Internal Fit and Bond Strength of Customised CAD/CAM 3D-Printed and Milled Resin-Based Posts vs Relined Fibre Posts

This study assessed the internal adaptation and push-out bond strength (PBS) of customised CAD/CAM 3D-printed (Varseosmile Crown Plus, Bego, Germany - 3DP) and milled (Enamic, Vita, Germany - MP) resin-based posts vs prefabricated fiber posts relined with resin composite (RelyX fiber post and Filtek Bulkfil Composite, 3M Health Care, USA - RFP).

Twenty-four premolars were decoronated, root canal treated, then divided into three groups: 3DP, MP, and RFP (control group). Impressions of the prepared teeth in the 3DP and MP groups were taken using light-body polyvinyl siloxane, then 3D scanned for CAD/CAM design and fabrication. In the RFP group, fibre posts were relined with resin composite and adapted to the post space. Cement gaps were evaluated at the coronal, middle, and apical thirds using micro-computed tomography. All posts were cemented with self-adhesive resin cement, and PBS was tested at the three root thirds using a universal testing machine. Data were analysed using Two-way ANOVA and Bonferroni post-hoc tests (P = .05).

RFP exhibited the least cement space, with statistically higher internal adaptation compared to 3DP and MP (P < .001). However, no significant differences were found in PBS among the 3 tested fabrication techniques (P > .05). The root section had no statistically significant effect on internal adaptation (P > .05) but significantly affected PBS (P < .05). The poorest adaptation and the lowest PBS were found in the apical section.

3D printing of resin-based posts demonstrates the potential to fabricate anatomically customised CAD/CAM posts with clinically acceptable internal adaptation and bond strength comparable to milled and relined counterparts. These findings support its application in flared or non-circular canals, though further evaluation of fatigue and fracture resistance is required to establish clinical durability.