Objectives: To evaluate the effect of triangular mesh reduction on the trueness of digitized complete-arch dentate and edentulous maxillectomy defects models.

Material and methods: Twenty gypsum maxillectomy defect models (dentate and edentulous group: n = 10) were digitized using the Trios 3 intraoral scanner, scanning the teeth, mucosa and maxillectomy defect. These datasets (reference, R₀) were saved as standard tessellation language (STL) files, and triangular mesh reduction was performed using the Meshmixer reduction tool. Digital test-datasets with file sizes reduced by 50%(R₁), 75%(R₂), and 90%(R₃) were generated (each: n = 20). Each test-dataset was compared to the R₀file using a 3D evaluation software (GOM Inspect), applying automated pre-alignment followed by a best-fit alignment, and root mean square (RMS) 3-dimensional (3D) deviations were calculated. Statistical analyses were performed, at a level of significance of α=0.05.

Results: The number of triangles, and STL file size were synchronized with each other and inversely proportional to the amount of mesh reduction. The resulting mean percentages of the STL file sizes were 50.00% for R₁, 24.93% for R₂, and 10.00% for R₃. There were no 3D deviations at 50% triangular mesh reduction. The 3D deviations increased with the amount of mesh reduction: at 75% reduction the median deviations were lower (dentate:0.0016 mm, IQR:0.0015-0.0018; edentulous:0.0016 mm, IQR:0.0015-0.0016), than at 90% (dentate:0.004 mm, IQR:0.0038-0.0041; edentulous:0.003 mm, IQR:0.0036-0.0039). A statistically significant increase in 3D deviations was observed with higher degrees of mesh reduction (p<0.001).

Conclusions: Triangular mesh reduction results in a significant increase in 3D deviations if the reduction is more than 75%.

Clinical significance: Digital models of patients with maxillectomy defects can be saved with a mesh reduction of 50% without affecting the trueness. The use of a 50% mesh reduction decreases the required storage capacity by 50%.