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: 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

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*

PURPOSE: The purpose of this study was to evaluate the diagnostic performance of dental students in detection of mandibular condyle fractures and the effectiveness of reference panoramic images. MATERIALS AND METHODS: Forty-six undergraduates evaluated 25 panoramic radiographs for condylar fractures and the data were analyzed through receiver operating characteristic (ROC) analysis. After a month, they were divided into two homogeneous groups based on the first results and re-evaluated the images with (group A) or without (group B) reference images. Eight reference images included indications showing either typical condylar fractures or anatomic structures which could be confused with fractures. Paired t-test was used for statistical analysis of the difference between the first and the second evaluations for each group, and student's t-test was used between the two groups in the second evaluation. The intra- and inter-observer agreements were evaluated with Kappa statistics. RESULTS: Intra- and inter-observer agreements were substantial (k=0.66) and moderate (k=0.53), respectively. The area under the ROC curve (Az) in the first evaluation was 0.802. In the second evaluation, it was increased to 0.823 for group A and 0.814 for group B. The difference between the first and second evaluations for group A was statistically significant (p<0.05), however there was no statistically significant difference between the two groups in the second evaluation. CONCLUSION: Providing reference images to less experienced clinicians would be a good way to improve the diagnostic ability in detecting condylar fracture.
Humans ; Mandibular Condyle ; Mandibular Fractures ; Radiography, Panoramic ; ROC Curve ; Students, Dental

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 analyze the possible association between magnetic resonance imaging signal intensity of temporo-mandibular joint disk and posterior attachment, and the type and extent of disk displacement, disk configuration, effusion and clinical signs in patients with internal derangement. MATERIALS AND METHODS: Magnetic resonance images of the 132 temporomandibular joints of 66 patients with temporomandibular joint displacement were analyzed. The clinical findings were obtained by retrospective review of the patients' records. The type and extent of disk displacement, disk configuration and effusion were evaluated on the proton density MR images. The signal intensity from the anterior band, posterior band and posterior attachment were measured on MR images. The associations between the type and extent of disk displacement, disk configuration, effusion and clinical signs and the MR signal intensity of disk and posterior attachment were statistically analyzed by student's t-test. RESULTS: Of 132 joints, 87 (65.9%) showed anterior disk displacement with reduction (ADR) and 45 (34.1%) showed anterior disk displacement without reduction (ADnR). The signals from posterior attachments were lower in joints with ADnR than those of ADR (p<0.05). The results showed statistically significant (p<0.05) association between the type and extent of disk displacement and disk configuration, and decreased signal intensity of posterior attachment. There were no statistical associations between pain, noise and limited mouth opening, and signal intensity of disk and posterior attachment. Conclusions : The average signal from posterior attachment was lower in joints with ADnR than that of ADR. The type and extent of disk displacement and disk configuration appeared to be correlated with the signal intensity from posterior attachment.
Humans ; Joints ; Magnetic Resonance Imaging* ; Mouth ; Noise ; Protons ; Retrospective Studies ; Temporomandibular Joint Disc* ; Temporomandibular Joint*

PURPOSE: To analyze the possible association between magnetic resonance imaging signal intensity of temporo-mandibular joint disk and posterior attachment, and the type and extent of disk displacement, disk configuration, effusion and clinical signs in patients with internal derangement. MATERIALS AND METHODS: Magnetic resonance images of the 132 temporomandibular joints of 66 patients with temporomandibular joint displacement were analyzed. The clinical findings were obtained by retrospective review of the patients' records. The type and extent of disk displacement, disk configuration and effusion were evaluated on the proton density MR images. The signal intensity from the anterior band, posterior band and posterior attachment were measured on MR images. The associations between the type and extent of disk displacement, disk configuration, effusion and clinical signs and the MR signal intensity of disk and posterior attachment were statistically analyzed by student's t-test. RESULTS: Of 132 joints, 87 (65.9%) showed anterior disk displacement with reduction (ADR) and 45 (34.1%) showed anterior disk displacement without reduction (ADnR). The signals from posterior attachments were lower in joints with ADnR than those of ADR (p<0.05). The results showed statistically significant (p<0.05) association between the type and extent of disk displacement and disk configuration, and decreased signal intensity of posterior attachment. There were no statistical associations between pain, noise and limited mouth opening, and signal intensity of disk and posterior attachment. Conclusions : The average signal from posterior attachment was lower in joints with ADnR than that of ADR. The type and extent of disk displacement and disk configuration appeared to be correlated with the signal intensity from posterior attachment.
Humans ; Joints ; Magnetic Resonance Imaging* ; Mouth ; Noise ; Protons ; Retrospective Studies ; Temporomandibular Joint Disc* ; Temporomandibular Joint*

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*