The aim of the present study was to measure the density of the bone trabecula of intraoral X-ray film directly and to estemate the effect of scattered X-rays on the photographic contrast. The film used was Dental X-ray Film (Fuji Film). The film was developed statistically for 5min. at 20°C using RD-I developer. As the tube voltage three different voltages of 60kV, 80kV and 100kV were used. Total filtration was performed at 2.6mmAl. According to the Groedel's technique, experimental apparatus was determined with a geometrical arrangement adjusted to 210cm for focus object distance and 40cm for object film distance. The exposure field was 6cm φ at the surface of the object. Photogram of the dried mandible was also taken and used as the standard image with no influences from the scattered X-ray. As the scatter, water phantom of 1 to 5cm was placed just before the film and the effect of scattered X-ray on the bone trabecular photographic contrast was examined.
For measurements of density, microphotometer of magnifying projection method was developed. This microphotometer is characterized by that the granularity of the film can be eliminated by adjustment of MTF of the lens and that the focus can be adjusted to the double emulsion layer of the film. Measurements by the microphotometer were performed with an aperture at 20μm φ.
As the model for bone trabecula, fine lead lines of 100μm to 10mm in width and 2mm in thickness were prepared and assumed as complete absorbant of X-ray for bone trabecula of each width. These lead lines were X-ray photographed and examined of the effect of scattered X-ray coming into the radiopaque line. Then, actual photographic contrast of the bone trabecula was measured.
As to the effect of tube voltage the optimum tube voltage was determined by measuring the contrast of bone trabecula with water phantom at 3cm and tube voltage at 60, 80 and 100kV.
The following results were obtained.
(1) The peak of the width of the bone trabecula of the mandible appeared in the range of 500 to 700μm.
(2) For bone trabecula of less than 500μm in width, the photographic contrast value became lower than the actual value under the influence of spatial frequency response of the experimental apparatus.
(3) The scattered X-ray decreased the photographic contrast of the bone trabecula more with an increase in the thickness of water phantom. As compared to the mean photographic contrast of the bone trabecula in the absence of scattered X-ray, the contrast decreased to less than one half in the presence of scattered X-ray from the water phantom at a thickness of 5cm.
(4) It was found that scattered X-ray gave influences on the film only as an exposure uniformly with no influences on the spatial frequency of the object.
(5) Under the influences of tube voltage of the bone trabecula obtained through a water phantom of 3cm, which was considered to be close to the human mandible, the photographic contrast became poorer with an increase in the tube voltage from 60, 80 to 100kV. Thus, it was shown that higher photographic contrast can be obtained with lower voltage.
(6) The photographic contrast of the bone trabecula of a patient as determined using Ultra Speed Film (Kodak), which is applied clinically, ranged from 0.12 to 0.23.

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Since Garré's osteomyelitis of the mandible was first reported by Pell and associates in 1955, this disease was differentiated from other types of osteomyelitis on clinical and radiological findings.
The aim of this paper is to describe in detail the clinical and radiological findings of Garré's osteomyelitis in the mandible.
Five cases of Garrés osteomyelitis of the mandible (three males and two females) were presented in this paper. Age distribution was 9 to 13 yeares, and the mean age was 10.2 yeares. Chief complaint was painless swelling on the mandibular region.
Periapical abcess in the mandibular first molar was seen in four cases radiologically, and five cases revealed periosteal reaction in the infected region. Most of the periosteal reaction was onion peel type. Moderate osteosclerosis around periapical foci and localized thickning of the cortical bone were also recognized radiologically.

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Five cases of mucoepidermoid tumor of the mandible were studied on clinical, radigoraphic and histopathologic findings. The cases consist of 2 males and 3 females, aged from 58 to 75 years old.
Three of the five cases were central type and the others peripheral type, and histopathologically classified into low grade malignancy and high grade malignancy. In the central type, radiographic findings of the low grade malignancy were well-difined with portional ill-defined margin. However, the high grade malignancy were radiographically ill-defined. On the other hand, in the peripheral type both of two cases were low grade malignancy. these radiographic findings showed U-shaped bone deptruction on the retromolar region and ramus. Extirpated specimens indicated the necessary of radiologic information of the lingual cortex of the mandible.

