Effect of 3D printing technology, build orientation, and shell thickness on the accuracy of full-arch dental models for fixed dental prostheses: an in vitro study

The purpose of this study was to assess the effect of 3D printing technology (SLA vs. DLP), print orientation (0°, 10°, 20°), and model shell thickness (2 mm vs. 4 mm) on the manufacturing accuracy of full-arch dental casts with teeth preparations. A reference STL file of a maxillary arch, featuring preparations for a posterior crown and a three-unit bridge, was used to fabricate 144 printed models (72 with SLA and 72 with DLP). Each technology group was subdivided based on print orientation (0°, 10°, 20°) and shell thickness (2 mm, 4 mm), resulting in 12 subgroups with n = 12 each. All models were scanned and analyzed for global and landmark-level deviations using surface superimposition (Geomagic Control X). Trueness was calculated via root mean square (RMS) error, and precision was determined as standard deviation (SD). Data were statistically analyzed using the Kruskal-Wallis test to assess trueness, and precision was evaluated using Levene's median-based test (α = 0.05). Printing technology (DLP vs. SLA), model orientation, and shell thickness showed no significant impact on the overall accuracy, as measured by trueness (RMS: p = 0.453-1.000) and precision (SD: p = 0.117). The overall trueness (RMS) values ranged from 73.9 to 194 µm, with all groups remaining below the clinical acceptability threshold (< 0.2 mm). Isolated significant differences were observed at specific anatomical points but did not impact overall model performance. The type of printing technology, orientation angle, and shell thickness did not significantly affect the global accuracy of full-arch models for fixed prosthodontics.