Biaxial flexural strength and Weilbull characteristics of adhesively luted hybrid and reinforced CAD/CAM materials to dentin: effect of self-etching ceramic primer versus hydrofluoric acid etching

Abstract

This study evaluated the influence of the surface treatment and aging on the biaxial flexural strength of ceramic materials cemented to a dentin analogue. One hundred twenty disc-shaped specimens were allocated into 12 groups considering three study factors: ceramic material (lithium disilicate, leucitebased ceramic and hybrid ceramic), surface treatment (10% hydrofluoric acid etching + silane or selfetching glass-ceramic primer) and Aging (with 10,000 thermocycles of 5-37-55°C or without). A tri-layer assembly was designed to mimic a cemented restoration (Variolink N) into a dentin analogue. All samples were submitted to the biaxial flexural strength assay. The flexural strength in MPa was calculated using the finite element method for each sample considering thickness, material properties, and the load to fracture during the in vitro test. Fractographic analysis was also performed. The data was evaluated using three-way ANOVA and Tukey test ( = 5%). ANOVA showed influence for the Material*Treatment*Aging interaction on the flexural strength (p = 0.011). The highest strength was calculated for lithium disilicate ceramic + self-etching ceramic primer without aging (499 ± 17 MPa)A and the lowest value for hybrid ceramic material + acid etching with aging (424 ± 48 MPa)E. According to the Weibull modulus, the most predictable strength was calculated for lithium disilicate + acid etching after aging. Acid etching or self-etching ceramic primer promotes similar immediate biaxial flexural strength for each evaluated ceramic. In the long-term, superior strength was observed using acid etching for lithium disilicate and the self-etching ceramic primer for the hybrid ceramic while no difference was observed for leucite-based ceramic.

Effect of occlusal anatomy of CAD/CAM feldspathic posterior crowns in the stress concentration and fracture load

“…As this study's limitations, is important to emphasize that a load to fracture test does not replicate all the clinical loads to which the restoration can be exposed. The thermoaging also can reduce the bond strength between the restoration and cement and reduce the failure load values (Tribst et al, 2020 ). The isotropic material simulated in the finite element study is a simplification and cannot be found in the clinic, also different patient's occlusion can influence the load incidence pattern and modify the biomechanical response (da Fonseca et al, 2018 ).…”

Influence of occlusal anatomy on acrylic resin CAD/CAM crowns fracture load and stress distribution.

“…In addition, the finite element method is extensively applied in dental materials mechanical assessment, allowing the simulation of different structures that compose the dental restoration [2,6,10,16,[22][23][24][25][26][27]. This numerical approach allows the stress maps visualization and quantitative measurements of stress peaks, indicating with acceptable precision the failure area of possible fracture origin [23,32].…”

“…As study's limitations is important to relate that a single compressive load to failure not replicate all of the clinical loads to which the restoration is exposed. The thermocycling also can reduce the bond strength between a cemented restoration increase the failure susceptibility [32,33]. The isotropic material simulated in the finite element study cannot be found in the clinics and patient's occlusion can modify the load application pattern [32].…”

Effect of active application of self-etching ceramic primer on the long-term bond strength of different dental CAD/CAM materials

“…The authors indicated that the self-etching ceramic primer is a satisfactory alternative to replace the use of hydrofluoric acid in dental treatments ( 16 ). There is also reports that ME&P can be applied as an alternative also for for Leucite based ceramic ( 10 , 17 ). The present study, however suggests that the manufacturers protocol should be followed regardless the restorative material.…”

“…According to the literature, when the treating the CAD/CAM materials with self-etching ceramic primer, it is expected the occurrence of the a physicochemical conditioning through a mild etchant (ammonium polifluoride) and a trimethoxypropyl methacrylate for silanization, resulting in a reduced number of defects on the ceramic surface ( 18 ). This topographical change is more superficial than those produced by conventional acid etching, which might favor a better fatigue performance ( 18 ) and fracture load ( 17 ). The same principle can be applied to the bond strength durability when the active application is part of the protocol.…”