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Volume 37 (1997)
- Issue 4 Pages 275-
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Volume 37, Issue 4
Displaying 1-8 of 8 articles from this issue
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Hiroko MIYAZU, Takashi SAKURAI, Sukenao NUMAYAMA, Nobuaki FURUYA, Isam ...1997 Volume 37 Issue 4 Pages 275-286
Published: December 31, 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSMagnetic resonance imaging (MRI) has recently been used for the diagnosis of internal derangements of the temporomandibular joint (TMJ). Morphological evaluation of the internal derangements of TMJ has shown remarkable progress. However, there are still many questions regarding the relationships between the state of the articular disc and limitation of motion of the mandibular head. In this study, we used MRI to investigate the relationships between these factors in TMJ patients, especially with regard to the range of condylar movement. Bone configurations and articular disc conditions were analyzed in a total of 367 TMJ of 255 internal derangement patients using magnetic resonance imagnig. We examined the influence of articular disc condition on functional disorder and identified the tendencies of the pathology of patients with internal derangements. When we evaluated the direction of disc displacement, anterior disc displacement was most frequently observed. Anterolateral displacement (19.6%) was more frequent than anteromedial displacement (4.1%), and lateral rotary displacement (11.2%) was more frequent than medial rotary displacement (4.1%). Therefore, the articular disc displaced more readily laterally, rather than medially. With regard to the relationship between the articular disc configuration and reduction, enlargement of the posterior band (87.5%) and biconvex (74.3%) discs showed a tendency for articular disc displacement that did not reduce, while discs with even thickness (38.3%) showed a tendency of articular disc displacement which would reduce. Folding (63.6%) and biconvexity (58.6%) tended to limit condylar movement while less limitation occurred with discs of even thickness (17.0%). In cases of disc displacement without reduction, there was a significantly higher percentage of cases with limited condylar movement than in cases of displacement with reduction (p<0.001). In conclusion, this study suggested that the shape of the disc and the presence or absence of reduction markedly influence the functional disorder of TMJ.View full abstractDownload PDF (5312K) -
Yasumasa SAIGO1997 Volume 37 Issue 4 Pages 287-298
Published: December 31, 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSThe purpose of this study was to measure bone mineral content by rotational panoramic radiography. The dual energy subtraction method was applied to panoramic radiographs to allow accurate measurement of bone mineral content without hindrance by soft tissue. A one-shot dual energy subtraction method was carried out using Fuji Computed Radiography (FCR 7000) and a CR-workstation. Panoramic radiographs were obtained using a Morita Super-Veraview with a tube voltage of 80kV, total filtration of 2.0mm of aluminum and tube current of 10mA. A Cu-filter was placed between the first and second imaging plates (IP). Ce, Sm and Gd filters were used as additional filters for single exposure dual energy subtraction using preliminary computer simulation. To separate bone mineral content from soft tissue on panoramic radiographs, weighting factors which eliminated the effects of bone or soft tissue were obtained using an experimental phantom which consisted of water and aluminum cylinders. Aluminum cylinders (3∼12mm) were arranged in a tooth-shaped rows in water and used as the reference for the mandible. This phantom was placed on the panoramic equipment in place of the mandible, and the panoramic phantom image was taken. This phantom image or subtraction image was processed with weighting factors and the aluminum cylinders were evaluated by converting into CaHPO4 of standard Phantom (Compact Bone). The Sm filter was concluded to be the most effective. Adequate correlation between compact bone density and aluminum cylinder thickness was demonstrated.View full abstractDownload PDF (3075K) -
Tsutomu KATADA, Shin-ichi WADA, Kadzuo MAEDA1997 Volume 37 Issue 4 Pages 299-315
