Effect of triangular mesh resolution on the geometrical trueness of segmented CBCT maxillofacial data into STL format

To determine the optimal level of mesh reduction that would maintain acceptable levels of geometrical trueness while also minimizing the impact on other parameters such as file size and processing time.

Intraoral and extraoral maxillofacial defects were created on 8 cadaver heads and scanned by using a CBCT scanner (NewTom 3D Imaging, Verona). DICOM data were segmented to produce head (n=8) and skull models (n=8) saved as standard tessellation language (STL) files. A further processing of head models was preformed to produce face (n=8) and ear models (n=8). A mesh reduction process was performed for each STL model (reference, R₀) by generating 50% (R₁), 75% (R₂), and 90% (R₃) reductions. The 3 datasets were compared to the R₀ file using 3D evaluation software (GOM Inspect) using a global best-fit algorithm, to calculate the root mean square (RMS) deviations. Statistical analyses were performed at a level of significance of α=0.05.

There was no 3D deviation after the 50% triangular mesh reduction in the 4 datasets. Minor 3D deviations were observed after 75% reduction, in all groups. After 90% reduction, higher 3D deviations were observed, and especially in head and skull. Statistically significant increase in 3D deviations was observed with higher degrees of mesh reduction (p < 0.001).

The resolution of CBCT-based maxillofacial defect models can be reduced up to 50%, with neglectable concern to inaccuracy.

Accurate maxillofacial models can be obtained from CBCT DICOM files after segmentation and export as STL files, even when the mesh resolution is reduced up to 50%. This information can be valuable for practitioners and researchers working with 3D models of maxillofacial defects.