Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University, Goethestrasse 70, 80336, Munich, Germany.
Estetic Ceram Ag, Landstrasse 109, 9495, Triesen, Liechtenstein.
J Mech Behav Biomed Mater. 2022 Apr;128:105134. doi: 10.1016/j.jmbbm.2022.105134. Epub 2022 Feb 17.
This investigation evaluated the impact of multiple firings during the veneering process of all-ceramic restorations on the thermal properties and bond strength between veneering ceramics and zirconia.
For the measurements of the coefficient of thermal expansion (CTE) prismatic specimens of four different veneering ceramics (ZRT/ZRO/HFZ/STR; N = 40/n = 10 per veneering ceramic) and rod-shaped zirconia specimens (N = 2) were produced. 2 specimens of each veneering ceramic were fired 2, 4, 6, 8, and 10 times simulating dentine-firing. Measurements were performed in a dilatometer and glass transition temperature (Tg) was determined graphically. To analyze bond strength (BS), crack initiation test specimens were prepared using the same veneering ceramics and zirconia (N = 600/n = 150 per veneering ceramic). 30 specimens of each veneering ceramic were fired 2, 4, 6, 8, and 10 times. Half of them were thermocycled (5000 cycles, 5 °C/55 °C, 20s). The crack initiation test was conducted in a universal testing machine. Data was analyzed using ANOVA with partial eta squared statistics and post-hoc Scheffé test as well as Pearson correlation test.
CTE was mostly affected by the choice of veneering ceramic (p < 0.001/η = 0.983). For the leucite-free ceramic, the CTE values were in same value range (p = 0.171) along the number of firings. Tg was not influenced by the number of firings. The highest effect on BS showed veneering ceramics (p < 0.001/η = 0.055) followed by the number of firings (p = 0.011/η = 0.023). The global difference in BS was lower for 10 firings compared to 2 firings (p = 0.048). Highest BS were measured for the leucite-free veneering ceramic (ZRT). Artificial aging by thermocycling showed no impact on BS (p = 0.755). Correlations were found for HFZ between the BS and the CTE (r = -0.651/p = 0.021). A correlation between CTE and Tg was observed (r = 0.303/p = 0.029).
Thermal stability seemed to be more predictable for leucite-free veneering ceramics with superior BS. All BS results exceeded the minimum clinical requirements.
本研究评估了全瓷修复体贴面过程中多次烧制对贴面陶瓷与氧化锆之间热性能和结合强度的影响。
为了测量热膨胀系数（CTE），制作了四种不同贴面陶瓷（ZRT/ZRO/HFZ/STR；每种陶瓷 N=40/n=10）和棒状氧化锆试件（N=2）的棱柱体试件。每种贴面陶瓷的 2 个试件模拟牙本质烧制进行 2、4、6、8 和 10 次烧制。在膨胀计中进行测量，并通过图形确定玻璃化转变温度（Tg）。为了分析结合强度（BS），使用相同的贴面陶瓷和氧化锆制备裂纹起始测试试件（每种陶瓷 N=600/n=150）。每种贴面陶瓷的 30 个试件进行 2、4、6、8 和 10 次烧制。其中一半进行热循环（5000 次循环，5°C/55°C，20s）。在万能试验机上进行裂纹起始试验。使用方差分析和事后 Scheffé 检验以及 Pearson 相关检验分析数据。
CTE 主要受贴面陶瓷选择的影响（p<0.001/η=0.983）。对于不含白榴石的陶瓷，在烧制次数相同的情况下，CTE 值处于相同的范围（p=0.171）。Tg 不受烧制次数的影响。对 BS 影响最大的是贴面陶瓷（p<0.001/η=0.055），其次是烧制次数（p=0.011/η=0.023）。与 2 次烧制相比，10 次烧制的 BS 全球差异较低（p=0.048）。最高的 BS 是在不含白榴石的贴面陶瓷（ZRT）中测量得到的。热循环人工老化对 BS 没有影响（p=0.755）。HFZ 之间的 BS 和 CTE 之间存在相关性（r=-0.651/p=0.021）。观察到 CTE 和 Tg 之间存在相关性（r=0.303/p=0.029）。
对于具有优异 BS 的不含白榴石的贴面陶瓷，热稳定性似乎更具可预测性。所有 BS 结果均超过最低临床要求。
