Effect of PolyJet print orientation on the fit of thermoformed aligners: An in vitro scanning electron microscopy study

Aim: The study aimed to compare the fit of thermoformed aligners fabricated on the original dental model over the corresponding dental models created using rapid-prototyping, in horizontal or vertical orientations using scanning electron microscopy (SEM). Methods: This study involved scanning 10 dental models using a Maestro 3D Desktop Scanner. The 10 processed STL files were then additively manufactured into 20 models using a PolyJet printer, 10 models printed in horizontal or vertical orientations, respectively. Two thermoformed aligners using 0.75 mm Duron blanks were fabricated over each original dental model with a Biostar machine and were adapted over the corresponding additively manufactured models. Models manufactured in two different orientations along with aligners were sectioned on the upper and lower-central incisors, first premolars and first molars and were prepared for SEM evaluation. The difference in data between the two groups was determined using an unpaired t -test. Results: The fit of aligners on additively manufactured dental models in vertical or horizontal orientations was generally comparable. Across all regions evaluated, the mean measured discrepancies ranged below 196.2 ± 44.32 µm, which falls within ranges previously reported in the literature as clinically acceptable for thermoformed aligners (117.76 ± 23.58–196.2 ± 44.32 µm). Conclusion: SEM evaluation revealed that thermoformed aligners fabricated on the original dental models demonstrated a comparable fit on rapid-prototyped dental models, with no significant differences observed between models fabricated in horizontal or vertical three-dimensional printing orientations.