Comparison in Accuracy of Orthodontic Retainers Fabricated via Digital Printing Versus Thermoplastic Technique

Introduction: Limited evidence exists on the dimensional accuracy of three-dimensional (3D) printed orthodontic retainers utilizing the newest printing technologies. This study aimed to evaluate the dimensional accuracy of 3D-printed orthodontic retainers in comparison with retainers fabricated from a pressure-form, thermoplastic technique (PFTT). Methods: Four groups of retainers (n=7 per group) were printed using four printers: AsigaPro4K80, NextDent 5100, SprintRay ProS, and Formlabs Form3B. The control group (n=7 retainers) was fabricated using PFTT. A polyvinyl siloxane impression of the intaglio surface per retainer was made and optically scanned. Metrology software (Geomagic Control X) was used to digitally superimpose the intaglio surface of each retainer onto the digital master cast using a best-fit algorithm. Surface deviation values (range, root mean square (RMS), and average)between retainers and master casts were calculated and analyzed with analysis of variance and Tukey tests ( = 0.05).Results: For the maximum-to-minimum range of surface deviation, Asiga, NextDent, and SprintRay groups showed significantly more deviation from the master cast than Formlabs and PFTT. Additionally, the Asiga group exhibited significantly higher RMS deviation from the master cast than all other groups. Also, the Asiga and NextDent groups were significantly inclined to have a positive average surface deviation from the master cast than SprintRay, Formlabs, and PFTT groups. Conclusions: Significant differences in accuracy were found among retainers fabricated from various 3D-printers and a PFTT. Despite these differences, all fabrication methods produced accuracies that were within the clinically acceptable range of 0.25 mm.