研究目的
To investigate the influence of the position/angulation of the mandible relative to the x-ray beam of a CBCT machine on the dimensional accuracy of measurements.
研究成果
The position of the mandible with respect to the x-ray beam has a clinically insignificant effect on dimensional accuracy up to 40° angulation. Statistically significant differences were found but are not clinically relevant. Radiographic markers improve precision, and further research is needed on error propagation in digital implant workflows.
研究不足
Use of a single dry mandible without soft tissue or metal restorations may not fully represent clinical conditions. Only one CBCT unit with specific exposure parameters was used, and results may vary with different systems or software. The voxel size of 0.400mm sets a minimal clinically significant difference, and error accumulation in digital workflows was noted.
1：Experimental Design and Method Selection:
An in-vitro study using a dry human mandible to simulate varying angulations (0°, 10°, 20°, 30°, 40°) in coronal and sagittal orientations relative to the x-ray beam. A control dataset was established at 0° angulation. Dimensional deviations were measured using inspection software with a best-fit alignment algorithm to minimize human error.
2：Sample Selection and Data Sources:
One dry human mandible with four teeth and no restorations was used. Radiographic markers (CT-Spot?) were applied at specific anatomical sites. CBCT scans were captured sequentially at each angulation.
3：List of Experimental Equipment and Materials:
I-CAT Next Generation CBCT unit, custom-fabricated stand, wooden wedges for angulation, radiolucent foam pad, measuring device for distance consistency, inspection software (Geomagic Qualify 12.0), and software for data conversion (3D Slicer 4.5.0).
4：0), and software for data conversion (3D Slicer 0).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The mandible was mounted with the occlusal plane parallel to the horizontal plane at 0°. Angulations were achieved using wedges. Five CBCT scans per angulation were exposed with specific parameters (kVp=120, mA=5, mAs=18.54, 8.9sec, 0.4 voxel). DICOM data were converted to STL files, and dimensional deviations were calculated at 15 standardized points using automated software alignment.
5：0°. Angulations were achieved using wedges. Five CBCT scans per angulation were exposed with specific parameters (kVp=120, mA=5, mAs=54, 9sec, 4 voxel). DICOM data were converted to STL files, and dimensional deviations were calculated at 15 standardized points using automated software alignment.
Data Analysis Methods:
5. Data Analysis Methods: Linear mixed effects regression and non-parametric multivariate ANOVA were used to compare accuracy and precision, respectively, with statistical software R (version 3.4.3).
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