Park Mi-Gyoung
Professor and Chairman, Department of Dental Laboratory Science, College of Health Sciences, Catholic University of Pusan, Busan, Republic of Korea.
J Prosthet Dent. 2025 Jan;133(1):258-263. doi: 10.1016/j.prosdent.2023.01.023. Epub 2023 Feb 18.
Evaluating the effect of low-temperature degradation (LTD) on multilayered zirconia blocks is important for the long-term life of zirconia restorations.
The purpose of this in vitro study was to analyze the changes in color, translucency, and hardness of a single layer of multilayered zirconia after an LTD treatment.
Ninety multilayered 10×10×1.0-mm zirconia specimens (3M Lava Esthetic) were designed using Auto CAD 2006 (Autodesk) and divided into 6 groups (n=15) based on LTD (no treatment, LTD treatment) and the inherent layer type (incisal, transition, and body). The hardness of each specimen was measured using a microVickers hardness tester. The CIELab color coordinates were measured using a spectrophotometer, and the data were used to calculate the color difference and translucency (TP). Data were analyzed using 2-way ANOVA and the Scheffé test (α=.05).
LTD treatment did not alter the hardness of multilayered zirconia (P=.572). A significant difference was found in the hardness between the layers of multilayered zirconia (P<.001). LTD treatment did not alter the b∗ or L∗ values (P=.773, P=.701) but did change the a∗ values (P<.001). On LTD treatment, the a∗ value was found to decrease. The L∗, a∗, and b∗ values differed based on the respective layer within the material (P<.001). As layers progress from the incisal to the body, the L∗ value decreased and the a∗ and b∗ values increased. In all groups, the color difference values were highest in the following order: the incisal and transition layers < the transition and body layers < the incisal and body layers. On LTD treatment, the color difference between the layers decreased. The LTD treatment did not affect the TP value (P=.208), but the TP value for each layer showed a significant difference (P<.001).
LTD treatment did not affect the optical properties or hardness of the multilayered zirconia. The hardness of the multilayered zirconia increased from the incisal to the body layer. In multilayered zirconia, the brightness decreased from the incisal to the body layer, and red and yellow color changes were observed. The TP of multilayered zirconia increased from the incisal to the body layer.
评估低温降解（LTD）对多层氧化锆块体的影响对于氧化锆修复体的长期使用寿命至关重要。
本体外研究的目的是分析单层多层氧化锆在LTD处理后的颜色、半透明度和硬度变化。
使用Auto CAD 2006（欧特克公司）设计90个10×10×1.0毫米的多层氧化锆标本（3M Lava Esthetic），并根据LTD（未处理、LTD处理）和固有层类型（切端、过渡和主体）分为6组（n = 15）。使用显微维氏硬度计测量每个标本的硬度。使用分光光度计测量CIELab颜色坐标，并将数据用于计算色差和半透明度（TP）。使用双向方差分析和谢费检验（α = 0.05）分析数据。
LTD处理未改变多层氧化锆的硬度（P = 0.572）。多层氧化锆各层之间的硬度存在显著差异（P < 0.001）。LTD处理未改变b∗或L∗值（P = 0.773，P = 0.701），但改变了a∗值（P < 0.001）。经LTD处理后，发现a∗值降低。L∗、a∗和b∗值因材料内各自的层而异（P < 0.001）。随着层从切端向主体推进，L∗值降低，a∗和b∗值增加。在所有组中，色差值按以下顺序最高：切端和过渡层 < 过渡和主体层 < 切端和主体层。经LTD处理后，层间色差减小。LTD处理不影响TP值（P = 0.208），但每层的TP值显示出显著差异（P < 0.001）。
LTD处理不影响多层氧化锆的光学性能或硬度。多层氧化锆的硬度从切端到主体层增加。在多层氧化锆中，亮度从切端到主体层降低，并且观察到红色和黄色的颜色变化。多层氧化锆的TP从切端到主体层增加。
