Damage Maps for Layered Ceramics under Simulated Mastication

Abstract

Ceramic restorations, whether monolithic (single layer) or porcelain veneered, often chip and fracture from repeated occlusal loading. Occlusion involves the opposing tooth sliding along the cuspal incline surface with an applied biting force (off-axis loading). We hypothesize that off-axis contact–load–slide–liftoff fatigue as compared to normal axial fatigue loading produces different fracture modes and fatigue lifespan of layered ceramics. Monolithic glass plates were epoxy bonded to polycarbonate substrates as a transparent model for an all-ceramic crown on dentin. Off-axis and axial (control) cyclic loading was applied through a hard sphere in water with a mouth-motion machine. The off-axis loading is more deleterious for contact-induced occlusal surface fracture, but less harmful for flexure-induced cementation surface fracture of brittle layers than the axial loading. This is because of the tangential load component associated with the off-axis loading. Clinical relevance is discussed.

ADM guidance-Ceramics: all-ceramic multilayer interfaces in dentistry

“…The low thermal diffusivity is of practical importance during cooling of the bilayer from the sintering temperature [6,44,75,76,79,80]. Fast cooling has been identified as a major contributor to the internal stress build-up and has been regarded as possibly the main reason for the increased chipping rates on veneered zirconia prostheses [18,68,81]. Consequently, current practical recommendations to dental technicians include a slow cooling protocol as the final step of the veneering procedure [18,20,68,71].…”

Probability of survival of implant-supported metal ceramic and CAD/CAM resin nanoceramic crowns

“…Step-stress accelerated life testing was performed in an axial direction at constant frequency of 2 Hz with the spherical indenter positioned 1 mm from the cusp tip, at the slope of the mesio-lingual cusp incline as done for the SLF test, which allowed for sliding of the indenter (0.3-0.5 mm) [19]. Crowns were submerged in water at room temperature throughout mechanical testing.…”

Fatigue and damage accumulation of veneer porcelain pressed on Y-TZP

“…14 Off-axis loading adds a tangential loading component which accelerates partial cone propagation requiring less than half the number of load cycles to propagate to the cementation interface compared to axial loading. 12 Reliability of hand-layered porcelain veneered onto alumina and Y-TZP in an off-axis fatigue scenario have been compared and found to be similar. 15 However, the failure modes were different and were representative of clinical failure.…”

“…[12][13][14] It has been demonstrated that mouth-motion biaxial loading in water (indenter contacts, applies the load, slides 0.5 mm, and lifts off the specimen surface, simulating occlusal function), on glass bi-layer systems creates partial cone cracks (distorted classic cone cracks) that are more aggressive than outer and inner cone cracks observed in axial loading, and develop faster and in a steeper angle towards the cementation surface. 14 Off-axis loading adds a tangential loading component which accelerates partial cone propagation requiring less than half the number of load cycles to propagate to the cementation interface compared to axial loading.…”