The purpose of this study was to examine the antibacterial activity of composite resin with glass-ionomer filler particles versus that of contemporary commercial composite resins. Three composite resins were used: Beautifil II (containing S-PRG filler), Clearfil AP-X, and Filtek Z250. Resin blocks were bonded to maxillary first molars, and plaque accumulation on the resin block surface was examined after 8 hours. For the antibacterial test, the number of Streptococcus mutans in contact with the composite resin blocks after incubation for 12 hours was determined, and adherence of radiolabeled bacteria was evaluated. Less dental plaque was formed on Beautifil II resin block as compared to the other two materials. Antibacterial test revealed that there were no significant differences in the number of Streptococcus mutans among the three composite resins. However, the adherence of radiolabeled bacteria to the saliva-treated resin surface was significantly (p<0.01) lower in Beautifil II than in the other two materials. These results suggested that Beautifil II could reduce dental plaque formation and bacterial adherence, leading to prevention of secondary caries.

No abstract

No abstract

Scanning tunneling microscopy (STM) observation was performed for the surface of diamond epitaxial film which was grown on a diamond (001) substrate by microwave plasma-assisted chemical vapor deposition (CVD). The surface was stable even in air, and it showed a reflection high-energy electron diffraction (RHEED) pattern of the 2×1/1×2 structure. Images of the atomic level corresponding to the RHEED pattern were obtained by STM in air. Significant extension of dimer rows was observed over the entire surface. Strong similarity between Si(001) grown by molecular beam epitaxy (MBE) and diamond (001) grown by CVD was shown.

We have successfully developed 4H-SiC devices including metal–oxide–semiconductor field-effect transistors (MOSFETs) and Schottky barrier diodes (SBDs) with a rated voltage of 3.3 kV. The conduction loss of the SiC-MOSFET was reduced to as low as that of the Si-insulated gate bipolar transistor (IGBT) by the n-type doping of the junction field-effect transistor region (JFET doping). The JFET doping technique is effective in reducing the temperature coefficient of resistance in the JFET region, leading to the decreased on-resistance of the SiC-MOSFET at high temperatures. These devices have been applied to 3.3 kV/1500 A modules for the world’s first all-SiC traction inverter. The switching loss of the new traction inverter system is approximately 55% less than that of a conventional inverter system incorporating Si modules.

This study aimed to evaluate the effectiveness of self-etching and phosphoric acid-etching orthodontic adhesives for enamel bonding in simulated clinical conditions. By using two self-etching (Transbond Plus, TP; Beauty Ortho Bond, BB) and two acid-etching (Transbond XT, TX; Superbond Orthomite, SB) adhesives, orthodontic brackets were bonded on human premolars (n=10 for each adhesive). Ten teeth without bracket bonding, i.e., intact enamel surfaces, were used as control for SEM observation. After 7-day storage in lactic acid solution, bracket debonding force by means of debonding pliers, adhesive remnant index (ARI), and enamel surface morphology were examined. All the tested adhesives exhibited sufficient bond strength for clinical use. The ARI scores were almost the same among the four adhesives. In terms of SEM observation, the enamel surfaces in the control and TP groups showed a slight change after immersion in lactic acid solution, while the BB group showed less change on the enamel surface compared with the TP group. Meanwhile, the two acid-etching adhesives caused considerable demineralization. Taken together, these findings indicated that the action of self-etching systems was evidently more conservative.

Conduction measurements with simultaneous observations by transmission electron microscopy (TEM) were performed on a thin NiO film, which is a candidate material for resistance random access memories (ReRAMs). To conduct nanoscale experiments, a piezo-controlled TEM holder was used, where a fixed NiO sample and a movable Pt-Ir counter electrode were placed. After the counter electrode was moved to make contact with NiO, I-V measurements were carried out from any selected nanoregions. By applying a voltage of 2 V, the insulating NiO film was converted to a low resistance film. This phenomenon may be the "forming process" required to initialize ReRAMs. The corresponding TEM image indicated a structural change in the NiO layer generating a conductive bridge with a width of 30-40 nm. This finding supports the "breakdown" type forming in the so-called "filament model" of operation by ReRAMs. The inhomogeneity of resistance in the NiO film was also investigated.

No abstract