In vitro comparison of resin cement bond strength to milled and 3D-printed resins.

Objective

Contemporary minimally invasive strategies for fixed rehabilitation emphasize tooth structure preservation, with secure adhesion between thin restorations and resin cement vital to avoid failure. This study compares bond strengths of a common resin cement to 4 modern milling and 3D-printing resin-based restorative materials, with conventional lithium disilicate as control.

Methods

Rectangular beams (12.5 mm × 2 mm × 2 mm) were pressed (EMX: IPS e.Max Press), milled (TET: Tetric CAD; LAV: Lava Ultimate), or 3D-printed (PRO: Straumann P Pro Crown&Bridge; SPR: SprintRay Ceramic Crown). After surface-treatment following manufacturer's recommendations and application of universal adhesive, including on the lithium disilicate control, beams were cemented with RelyX Universal, forming 25 mm-long specimens. Specimens (n = 15) were subjected to a 4-point bend test after 24 h or artificial-aging with thermocycling. Bond strengths were calculated and statistically analyzed using ANOVA and pairwise comparisons (α = 0.05).

Results

Three of the 4 resins demonstrated significantly higher bond strengths (82-84 MPa) than the control (50 MPa); PRO was not significantly different (67 MPa). Aging significantly reduced the cement bond strength to the 2 milled materials (TET, LAV). Although the bond strength of PRO 3D-printed material did not significantly decrease following artificial aging, the majority of these specimens succumbed to cohesive failure. After thermocycling, additional tests using monolithic PRO beams confirmed a significant decrease in cohesive strength.

Conclusions

Bond strength between resin cement and modern milled and 3D-printed resins were generally higher than the lithium disilicate control. Artificial aging tended to decrease bond strengths, except for SPR. Cohesive strength of PRO 3D-printed resin was significantly lower after artificial aging.