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSMPR-CT is used for preoperative examination of dental implants, and good MPR images can be obtained from volume data. By analysis of these images, it is possible to determine know bone structure, quality and distance of important anatomical structures. MPR-CT allows better diagnosis than the conventional panoramic, periapical, tomographic methods. Visualization of the mandibular canal and accuracy of distance measurement were examined in MPR-CT images obtained by helical scanning. With changes in exposure conditions of helical scanning (130kVp, 100mA), distortion in images which appeared to influence distance measurement and a correction methods were examined. Columnar phantom of Mix-DP with contrast media and the lower jaws of cadavers for autopsy training were used. The lower jaws were scanned in water. Reconstitution function was used at normal and high resolution modes. The profile image which was perpendicular to the dental arch of the jaw with image processing apparatus this data (Orthocuts Reformat image) was made in 2mm interval. A positioner was used to obtain images from the same position. The values on images obtained under each condition were compared for the distance of the mandibular canal from the alveolar crest of the lower jaw with a computer. A method for simulation of distorsion in images was sought by convolution of SSP and subject CT value profile of helical scan. The result showed that the distortion of the images changed under each imaging condition and between each specific examined. Slice thickness had the greatest effect. Distortion of MPR image showed good agreement with the simulation. Availability of correction in images by simulation of distorsion of MPR image was recognised in the lower jaw structured of compact bone.View full abstractDownload PDF (9126K) -
Yoshihiko HAYAKAWA, Norio KOBAYASHI, Hitoshi SHIBUYA, Yuji KOUSUGE, Hi ...1997 Volume 37 Issue 4 Pages 316-319
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSObjectives: X-ray transmittance of two CCD-based sensors, an imaging plate and three dental x-ray film packets for intraoral radiography was measured. Methods: A dental x-ray machine, Coronis 20 (Asahi Roentgen Industry), and a type 660 ionizing dosimeter (Victoreen, Inc.) were used. A type 660-3 flat probe was set 10 cm from the cone tip. A lead disk 2 mm thick with a hole 10 mm in diameter at the center covered the cone tip. The hole was shielded by an intraoral sensor for transmittance measurement. Measurements at 60 or 70 kVp, 10 mA, 1.0 second were repeated five times. Results: The x-ray transmittance of the CDR sensor was zero, i. e. less than the detectable minimum (0.3%). That of the Pana Digital sensor ranged from 6 to 10%, while that of the Digora imaging plate ranged from 36 to 39%. Two kinds of Eastman Kodak film packets containing a lead foil had 13-17% transmittance. The DIF-1100 film with a lead-containing vinyl packet showed 46 to 49% transmittance. Conclusion: The two CCD-based sensors examined had lower x-ray transmittance than dental x-ray film packets containing thin lead foil. However, Digora imaging plates and film with lead-containing vinyl packets showed relatively high x-ray transmittance.View full abstractDownload PDF (2114K) -
Hitoshi SHIBUYA, Toshimichi MORI, Yoshihiko HAYAKAWA, Yoshiko OTA, Kin ...1997 Volume 37 Issue 4 Pages 320-326
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSTo measure exposure reduction in general dental practice using digital x-ray imaging systems for intraoral radiography with additional x-ray beam filter. Two digital x-ray imaging systems, Pana Digital (Pana-Heraus Dental) and CDR (Schick Technologies), were applied for intraoral radiography in general dental practice. Due to the high sensitivity to x-rays, additional x-ray beam filters for output reduction were used for examination. An Orex W II (Osada Electric Industry) x-ray generator was operated at 60kVp, 7mA. X-ray output(air-kerma; Gy) necessary for obtaining clinically acceptable images was measured at 0 to 20cm in 5cm steps from the cone tip using an ionizing chamber type 660 (Nuclear Associates) and compared with those for Ektaspeed Plus film (Eastman Kodak). The Pana Digital system was used with the optional filter supplied by Pana-Heraus Dental which reduced the output to 38%. The exposure necessary to obtain clinically acceptable images was only 40% of that for the film. The CDR system was used with the Dental X-ray Beam Filter Kit (Eastman Kodak) which reduced the x-ray output to 30%. The exposure necessary to obtain clinically acceptable images was only 20% of that for the film. The two digital x-ray imaging systems, Pana Digital and CDR, provided large dose savings (60-80%) compared with Ektaspeed Plus film when applied for intraoral radiography in general dental practice.View full abstractDownload PDF (917K) -
Masaaki HITOMI, Akihiko SAKATOKU, Keiichi UCHIDA, Tsunekatsu FUKASAWA, ...1997 Volume 37 Issue 4 Pages 328-329
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSDownload PDF (1882K) -
1997 Volume 37 Issue 4 Pages 330-333
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSDownload PDF (474K) -
1997 Volume 37 Issue 4 Pages 343
Published: 1997
Released on J-STAGE: September 05, 2011
JOURNAL FREE ACCESSDownload PDF (1203K)
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