used clinically with an effective anti-plaque property.

Anti-Infective Agents, Local↗

PubMed2001

Control of hydroxyapatite crystallinity by mechanical grinding method.

Crystallinity of hydroxyapatite reflecting crystal size and crystal elastic strain was controlled by the mechanical grinding (MG) technique using a set of container and balls made of SUS304 stainless steel or agate. Variation in the crystallinity through MG was monitored by the XRD method and represented by the broadening of the diffraction peak. Effect of changes in crystallite size and strain on the crystallinity was also examined using the Hall-plot method. Crystallinity rapidly decreased with milling time. Significant crystallographic diffraction peaks disappeared and a broad diffraction around 2theta=32 degrees was observed after MG for 72 h. The broadening was dominantly due to an increase in crystal strain in addition to fine crystallite size. Contamination from the container and balls during MG was more suppressed using agate than SUS304 stainless steel. The recovery process of crystallinity during heating between 300 degrees C and 1200 degrees C was examined focusing on the decrease in residual elastic strain. Low crystallinity was maintained at annealing temperatures below 800 degrees C but lattice defects were recovered above 1000 degrees C.

Journal Article↗

PubMed2001

Soluble products from Eikenella corrodens stimulate oral epithelial cells to induce inflammatory mediators.

In the inflammatory response elicited by bacterial colonization in periodontal pockets, pocket epithelial cells not only serve as a barrier to isolate the pocket microenvironment from external stimuli but also regulate the functions of neighboring cells including fibroblasts and inflammatory cells. To elucidate this mechanism, we characterized the effects of periodontopathic bacterium Eikenella corrodens 1073 components on the production of some inflammatory mediators in a human oral epithelial cell line (KB). In enzyme-linked immunosorbent assay (ELISA), the E. corrodens supernatant induced interleukin-6 (IL-6), IL-8 and prostaglandin E2 but not interferon-gamma (IFN-gamma) production by KB cells. After incubation with E. corrodens supernatant, KB cells showed a marked increase in the levels of IL-6, IL-8 and PG G/H synthase (cyclooxygenase)-2, but not IFN-gamma, gene expression by reverse-transcriptase polymerase chain reaction. All these E. corrodens products responsible for production of these inflammatory mediators resisted freezing and boiling and were present in a 10-kDa filtrate. These results imply that these soluble small-molecular-mass products from E. corrodens stimulate various inflammatory mediator productions by human oral epithelial cells and may play a role in the initiation of periodontal inflammation and subsequently perpetuate the inflammatory response during chronic infection.

Bacterial Adhesion↗

PubMed2001

Bactericidal effect of dentin primer containing antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human carious dentin.

The aim of this study was to investigate the bactericidal effect of a dentin primer incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human dentinal carious lesions. To evaluate the antibacterial activity of MDPB against anaerobes, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against obligate anaerobes and facultative anaerobic strains of lactobacilli were determined. Bacteria were recovered from carious dentin samples obtained from the teeth of patients, and the bactericidal activities of the experimental primer containing 5% MDPB and three commercially available primers were compared by counting the number of viable cells after contact with diluted solutions of each primer for 30 s. MDPB showed strong antibacterial activity against anaerobes, the MIC and MBC values ranging from 3.9 to 31.3 micrograms/ mL-1 and 15.6-125 micrograms/ mL-1, respectively. Experimental primer containing MDPB was the most bactericidal among the materials tested (ANOVA, Fisher's PLSD test, P < 0.05) and was able to kill the bacteria completely even when diluted 40 times, while the three commercial products exhibited little activity at 40 times dilution. These results indicate that incorporation of MDPB into dentin primer could be beneficial for eliminating the residual bacteria in cavities.

Analysis of Variance↗

PubMed2001

Effects of plaque control on the patency and occlusion of dentine tubules in situ.

To elucidate the nature of dentine hypersensitivity, the effects of plaque control on the patency and occlusion of dentinal tubules were investigated systematically in situ using human dentine slabs embedded in partial dentures. The dentine slabs were divided into three groups. In group I, the dentine slabs were kept in an oral cavity without plaque control. In group II, plaque was removed mechanically by brushing. Plaque control was carried out chemically using chlorhexidine in group III. After being kept in the oral cavities for 1, 2 and 3 weeks, the slabs were removed from the partial denture, followed by SEM observation to determine the morphological changes of the dentinal tubules. When no attempt was made to remove plaque, the diameter of tubule orifices increased to 390% of the original values within 3 weeks. In contrast, dentinal tubules were found to be occluded, i.e. the tubule orifices became <20% of the original value within 1 week when plaque control efforts were made, using either method of plaque control. We conclude that plaque control plays one of the key roles in the patency versus occlusion of dentinal tubules, and thus in the aetiology and natural reparative process of dentine hypersensitivity.

Adult↗

PubMed2001

Cytotoxicity of intracanal bleaching agents on periodontal ligament cells in vitro.

Intracoronal bleaching of nonvital teeth is a simple and conservative procedure for esthetic restoration of discolored teeth. However it is possible that damage to the periodontal ligament may occur if the bleaching agents contact this tissue. The purpose of this study was to examine the cytotoxicity of intracanal bleaching agents on human periodontal ligament (PDL) cells in vitro. Three bleaching agents, 30% hydrogen peroxide (H2O2), 2.0 g/ml sodium perborate (SP) solution, and 2.0 g/ml SP in H2O2, were diluted from 10(-3) to 10(-7) with Eagle's minimal essential medium and incubated with PDL cells isolated and cultured from extracted teeth. Cytotoxicity was assessed quantitatively by determining the amount of lactic dehydrogenase activity released from the cells after exposure to the agents for 24 or 72 h. Dose-response curves were plotted, and TD50 values (dilution causing the release of 50% of control lactate dehydrogenase activity) and 95% confidence limits determined. The rank order of the TD50 values after exposure for 24 h was SP in H2O2 (most toxic) > H2O2 > SP solution (least toxic). After 72 h SP in H2O2 still produced the greatest cytotoxic effect. However the SP solution was more cytotoxic than H2O2 at this time point. It is concluded that the mixture of SP with H2O2 was the most toxic to the PDL cells in vitro.

Borates↗