This study examined the influence of centrifugal force on the filler loading of composites using a light-polymerizing apparatus combined with a centrifuge. To assess uneven filler particle distribution resulting from specimen rotation, two lowviscosity composites （Palfique Estelite LV and Revolution Formula 2） were placed in test tubes, centrifuged, and subsequently light-polymerized with the apparatus. After each specimen was sliced into four disks（2-mm thickness） , the inorganic filler content and Knoop hardness number（KHN）of each disk were determined. The results suggested that filler loading of composites could be increased by application of centrifugal force if the filler and monomer components were properly arranged.

This study examined the effects of monomer composition, original filler content, and application of centrifugal force on the resulting filler loading of composites. Either Bis-MPEPP or UDMA was mixed with TEGDMA at a molar ratio of 1：1. Silane-treated silica (14 -20 wt％) was added to each mixture. After the mixtures were centrifuged and light-polymerized, rate of increase was determined as the filler increment of 2.0-mm-high, disk-shaped sections of specimen when compared against the uncentrifuged filler content. Both the original filler loading and monomer composition influenced the filler content of the centrifuged composites. Fillers in Bis-MPEPP-based composites exhibited a higher rate of condensation after application of centrifugal force than did UDMA-based composites. The results were suggestive of underlying relationships among the composition, component stability, and post-polymerization properties of flowable composites.

No abstract

Our department has been researching the influences of changes in particle size distribution on the physical properties of luting agents.It is said that luting agents are largely affected by contact with water. In the present study, changes in the physical properties after contact with water at the time of cementation were determined in several types of glass-ionomer cement for Luting (G cement), which differed in particle size distribution, by using an ivory or agar jig. The physical properties of G cement were also examined after pretreatment of the abutment tooth with a surfacetreatment agent and a temporary cement inside the ivory jig.As a result, the greater the content of fine particles was, the greater the compressive strenght, tensile strength and scratch hardness of G cement tended to be. G cement containing high proportions of fine particles was not likely to be affected by water. Pretreatment suchas temporary cementation or surface-treatment prior to cementation for crown or bridge formation was found to be effective for preventing deterioration of the physical properties of G cement.

The gingival margins of restorations are mostly placed subgingivally because of