Force systems of direct printed and thermoformed aligners with different trimlines during rotational movements: an in vitro analysis.

Authors

Emilia von Waldthausen, Lisa-Marie Mai, Philipp Meyer-Marcotty, Anja Quast, Jonas Q Schmid, Phillipp Brockmeyer, Wolfram Hahn, Bernhard Wiechens

Published in

Progress in orthodontics. Volume 27. Issue 1. Jun 22, 2026. Epub Jun 22, 2026.

Abstract

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°.
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.
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.
The results highlight the improved geometric accuracy and underscore the potential of 3D-printed aligners to improve force control and warrant further clinical investigation.

PMID:
42329549
Bibliographic data and abstract were imported from PubMed on 22 Jun 2026.

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