Growth Rate of and Gene Expression in Bradyrhizobium diazoefficiens USDA110 due to a Mutation in blr7984, a TetR Family Transcriptional Regulator Gene.

Previous transcriptome analyses have suggested that a gene cluster including a transcriptional regulator (blr7984) of the tetracycline repressor family was markedly down-regulated in symbiosis. Since blr7984 is annotated to be the transcriptional repressor, we hypothesized that it is involved in the repression of genes in the genomic cluster including blr7984 in symbiotic bacteroids. In order to examine the function and involvement of the blr7984 gene in differentiation into bacteroids, we compared the free-living growth/symbiotic phenotype and gene expression between a blr7984-knockout mutant and the wild-type strain of Bradyrhizobium diazoefficiens USDA110.

Development of MDP-based one-step self-etch adhesive--effect of additional 4-META on bonding performance.

We designed three experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step (EX) adhesives consisting of MDP, urethane dimethacrylate, and triethylene glycol dimethacrylate adhesives with different water contents (98.4, 196.8, and 294.

Differentiation of banding patterns between Streptococcus mutans and Streptococcus sobrinus isolates in rep-PCR using ERIC primer.

Background: Streptococcus mutans and Streptococcus sobrinus are considered to be important bacterial species in the initiation of human dental caries. Therefore, the establishment of a reliable genotyping method to distinguish S. mutans from S.

Effects of particle size of silica filler on polymerization conversion in a light-curing resin composite.

Objectives: The effect of visible light passing through a resin composite with different particle sizes of spherical silica filler on the curing depth and Knoop hardness of the resin composite was examined. The null hypotheses tested were that the particle size of silica filler has no effect on (1) the transmitted amount of visible light passing through the resin composite, (2) the curing depth of the resin composite, and (3) the ratio of the Knoop hardness of the hardened resin composite.

Methods: A series of different experimental resin composite pastes with different particle sizes of silica filler were prepared.

Effect of reacted acidic monomer with calcium on bonding performance.

We determined the number of reacted and unreacted 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) molecules with calcium during the demineralization process of hydroxyapatite or dentin by 10-MDP-based one-step (Clearfil Tri-S Bond, TS) or two-step self-etch adhesive (Clearfil SE Bond Primer, SE). We then examined the effects of the number of reacted and/or unreacted 10-MDP molecules on the initial bond strength and bond durability of the resultant adhesive layer. The null hypotheses were that (1) the etching efficacy of tooth apatite by 10-MDP used in TS was the same as that in SE, and (2) the unreacted 10-MDP polymer included within the adhesive layer does not affect bond durability.

Unique functions of hydroxyapatite with mutans streptococci adherence.

Objective: Hydroxyapatite (HA) is used as a construction material for artificial supplementation of enamel tooth surfaces to improve oral hygiene. This study examined in vitro HA interactions with mutans streptococci (MS) and bacterial adherence to small (nanosize) crystal form of HA beads having a protean hexagonal structure. The adsorption and physical effects of HA employed in vivo is also described.

Stimulatory Effects of CO(2) Laser, Er:YAG Laser and Ga-Al-As Laser on Exposed Dentinal Tubule Orifices.

We investigated the effects of lasers irradiation on the exposed dentinal tubule. Human tooth specimens with exposed dentinal tubule orifices were used. Three types of lasers (CO(2) laser, Er:YAG laser and Ga-Al-As laser) were employed.

Effect of solvent type on the degradation of 4-MET.

This study sought to investigate the degradation mechanism of 4-methacryloyloxy ethyl trimellitic acid, 4-MET, which is commonly used as an acidic monomer in solvated self-etching primers or one-step bonding agents. To this end, we examined the effects of solvent type used--such as ethanol, methanol, and acetone--on the degradation mechanism of 4-MET by using the 13C NMR technique. The degradation mechanism of 4-MET was strongly dependent on the type of solvent used.

Effect of polymerization accelerator on dentin bonding of one-step bonding agent.

The aim of this study was to enhance the bond strength of one-step bonding agents to dentin. In particular, the focus was on using Catabrush the applicator system of AQ Bond Plus. Catabrush was supplemented with N-phenylglycine and aromatic sulfinate as polymerization accelerators, as N-phenylglycine was reportedly beneficial in improving the bond strength to dentin.

Effect of base monomer's refractive index on curing depth and polymerization conversion of photo-cured resin composites.

