Mechanical properties of 3D‐printed and milled composite resins for definitive restorations: An in vitro comparison of initial strength and fatigue behavior

Abstract

ObjectiveTo evaluate the flexural strength and fatigue behavior of a novel 3D‐printed composite resin for definitive restorations.Materials and MethodsFifty 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 (σin) (n = 30 per group) and biaxial flexural fatigue strength (σff) (n = 20 per group) were measured using piston‐on‐three‐balls method, employing a staircase approach of 105 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).ResultsSignificant differences in σin and σff among the groups (p < 0.001) were detected. The NHC group provided the highest mean ± standard deviation σin and σff (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.ConclusionsThe 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 SignificanceThe 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.

3D Printed Materials for Permanent Restorations in Indirect Restorative and Prosthetic Dentistry: A Critical Review of the Literature

“…Prause et al [ 57 ] also compared the flexural strength and Weibull modulus of 3D printed composite resins with milled composite resins and PICN for definitive restorations and found that the 3D printed composite resin exhibited the lowest biaxial flexural strength. Moreover, they also observed that the fracture origin of the 3D printed composite resin was correlated with the flaws introduced by the mixing procedure taking place during the 3D printing process.…”

“…One of the main disadvantages concerning printable resins is linked to their filler volume. It has been shown that a greater amount of filler might impair the resin’s flow during the building process, therefore increasing the risk of incorporating air bubbles or areas of non-homogenous microstructure, consequently impairing mechanical properties [ 57 ]. For this reason, the printable resins currently available on the market consist of a significantly smaller amount of filler (30–50 wt%) compared to the resins designed for subtractive manufacturing (80–85 wt%).…”

“…For this reason, the printable resins currently available on the market consist of a significantly smaller amount of filler (30–50 wt%) compared to the resins designed for subtractive manufacturing (80–85 wt%). This reduced amount of filler correlates linearly with the flexural strength [ 68 ] and resulted therefore in lower values of initial strength for the 3D printed specimens compared to the milled ones, which showed higher filler load [ 57 ]. Also, zirconia seems to have lower flexural strength when 3D printed than milled, but this property was shown to be highly dependent on the building direction.…”

Direct ink writing with dental composites: A paradigm shift toward sustainable chair-side production

“…However, importantly, the filler size of this product is similar to that of microfilled composites, and the filler content remains lower than that of most flowable composites [36]. Since microfilled composites with low filler contents may exhibit low wear resistance and poor mechanical properties, further studies are warranted to evaluate the in vitro and clinical performance of these novel materials [37,38].…”