RESUMO
Zirconia-reinforced lithium silicate (ZLS) is utilized as a material for prosthetic tooth crowns, offering enhanced strength compared to other dental glass-ceramics. In this study, we investigate a commercial ZLS material, provided in a fully crystallized form. We examine the effects of an optional post-processing heat treatment on micro-contact damage using controlled indentation tests simulating the primary modes of contact during chewing: axial and sliding. Our findings indicate that the heat treatment does not affect mechanical properties such as the elastic modulus, hardness and indentation fracture toughness. However, it does enhance the resistance to contact damage by fracture and chipping in both axial and sliding modes, as well as the resistance to crack initiation measured from sliding tests. This improvement is attributed to the refinement of the flaw population achieved through the heat treatment. The results are analysed using principles of contact and fracture mechanics theory, discussing their significance in prosthetic dentistry.
RESUMO
The damage to human dental enamel under cyclic, axial contacts in a silica particle medium is investigated. It is found that such damage is hierarchical, affecting different length-scales of the enamel structure. At the contact surface, it consists of micron-sized defects, with an attendant increase of surface roughness due to microindentation of the abrasive particles. Below the surface, demineralization of the enamel is observed, which is attributable to inelastic processes at the nanoscale. Axial-only contacts in particulate media result in negligible wear at the macroscopic scale, but may degrade the fracture strength. Potential implications of these results in the fields of dentistry and biology are discussed.
