Biocompatibility of a novel directly printed orthodontic aligner at variable material thicknesses.

Direct printed aligners (DPAs) represent a revolution in aligner orthodontics, enabling in-office fabrication of customized removable orthodontic appliances and precise, region-specific thickness modulation within a single aligner. Accordingly, this study assessed whether the manufacturer's standard 20-minute UV post-cure is adequate to ensure biocompatibility of DPAs made from LuxCreo DCA resin (LuxCreo Inc., Chicago, IL, USA) as appliance thickness increases up to 6 mm. Specimen discs (Ø 10 mm) of varying thickness (0.5, 1, 2, 4, and 6 mm) were 3D printed and post-processed according to the LuxAlign (LuxCreo Inc., Chicago, IL, USA) closed end-to-end workflow. Thickness was verified by digital caliper and biocompatibility was assessed using the AlamarBlue assay on human gingival fibroblasts. Printed specimens closely matched nominal dimensions and cell viability always remained above 70%, the ISO 10993-5 threshold for non-cytotoxicity. No significant differences were observed between the standard 0.5 mm and thicker groups (1-6 mm), indicating that increased thickness did not further impair biocompatibility. These findings demonstrate that the standardized LuxAlign workflow, including a 20-minute UV-curing, produces dimensionally accurate, non-cytotoxic appliances from LuxCreo DCA resin up to 6 mm thickness, supporting safe clinical use without extending post-curing.