Effect of different lengths of post-curing UV light exposure on the mechanical properties of 3D-printed aligners: An in vitro study

OBJECTIVE: To investigate the effect of different durations of post-curing ultraviolet (UV) light exposure on the compressive strength, amount of displacement and water absorbed by direct-printed aligners. DESIGN: An in-vitro randomised control trial. SETTING: Orthodontics laboratory in Maulana Azad Institute of Dental Sciences, New Delhi, India. METHODS: Dental LT V2 resin was used to print 30 aligners, which were divided into three groups and subjected to different post-print UV light exposures. Each group was subjected to compression loading of 1000 N to evaluate their load vs. displacement behaviour. The amount of water absorbed by aligners in each group was also evaluated. Data were analysed using one-way analysis of variance (ANOVA) and repeated measures ANOVA. RESULTS: The '60-min cure' group bore the maximum mean compressive load (1016.03 ± 37.27 N) and had the least mean displacement (2.87 ± 0.52 mm) and water absorption (0.18 g).The '40-min cure' group did not show significant results for any of the tests carried out. CONCLUSION: Aligners subjected to 60 min of post-print UV light exposure were the most rigid and had highest compressive strength. Increasing the duration of post-UV light curing reduced the amount of water absorbed by the aligners. Since the '60-min cure' group was excessively rigid, a post-curing duration of 40 min is recommended to provide sufficient flexibility for comfortable daily use and wear.