Does Printing Orientation Matter in PolyJet 3D Printed Teeth for Endodontics? A Micro-CT Analysis

This study aimed to identify the optimal printing orientation (X, Y, or Z axis) and positioning of a mandibular molar presenting an isthmus using PolyJet™ technology. The influence of these parameters on dimensional accuracy and on the behavior of 3D-printed teeth (3DPT) during endodontic preparation with ProTaper Gold^® system was evaluated. Six groups (XA, XB, YA, YB, ZA, ZB; n = 10) were printed with different axis orientations and distinct isthmus positions relative to the build platform. All samples underwent micro-computed tomography scanning before and after endodontic preparation. Regarding preoperative analyses-canal volume, centroids, and total tooth volume and area-no significant differences were found between groups XA-YA or XB-YB (<i>p</i> > 0.05), supporting their comparability. In contrast, groups ZA and ZB differed significantly from all others (<i>p</i> < 0.05), failing to meet equivalence required for further comparison, and were therefore excluded. Postoperative evaluation-volume change, centroid displacement, transportation, and unprepared areas-revealed no significant differences between XA-YA and XB-YB. Within the limitations of this study, both printing orientation and position affected the accuracy and repeatability of 3DPT, with positioning exerting the greatest influence, while their behavior towards endodontic preparation remained consistent across orientations.