We have determined the size of the blurred image of the object at the focal plane and also at the site apart from the focal plane both theoretically and experimentally in orthopantomography.
On the other hand, in 1974 Welander introduced a theoretical approximate formula between Q, the size of theobject, and do, the size of the imageafter mathematicalanalysis:
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This theoretical approximate formula is eventually in agreement with the results we obtained through different method. However, there is a problem that this theoretical approximate formula contains considerable errors. Among others, the most important one is that the rate of magnification is neglected partly. This is because the distance from the film differs between the central part and the marginal part of the slit on the circular arc of the object. In addition, the surface of the film may by curved. Thus, in the strict sense this formula may be unsatisfying one. Nonetheless, in the scope of ordinary clinical practice it appears to be valuable enoughfor use.

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Following the radiation therapy for oral cancer, radiation osteitis or osteoradionecrosis often occurs in jaw bones than the other skeletal bones, because of the fact that jaw bones are easily affected with bacterial infection. Clinical and radiographical analysis of the radiation osteitis in jaw bones, and to clarify the relationship between the mandibular absorbed dose and radiation osteitis as well as the etiologicfactors, are not only important for carrying out radiotherapy but also of great significance in relation to the prophylaxis or the inhibition of radiation osteitis, and further they will serve to give many suggestions for dental treatments to be done later.
In this study, the radiation injury of jaw bone following radiotherapy was analysed clinically and radiographically in detail and the criteria in radiographic diagnosis at early stage of the development of radiation osteitis were established. The relationship between the mandibular absorbed dose and radiation osteitis as well as the etiologic factors was also investigated, and further the correlation between the occurrence of radiation osteitis and the tooth extraction as well as the time of its performance at the irradiated site was experimentally pursued.
As the results, radiation osteitis appeared relatively at earlier time after radiotherapy, and it was found out that a radiographic diagnosis at an early stage was possible to be made by means of periodical x-ray examinations as being judged from its typical radiographicchanges. Also at the time of external irradiation for oral cancer, the irradiated side of jaw bone was included within the range of 100 % of depth dose but in the case of interstitial irradiation the absorbed dose of bone was less influential. It was made clear that the incidence of radiation osteitis caused by tooth extraction etc. was more frequent when the TDF value at jaw bone was less than 90, and it was liable to cause radiation osteitis even if no etiologic factor was present when the TDF value was more than 100. Further, it was suggested that radiation osteitis was apparently induced by tooth extraction from the experimentalresults in rats, and that the occurrence of radiation osteitis can be inhibited when the radiotherapy was not allowed to start until the time when the formation of granulation tissue at the socket is considered active.

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There have been few reports described in detail about the dental manifestations of the oral-facial-digital syndrome in adult. A case of an 18-year-old Japanese female with the anomalous dentition is reported here.
In the family history of the patient, no speciality was found except cousinhood of her parents. The extremities were normal in appearance, but prognathism and slight asymmetry of the mandible were observed. As for the intraoral findings, the thick labial frenulumencroached on the alveolar process of the mandible at the midline. Multiple and thick labial frenula were observed on the upper jaw, but cleft of the alveolar process by them was not found. The palate was high-vaulted, but not cleft. Slight ankyloglossia and many odd-shaped teeth were found. All the third molars and the upper lateral incisors were congenitally missing. The marked development was observed on the marginal ridges, labial ridges and the lingual tuberculum of the four lower incisors. The right lower central and lateral incisors were fused. Each incisal edge of the four canines wasflat like an incisor, and the lingual side of the lower canines was shovel-shaped. The lingual tuberculum of the upper canines was markedly accentuated. The slight prominence of the labial and thebuccal collar was observed on the four canines and the lower first premolars. The cusps of the posterior teeth were relatively round, comparing with normal teeth. Theocclusal surface of the posterior teeth was flattened with a various degrees of wrinkling, especially the lower second premolars were almost round and there were supernumerary and small cusps on them. Roentgenographic examination revealed rhizomikry in entire dentition, especially all the first molars had only one root. The irregular thickning of lamina dura was also noticed.
The report of two cases of typical oral-facial-digital syndrome type II (Goldstein, et al.: JADA., 89: 377, 1974) described the anomalies about midline cleft of the lower alveolar process, multiple anomalous crowns and pyramidal molar roots, which were the same as reported here.
Those anomalies may be considered as important signs for the differential diagnosis of oral-facial-digital syndrome.

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