Impact of Chemical Aging on the Fracture Resistance of Two Ceramic Materials: Zirconia-Reinforced Lithium Silicate and Lithium Disilicate Ceramics

Abstract

BACKGROUND: The reason for the development of high strength zirconia is that zirconia offers enough high strength of about 1000 MPa and high strength glass ceramic in the range of 360–400 MPa, to provide safely ceramic options for many indications.
 AIM: This study aims to evaluate the fracture resistance of zirconia-reinforced lithium silicate (ZLS) ceramic and lithium disilicate ceramic restorations.
 MATERIALS AND METHODS: In this in vitro study, forty crowns were fabricated by CAD/CAM technology, all samples were divided into two groups (n = 20) according to ceramic material used: Group Z ZLS ceramic (celtra due) and Group L lithium disilicate ceramic blocks (IPS E-MAX). Further subdivided into two subgroups according to the aging procedure (n = 10): (a) Subgroup – ZA: Aging. (b) Subgroup – ZB: No aging. (c) Subgroup – LA: Aging. (d) Subgroup – LB: No aging. All samples were subjected to universal testing machine (Instron) to evaluate the effect of the chemical aging on the fracture resistance.
 STATISTICAL ANALYSIS: One-way ANOVA analysis was used to compare measurements among groups.
 RESULTS: ZLS showed higher fracture resistance than lithium disilicate, but there was no statistical difference between them. Aging affected on the fracture resistance of two different ceramic materials but within an acceptable range.
 CONCLUSION: ZLS gave rise to higher fracture resistance than lithium disilicate and aging decrease fracture resistance of both types of ceramic. The postulated hypothecs of this study were zirconia reinforced, lithium silicate will be higher fracture resistance than lithium disilicate, and chemical aging will have a huge effect.