Flexural Strength of Vitreous Ceramics Based on Lithium Disilicate and Lithium Silicate Reinforced with Zirconia for CAD/CAM

Abstract

The dental prosthesis market is rapidly evolving to meet patient and clinical demands. These new materials must have good flexural strength, toughness, aesthetic properties, and reliability in performance for structural applications. The present work aimed to compare the bending strength of 4 types of chairside lithium disilicate (Li2Si2O5) glass-ceramics used for dental prosthesis and to analyze the influence of heat treatment on the transformation of lithium metasilicate (Li2SiO3) into lithium disilicate. The three-ball test for the biaxial flexion test (B3B) was used. Weibull statistical analysis was used, and it showed that samples with a higher percentage of zirconia have a greater tendency to fail. The flexion tests showed that the addition of more than 10% of zirconia reduced the flexural strength. The heat treatment process improves and provides greater mechanical strength. The XRD results indicated that the samples with the lowest percentage of zirconia exhibited greater crystallinity and corroborated the microstructural analysis. SEM analyses showed a greater amount and elongated crystals of lithium disilicate when comparing samples with a higher percentage of zirconia. Therefore, samples with lower zirconia showed greater flexural strength than samples with higher additions of zirconia.

Influences of Different CAD/CAM Ceramic Compositions and Thicknesses on the Mechanical Properties of Ceramic Restorations: An In Vitro Study

“…Colombo et al [ 59 ] reported that ZLS had the highest hardness when compared to hybrid ceramics and resin nano-ceramics. However, Corade et al [ 43 ] stated that LD showed a higher hardness than ZLS, which is inconsistent with the current findings. This might be related to the different methodology, ceramic specimen dimensions, absence of polishing procedures, and the use of non-crystallized ZLS, which differed from that used in the current study.…”

“…The specimens were sectioned using a precision cutting machine (Isomet 5000, Buehler, Lake Bluff, IL, USA) with copious cooling water into the thicknesses of 0.5, 1, and 1.5 mm, with the same dimensions of the block, according to the International Organization of Standards (ISO standards 6872:2015) [ 43 ]. The specimens were polished using 500-grit silicon carbide discs for 60 s at a speed of 200 rpm with a water-cooling system, using a polishing machine (MetaServ 250 Grinder-Polisher with Vector Power Head, Buehler, IL, USA).…”

“…The surface microhardness was measured for all the specimens using a microhardness testing machine (MicroMet 6040, Buehler LTD., Lake Bluff, IL, USA) according to the ASTM C1327-15 standard [ 43 ]. A load of 50 gms was applied for 20 s to three different regions of each specimen through the use of Vickers hardness indenter [ 44 ].…”

Load-bearing capacity of pressable lithium disilicates applied as ultra-thin occlusal veneers on molars

“…The heat treatment process improves and provides greater mechanical strength. It has been shown that the specimens with the lowest percentage of ZrO 2 exhibited greater crystallinity and corroborated the microstructural analysis (Corado et al, 2022). SEM analyses showed a greater amount of elongated crystals of lithium disilicate when comparing samples with higher percentage of ZrO 2 .…”

“…On the other hand, it has been shown that ZrO 2 being content of a lithium-disilicate ingot did not improve mechanical properties in studies comparing different pressed lithium disilicates (Hallmann et al, 2019;Sieper et al, 2017). Flexion tests showed that the addition of more than 10% of ZrO 2 reduced the flexural strength (Corado et al, 2022). The heat treatment process improves and provides greater mechanical strength.…”