The news of the discovery of X-rays was first published in Japan by the medical journal “TOKYO IJI SHINSHI” No. 935 on February 29, 1896, the year after the discovery. Some of the Japanese scientists who learned of the discovery of X-rays tried to generate X-rays and almost all of them succeeded in this attempt in 1896. While there is no evidence of the X-rays being applied in clinical dentistry at that time, a dentist in New Orleans, Luisiana, by the name of Dr. C. H. Kells Jr. had already installed X-ray equipment in his clinic by the middle of 1896 and he used roentgenography in his daily practice. In the Meiji and Taisho eras (from 1867 to 1926) there were seven dental schools in our country. During the nine years from 1913 to 1921, teachers of dental roentgenology were appointed at each of the five dental schools. Unfortunately no information regarding the education in dental roentgenology could be gained at the two of those seven schools. Thus, somewhat belatedly, the education and clinical practice of dental roentgenology commenced in our country. It was in 1928 that Shimadzu Seisakusho Co. began making X-ray equipment for dental use, and this was the first dental X-ray equipment to be manufactured in our country. When roentgenography was first practiced both in our country and in foreign countries, dry plates or films for conventional photography were used, and these were wrapped in waterproof black paper by the dentist himself. The first dental X-ray films were made and marketed by Fuji Shashin Film Co. in 1943. In the USA, the first waterproof dental X-ray films were made available commercially in 1913. In our country, the textbook of dental roentgenology entitled “DENTAL ROENTGENOLOGY” was published in 1916 which was written by Dr. G. Fujinami and Dr. N. Teruuchi. This was probably the first textbook of dental roentgenology published in our country. The first academic society for oral radiology “SHIKA HOSHASEN SHUDANKAI” was established in 1951, but this was considerably later than the “GERMAN SOCIETY OF DENTAL ROENTGENOLOGY” (“DEUTSCHE ZAHNÄRZTLICHE RÖNTGENGESELLSCHAFT”) which was established in 1914.

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We investigated the reliability of clinical findings in evaluating the status of the temporomandibular joint with internal derangement. Materials and methods: Two hundred eighty-nine patients were examined clinically and by MR imaging at 0.3 Tesla (MRP-7000 HITACHI MEDICO, Tokyo). Using the MR image findings as a standard, accuracy, sensitivity, specificity and positive and negative predictive values were calculated. Remarkable clinical findings were TMJ pain, clicking, crepitus and limitation of opening. Results: Two hundred twenty-five joints evaluated as negative for displacement of the disc, 122 joints as anterior disc displacement with reduction, 138 joints as anterior disc displacement without reduction, 57 joints as osteoarthrosis and 36 joints as sideways disc displacement. When the TMJ pain was present sensitivity in diagnosing internal derangement in the TMJ was 49% (155 of 317). In patients with anterior disc displacement with reduction of the TMJ, clicking sound was presented in 72% (88 of 122). Twelve of 57 joints (21%) with osteoarthrosis demonstrated crepitus sound. Limitation of opening was found in 47% (70 of 149), of patients with anterior disc displacement without reduction of the TMJ. Conclusion: Diagnostic reliability of clinical findings alone was low when evaluating the status of internal derangement in TMJ.

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The clinical image quality created by an intraoral digital imaging system using Digora^® was evaluated by comparing it with conventional Ektaspeed^® Plus film. An imaging plate (IP) of the Digora^® system was inserted into the packet which contained a film in the front wrapped with black paper to protect the IP from light. Both Digora^® and film images can be obtained at the same time in the same geometry. The exposure time which gave the proper density was determined for observation of the film image. A hundred periapical images for each system were obtained in a total of 45 patients. The clinical usefulness of each system was assessed based on the visibility of the anatomical structures and the pathologic conditions in the coronal, alveolar and the apical regions. The evaluation was made separately for each system at an interval of 1 week. Five observers were asked to evaluate the image quality in assessing pathologic conditions of these regions using the following five-point rating scale: 1, excellent; 2, good; 3, fair; 4, poor; and 5, not acceptable. Three to 5% of the answers were “not acceptable” on the images by Digora^® system compared with 5-10% by film images. The number of “not acceptable” answers is significantly lower in the Digora^® system than the film in the apical region of the upper and lower anterior teeth and the alveolar region of the lower posterior teeth using chisquare test. The results were also compared using Wilcoxon's signed rank test for each observer. The results showed that: 1) in the coronal region, two of five observers judged the Digora^® systsm to be either better or worse than film, 2) in the alveolar region, all observers agreed that the Digora^® system was better than or equal to film, and 3) in the apical region, four of them judged Digora^® to be better than or equal to film. These results suggest that the Digora^® system could be used for a variety of dental diagnostic purposes.

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Since the introduction of cephalometric radiology by Broadbent to dentistry, this technique has been widely used for radiometry of the maxillo-facial-cranium. In this study, ceplalometric radiography was used to quantitatively and qualitatively analyze a foreign body in the tongue. A 77-year-old man, whose tongue was injured by an airturbine steel bur during dental treatment, was referred by his dentist to our department to search for a broken steel bar in the tongue. Panoramic, postero-anterior, and lateral cephalometric radiographic examinations were performed for the patient. Of the individual radiographical examination, the cephalometric radiography gave the exact position of the foreign body in the tongue. According to the radiographical examinations, mainly by cephalometric radiography, the three dimentional position of the forign body in the tongue could be determined. The location of the foreign body, which was determined by radiographical examination, was found exactly at the position indicated by radiography. These results suggest that cephalometric radiography may be suitable for localizing the radiopaque foreign bodies in the tongue.

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As an educational tool of oral radiology, a computer simulation system of the intra-oral radiography using the three-dimensional computer graphics (3D graphics) was established. The ray-tracing technique was used to render a 3D graphic. The procedure for creating a 3 D graphic is: 1) Create the teeth models as a semitransparent object, 2) create a X-ray tube model as a spotlight, 3) create a film model as a shadow picture's screen, 4) align the tube, the teeth and the film model in the three-dimensional matrix according to the X-ray projection geometric order, and 5) render a 3D graphic in appropriate viewpoints. A translucent image of teeth corresponding to a dental radiograph was obtained. High quality 3D graphics to demonstrate the imaging techniques, such as bisecting-the-angle, paralleling, and tube shift projection techniques, were created.

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