The following conclusions were obtained from the non-reconstructed and reconstructed subtraction images of the standard intraoral radiographs which were taken with paralleing technique with Rinn XCP only and with occlusal bite registration for geometric standardization using bilateral mandibular premolar and molar regions of two dry humad skulls. 1. The SD of the overall subtraction images of the premolars and molars of the non-reconstructed, tnat is, the manual superimposition showed statistically significant difference between the non-registered and registered groups. 2. In non-reconstructed and non-registered cases, the quality of the subtraction images were improved when superimposition was focally done and this was more evident in areas where the radiographic imaged tend to be distorted due to anatomic readons. 3. In non-restructed and registered cases, the subtraction images were consistent regardless of the anatomic site or the focus superimposition. This means that the geometric standardization with only occlusal bite registration could produce serial radiographs which is suitable for subtraction. 4. The SD of the overall subtraction images of the premolars and molars of the reconstructed, that is, the automatic superimposition showed statistically insignificant difference between the non-registered and registered groups. This means that using reconstruction, subtraction radiography is possible without occlusal bite registration. 5. In reconstructed and non-registered cases, compatible quality of the subtraction images were obtained regardless of the anatomic site or area of the corresponding points. 6. In reconstructed and registered cases, best subtraction images whose quality showed sensitivity to the areas of corresponding points were obtained.
Bicuspid ; Jaw Relation Record ; Molar ; Radiography* ; Skull

PURPOSE: The aim of this study was to assess the validity of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error. MATERIALS AND METHODS: Twenty periapical radiographs used baseline images were copied to exclude the influence of exposure geomety and contrast differences. These subsequent images were displaced by 0.1-0.5 mm in the x-, y- and xy-directions, rotated by 0.5-3o and distorted by angular contraction of 1-5o in x- and y-axis before subtraction. Pearson correlation coefficients(r) were calculated between the standard deviation of gray levels in the subtracted image and misplacement and paired t-tests were performed to compare standard deviations. RESULTS: Linear displacement showed high correlation coefficients of 0.997, 0.997 and 0.995 in x-, y- and xy-axis respectively. Statistically significant different standard deviation existed among all linearly displaced groups(p<0.05). Relatively low correlation coefficients of 0.982 and 0.959 in x- and y-axis distortion were demonstrated. The standard deviations between the two distortion groups were statistically significantly different(p<0.05). CONCLUSION: Standard deviation of gray level distribution in digital subtraction images is satisfactory but not perfect similarity measure to assess superimposition errors.
Radiography*

PURPOSE: This study was done to evaluate the absorbed doses in organs of the head and neck for the conventional temporomandibular joint tomography. MATERIALS AND METHODS: Dosimetry was performed with 32 LiF thermoluminescent dosimeters, which were placed in a tissue-equivalent phantom when the temporomandibular joint was examined by both lateral and frontal temporomandibular joint tomography. RESULTS: For lateral tomography, parotid gland and preauricular area towards tube showed relatively high absorbed dose of 1056.9 microGy and 519.9 microGy respectively. For frontal tomography, the two largest absorbed doses were 259.2 microGy in orbit towards tube and 212.0 microGy in lens towards tube. CONCLUSION: Conventional temporomandibular joint tomography showed relatively low absorbed doses on critical organs. Thus, responsible use of it may not be limited.
Head* ; Neck* ; Orbit ; Parotid Gland ; Radiation Dosage ; Radiography ; Temporomandibular Joint*

PURPOSE: To describe the MRI findings of the retrodiskal tissue in patients presenting with TMJ internal derangement and to correlate these findings with clinical and other MRI manifestations. MATERIALS AND METHODS: One hundred eighteen joints of 63 patients with TMJ internal derangement were examined by MRI. T1-weighted sagittal MR images taken in both closed- and open-mouth were evaluated for the presence of demarcation between disk and retrodiskal tissue, the presence of low signal intensity, and the depiction of the temporal part of the posterior attachment. The results were correlated with the duration of TMJ internal derangement, the presence of pain, and other MRI findings, including the type of internal derangement, the extent of disk displacement, the degree of disc deformation, and the presence of osteoarthrosis. RESULTS: A significant relationship between the presence of low signal intensity in the retrodiskal tissue and other MRI findings was determined. Low signal intensity on the open-mouth view was observed more frequently in patients with disc displacement without reduction, severe disc displacement and deformation, and osteoarthrosis (p< 0.05). The demarcation between disk and retrodiskal tissue, and the depiction of the temporal part of the posterior attachment (TPA) were correlated neither with clinical, nor with other MRI findings. CONCLUSION: This study suggests that low signal intensity in the retrodiskal tissue on open-mouth MR image can be indicative of advanced stages of disk displacement.
Humans ; Joints ; Magnetic Resonance Imaging* ; Osteoarthritis ; Temporomandibular Joint Disorders ; Temporomandibular Joint*

Magnetic resonance imaging with its superior soft tissue contrast resolution and absence of beam hardening artifacts, combined with its ability to perform multiplanar imaging, is now effective tool in diagnostic imagings. Magnetic resonance is primarily a phenomenon that involves atomic nuclei. It provides totally new clinical informations with no known hazards through the use of very weak interactions with endogenous stable magnetic atomic nuclei. This article briefly summarized the basic mechanism of generation and detection of the signals and general sorts of tissue properties which can influence the signals and thereby give rise to tissue contrast. It also describes how the machine-operating parameters can be used to manipulate the tissue contrast observed in the image.
Artifacts ; Magnetic Resonance Imaging*

