The fracture resistance of a CAD/CAM Resin Nano Ceramic (RNC) and a CAD ceramic at different thicknesses

Effect of air-particle pressures on the surface topography and bond strengths of resin cement to the hybrid ceramics

“…Therefore, it is thought that the observed decrease in bonding strength when the pressure was increased up to 0.3 MPa was due to the high-pressure airborne-abrasion weakening the fracture toughness of the material, rather than simply decreasing the bonding strength. Chen et al 17) reported that applying airborne-abrasion to the surface of Lava Ultimate samples did not affect the fracture toughness of the material. They used 50-µm alumina particles (the same as used in the present study), but they did not report the pressure used for the surface treatment.…”

Fatigue behavior of resin-modified monolithic CAD–CAM RNC crowns and endocrowns

“…As it was expected, this occlusal intervention had a weakening effect on fatigue resistance of crowns of group F due to a critical alteration of the restoration's thickness just underneath the occlusal loads. Beforehand, Chen et al [11] have already shown an increasing linear relation between thickness and fracture strength of Lava Ultimate restorations. Interestingly, that occlusal intervention was uninfluential for modified endocrowns of group C, if compared to unmodified thicker endocrowns of group A.…”

“…It has been introduced by the manufacturer as a resin nano-ceramic (RNC) material as the dimethacrylate resin matrix is charged with silica and zirconia nano-fillers to an extent of approximately 80% by weight. Improved flexural strength and toughness [8] compared to previous resin composite blocks (Paradigm MZ100, 3M Espe) and similar fatigue resistance [10] as well as fracture strength to glass-ceramics [11] have been reported for Lava Ultimate restorations. Some concerns arise about the esthetics of this material, as blocks are monochromatic and an esthetic modification of the raw workpiece after milling may be necessary depending on esthetic needs of the patient.…”

“…This result was not unexpected, as no direct loading or damage at the buccal veneer bonded interface occurred during any phase of the fatigue loading. Certainly the optimal bonding procedure between Lava Ultimate restorations and the restorative resin veneer [35] was able to counteract thermal and mechanical stresses during fatigue but the distance between this buccal resin veneer and the occlusal loads should have played a major role on veneer integrity, as stress distributed within a resin restoration is known to be concentrated around the loading contacts and not transmitted to peripheral areas [11,36,37]. A further demonstration is the fact that the occlusal resin filling of restorations of groups C and F was always debonded during fracture, as a consequence of the proximity with the occlusal origin of the overloading event.…”

“…Moreover, to further improve the standardization of the study set-up resin composite root dies were fabricated in series using a resin composite with a standardized silicon mold instead of prepared natural teeth. A resin composite with an elastic modulus (22 GPa) similar to that of the dentinal tissue was employed as substitute for dentin [9,11,18,19].…”