Mechanical properties of 3D‐printed and milled composite resins for definitive restorations: An in vitro comparison of initial strength and fatigue behavior
Elisabeth Prause, Tine Malgaj, Andraž Kocjan, Florian Beuer, Jeremias Hey, Peter Jevnikar, Franziska Schmidt
Abstract
Abstract Objective To evaluate the flexural strength and fatigue behavior of a novel 3D‐printed composite resin for definitive restorations. Materials and Methods Fifty disc‐shaped specimens were manufactured from each of a nanohybrid composite resin (NHC), polymer‐infiltrated ceramic network (PICN), and 3D‐printed composite resin (3D) with CAD‐CAM technology. Biaxial flexural strength ( σ in ) ( n = 30 per group) and biaxial flexural fatigue strength ( σ ff ) ( n = 20 per group) were measured using piston‐on‐three‐balls method, employing a staircase approach of 10 5 cycles. Weibull statistics, relative‐strength degradation calculations, and fractography were performed. The results were analyzed with 1‐way ANOVA and Games‐Howell post hoc test ( α = 0.05). Results Significant differences in σ in and σ ff among the groups ( p < 0.001) were detected. The NHC group provided the highest mean ± standard deviation σ in and σ ff (237.3 ± 31.6 MPa and 141.3 ± 3.8 MPa), followed by the PICN (140.3 ± 12.9 MPa and 73.5 ± 9.9 MPa) and the 3D (83.6 ± 18.5 MPa and 37.4 ± 23.8 MPa) groups. The 3D group exhibited significantly lower Weibull modulus ( m = 4.7) and up to 15% higher relative strength degradation with areas of nonhomogeneous microstructure as possible fracture origins. Conclusions The 3D‐printed composite resin exhibited the lowest mechanical properties, where areas of nonhomogeneous microstructure developed during the mixing procedure served as potential fracture origins. Clinical Significance The clinical indications of the investigated novel 3D‐printed composite resin should be limited to long‐term provisional restorations. A cautious procedure for mixing the components is crucial before the 3D‐printing process, since nonhomogeneous areas developed during the mixing could act as fracture origins.