The effect of extended aging on the optical properties of different zirconia materials

Abstract

Purpose The purpose of this study was to determine if the optical properties of zirconia and glass–ceramic (e.max) were affected by low-temperature degradation (aging). Methods Experiment samples were fabricated with seven zirconia brands (n = 10): Zenostar, Zirlux, Katana, Bruxzir, DD-BioZX2, DD-cubeX2, NexxZr; and e.max were used as a control. This resulted in a total of 80 samples in the experiment. The L*, a* and b* were measured for each sample, and then the optical properties including translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were calculated. The samples were aged (20, 40, 60, 80, 100 h), and the optical properties were calculated after each interval. Results Most zirconia brands had lower L*, higher a*, higher b* with increased aging, which visually corresponds to darker, redder, and more yellow. Aging also increased CR, lowered TP, and lowered OP. e.max was also affected by aging but still had the highest TP (23.9 ± 2.8), L* (81.7 ± 3.4), and lowest CR (0.41 ± 0.05) compared to any zirconia. The Zenostar had the closest TP (24.1 ± 0.4), and L* (90.2 ± 0.5) values to e.max before aging. However, after 100 h of aging, the DD-cubeX2 was least effected and had the highest TP (22.2 ± 0.6) and lowest CR (0.43 ± 0.01) compared with other zirconia samples and highest OP (11.3 ± 0.2) of all ceramic samples. Conclusions The optical properties of zirconia and e.max materials were affected by aging with the effects increasing with time. The magnitude of change was affected by seven brands of dental zirconia.