Evaluation of the mechanical behavior of bulk-fill and conventional flowable resin composites using dynamic micro-indentation.

The purpose of this research was to investigate the mechanical behavior of commercially available bulk-fill and conventional flowable resin composites using the dynamic micro-indentation method. The effect of inorganic filler content on mechanical properties was also assessed. Weight percentages of the inorganic filler in the resin composite were measured using the ashing technique. The results showed that dynamic hardness and elastic modulus tended to increase with inorganic filler content. Furthermore, the differences in mechanical properties between top and bottom surfaces were less pronounced in bulk-fill flowable resin composites compared with conventional flowable resin composites. In conclusion, the mechanical properties of bulk-fill flowable resin composites are affected by filler content. Moreover, bulk-fill flowable resin composites have a higher polymerization depth than conventional flowable resin composites when sample thickness is 4 mm.

[Development of a pin-hole camera using a phosphor plate, and visualization of the scattered X-ray distribution and optical image].

In order to obtain an image of scattered X-ray in the diagnosis domain, we have newly developed a pin-hole camera. Because of the necessity of the X-ray shielding, the pin-hole part has a depth corresponding to that of the shielded material. As a result, efficiencies of obliquely incident X-rays are reduced. To decrease the descent of the efficiencies, we developed a large camera using a 10 × 12 inch size phosphor plate as an X-ray detector. A phantom was irradiated by X-rays with conditions of 500 mAs and 5000 mAs, and images of scattered X-rays were obtained. The former image showed scattered X-rays from the phantom. The latter image showed those from the air of beam axis as well as from the phantom. Moreover, we made a new proposal to obtain an optical image using the fading effect.