Abstract Objectives For posterior partial restorations an overlap of indication exists where either ceramic or resin-based composite materials can be successfully applied. The aim of this study was ...to compare the fatigue resistance of modern dental ceramic materials versus dental resin composites in order to address such conflicts. Methods Bar specimens of five ceramic materials and resin composites were produced according to ISO 4049 and stored for 14 days in distilled water at 37 °C. The following ceramic materials were selected for testing: a high-strength zirconium dioxide (e.max ZirCAD, Ivoclar), a machinable lithium disilicate (e.max CAD, Ivoclar), a pressable lithium disilicate ceramic (e-max Press, Ivoclar), a fluorapatite-based glass-ceramic (e.max Ceram, Ivoclar), and a machinable color-graded feldspathic porcelain (Trilux Forte, Vita). The composite materials selected were: an indirect machinable composite (Lava Ultimate, 3M ESPE) and four direct composites with varying filler nature (Clearfil Majesty Posterior, Kuraray; GrandioSO, Voco; Tetric EvoCeram, Ivoclar-Vivadent; and CeramX Duo, Dentsply). Fifteen specimens were tested in water for initial strength ( σin ) in 4-point bending. Using the same test set-up, the residual flexural fatigue strength ( σff ) was determined using the staircase approach after 104 cycles at 0.5 Hz ( n = 25). Weibull parameters σ0 and m were calculated for the σin specimens, whereas the σff and strength loss in percentage were obtained from the fatigue experiment. Results The zirconium oxide ceramic showed the highest σin and σff (768 and 440 MPa, respectively). Although both lithium disilicate ceramics were similar in the static test, the pressable version showed a significantly higher fatigue resistance after cyclic loading. Both the fluorapatite-based and the feldspathic porcelain showed equivalent initial and cyclic fatigue properties. From the composites, the highest filled direct material Clearfil Majesty Posterior showed superior fatigue performance. From all materials, e.max Press and Clearfil Majesty Posterior showed the lowest strength loss (29.6% and 32%, respectively), whereas the other materials lost between 41% and 62% of their flexural strength after cyclic loading. Conclusions Dental ceramics and resin composite materials show equivalent fatigue strength degradation at loads around 0.5 σin values. Apart from the zirconium oxide and the lithium disilicate ceramics, resin composites generally showed better σff after 10,000 cycles than the fluorapatite glass-ceramic and the feldspathic porcelain. Resin composite restorations may be used as an equivalent alternative to glass-rich-ceramic inlays regarding mechanical performance.
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 (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).
Results
Significant 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.
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.
Abstract Objective The aim of this study was to measure the linear elastic material properties of direct dental resin composites and correlate them with their fatigue strength under cyclic loading. ...Methods Bar specimens of twelve resin composites were produced according to ISO 4049 and tested for elastic modulus (Emod) in 3-point bending ( n = 10), flexural strength (FS) ( n = 15) and single-edge-notch-beam fracture toughness (FT) ( n = 15), both in 4-point bending. Using the same specimen geometry, the flexural fatigue strength (FFS) was determined using the staircase approach after 104 cycles at 0.5 Hz in 4-point bending ( n = 25). The observation of the fracture surface and fracture profiles was conducted using a scanning electron microscope in order to evaluate the respective fracture mechanisms according to the two different loading conditions. Results Materials were ranked differently according to the tested parameters. Only weak correlations were found between any of the initial properties and FFS or strength loss. The best correlation to FFS was found to be the Emod ( r2 = 0.679), although only slightly. Crack path in both loading conditions was mainly interparticle, with the crack propagating mainly within the matrix phase for fatigued specimens and eventually through the filler/matrix interface for statically loaded specimens. Fracture of large particles or prepolymerized fillers was only observed in specimens of FS and FT. Initial properties were better associated with microstructural features, whereas the fatigue resistance showed to be more dependent on aspects relating to the matrix phase. Significance Our results show that linear elastic properties such as elastic modulus, flexural strength and fracture toughness are not good descriptors of the fatigue resistance of dental resin composite under cyclic bending, and may therefore have limited clinical relevance.
