Comparative Assessment of Milled and 3D-Printed Hybrid Ceramics: Effect of Build Orientation on Specimen Strength versus Crown Fracture Resistance

Abstract

This article aims to compare the flexural properties, fracture toughness, and fracture resistance of 3D-printed hybrid material (Varseosmile Crown plus, VS) at various build orientations versus milled hybrid materials (Cerasmart 270, CS, and Vita Enamic, E).

Specimens of 3D-printed material (VS) were fabricated at four build orientations (30, 45, 60, and 90 degrees; n = 10). Two milled hybrid ceramics (CS and E) served as comparative groups (n = 10). Flexural properties and fracture toughness were assessed on standardized bar specimens following ISO 6872:2024. Fracture resistance was tested on cemented crowns (n = 10). Statistical analysis was performed using Welch's ANOVA with Dunnett T3 post hoc comparison at α = 0.05.

CS exhibited the highest flexural strength (230.19 ± 13.59 MPa), fracture toughness (1.88 ± 0.07 MPa·m1/2), and fracture resistance (4,161.75 ± 597.50 N). E demonstrated the highest flexural modulus (26.79 ± 1.36 GPa). VS had lower values in all test parameters of this study compared to CS and E. Among VS specimens, building orientation significantly influenced flexural properties and fracture toughness, with a 90-degree building orientation yielding optimal results (flexural strength: 111.49 ± 4.15 MPa, flexural modulus: 2.32 ± 0.10 GPa, fracture toughness: 1.05 ± 0.05 MPa·m1/2, and fracture resistance: 2,296.52 ± 282.81 N). However, building orientation did not significantly affect the fracture resistance of the cemented crown.

Milled hybrid ceramics demonstrated superior strengths to the 3D-printed specimens. While 90-degree orientation optimized strength in standardized specimens, this benefit did not translate to a significant improvement in the fracture resistance of cemented crowns, suggesting that clinical geometry and cementation may affect the effects of build anisotropy.