Comparison of dimensional accuracy of 3D printing model for clear aligner among various orientation types and hollow types

Purpose: The objective of this study was to investigate the effect of printing protocol focusing upon the accuracy of 3D-printed dental models. Materials and Methods: In total, 6 groups of 10 identical maxillary dental models (Formlabs dental model resin) were produced with a stereolithography (SLA)-based 3D printer using 6 printing protocols, Group 1: Hollow/Horizontal (HH), Group 2: Hollow/Oblique (HO), Group 3: Hollow/Vertical (HV), Group 4: Non-hollow/Horizontal (NHH), Group 5: Non-hollow/Oblique (NHO) and Group 6: Non-hollow/Vertical (NHV). Deviation analysis (GOM Inspect) using the best-fit algorithm was conducted to assess accuracy. Trueness and precision of 5 tooth types which were further classified by 3 surface points on anterior teeth and 5 surface points on posterior teeth, were calculated. Thereafter, Kruskal–Wallis was conducted to determine if there were any differences in trueness/precision among the 6 printing protocols. Results: Accuracy of clear aligner models showed significant differences (p <.05) among the 6 printing protocols. Majority of values were within clinically acceptable limits (<0.2 mm) except for first molars and second molars. HV showed significant worst accuracy while NHH was the best printing protocol. Other groups (HH/NHV/HO/NHO) were ranked in middle. Inaccuracy was varied depending on tooth type and surface points. Second molars showed greatest defects at significant level in all printing groups. Color surface maps of 3D model superimposition demonstrated non-uniform deviations. Conclusions: The printing protocols with differences in hollow types and printing orientations can significantly affect the dimensional accuracy of 3D printed models for clear aligner. Overall deviations showed location-specific deviations.