Fracture resistance of 3D-printed endocrowns fabricated using different pulpal build-up materials in teeth restored with deep margin elevation

The aim of this study was to comparatively evaluate the effect of three different composite materials used for pulpal build-up on the fracture resistance and fracture pattern (repairable/irreparable) of endocrown restorations fabricated using three-dimensional (3D) printing technology in endodontically treated molar teeth with deep margin elevation (DME) after thermomechanical aging. In this in vitro study, a total of 40 extracted human molar teeth were randomly divided into four groups (n=10). In the control group, the pulpal floor was restored with Gænial Universal Flo without applying DME. In the experimental groups, DME was performed and the pulpal floor was restored with G-ænial Universal Flo (G2), G-ænial Posterior (G3) and EverX Posterior (G4) composite resins, respectively. All specimens were restored with endocrowns fabricated using 3D printing technology and were subjected to a thermomechanical aging protocol. After aging, fracture resistance tests were performed using a universal testing machine. The mean fracture resistance values were 2117.1 ± 795.6 N for the control group, 2080.9 ± 1420.8 N for the G-ænial Universal Flo group, and 1152.9 ± 345.1 N for the EverX Posterior group. Kruskal–Wallis analysis revealed a statistically significant difference among the groups. Post-hoc analyses demonstrated significant differences between the control group and the EverX Posterior group and between the G-ænial Posterior group and the EverX Posterior group. The fracture pattern analysis was conducted descriptively and no statistical comparison was performed between the groups regarding fracture types. The distribution of fracture types was reported as descriptive findings. In conclusion, the type of composite material used for the pulpal build-up significantly affected the fracture resistance of 3D-printed endocrown restorations, whereas it did not significantly influence the fracture pattern. These findings suggest that the mechanical properties of restorative materials should be carefully considered when restoring endodontically treated teeth. Further in vivo and clinical studies are recommended to support the results obtained under laboratory conditions.