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The radiographic findings of 9 cases of Non-Hodgkin lymphoma occured in the jaws were analyzed.
The outline is as the follows.
1. There was no sexual preference with four males and five females. The age of patients ranged from 4 to 78 years, with a mean of 49 years. Of nine cases, three cases occured in the mandible, three in maxillary sinus, three in the gingivo-alveolar region and one in both upper and lower gingivo-alveolar region at the same time.
2. The radiographic appearances were quite varied. Although the findings showed a diffuse bone destruction, they could not differentiated from the other malignant tumor.
3. Radiographically, there were ill-defined margin in the diffuse lymphoma, and moderate defined margin in the follicular lymphoma.

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The aim of the present study was to determine the allowable range of X-ray projection angle for the second and thereafter roentgenographies in relation to the direction of X-ray beam at the initial one in order to obtain the identical view when several roentgenograms taken with lapse of days should be compared in intraoral roentgenography.
Experimental procedures used were as follows:
The unit was geometrically arranged so as to obtain Object Focus Distance of 510mm and Object Film Distance of 67mm and prepared to permit changing of projection angle freely with precision of 0.5°.
The methods used were bisecting angle method (with film-dental axis of 10°, 20°, and 30°C) and paralleling method.
At each roentgenography, the film which produced an isometric image of the tooth length was regarded as the standard view, and roentgenography was performed with projection angles adjusted towards the direction which gives shorter image of the tooth length (1° to 5°).
The X-ray site was 45 for the maxilla and 56 for the mandibulla.
For collection of data, the dental film of the original data was magnified 3.1 times and printed on gravure film with transparent base.
Using a microphotometer, the septa interalveolaria between 4 and 5 and that between 5 and 6 were scanned from the processus alveolaris to the body and the data obtained were input a mamory of 2KW through A/D converter of 8 bits.
The aperture of the microphotometer was 0.25×2.5mm².
From the mircophotometer, the function of density level of trabeculation was subjected to Fourier transformation and then further to inverse Fourier transformation through a low cut filter with a cut off frequency of 0.2 1p/cm to obtain a function of traf eculation only.
Using the data processed as described above, cross correlation coefficient betvc een the standard view and those views obtained with various angles.
For gross assessment of the image of trabeculation, the standard view and the views taken at various angles were shown to seven dentists with clinical experiences of 4 to 5 years to let then choose the views differing from the standard view.
Following results were obtained.
1) At each roentgenography, the views with cross correlation coefficient of 75% or higher for the correlation with the standard view was regarded as identical view. It was found the maxilla should be projected with the angle within 2° irrespective of the methods used. On the other hand, the mandibula should be projected with the angle of less than 5° when paralleling method is used and less than 45° for the film-dental axis angle of 10° and less than 3° for those of 20° and 30° when the bisecting method is used.
2) When the film is set with changing of the film-dental axis angle with lapse of time on the assumption that requirements for the bisecting method are always met, the film should be set at angles within 5° from the initial film-dental axis angle.
3) When a film holder for standardized intraoral roentgenography was used, little or on reduction in coefficient for correlations between views taken with lapse of time.
4) When difference was found grossly between two films taken on different days with film setting by free hand, the X-ray projection angle differed by more than 3°.

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A case of bifid condyle in a 75-year-old man is presented. He was referred by his dentist to our department for evaluation of an abnormal morphology of his left condyle, which was found accidentally during routine panoramic radiography.
Past history revealed that he has experienced a hit on his chin 6 months ago. Physical examination showed clicking sounds on his left temporomandibular joint during opening mouth. He also complained otalgia occasionary.
Radiological examinations, such as transcranial projection, orbito-ramus projection, and sagittal and frontal tomography of the bilateral TMJ were added to panoramic radiography. These radiographs revealed that his right condyle was apparently normal, but the left condyle was divided into two parts. The outer part of the divided condyle was larger than the medial one. Because of no radiological findings of mandibular fracture, the abnormal left mandibular head was diagnosed as bifid condyle.
It is postulated that the bifid condyle arise as a result of ossification disturbance by some physical irritations in the early developmental period of the condyle.

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