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Biomedical subjects

H Shimokobe

Publications and source records attributed to H Shimokobe.

At least 19 recordsLinked to original sources
PubMed1994

Caries-preventive effect of glass ionomer sealant reapplication: study presents three-year results.

The caries-preventive effect of glass-ionomer sealant depends on both retention of sealant and fluoride release. In this study, the retention rate was maintained by sealant reapplication over three years. Caries reduction was 76.1 percent at one year, 69.9 percent at two years and 66.5 percent at three years. Reapplication is an acceptable procedure and seemed to improve caries reduction.

Chi-Square Distribution↗
PubMed1994

The three-dimensional structure of Tomes' processes and their relationship to arrangement of enamel prism in dog teeth.

The relationship between the course of enamel prisms and the direction of secretory face in Tomes' process of ameloblast was examined three-dimensionally in the dog tooth by light and electron microscopy, as well as by reconstruction. Scanning electron microscopic observation on the developing enamel surface after the dissolution of the enamel organ showed numerous groups of pits with bulbous faces inclined in the same sidewards direction, while those faces in neighboring groups were inclined in an opposite direction. Tangential semithin sections from demineralized tooth germs were serially cut from the enamel surface to the enamel-dentin junction. These sections showed numerous belt-like zones arranged perpendicular to the meridian of the tooth. A straight row of enamel prisms perpendicular to the boundaries of the belt-like zones was selected at 142 microns from the enamel-dentin junction. The row of prisms and their successive Tomes' processes were reconstructed from micrographs with a personal computer. The cut ends of the enamel prisms initially perpendicular to the boundaries appeared as a sine curve, viewed from the enamel-dentin junction. In a single belt-like zone, the horizontal tilt angles of the enamel prisms towards the enamel-dentin junction tended to be largest at the center of the zone, and smallest near the boundaries. The long axis of each enamel prism was at right angles to the secretory face of the Tomes' process. The secretory faces in a single belt-like zone were inclined in the same sidewards direction and the secretory faces in neighboring zones were inclined in opposite directions. The results suggest that the direction of the sidewards displacement in ameloblasts is related to that of the secretory face of Tomes' processes. Further, one group of ameloblasts with their secretory faces inclined in the same sidewards direction form one belt-like zone.

Ameloblasts↗
PubMed1994

Contraction stress and marginal adaptation of composite restorations in dentinal cavity.

The influence of contraction stress in composite resins on both the shear bond strength to dentin (BS) and marginal adaptation in a standardized dentin cavity was investigated using three restorative resin systems. A teflon ring mold (TF) or copper ring with a roughened inner surface (CP) placed on human tooth dentin was filled with the composite resin, and a shearing test was then performed. ANOVA of BS demonstrated a significant influence from the resin systems and type of molds. BSCP tended to be lower than BSTF in all three systems. This suggested that the inner surface of the CP restricted the flow of resin and then contraction stress occurred at the interface of the bond to the dentin. The system which demonstrated the smallest difference between BSTF and BSCP also showed the best adaptation. This result indicates that contraction stress in the composite resin plays an important role in marginal adaptation.

Analysis of Variance↗
PubMed1987

Effect of peptide bond splitting on ouabain sensitive conformational changes in Na+,K+-ATPase treated with N-[p-(2-benzimidazolyl)phenyl]maleimide.

Trypsin treatment of N-[p-(2-benzimidazolyl)phenyl]maleimide modified enzyme caused a marked reduction in Na+,K+-ATPase activity and in the amount of the alpha-chain, which contains the phosphorylation and ouabain binding sites. However, these preparations retained nearly 90% of the ouabain binding capacity and showed ouabain sensitive dynamic fluorescence changes accompanying the hydrolysis of ATP. The data showed that the three dimensional structure of Na+,K+-ATPase, which is important in the dynamic fluorescence change, is little affected in spite of extensive covalent bond splitting in the alpha-chain of Na+,K+-ATPase.

Electrophoresis, Polyacrylamide Gel↗
PubMed1986

Reversible change in light scattering following formation of ADP-sensitive phosphoenzyme in Na+,K+-ATPase modified with N-[p-(2-benzimidazolyl)phenyl]maleimide.

