Effect of finish line design and cementation on fracture resistance of 3D printed definitive crowns

While 3-dimensional (3D) printing has emerged as a suitable technique for fabricating definitive restorations, the influence of cervical finish line design, cementation strategy, and artificial aging on fracture resistance remains unclear.

This in vitro study aimed to identify the optimal preparation design and cementation method based on the fracture resistance of 3D printed definitive premolar crowns immediately or after aging.

A total of 120 3D printed definitive crowns were fabricated using printing resin fortified with ceramic fillers for extracted maxillary premolars and divided into 12 test groups (n=10). Tooth preparations included chamfer, shoulder, or knife edge designs with uniform occlusal reduction and convergence angles. Crowns were cemented either with self-adhesive resin cement or conventional glass ionomer cement and tested after either 24 hours or after artificial aging (1 200 000 load cycles, 10 000 thermocycles and 6-month water storage). Fracture resistance was evaluated using a universal testing machine. Acoustic emission (AE) analysis was used to detect initial crack propagation and initial failure. Failure modes were assessed using stereomicroscopy and scanning electron microscopy (SEM). Statistical analysis was performed with a 3-way ANOVA (α=.05).

No statistically significant differences were found in initial failure loads (P>.05). Final fracture resistance was significantly influenced by the cement type (P=.012) and aging (P<.001), whereas finish line design had no significant effect (P=.200).

Cementation with self-adhesive resins may enhance the mechanical performance of 3D printed definitive crowns; however, the influence of porosities within the material's structure, which may lead to potential weakness against wear, should be considered.