Effect of print orientation of 3D-printed aligner templates on the volumetric accuracy of transferred composite attachments: an in vitro study

Objectives: This study aimed to evaluate the effect of print orientation on the dimensional accuracy of attachments in directly 3D-printed orthodontic aligners. Materials and methods: For n = 10 patients, 34 single-tooth aligner segments were digitally designed (17 for tooth 1.1 and 17 for tooth 1.6) incorporating a planned 3 mm horizontal rectangular buccal attachment. These aligners were printed in TC-85 DAC resin (Graphy Inc, Seoul, Korea) at different inclinations (8 in anterotation and 8 in postrotation, at 10° intervals from the horizontal) and used as templates to transfer attachments onto corresponding 3D-printed dental models. This models with transferred attachments were scanned with a laboratory scanner and superimposed onto the attachment surface of the master digital file. Percentage volume deviations of the transferred versus planned attachment were quantified using Geomagic Control software (v.2020.1.1, ©2020 3D Systems, Inc., Rock Hill, SC) and analysed with an unpaired two-tailed t-test (P < 0.05). Results: For tooth 1.1, the mean volumetric deviation of transferred attachments was significantly lower in postrotation orientations (88.87% ± 4.13) than in anterotation (69.01% ± 4.33), indicating that positioning the template with the vestibular surface facing the build platform improves accuracy (p < 0.0001). For tooth 1.6, no statistically significant difference was found (p = 0.0992; 78.16% ± 2.26 vs. 79.99% ± 1.87). Conclusions: Composite attachments transferred with 3D-printed templates exhibited a volumetric alteration respect the master digital file and print orientation particularly affects anterior teeth’s attachments. Clinical relevance: Aligners orientation during 3D-printing is crucial to ensure accurate attachments transfer, especially anterior regions.