Reliability of lithium di-silicate and monolithic zirconia ceramics with different thickness cemented to a dentin analogue material

Description

The study assessed the reliability of disk-shaped specimens made with two monolithic zirconia (5Y-TZP and 3Y-TZP) and a Lithium Disilicate, with thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm cemented on an epoxy-resin substrate, through step-stress accelerated life testing (SSALT). Step-stress accelerated life testing (SSALT) comprises 18 specimens distributed into three profiles: mild (n=9), moderate (n=6), and aggressive (n=3). Each profile started at 300 N and finished at 3,000 N. The mild profile was designed with 200 N load increase at each 20,000 cycles up to 320,000 cycles; the moderate profile was designed with a 250 N load increase each 15,000 cycles up to 195,000 cycles; the aggressive profile had 300 N load increase at each 10,000 cycles up to 110,000 cycles. The data were analyzed at 90% two-sided confidence interval using the software Synthesis 9, Alta Pro, Reliasoft, Tucson, AZ, USA. 3Y-TZP 1.5mm was the only group to have specimens that survived. The beta value (β) was ˂1 for 3Y-TZP, suggesting early damage in the 7 specimens that failed; β ≈ 1 for Lithium Disilicate 1.0 mm and 1.5 mm, 5Y-TZP 1.0 mm and 1.5 mm, 3Y-TZP 0.5 mm and 1.0 mm suggested stability of failure rate over time; β ˃ 1 for Lithium Disilicate 0.5 mm and 5Y-TZP 0.5 mm suggested increased failure rate over time. Lithium Disilicate ceramic demonstrated high reliability irrespective of thickness as well as 3Y-TZP 1.5 mm and 0.5 mm, but reliability was significantly reduced in 3Y-TZP 1.0 mm (86%). No significant difference was observed among the 3 thicknesses of 5Y-TZP groups. Lithium Disilicate 0.5 mm and 3Y-TZP 1.0 mm groups were not different from 5Y-TZP 0.5mm and 1,5 mm. The contour plot of Weibull modulus (m) versus characteristic strength, using load at failure during fatigue, showed that group 3Y-TZP 1.5 mm presented the highest load at failure followed by 3Y-TZP 0.5 mm. There was no difference among the Lithium Disilicate groups. The 5Y-TZP 1.0 mm showed the lowest values, followed by 5Y-TZP 0.5 mm, 5Y-TZP 1.5 mm and 3Y-TZP 1.0 mm which were not different from each other. In summary, 5Y-TZP presented lower reliability than the other ceramics, particularly when compared to all Lithium Disilicate groups and 3Y-TZP 0.5 mm and 1.5 mm. There was significant intra-group reduction in reliability and characteristic strength in intermediate thickness (1.0 mm) of 3Y-TZP and 5Y-TZP. Fatigue behavior of Lithium Disilicate ceramic was not markedly affected by thickness.

Institutions

Categories

Funding

Licence