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Influence of Water Storage on the Mechanical Properties of 3D-Printed Aligners: An In Vitro Study

K. Puchert, Paul Ritzert, Sebastian Wille, Jusef Naim, Sinan Şen · 2025 · 2 citationsRead the paper

Directly printed aligners represent a promising alternative to conventional thermoformed aligners. The aim of this in vitro study was to compare the effects of water on the mechanical properties of directly printed aligners with those of conventionally manufactured thermoformed PET-G foils. Dental LT Clear V2 (LT), V Print Splint Comfort (VP), and TC-85 DAC (TC) were examined. Biolon (BL), a conventional PET-G material, served as the thermoplastic reference material. All samples were tested before and after 14 days of water storage at 37 °C. We performed a three-point bending test and an indentation test, and examined changes in the abrasion resistance and hygroscopic volume. The resistance of all printed specimens decreased significantly after water storage. VP and TC were less resilient than BL overall. LT and BL exhibited the lowest indentation creep (BL: 0.08 ± 0.01, LT: 0.13 ± 0.02, VP: 0.21 ± 0.02, TC: 0.24 ± 0.02). Furthermore, the abrasion of LT (0.72 ± 0.21 mm3) was significantly lower than that of BL (1.12 ± 0.37 mm3). In conclusion, the water sorption of the printed test specimens had a significant influence on the mechanical properties, with a reduction in the flexural modulus, Martens hardness, and plastic hardness.

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Water storage significantly reduced the flexural modulus of all 3D-printed materials. — LT: 2000 to 1485 MPa; VP: 866 to 557 MPa; TC: 967 to 320 MPa (14 days in distilled water at 37 °C)
LT material exhibited lower abrasion volume than the thermoplastic reference. — 0.72 ± 0.21 mm3 (LT) vs 1.12 ± 0.37 mm3 (BL) (10,000 chewing cycles at 50 N load with thermal cycling)
LT and BL showed the lowest indentation creep. — BL: 0.08 ± 0.01; LT: 0.13 ± 0.02 (Indentation test after water storage)
Water storage caused the flexural modulus of LT to converge with the reference material. — LT: 1485 ± 153 MPa vs BL: 1543 ± 67 MPa (After 14 days in distilled water at 37 °C)
DLP-printed materials (VP, TC) were significantly softer and more prone to deformation than BL and LT. (Especially after water storage)

Setup: 15 bending specimens and 15 indentation disks per material; 8 splint sections and 8 truncated cones per material.
How: The study compared three 3D-printed materials (SLA: LT; DLP: VP, TC) against a thermoformed PET-G reference (BL) using three-point bending, indentation, and chewing simulation tests. Samples were tested in dry states and after 14 days of immersion in distilled water at 37 °C.
Limitations: In vitro study cannot fully reflect dynamic intraoral conditions or patient variability. · VP and TC specimens were provided by manufacturers, preventing direct verification of printing protocols. · LT material is currently approved for splints/retention, not specifically for aligners. · Potential drying of specimens prior to testing may have affected indentation results.

Summarized by Gemma 4 from the open-access full text · 9 Oct 2026. Read it