Effect of print angulation on the accuracy and precision of 3D-printed orthodontic retainers

Introduction: The study aimed to (1) compare the accuracy and precision of 3- dimensional (3D) printed retainers at various angulations and (2) evaluate the effect of angulation on printing time and the amount of resin consumed. Methods: Using a stereolithography 3D printer, 60 clear retainers were printed at 5 angulations (n = 12, each): 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. Samples for each group were randomly printed in a batch of 6 retainers at all print angulations as print 1 and print 2 cycles. Digital images of the original and printed samples were superimposed. Discrepancies on 8 landmarks were measured by 2 independent examiners, and 0.25 mm was set as the clinically acceptable threshold to determine the accuracy of the retainers. Results: Deviations ranged from 0.074 mm to 0.225 mm from the reference retainer at the cusp tips and incisal edges at all angulations, falling within the threshold of clinical acceptance. However, smooth surface measurements with deviations up to 0.480 mm were deemed clinically not acceptable. Three-dimensional printing at 15 degrees was estimated to be the most time-efficient, whereas 3D printing at 45 degrees was shown to be the most cost-effective setting. Conclusions: Three-dimensional printed retainers, using a stereolithography printer, were found to be accurate within 0.25 mm at all print angulations at the cusp tips and incisal edges compared with the digital reference file. Smooth facial surfaces did not meet clinical acceptability. Print angulations were shown to affect the cost and amount of resin used.