Modern 3D cephalometry in pediatric orthodontics-downsizing the FOV and development of a new 3D cephalometric analysis within a minimized large FOV for dose reduction.

Objectives: Dose reduction achieved by downsizing the field of view (FOV) in CBCT scans has brought no benefit for pediatric orthodontics, until now. Standard 2D or 3D full-size cephalometric analyses require large FOVs and high effective doses. The aim of this study was to compare a new 3D reduced-FOV analysis using the Frankfurt horizontal (FH) plane as reference plane with a conventional full-size analysis using the Sella-Nasion (S-N) plane as reference plane.

Materials And Methods: Thirty-eight CBCT data sets were evaluated using full- and reduced-FOV analysis. The measurements of a total of 20 skeletal and dental standard 3D full-size variables were compared with the measurements of 22 corresponding 3D reduced-FOV variables. Statistical analysis was performed to prove mathematic relation between standard and alternative variables. Regression analyses were carried out.

Results: Coefficients of determination (R) between 0.15 and 0.95 (p < 0.001-0.055) were described. All variables showed obvious relations of different strength except for SNA and its alternative Po_R-Or_R-A (°) (R = 0.15, p = 0.055), but a second variable Ba_A (mm) showed stronger relation (R = 0.28, p = 0.003).

Conclusions: All standard variables related to the reference plane S-N could be described with alternative variables related to the FH. Further research should define more reliable landmarks for coordinate systems and reference points.

Clinical Relevance: Minimized large FOVs meet the demand of 3D cephalometric analyses and enable the application of CBCT scans in pediatric orthodontic patients in many specific indications. Dose reduction is accompanied by increasing access to all the advantages of 3D imaging over 2D imaging.