Papers by Author: Tatsushi Kawai

Abstract: Three kinds of dental zirconia (Cercon, NANOZR, and P-NANOZR) were ground and polished with seven kinds of clinical device and materials. After these grinding and polishing, the surface roughness and the glossiness were analyzed. The crystal phases of the surface were analyzed with a micro X-ray diffractometer. The results demonstrated that all three zirconia showed the smallest roughness and the highest glossiness when they were polished with diamond-containing polishing pastes. Tetragonal to rhombohedral transformation was observed on the ground and polished surfaces of Cercon and ZENOSTAR, whereas monoclinic phase was also detected on the ground and polished surface of P-NANOZR. The polishing with diamond-containing pastes showed the smallest transformation amount of rhombohedral and monoclinic phases. It is concluded that dental zirconia can be well polished with diamond-containing pastes, and the phase transformation are also reduced.

Abstract: Titanium oxide (TiO2) has lately attracted considerable attention as a new material in dentistry because of its catalytic activity and biocompatibility. In the present study, we developed a novel root canal sealer consisting of TiO2 and evaluated its mechanical properties in vitro. The newly developed root canal sealer containing TiO2 has satisfied the requirement of ISO formulation 6876. Our results suggest that the newly developed root canal sealer has excellent physical characteristics, which may make it suitable for clinical use as a root canal sealer material.

Abstract: There is little information concerning the physical properties of various commercialized water-based temporary filling materials. In this study, the setting characteristics of 5 water-based temporary filling cements, i.e., Caviton, HY-seal, Lumicon, Cavit-G, and Cavit-W, were examined. Reinforced plastic pipes were filled with the test materials, and the specimens were then immersed in distilled water at 37°C. Setting time of each specimen was determined by a penetration test using a Vicat penetrometer; and setting layer depth was measured with micrometer calipers. Cavit-W exhibited the fastest setting time, whereas Caviton and HY-seal demonstrated the slowest setting time. These results indicate that the setting properties of these materials used in this study were significantly different for each material, which showed some changes on the surface and the internal part after the start of water absorption.