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

A few mol! Al 2 O 3 -doped ZnO sintered body forms a substitutional solid solution and the semi-conducting property is drastically affected by the content of the dissolved Al. It was suggested from the results of XRD and EPMA that Al existed in the ZnO sintered body in the form of ZnAl 2 O 4 . Furthermore, the distribution of ZnAl 2 O 4 was visualized by AFM and SEM. It was, however, difficult for these techniques to detect dissolved Al in ZnO grains directly. The SIMS mapping suggested that the trace amount of Al approximately 0.3 atomic! dissolved into ZnO grains because of high sensitivity for trace impurities. This result was consistent with the change in lattice constants of ZnO with Al dissolution.

No abstract

This study was conducted to examine the ultrastructures of eight recently improved light-cure restorative composite resins with scanning and transmission electron microscopes (SEM and TEM). Additionally, Vickers hardness, volume/weight fraction of filler, and chemical composition were analyzed. Composite resins selected for evaluation were Beautifil II, Clearfil AP-X, Clearfil Majesty, Estelite Σ, Filtek Supreme, Filtek Z250, Solare, and Synergy. SEM and TEM images revealed a great diversity in ultrastructure, and Vickers hardness test showed significant differences amongst all the composite resins (except between Clearfil Majesty and Estelite Σ, and between Filtek Supreme and Filtek Z250). By means of EDX, similar elements such as C, O, and Si were detected, but the concentration was different in every composite resin. Results obtained in this study served to validate that the methods employed in this study -SEM and TEM at high magnification -were useful in examining the ultrastructures of composite resins. It was also found that the ultrastructure, size of filler particles, volume/weight fraction of filler, and chemical composition of the composite resins had an effect on Vickers hardness. Given the great diversity of ultrastructures amongst the composite resins, which stemmed from the different revolutionary technologies used to manufacture them, further studies are warranted in the search of clinical applications that optimally match the differing properties of these materials.