Dimitriadis Konstantinos, Sfikas Athanasios Konstantinou, Kamnis Spyros, Tsolka Pepie, Agathopoulos Simeon
Division of Dental Technology, Department of Biomedical Sciences, University of West Attica, Athens, Greece.
Experimental Techniques Centre, Brunel University London, Uxbridge, United Kingdom.
J Adv Prosthodont. 2022 Apr;14(2):96-107. doi: 10.4047/jap.2022.14.2.96. Epub 2022 Apr 27.
Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this study.
Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HT (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 "Dentistry - Ceramic materials", were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A and Group B) were merely the sintered specimens. The specimens of the second subgroups (Group A and Group B) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A/A, and B/B) was evaluated by the t-test. In all tests, values smaller than 5% were considered statistically significant.
A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant.
The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.
本研究的主要目的是对通过研磨技术（计算机辅助设计与计算机辅助制造，CAD-CAM）和多次烧制循环制备的高透明度氧化锆进行微观结构和物理力学特性分析。
制备了两组符合ISO 6872《牙科 - 陶瓷材料》尺寸要求的两种商用高透明度钇稳定牙科氧化锆样品，VITA YZ-HT（A组）和Zolid HT + White（B组）。每组样品分为两个亚组。第一亚组（A组和B组）的样品仅为烧结样品。第二亚组（A组和B组）的样品进行4次热处理循环。比较了各亚组（即热处理前后）的微观结构特征（微观结构、密度、晶粒尺寸、晶相和微晶尺寸）和四项力学性能（弯曲强度、弹性模量、维氏硬度和断裂韧性）。通过t检验评估亚组（A/A和B/B）之间的统计学显著性。在所有测试中，小于5%的值被认为具有统计学显著性。
观察到A组和B组均具有均匀的微观结构，无残余孔隙，晶粒尺寸分别在500至450纳米之间。在X射线衍射图中仅记录到结晶态钇稳定四方氧化锆。热处理后力学性能有所下降，但差异无统计学显著性。
所制备的氧化锆陶瓷材料可安全地（即根据ISO 6872）用于广泛的固定修复体，如用于涉及磨牙修复的三单位假体的下部结构陶瓷以及用于涉及四个或更多单位假体的下部结构陶瓷。因此，研磨技术是生产牙科固定全陶瓷修复体氧化锆下部结构的有效制造技术。
