Purpose: Panoramic TMJ projection as parasagittal views of the temporomandibular joint (TMJ)(lateral Panoramic TMJ radiography), has been reported to be useful for the observation of both structural bone change and condylar position in fossa, but there have been no reports of large-scale studies using lateral panoramic TMJ radiographs. The purpose of this study was to investigate whether the bony outlines of anatomical landmarks of the TMJ can be observed in the radiographs of 86 joints. Material and Method: Forty-three patients were examined using lateral panoramic TMJ projection in AZ3000^TM rotational panoramic X-ray unit (ASAHI Roentgen Industry Company, Limited, Kyoto, JAPAN). The radiographs of the patients were investigated by two oral radiologists to evaluate whether four sites, postglenoid spine, articular eminence, glenoid fossa and condylar head, could be observed. Results: The condyle could be observed in 100% (86 of 86) of the joints. The postglenoid spine, articular eminence and glenoid fossa could all be observed in 58% (50 of 86) of the joints. Thus all four sites could be observed in 58% of the cases. Bilaterally, all four sites could be observed in 42% (18 of 43) of the patients. Conclusion : In the lateral panoramic TMJ radiographs many of the bony outlines could not be observed. Further study of panoramic TM Jprojection may be needed to solve this problem.

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Purpose: A panoramic TMJ projection for lateral views has been reported as very useful for the observation of the condylar position in the fossa. We reported the visibility of bony outlines on lateral panoramic TMJ images with an AZ3000^TM rotational panoramic X-ray unit (ASAHI Roentgen Industry Company, Limited, Kyoto, JAPAN) in a previous study (part 4). In this study, we investigated the optimal image layer thickness to improve the visibility of the TMJ images. Material and Method: We altered the AZ3000^TM so that we could adjust the width of slit (named AZ3000TU) to change the image layer thickness. The image layer thicknesses at various combinations of the first and second slits were defined with a wire mesh phantom. A tissue equivalent phantom was positioned and the panoramic lateral TMJ projection was taken with different image layer thickness. The phantom shifted 2.5-5mm inside and outside from standard position in the horizontal plane to simulate miss-positioning of the patient using various combinations of the slits. Four sites, postglenoid spine, glenoid fossa, articular eminence and condyle, in the radiographs were evaluated to find out the best slit combination and whether the sites could be observed or not by two oral radiologists. Results: The image layer thickness was 6mm at 1.2/8mm slit combination, 8mm at 1.0/7mm, 11mm at 0.5/5mm and 25mm at standard lateral mode. When the image layer thickness was at 6, 8 and 11mm, the four sites of TMJ were all observed. At 25mm image layer thickness, the mid cranial base superimposed TMJ strongly. In the case of 6mm-image layer thick ness, by positioning the phantom 5mm lateral from the standard position in the horizontal plane the postglenoid spine was difficult to observe in the radiograph. Conclusion: In the radiographs at the standard position where the image layer was less than 11mm, all four sites of TMJ were observed. However, at 6mm image layer thickness (the thinnest), when the object was positioned 5 mm lateral from the standard position, the postglenoid spine was difficult to detect.

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The limited cone beam X-ray CT (Ortho-CT) was developed on the basis of multi-functional panoramic apparatus, SCANORA (Soredex Co. Helsinki Finland). The imaging intensifier (I.I.) was built in this apparatus as a X-ray detection device instead of X-ray film. The signal provided from I.I. was converted from analog into digital by an analog-digital converter and image reconstitution was done as a three. directional image of the dimensions 3.8cm of width, 3.0cm height and 3.8 cm depth with the personal computer. The “3DX Multi image micro CT” (3DX) was developed along similar lines by MORITA Co., Ltd. (Kyoto, JAPAN).
In this study, the stochastic effect on organ and tissue caused by examinations using Ortho-CT and 3DX was measured. The effective dose was estimated according to the recommendation of ICRP60 and was compared with those of panoramic radiography and computed tomography. The irradiation conditions were as follows: 85kV, 10mA with the filtration of 3mmAl and added 1mmCu for Ortho-CT, and 80 kV, 2 mA and the filtration of 3.1mmAl for 3DX. The measurement of organ and tissue dose was performed using an anthropomorphic Rando woman phantom (Alderson Reseach Laboratories Co., Stanford, CN), as well as by using two different type of thermoluminescent dosimeter (TLD); Panasonic UD-170A (BeO) and UD-110S (CaSO₄: Tm). The UD-170A was for dose measurment of the inner useful X-ray beams, while the UD-110S was for outer beams. The measured organ and tissue were those recommended with ICRP60 (gonad, breast, bone marrow, lung, thyroid gland, esophagus, stomach, colon, liver, bladder, skin, brain, thymus, adrenal, kidney, spleen, pancreas, upper large intestine, uterus, eyes and major salivary gland). The imaging by Ortho-CT was made in the left maxillary 1st molar, left mandibular 1st molar and temporomandibular joint. 3DX measurement was made in the maxillary incisor region and middle ear regions other than the regions mentioned above.
The skin dose measurement with Ortho-CT showed that mean values were within avariation of 750-615μSv. The effective dose for the mandible, maxilla and TMJ with Ortho-CT was 13.2μSv-23.0μSv. The resultant effective dose for the maxillary incisor, maxillary 1st molar, mandibular 1st molar, TMJ and middle ear regions with 3DX were 7.4μSv, 6.3μSv, 11.7μSv, 9.3μSv and 14.2μSv, respectively. It was found that the effective dose values were lower when compared with those in CT or panoramic radiography. Furthermore since three-directional images and three-dimensional images can be obtained easily, we suggest that these system will be useful for diagnostic imaging in dentistry.

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Melanotic neuroectodermal tumor of infancy (MNTI) is characterized by a rapidly growing mass in the anterior maxilla of infants under the age of one year without predilection to sex. It is either pigmented or non-pigmented in color and either exophytic or endophytic in involving the bone. Any tooth involved in the lesion can be displaced. MNTI is thought to be mesenchymal in origin, probably arising from the neural crest and is also thought to be benign in nature. We report here one case of MNTI and discuss its multicentricity, recurrent tendency and pattern of generization based on the CT findings for our case.

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The purpose of this study was to assess the condition and viability of the autogenous particulate marrow and cancellous bone grafted for alveolar cleft. In this investigation, 2 unsuccessful cases (7-year-old male and 10-year-old female) that showed marked bone resorption on CT images obtained 1 month after the operation were evaluated. The viability of bone grafts was documented by means of bone scintigraphy and MRI.
On the scintigrams and MRI of the 2 cases obtained 3 months after the operation, there was no evidence of acute inflammation in the operated alveolus. The scintigrams of the 2 cases revealed the decreased uptake at the cleft region and the increased uptake at the adjacent alveolus of the cleft. The decreased uptake of the cleft area gradually became wider and clearer until 14 months after the operation. On the other hand, the increased uptake at the adjacent alveolus of the cleft still partially remained at 14 months after the operation.
On T1-weighted MRI obtained 3 months after the operation of the second case, the grafted bone showed partially hyper intensity similar to the fatty tissues. This area extended to the adjacent alveolus on the MRI obtained 14 months after the operation.
From these findings we suggest that scintigraphy may be useful to evaluate postoperative avascular necrosis in the alveolar cleft, and that MRI may be useful in assessing the fatty marrow maturation of the bone bridge.

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