Understanding baseline information on the mechanical properties of primary teeth is important in pediatric dental care. The purpose of the present study was to investigate distributions of microhardness of entire cross-sectioned primary molars using a Vickers microhardness test and observe microstructure by a confocal laser scanning microscopy. Sound mandibular primary molars of Hellman's dental age III B were sectioned and polished for indentation testing. Sixty-five indentations in both enamel and dentin were made in each specimen, using eight indentation lines corresponding to eight directions and including an additional indentation in the center of each specimen. The features of microstructures were observed. The area of peritubular dentin and intertubular dentin were also evaluated. Microhardness was found to decrease progressively toward the center in all directions with the exception of the lingual and mesiolingual directions in enamel. In dentin, this trend was found in all directions with small deviations. Hard regions with large area of peritubular dentin were found at the microstructural level. The microhardness of cross-sectioned sound primary molars have a gradient. It is suggested that peritubular dentin is not negligible with respect to its microhardness from a structural point of view.

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Stress distributions of endodontically treated teeth were estimated by using finite element analysis for evaluating root fracture. The finite element model was generated based on x-ray CT data and mechanical properties of alveolar bone, natural teeth and a partial denture were assigned. The result showed that stress concentration was observed at the boundary area between the natural teeth and the partial denture when a vertical load was applied, possibly associated with root fracture of teeth clinically observed. Higher stress concentration was observed under a lateral loading than under the vertical loading. By contrast, stress concentration was less observed when mechanical properties of the natural teeth and the partial denture were assumed to be the same. The present technique would be useful for designing an optional partial denture to prevent root fracture of teeth.

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It is in an increase trend recently as the tooth extraction caused with the root fracture. The condensation methods of root canal filling are paid attention as the potential cause of root fracture. The purpose of this experiment is to evaluate the influence that the condensation methods of root canal filling procedure relate to root fracture. It was experimented by using a suspected three dimensions photo-elastic model, and about the stress that breaks out on the inside of tooth and the periodontal tissues, when the root canal is pressed with the three kinds of spreader that is used to root canal filling.
The curved root was influenced to the stress between inside and outside of the root curve at the same tooth during root canal filling procedure. The complex root form of tooth had many stress points in its surfaces.

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This study analyzed tibio-femoral joint kinematics and contact area during knee flexion at 0°, 30°, 60°, 90° and 135° using magnetic resonance imaging with a 3D-fat-suppressed fast low angle shot sequence (3D-FLASH). At a 200N loading situation, knee flexion angles were chosen to be 0°, 30°and 60°. Sagittal and coronal images were obtained under the loading and unloading situations from 6 healthy male Japanese volunteers. At unloading situation, from 0° to 90° the centroids of the medial and lateral contact areas translated backward and outside. From 90° to 135° the centroids of the medial and lateral contact areas translated backward and inside. The contact areas tended to decrease, but from 60° to 135° knee flexion the medial contact area was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of centroids of the medial and lateral contact areas decreased with an increase of knee flexion, and the centroids moved roughly straight backward as well. The contact areas increased at each knee flexion angle as compared to unloading situation. These results showed good correlation with previous ones found in the other studies of knee kinematics.

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In previous studies, the elastic stress field near the crack tip was investigated by digital image correlation and the 2-D intelligent hybrid method. In this study, the 2-D nonlinear hybrid method was developed to analyze the elastic-plastic singular stress field near the crack tip from the displacement data obtained by digital image correlation. Then, the 2-D nonlinear hybrid method was carried out to evaluate a stress, strain and the J integral. The 3-D elastic-plastic finite element method was conducted on the same specimen as the experiment, and the validity of this approach was discussed from the comparison of the experiment and 3-D finite element method.

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The temperature image measured in the infrared thermography has a temperature change by the inflow appearance of heat near the free surfaces, and the obtained sum of the principal stresses is not a true value. The data of the sum of the principal stresses were measured on the CNS specimens subjected to seven kinds of mixed-mode loading by the infrared thermography. After estimating the nodal forces from the sum of the principal stresses by an inverse analysis, the error included in the experiment field was modified by the intelligent hybrid method. However, it has the influence by heat conduction on an infrared stress measuring method. Then, the temperature field was corrected in nonsteady-heat-conduction inverse analyses. Thereby, the stress intensity factors of mixed mode were able to be evaluated with less than 6% of error by the infrared hybrid method in consideration of the influence of heat conduction.

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The deformation of new containers for liquid products subjected to static pressure and impact loads due to dropping was investigated, and compared with that of conventional paper containers. The new containers consist of a paper container with and without ribs and a liquid packaging bag and contain about 1000ml of water. The paper container and bag in the new containers were made of a sheet of recycled paper and a plastic film, respectively. The collision with the bottom and corner due to drop from heights of 1m and 2m was carried out. Results showed that the values of bulge of the new containers with ribs subjected to static pressure and impact loads are smaller than those of the new containers without ribs and the conventional containers. Furthermore, the new containers with and without ribs subjected to impact loads do not leak liquid for both corner and bottom drop from heights of 1m and 2m. In contrast, the conventional containers leak liquid for both corner and bottom drop from a height of 2m.

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Some of the Japan's oldest nuclear power plants are now entering their more than 30th year, which is close to their designed lifespan. The Rules on fitness-for-service for nuclear power plants issued in May 2000 allows allowable flaw sizes in operating plant components. In these circumstances, water jet peening against SCC processed on the shroud of many nuclear plants. In such a process, discriminating processed area on the shroud became very important on In-situ work. It was clarified that millimeter wave reflection detection makes cost- and time-effective discriminating tool, compared with X-ray diffraction, sonic velocity measurement and electric resistance measurement.

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