The influence of 3-dimensional printing layer thickness on model accuracy and the perceived fit of thermoformed retainers

Introduction: This study aimed to investigate the accuracy of dental model printing using 2 different layer height settings and how these settings affect the fabrication of thermoformed retainers. Methods: Subjects were recruited from the Department of Orthodontics at Case Western Reserve University and scanned according to specific selection criteria. A total of 30 stereolithography files were produced and used as reference files. The stereolithography files were printed at the recommended layer height of 100 mu m and 170 mu m with a Sprint Ray Pro 95 3-dimensional (3D) printer (Sprint Ray, Los Angeles, Calif). All printed models were scanned using the same iTero intraoral scanner (Align Technology, San Jose, Calif) as was used for the initial intraoral scan as well. The accuracy of the printed models was based on the evaluation of root mean square values resulting from 3D superimpositions. Afterward, vacuum-formed retainers were fabricated. The vacuum-formed retainers were evaluated by the patient and an American Board of Orthodontics-certified orthodontist. Results: No difference was observed in the maxillary arch (P = 0.85) and the mandibular arch accuracy (P = 0.08) by assessing the root mean square values. No difference was observed in the doctor retainer score of the maxillary retainers (P = 0.37) and the mandibular retainers (P = 0.77). There was no difference in the patient retainer score of the maxillary (P = 0.08) and the mandibular retainers (P = 0.22) when comparing retainers. Conversely, less printing time was observed when printing the models with 170 mu m compared with 100 mu m (P <0.001). Conclusions: The accuracy of a dental model printed with a Sprint Ray Pro 95 3D printer was not affected by the 100 or 170 mu m layer height. Orthodontists and patients did not detect a statistically significant difference in retainer fit.