Comparative Evaluation of the Mechanical and Physical Properties of 3D-Printed Resin Posts

The aim of this in vitro study was to evaluate the internal adaptation and adhesion performance of a novel 3D-printed custom post system compared with three commercially available intra-canal post systems with different physical and surface characteristics. Twenty extracted human mandibular premolars were endodontically treated and divided into four groups according to the post system used: RelyX Fiber Post (3M ESPE), Splendor SAP Post (Angelus), everStick Post (GC), and custom 3D-printed posts fabricated from a permanent restoration resin. Following cementation with a self-adhesive resin cement, micro-computed tomography was used to assess cement thickness and gap formation in the apical, middle, and coronal regions, while push-out bond strength was evaluated using a universal testing machine. The 3D-printed custom posts exhibited the lowest mean cement thickness (39.27 ± 14.47 µm in the apical and 66.25 ± 47.98 µm in the coronal region), whereas the Splendor SAP group showed the highest values (reaching up to 219.76 ± 74.64 µm in the coronal region). In contrast, the highest push-out bond strength was observed in the RelyX Fiber Post (46.52 ± 26.00 MPa) and GC everStick (48.17 ± 4.64 MPa) groups in the coronal region, while the 3D-printed custom posts demonstrated the lowest overall bond strength values, dropping to 8.53 ± 3.56 MPa in the apical region. In all groups, bond strength significantly decreased from the coronal to the apical region. Within the limitations of this study, 3D-printed custom posts provided superior intra-canal adaptation but inferior adhesion performance compared with conventional post systems.