In this study, we examined the effect of the transmitted amount of visible light through a resin composite on the curing depth and polymerization conversion. Transmitted amount of visible light was strongly dependent on the magnitude of refractive index difference that existed between the resin and silica filler. More specifically, the differences arose from the type of base monomer used.

Efficacy of varying the NMEP concentrations in the NMGly-NMEP self-etching primer on the resin-tooth bonding.

It is well understood that the application of a self-etching primer enhances the bonding at the resin-teeth interface. In this study, we designed a self-etching primer consisting of N-methacryloyl glycine (NMGly) and N-methacryloyl-2-aminoethyl phosphonic acid (NMEP). The demineralization effects on the hydroxyapatite or dentin by the carboxylic acid in the NMGly and by the phosphonic acid in the NMEP and their effects on the bond strength of the resin to the tooth were examined.

Feasibility of eradication of mutans streptococci from oral cavities.

Objectives: Dental caries prevention programs using chlorhexidine (CHX) have been proposed, but CHX's effect in reducing levels of mutans streptococci (S. mutans and S. sobrinus) appears to last for only a few months.

Production of monoclonal antibody inhibiting dipeptidylaminopeptidase IV activity of Porphyromonas gingivalis.

Porphyromonas gingivalis is a Gram-negative anaerobic bacterial species implicated as an important pathogen in the development of adult periodontitis. We previously cloned a gene encoding dipeptydilaminopeptidase IV (DAPIV) from P. gingivalis.

Isolation and characterisation of dipeptidyl peptidase IV from Prevotella loescheii ATCC 15930.

A proline-specific dipeptidyl aminopeptidase, dipeptidyl peptidase IV (EC 3.4.14.

Effects of surfactants on glucosyltransferase production and in vitro sucrose-dependent colonization by Streptococcus mutans.

The presence of Tween 80 in media was associated with a significant increase in three glucosyltransferases(GTFs)(I, SI and S), especially GTF-I, produced by Streptococcus mutans strain PS14, indicating that the surfactant is a major cause of the enhanced GTF production observed in cultures in M4 medium. Lecithin and Tween 20 also enhanced GTF-I production, while Triton X-100 depressed it. At a lot concentration of 0.

Rapid isolation of chromosomal DNA from oral streptococci and polymerase chain reaction-oriented restriction fragment-length polymorphism analysis for genetic heterogeneity.

We have extensively modified the published method for the lysis of gram-positive bacteria to isolate chromosomal DNA from only 1 ml of oral streptococcal overnight culture. Cells were incubated with lysozyme and R Nase A in the presence of polyethylene glycol. After centrifugation, cells were lysed with sodium dodecyl sulfate and proteinase K.

Evaluation of three individual glucosyltransferases produced by Streptococcus mutans using monoclonal antibodies.

We previously established murine hybridomas producing a monoclonal antibody monospecific against three glucosyltransferases (I, SI and S) of Streptococcus mutans which contribute to dental caries formation. Here, we developed a new immunochemical technique (cross-dot system) with which individual levels of glucosyltransferases expressed by S. mutans can be evaluated.

A histopathological study of direct pulp capping with adhesive resins.

This study evaluated the histological pulp responses of four different adhesive resin systems placed directly on exposed pulp tissue. Gap formation between the respective resin and cavity walls was observed and correlated to the pulpal response. Occlusal cavity preparations creating mechanical pulp exposures were prepared in molars of wistar rats.

Effects of lining materials on the composite resins shrinkage stresses.

Recently, three types of lining materials have been used in dental clinics, conventional powder-liquid glass ionomer cement, light-cured powder-liquid glass ionomer cement and a light-cured single paste type. This study compared the effects of these lining materials on the shrinkage stress of light-cured composite resins during the early setting stage, when polymerization shrinkage occurs. After the second irradiation, the shrinkage stress of composite resins lined with light-cured powder-liquid type cements was approximately 1.

Abrasion biopsy in studies of mineral density of experimental enamel lesions.

The profile of mineral density of experimental enamel lesions was determined by means of sampling with a new abrasion biopsy technique. Three types of lesions were produced on bovine enamel slabs: (1) pre-softened in lactic acid buffer for 16 hr; (2) pre-softened and exposed to a test for acid resistance for seven days; and (3) pre-softened, exposed to the seven-day Intra-oral Cariogenicity Test with extra-oral immersions in 1000 ppm F solutions for one min twice daily (ICT/F), plus the seven-day test for acid resistance. Lesions were assessed with measurements of surface microhardness, microradiography of thin sections, and abrasion biopsy.