Objective: To evaluate three-dimensional position of the TMJ condyle within the glenoid fossa in different types of skeletal patterns. Materials and methods: Ninety CBCT images were consecutively selected and divided into skeletal class I, class II and class III. The images were analyzed locating landmarks in the different areas of the condyle and glenoid fossa. All landmarks presented acceptable reliability. The mean results were compared using ANOVA and Bonferroni post-hoc test (p < 0.05). Results: There was a tendency for the anterior joint space to be smaller than the posterior joint space. Statistical analysis, however, evidenced no significant differences between the anterior, superior and posterior joint spaces and the different skeletal patterns or between sides. Conclusion: There was non-concentricity of the condyle for all the groups studied, and no particular direction was statistically significantly favored. It is unclear whether the differences found would be clinically significant, considering anatomical individual variations.

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 &mu;m. The CBCT voxels were then downsampled to 100 &mu;m, 200 &mu;m and 300 &mu;m. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 &mu;m (p&lt;0.05). No significant differences were found between the different voxel sizes (p&gt;0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 &mu;m.

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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 &mu;m. The CBCT voxels were then downsampled to 100 &mu;m, 200 &mu;m and 300 &mu;m. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 &mu;m (p&lt;0.05). No significant differences were found between the different voxel sizes (p&gt;0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 &mu;m.

Imaging of the osseous structures of the temporomandibular joint is best accomplished using computed tomography (CT). Cone beam CT offers a reduced radiation dose and improved spatial resolution compared to multislice helical CT. This study evaluates comparative dosimetry for temporomandibular joint imaging using two different cone beam CT systems, the Hitachi CB MercuRay and Kodak 9000 3D. These systems demonstrate differing properties with respect to field-of view sizes, operational technique factors, and spatial resolution. The Kodak 9000 3D unit offers an effective radiation dose reduction of greater than ten-fold compared with the Hitachi CB MercuRay, depending on kVp and mA. A subsequent clinical study evaluating the effect of spatial resolution on the ability to detect osseous changes related to temporomandibular joint degenerative disease found no significant difference in diagnostic efficacy between high and low spatial resolution images, however, observers consistently associated high spatial resolution with superior image quality.

Imaging of the osseous structures of the temporomandibular joint is best accomplished using computed tomography (CT). Cone beam CT offers a reduced radiation dose and improved spatial resolution compared to multislice helical CT. This study evaluates comparative dosimetry for temporomandibular joint imaging using two different cone beam CT systems, the Hitachi CB MercuRay and Kodak 9000 3D. These systems demonstrate differing properties with respect to field-of view sizes, operational technique factors, and spatial resolution. The Kodak 9000 3D unit offers an effective radiation dose reduction of greater than ten-fold compared with the Hitachi CB MercuRay, depending on kVp and mA. A subsequent clinical study evaluating the effect of spatial resolution on the ability to detect osseous changes related to temporomandibular joint degenerative disease found no significant difference in diagnostic efficacy between high and low spatial resolution images, however, observers consistently associated high spatial resolution with superior image quality.

Objective: To evaluate three-dimensional position of the TMJ condyle within the glenoid fossa in different types of skeletal patterns. Materials and methods: Ninety CBCT images were consecutively selected and divided into skeletal class I, class II and class III. The images were analyzed locating landmarks in the different areas of the condyle and glenoid fossa. All landmarks presented acceptable reliability. The mean results were compared using ANOVA and Bonferroni post-hoc test (p < 0.05). Results: There was a tendency for the anterior joint space to be smaller than the posterior joint space. Statistical analysis, however, evidenced no significant differences between the anterior, superior and posterior joint spaces and the different skeletal patterns or between sides. Conclusion: There was non-concentricity of the condyle for all the groups studied, and no particular direction was statistically significantly favored. It is unclear whether the differences found would be clinically significant, considering anatomical individual variations.

Circular source and detector trajectories in cone-beam computed tomography (CT) are known to collect insufficient data for accurate object reconstruction. One model predicts that the lacking information corresponds to a shift-variant cone of missing spatial frequency components in the local Fourier domain. These predictions were experimentally verified by imaging small, localized objects and observing their Fourier transforms. Measurements indicated that the internal angle of the ‘missing cone’ varies as the angle of locally intersecting x rays with respect to the horizontal plane, as expected. Object recovery was also found to depend greatly on the distribution of the object’s frequency spectrum relative to the missing cone, as predicted. Findings agreed with more anatomically relevant phantoms, which showed preferential intensity discrepancies at gradients oriented within or near the missing cone. Methods for artefact correction are in general limited to approximation unless a priori information is incorporated.