Lecturer, Department of Dental Laboratory Science, College of Health Sciences, Catholic University of Pusan, Busan, Republic of Korea.
Associate Professor and Chairman, Department of Dental Laboratory Science, College of Health Sciences, Catholic University of Pusan, Busan, Republic of Korea.
J Prosthet Dent. 2018 Dec;120(6):969.e1-969.e6. doi: 10.1016/j.prosdent.2018.07.017.
Surface glazing and low-temperature degradation (LTD) can affect the mechanical properties of zirconia, which is used to fabricate monolithic ceramic crowns.
The purpose of this in vitro study was to assess the changes in flexural strength of monolithic ceramic crowns fabricated from translucent zirconia due to surface glazing and LTD.
Sixty plates of zirconia (25×4×1.2 mm) were milled and sintered. They were classified into 4 groups according to glazing and LTD (n=15): control, glazing, LTD, and LTD after glazing. A 3-point flexural test was performed with a universal testing machine. X-ray diffraction (XRD) was used to observe changes in the crystal structures of each group, and field emission scanning electron microscopy was used to observe the sizes of the crystal grains. Two-way analysis of variance was used to evaluate the results of the flexural strength tests, and the Tukey honestly significant difference test was performed for post hoc analysis (α=.05).
The flexural strength showed significant differences due to glazing (P<.01). No significant differences were found due to LTD (P>.05). The crystal grain size increased with decreasing flexural strength of the specimens. XRD showed monoclinic phases in the groups subjected to LTD.
Glazing significantly reduced the flexural strength of translucent zirconia. LTD decreased the flexural strength of glazed translucent zirconia, but not to a significant extent.
表面上釉和低温降解（LTD）会影响用于制造整体陶瓷冠的氧化锆的机械性能。
本体外研究的目的是评估由于表面上釉和 LTD 导致由半透明氧化锆制成的整体陶瓷冠的弯曲强度的变化。
铣削和烧结了 60 个氧化锆板（25×4×1.2mm）。根据上釉和 LTD 将它们分为 4 组（n=15）：对照、上釉、LTD 和上釉后 LTD。使用万能试验机进行三点弯曲测试。X 射线衍射（XRD）用于观察每组晶体结构的变化，场发射扫描电子显微镜用于观察晶粒尺寸。使用双向方差分析评估弯曲强度测试的结果，并进行 Tukey Honestly 显著差异检验进行事后分析（α=.05）。
由于上釉，弯曲强度存在显著差异（P<.01）。由于 LTD 没有发现显著差异（P>.05）。随着试样弯曲强度的降低，晶粒尺寸增大。XRD 显示经受 LTD 的组呈现单斜相。
上釉显著降低了半透明氧化锆的弯曲强度。LTD 降低了上釉半透明氧化锆的弯曲强度，但程度不显著。
