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Purpose: Intraoral views of teeth with dowel and post hole taken by small three-dimensional X-ray CT (3DX) were compared with three-dimensional images from specimen sections of the same extracted teeth. This comparison shows the usefulness of 3DX for examination of cracked teeth in the oral cavity., Materials and Methods: After taking dental tomographic images using 3DX for fractured teeth in the oral cavity, the fractured teeth were extracted and three-dimensional images for them and their cracks were obtained from a set of photographed sections. Then both sets of three-dimensional images for the fractured teeth were compared in terms of the form and region of the cracks., Discussion: The tooth cracks were observed at the root face region in the intraoral view. Also, in the extracted teeth, fracture lines were recognized from the three-dimensional images. Moreover, a discontinuous image was obtained in teeth from the dental tomographic image using 3DX. This discontinuous image in teeth was observed in the same region and direction as the cracks of the three dimensional image from specimen sections of the extracted teeth., Conclusions: The discontinuous images of teeth in the dental tomographic images from 3DX were observed in the same region and direction as the cracks of teeth in the three-dimensional images from specimen sections of the extracted teeth. It was confirmed that dental tomographic images from 3DX are useful for finding cracks in living teeth. However, dental tomographic images from small three-dimensional X-ray CT are not perfectly reliable because the discontinuous image is not found in some teeth where the cracks are recognized by images from specimen sections after extraction.

As an aid in instructions oral health care to university students, tooth conditions were examined using panoramic X-ray films. The materials were taken from 129 students of the University of Tokyo. The average age was 22 years 5 months. The results were as follows: 1. Lack of tooth was frequently found to be both maxillary and mandibular third molars. It was also occasionally found to be maxillary first premolars, mandibular lateral incisors, and mandibular second premolars. The average value for lack of tooth per individual was 0.9. 2. Root canal fillings were often found in mandibular first molars, maxillary central incisors, mandibular second molars and maxillary second premolars. The average value was 1.1. 3. Metal restorations were often made in first and second molars, especially in mandibular. The average value was 6.2. 4. As for maxillary third molar axis, the majority showed normal direction. In mandible, however, the normal direction was only found in 37.7% and the others showed troublesome axes. It seemed that careful attention should be given to the mandibular third molar conditions.

Two cases of personal identification based on the characteristic findings observed in the bones and teeth of unknown human remains are reported. In Case 1, a skeletonized cadaver could be identified as a 49-year-old male because the autopsy findings of the left clavicle of the cadaver, which was previously operated with metallic screw and wire after fracture, corresponded to the characteristic findings in an antemortem X-ray picture of the presumed person. In Case 2, a cadaver discovered at the seaside, could be identified as a 55-year-old male by comparison between ante- and postmortem dental X-ray findings such as root canal treatment and disease (radicular cyst) including the anatomical characteristics of the root. In forensic practice of personal identification of cadavers with advanced postmortem changes, it seems really important to find out an antemortem medical and/or dental chart and X-ray pictures as well as thorough examination for hard tissue of human remains.

The subjective contrast including the density component of radiograph as well was aimed at. In relation to the intraoral radiographs (18 cases) of the left first molar of the mandible and its surrounding tissue taken using tube voltage of 60-90 kV, the radiographs were evaluated based on the mean of the extracted subjective contrast values, resulting in the following findings: 1. A tendency was observed in the enamel and dentine of the central portion of crown, for the mean of the extracted subjective contrast values using tube voltage of 70 kV to be lower than that with 60 kV. 2. A tendency was found in the dentine on the cement side of the mesial and distal cervical portion and the periodontal membrane space of the cervical portion, for the mean of the extracted subjective contrast values to generally become larger as the tube voltage was increased. 3. A tendency was recognized in the alveolar lamina dura of the mesial and distal marginal alveolar portion, for the mean of the extracted subjective contrast values to become larger as the tube voltage was increased. From intraoral radiographs of teeth, the findings mentioned above have proved that good radiographs will be created using a tube voltage of 70 kV for enamel and dentine, and using 60 kV for dentine and cement in the area of the cervical portion or in case of the periodontal tissue.