Load-bearing properties of minimal-invasive monolithic lithium disilicate and zirconia occlusal onlays: finite element and theoretical analyses.
Load-bearing properties of minimal-invasive monolithic lithium disilicate and zirconia occlusal onlays: finite element and theoretical analyses.
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DOI：
10.1016/j.dental.2013.04.004
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发表时间：
2013-07
期刊：
影响因子：
--
通讯作者：
Zhang Y
中科院分区：
文献类型：
--
作者：
Ma L;Guess PC;Zhang Y
本研究的目的是验证这样一种假设，即整体二硅酸锂玻璃陶瓷咬合嵌体可以表现出接近于整体氧化锆的承载能力，这是因为相对于氧化锆而言，二硅酸锂与其支撑牙结构之间的弹性模数失配更小。不同厚度的陶瓷牙合嵌体分别粘结在牙釉质或牙本质上。咬合载荷通过釉质状可变形压痕或对照刚性压痕施加。采用有限元分析和经典的板基理论，严格分析了陶瓷凹槽(粘结)表面的弯曲拉应力，这是导致咬合嵌体整体断裂的原因。当与牙釉质粘结(牙本质支持)时，尽管二硅酸锂的抗弯强度(400 Mpa)仅为氧化锆(1000 Mpa)的40%，但其承载能力可接近氧化锆的75%。当粘结到牙本质上时(牙釉质完全去除)，二硅酸锂的承载能力约为氧化锆的57%，仍显著高于基于其强度的预期值。当使用可变形的压痕(珐琅、微晶玻璃或瓷器)而不是刚性压痕时，两种陶瓷都表现出略高的承载能力。当牙釉质支持时，微创二硅酸锂(0.6~1.4 mm厚)嵌体的承载性能可超过锆石的70%。此外，断裂载荷对修复厚度的依赖性相对较弱，这表明1.2 mm厚的二硅酸锂嵌体可以与1.6 mm的嵌体一样具有抗断裂能力。
The aim of this study was to test the hypothesis that monolithic lithium disilicate glass-ceramic occlusal onlay can exhibit a load-bearing capacity that approaches monolithic zirconia, due to a smaller elastic modulus mismatch between the lithium disilicate and its supporting tooth structure relative to zirconia. Ceramic occlusal onlays of various thicknesses cemented to either enamel or dentin were considered. Occlusal load was applied through an enamel-like deformable indenter or a control rigid indenter. Flexural tensile stress at the ceramic intaglio (cementation) surface—a cause for bulk fracture of occlusal onlays—was rigorously analyzed using finite element analysis and classical plate-on-foundation theory. When bonded to enamel (supported by dentin), the load-bearing capacity of lithium disilicate can approach 75% of that of zirconia, despite the flexural strength of lithium disilicate (400 MPa) being merely 40% of zirconia (1000 MPa). When bonded to dentin (with the enamel completely removed), the load-bearing capacity of lithium disilicate is about 57% of zirconia, still significantly higher than the anticipated value based on its strength. Both ceramics show slightly higher load-bearing capacity when loaded with a deformable indenter (enamel, glass-ceramic, or porcelain) rather than a rigid indenter. When supported by enamel, the load-bearing property of minimally invasive lithium disilicate occlusal onlays (0.6 to 1.4 mm thick) can exceed 70% of that of zircona. Additionally, a relatively weak dependence of fracture load on restoration thickness indicates that a 1.2 mm thin lithium disilicate onlay can be as fracture resistant as its 1.6 mm counterpart.
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