No anstract available.
Adolescent* ; Ameloblastoma* ; Child* ; Humans

The authors examined the condylar position and shape of condylar process from the transcranial radiographs and polytomographs of the 130 temporomandibular joints of 65 patients who complained symptoms of temporomandibular disorder and the followings were obtained ; 1. The age and sex distribution of the 65 patients showed peak incidence in 2nd decade (27.7%) followed by 3rd (18.5%) and 4th decade (18.5%) and female predominance (87.7%). 2. In polytomography 64 joints (49.2%) showed consistent condylar position from lateral to medial and 39 joints (30.0%) of them showed agreement with those of transcranial radiographs. Among the 66 joints (50.8%) which showed changes in condylar position, 48 joints (36.9%) showed agreement with lateral and central tomographic and transcranial radiographic position. 41 joints (31.5%) showed disagreement in condylar position between the polytomographic and transcranial radiographic images. 3. When the condylar position was classified as anterior, central and posterior, the posterior position was the most frequent position, that is , 42.3% of the transcranial radiography and 42.3%, 49.2% and 38.5% of the lateral, central and medial polytomographic radiographs. 4. In polytomography 84 joints (64.6%) showed consistent condylar shape from lateral to medial and 74 joints (56.9%) of them showed agreement with those of transcranial radiographs. Among the 46 joints (35.4%) which showed changes in condylar shape, 40 joints (30.1%) showed agreement with lateral and central tomographic and transcranial radiographic shape. 41 joints (31.5%) showed disagreement in condylar shape between the polytomographic and transcranial radiographic images.
Female ; Humans ; Incidence ; Joints ; Radiography* ; Sex Distribution ; Temporomandibular Joint ; Temporomandibular Joint Disorders

PURPOSE: To assess the radiographic findings of odontogenic cysts showing displacement of the mandibular canal using computed tomographic (CT) and panoramic images. MATERIALS AND METHODS: CT and panoramic images of 63 odontogenic cysts (27 dentigerous, 16 odontogenic keratocysts, and 20 radicular cysts) were analyzed to evaluate the following parameters: the dimension and shape of the cysts, and the effect of the cysts on the mandibular canal and cortical plates. RESULTS: Of the 63 cysts examined in the study, 35 (55.6%) showed inferior displacement of the mandibular canal and 46 (73.0%) showed perforation of the canal. There were statistically significant differences between CT and panoramic images in depicting displacement and perforation of the mandibular canal. Cortical expansion was seen in 46 cases (73.0%) and cortical perforation in 23 cases (36.5%). The radicular cysts showed cortical expansion and perforation less frequently than the other cyst groups. CONCLUSION: Large cysts of mandible should be evaluated by multiplanar CT images in order to detect the mandibular canal and cortical bone involvement.
Mandible ; Odontogenic Cysts* ; Radicular Cyst ; Radiography, Panoramic ; Tomography, Spiral Computed

The purpose of this study was to perform the radiographic measurements and temporomandibular joint evaluation in mandibular asymmetry. For this study, thirty-two patients who have mandibular asymmetry were selected and submentovertex, panoramic and lateral corrected tomographic radiagraphs were taken. Horizontal and vertical analysis using various landmarks on these radiographs were performed. Also radiographic and clinical evaluation of temporomandibular joint were obtained. Ther results were as follows ; 1. On the submentovertex radiograph, the mean distance of Pogonion to midline was 5.0(+/-)3.8mm. 2. The mean distance of Pogonion to Gonion between the deviated and the contra-lateral side(P<0.001). 3. The distance difference of Pogonion to Gonion between the deviated and the contra-lateral side was significantly realated to the degree of asymmetry(P<0.001). 4. On panoramic radiagraph,the condylar height of the contral-lateral side was significantly longer than the one of the deviated side(P<0.001). 5. On lateral corrected tomogram, bony of temporomandibular joint was observed in 11 condyles of the deviated side and 9 condyles of the contra-lateral side. Erosion and ostephyte were the most common changes in both the deviated and the contra-lateral sides.
Humans ; Temporomandibular Joint

PURPOSE: To compare the bone height of implant sites measured using panoramic radiography and spiral CT. MATERIALS AND METHODS: The available bone height was determined for 263 maxillary and mandibular implant sites in 59 patients. Distortion was calculated using the metal bar for the panoramic radiographs. RESULTS: Significant differences in mean bone height between the two imaging modalities were found in maxillary and mandibular anterior regions (p<0.05). The mean difference in bone height recorded by the two techniques was smallest in the maxillary and mandibular molar areas (0.8 mm), and greatest in the mandibular anterior region (1.3 mm). With the exception of the mandibular anterior region, ninety percent of all the sites showed measurement differences within 2 mm. CONCLUSION: A safety margin of 2 to 3 mm is called for when utilizing panoramic radiography, otherwise additional imaging modality such as computed tomography is necessary to obtain accurate measurements.
Dental Implants ; Humans ; Molar ; Radiography ; Radiography, Panoramic* ; Tomography, Spiral Computed*