Related Experiment Video
Updated: Jun 23, 2026
Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition
Published on: February 23, 2024
Force systems of direct printed and thermoformed aligners with different trimlines during rotational movements: an in
Emilia von Waldthausen1, Lisa-Marie Mai2, Philipp Meyer-Marcotty3
1Department of Orthodontics, Universitätsmedizin Göttingen, Göttingen, Germany. emilia.waldthausen@med.uni-goettingen.de.
Background:
The present study was conducted to quantify and compare the geometric accuracy and force application of thermoformed aligners (TFA) and direct-printed aligners (DPA) during mesial and distal rotation of a central upper incisor with a defined activation of 2°.
Methodology:
A 3D-printed model with a mounted central incisor was used to simulate 2° of rotational movement. Forces were recorded in three axes (Fx, Fy, Fz) over 60 minutes using a multi-axis force sensor. Three aligner types (thermoformed with straight trimline: TFAS, direct printed with straight trimline: DPAS, direct printed aligner with garlanded trimline: DPAG) were tested (n = 10 each). Vertical, transverse, and sagittal force components and their decrease were analyzed, and thickness measurements were taken.
Results:
Significant differences in resulting forces were observed between TFA, DPAS, and DPAG during both mesial and distal rotation. TFA generated significantly higher sagittal forces during mesial rotation (1.40 (0.30) N) compared to DPAS (-0.04 (0.05) N) and DPAG (0.11 (0.03) N; p < 0.001). Similar findings were observed for distal rotation (TFA 0.86 (0.16) N; DPAS -0.07 (0.06) N; DPAG 0.10 (0.09) N; p < 0.001). Transverse forces were generally lower, with only selected intergroup differences reaching significance. Time-resolved analysis revealed a pronounced initial force peak followed by continuous decay for TFA, while both DPA designs showed a gradual force increase with plateau formation. TFA showed the most pronounced material loss, whereas directly printed aligners most closely matched the planned thickness. In mesial rotation, significant group differences were found for facial (TFA: 0.42 (0.01) mm; DPAS: 0.71 (0.15) mm; DPAG: 0.63 (0.06) mm), incisal (0.60 (0.02) mm vs. 0.76 (0.11) mm vs. 0.65 (0.06) mm) and palatal surfaces (0.63 (0.01) mm vs. 0.94 (0.17) mm vs. 0.80 (0.06) mm; all p < 0.001). A comparable thickness pattern was observed for distal rotation.
Conclusion:
The results highlight the improved geometric accuracy and underscore the potential of 3D-printed aligners to improve force control and warrant further clinical investigation.
