Biomechanical force profiles and force decrease of direct printed versus thermoformed aligners with different trimlines: an in vitro analysis
Bernhard Wiechens, Philipp Meyer‐Marcotty, Emilia von Waldthausen, Lisa-Marie Mai, Jonas Q. Schmid, Phillipp Brockmeyer et al. · 2026 · 2 citationsRead the paper
Abstract Background This in-vitro study aimed to evaluate and compare the biomechanical force profiles of thermoformed and direct-printed aligners with different gingival trimlines during facial and palatal translation of a maxillary central incisor. Methods A 3D-printed model with a mounted central incisor was used to simulate 0.25 mm of bodily movement. Forces were recorded in three axes (Fx, Fy, Fz) using a multi-axis force sensor. Three aligner types (thermoformed with straight trimline: TFA S , and direct-printed with either straight: DPA S or garlanded trimline: DPA G ) were tested ( n = 10 each). Vertical, transverse, and sagittal force components and their decrease were analyzed. Forces were recorded over 60 min to characterize initial force delivery and early stress relaxation under standardized in vitro conditions. Results Thermoformed aligners exhibited the highest sagittal forces during facial movement (Fx − 0.70 N), while DPA G demonstrated significantly lower forces (Fx − 0.25 N; p < .001). During palatal translation, DPA S reached peak forces of 0.57 N, whereas DPA G showed lower, more controlled forces ( p < .001). Vertical forces (Fz) were significantly higher in TFA S (− 0.10 N), while DPA remained near zero or slightly extrusive ( p < .001). Conclusions In this in vitro model, DPA, particularly DPA G , showed lower sagittal force values and smaller vertical force components. In the first 60 min, DPA showed a pronounced early force decrease. Longer observation periods are required to describe force behavior beyond the initial seating phase.
What the full text shows
Shown in the lab- Direct-printed aligners with garlanded trimlines (DPA G) produced significantly lower sagittal forces during facial movement compared to thermoformed aligners (TFA S). — 0.25 N vs. 0.70 N (Facial translation of a maxillary central incisor)
- Direct-printed aligners (DPA) exhibited significantly lower vertical force components compared to thermoformed aligners. — DPA near zero vs. TFA S -0.10 N (Facial translation of a maxillary central incisor)
- Direct-printed aligners showed a more pronounced early force decrease over the first 60 minutes compared to thermoformed aligners. — '' (Initial seating phase)
- DPA G generated lower sagittal forces during palatal translation compared to DPA S. — '' (Palatal translation of a maxillary central incisor)
- TFA S generated sagittal forces approximately two to three times higher than DPA groups. — 2-3x higher (In vitro translation model)
- Setup
- n=10 per group; 0.75 mm material thickness; 60-minute observation period; 3D-printed model with modular incisor.
- How
- A multi-axis force sensor was used to measure forces (Fx, Fy, Fz) during 0.25 mm bodily translation of a 3D-printed maxillary central incisor. Three aligner types (thermoformed straight, direct-printed straight, and direct-printed garlanded) were tested under simulated physiological conditions (36.5°C, artificial saliva) and under a 3 kg simulated occlusal load.
- Limitations
- Absence of human periodontal ligament (PDL) simulation · Observation period limited to 60 minutes (not typical clinical wear) · Lack of quantification of local pressure distribution on tooth surface · Partial simulation of intraoral factors like enzyme activity and temperature cycling
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it