Department of Medical Biotechnologies, University of Siena, Siena, 53100, Italy.
Biomaterials and Tissue Engineering Research Group, School of Dentistry, University of Leeds, Leeds, LS2 9LU, UK.
J Dent. 2017 May;60:70-76. doi: 10.1016/j.jdent.2017.03.002. Epub 2017 Mar 6.
To compare three different compositions of Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) ceramic and a lithium disilicate ceramic in terms of flexural strength and translucency.
Three zirconia materials of different composition and translucency, Aadva ST [ST], Aadva EI [EI] and Aadva NT [NT](GC Tech, Leuven, Belgium) were cut with a slow speed diamond saw into beams and tabs in order to obtain, after sintering, dimensions of 1.2×4.0×15.0mm and 15.0×15.0×1.0mm respectively. Blocks of IPS e.max CAD LT were cut and crystallized in the same shapes and dimensions and used as a reference group [LD]. Beams (n=15) were tested in a universal testing machine for three-point bending strength. Critical fracture load was recorded in N, flexural strength (σ in MPa), Weibull modulus (m) and Weibull characteristic strength (σ in MPa) were then calculated. Tabs (n=10) were measured with a spectrophotometer equipped with an integrating sphere. Contrast Ratios were calculated as CR=Yb/Yw. SEM of thermally etched samples coupled with lineal line analysis (n=6) was used to measure the tested zirconia grain size. Data were statistically analyzed.
Differences in translucency, flexural strength and grain size were found to be statistically significant. CR increased and flexural strength decreased in the following order ST(σ 1215±190MPa, CR 0.74±0.01)>EI(σ 983±182MPa, CR 0.69±0.01)>NT(σ 539±66MPa, CR 0.65±0.01)>LD (σ 377±39Mpa, CR 0.56±0.02). The average grain size was different for the three zirconia samples with NT(558±38nm)>ST(445±34nm)>EI(284±11nm).
The zirconia composition heavily influenced both the flexural strength and the translucency. Different percentages of Yittria and Alumina result in new materials with intermediate properties in between the conventional zirconia and lithium disilicate. Clinical indications for Zirconia Aadva NT should be limited up to three-unit span bridges.
比较三种不同组成的氧化钇四方氧化锆多晶陶瓷（Y-TZP）和二硅酸锂陶瓷的抗弯强度和透光率。
使用不同成分和透光率的三种氧化锆材料，即 Aadva ST[ST]、Aadva EI[EI]和 Aadva NT[NT]（GC Tech，比利时鲁汶），用低速金刚石锯切割成梁和片，以便在烧结后获得尺寸分别为 1.2×4.0×15.0mm 和 15.0×15.0×1.0mm 的梁和片。IPS e.max CAD LT 块被切割并以相同的形状和尺寸结晶，并用作参考组[LD]。梁（n=15）在万能试验机上进行三点弯曲强度测试。记录临界断裂载荷，以 N 为单位，然后计算抗弯强度（σ，以 MPa 为单位）、威布尔模数（m）和威布尔特征强度（σ，以 MPa 为单位）。用配备积分球的分光光度计测量片（n=10）。计算对比率 CR=Yb/Yw。使用热蚀样品的 SEM 结合线性线分析（n=6）来测量测试的氧化锆晶粒尺寸。对数据进行了统计学分析。
透光率、抗弯强度和晶粒尺寸存在显著差异。透光率从高到低依次为 ST（σ1215±190MPa，CR0.74±0.01）>EI（σ983±182MPa，CR0.69±0.01）>NT（σ539±66MPa，CR0.65±0.01）>LD（σ377±39Mpa，CR0.56±0.02）。三种氧化锆样品的平均晶粒尺寸不同，NT（558±38nm）>ST（445±34nm）>EI（284±11nm）。
氧化锆成分对抗弯强度和透光率有很大影响。不同比例的氧化钇和氧化铝导致新材料的性能介于传统氧化锆和二硅酸锂之间。氧化锆 Aadva NT 的临床适应证应限于跨度不超过三单位的桥。
