Understanding the behaviour of different printable resins under clinical simulation is essential for optimal material selection. The study aims to evaluate and compare the optical behaviour of aligners printed using directed printed resins, TA 28 and TC 85.

Study consisted of two groups Group 1 – aligners printed using TC 85 and Group 2 – aligners printed using TA 28 resin. Aligners were designed using Direct Aligner Designer (DAD) software and fabricated with a uniform 0.5 mm thickness. Patients with Class I molar relationships, mild crowding, minimal rotation, and no history of periodontal disease were included in this study. Maxillary intraoral scans were performed using the Aoralscan 3 scanner. Aligners were printed using TA-28 and TC-85 resins and post-cured for 24 minutes with the Tera Harz Cure THC unit (405 nm UV LED). Aligners were air-dried and patients were instructed to wear the aligner for 14 days for 20–22 hrs. Control (unused) samples were fabricated alongside for comparison.

Shapiro–Wilk test confirmed normal data distribution; thus, paired and independent t -tests were applied. Intragroup comparisons showed statistically significant changes (p < 0.001) in all colour parameters (L*, a*, b*) after 14 days of wear in both groups. Intergroup analysis revealed no significant difference in L* values for unused (p = 0.07) or used aligners (p = 0.89). However, a* and b* values differed significantly between the groups (p < 0.001). The mean colour difference (ΔE) between groups was not statistically significant in either condition (p = 0.592).

Aligners printed with TC-85 and TA-28 resins exhibited clinically acceptable colour stability after intraoral use, with ΔE values within aesthetic thresholds. TA-28 showed slightly greater colour change, which may reflect differences in material composition and could inform clinical material selection.