An increase in light scattering (3.5 +/- 0.2%) was observed when pig kidney Na+,K+-ATPase preparations modified with N-[p-(2-benzimidazolyl)phenyl] maleimide were phosphorylated by ATP in the presence of 2 M Na+ with Mg2+ to form ADP-sensitive phosphoenzyme (E1P), which had a negative fluorescence intensity (-1.5 +/- 0.3%). Addition of K+ or ouabain to E1P reduced the light scattering to the original level observed in the absence of ATP. Stopped flow measurements showed that the fluorescence change accompanying the E1P formation (t1/2 = 0.1 s) occurred preceding the light-scattering change (t1/2 = 1 s). Oligomycin affected the rate of the scattering increase little, but it diminished the effect of K+ on E1P to reduce the light scattering and increase the fluorescence. The addition of 2 M Na+ to K+-sensitive phosphoenzyme (E2P) immediately decreased the fluorescence (t1/2 = 0.02 s) to form E1P which was followed by a slow increase in the light scattering (t1/2 = 0.25 s). Oligomycin reduced both rates of the above changes accompanying the transition of E2P to E1P. The data suggest the sequential appearance of species of E1P that precede E2P formation during the hydrolysis of ATP.

Adenosine Diphosphate↗
PubMed1986

Acceleration of the rate of fluorescence decrease by high concentrations of ATP under the condition of accumulation of ADP-sensitive phosphoenzyme in Na+,K+-ATPase.

Addition of up to 300 microM ATP in the presence of 2 M NaCl with MgCl2 to pig kidney Na+,K+-ATPase treated with N-[p-(2-benzimidazolyl)phenyl]maleimide seemed to be insufficient to saturate the rate of the fluorescence decrease. However, both the extent of the decrease and the amount of phosphoenzyme at a steady state were saturated below 20 microM ATP. Addition of Mg2+ with Na+ to the enzyme preincubated with 20 to 600 microM ATP gave nearly the same rate constant, which was below 50% of that obtained by adding 300 microM ATP to the Na+-form enzyme in the presence of Mg2+. High concentrations of ATP affected neither the rate of light-scattering change (Taniguchi, K. et al. (1986) J. Biol. Chem. 261, 3272-3281) after ADP-sensitive phosphoenzyme formation (E1P) nor that of the breakdown of E1P. A stoichiometric amount of [32P]Pi was liberated from [32P]E1P. The data suggested that ATP did not bind to E1P in such a way as to increase the extent of phosphorylation further or to accelerate dephosphorylation. The data also suggested that the reason for the large difference in the apparent affinity of ATP as evaluated from the rate and the extent of fluorescence change is the large dissociation constant for ATP of a Michaelis complex.

Adenosine Diphosphate↗
PubMed1976

Deformation of cavities and resin fillings in loaded teeth.

The purpose of the present work was to study (1) the deformation of selected types of cavities in axially loaded human teeth and (2) the possible effect of this deformation on the restorative quality of fillings in the cavities. Recently extracted wet teeth without any visible structural defects were used throughout the study. Standard Class III and large Class III cavities were prepared in maxillary incisors, while Class I, m-o, m-o-d, and Class V cavities were made in maxillary first premolars. For the second part of the study several of the cavities, etched of non-etched, were filled with restroative resins. Mounted in a measuring microscope the teeth were loaded in a way simulating biting or chewing; cavities with fillings were accepted only when no marginal gaps could be found. The results showed a deformation of empty cavities proportional to the load up to 16 kg, the decrease or increase in diameter being 0.1-1.0 mum/kg, depending on the type of cavity. Loading and unloading of teeth with filled cavities resulted in permanent or transitory gaps. The dimensional instability of cavities in loaded teeth indicates a severe risk of percolation by several restoratives and of marginal fracture of brittle fillings.

Acrylic Resins↗
PubMed1975

Adaptation of resinous restorative materials to acid etched enamel surfaces.

The purpose of this paper was to study by means of scanning electron (SEM) and optical microscopy the adaptation of the low-viscous non-composite. Nuva-Seal and of the three high-viscous composite restorative materials Adaptic, Compocap and Concise to phosphoric acid etched enamel surfaces from symmetric areas of pairs of contralateral human permanent anterior teeth. The SEM study demonstrated that the two types of material equally well reproduce the details of the enamel surface; the light microscopic observations showed that the length and shape of resin tags in the enamel surface are independent of the materials examined. The observations seem to allow the conclusion that bonding of composite restorative resins to phosphoric acid etched enamel surfaces is not conditioned by the employment of an intermediate film of a low-viscous non-composite resin.

Composite Resins↗
PubMed1975

Enamel damages caused by contracting restorative resins.

Several observations have shown that contraction stresses in restorative resins bonded to the enamel of cavity walls readily broke the enamel surrounding the cavities. The forces studied were caused by polymerization contraction, thermal contraction or elastic hysteresis. The bonding was obtained mainly by etching the cavity walls by phosphoric acid.

Acrylic Resins↗