Department of Oral Technology, Medical Faculty, University Hospital Bonn, 53111, Bonn, North Rhine-Westphalia, Germany; Department of Fixed Prosthodontics, Suez Canal University, Ismailia, Egypt.
Department of Prosthetic Dentistry, University Hospital, LMU Munich, Munich, Germany.
J Mech Behav Biomed Mater. 2023 Oct;146:106102. doi: 10.1016/j.jmbbm.2023.106102. Epub 2023 Aug 30.
Lithium disilicate (LDS) based glass ceramics are indispensable materials in the field of prosthetic dentistry due to their strength and excellent esthetics. Recently, novel fully crystallized LDS for the milling process have been introduced to the market, requiring only chairside polishing before delivery. Since limited data is available about subjecting this material to glazing, this study aimed to evaluate the wear properties, fracture resistance, and optical properties of the newly introduced fully crystallized LDS after glazing.
Lithium disilicate glass-ceramics (fully crystallized (LiSiCAD) and partially crystallized types (EmaxCAD), of shade A3, were used in the present study. The fully crystallized specimens were subjected to a glazing firing cycle in a furnace (LiSiCAD-G) and compared to a polished fully crystallized counterpart (LiSiCAD-P, negative control) and a glazed partially crystallized LDS (EmaxCAD, positive control). Rectangular-shaped ceramic specimens (n = 10, 12 × 6.5 × 1.5 mm) and enamel antagonists were used to test the wear resistance in a specially designed wear machine built at the Department of Oral Technology, University of Bonn, Germany. The volumetric enamel loss of antagonists was measured by means of overlapping virtual 3D models derived from micro-CT scans for the teeth before and after the wear test. The weight loss of ceramic specimens in milligrams was measured after 100,000 and 200,000 wear cycles. A spectrophotometer was used to calculate the CIELAB color parameters of the ceramic specimens against black and white backgrounds to measure the translucency. Fracture resistance was also assessed after thermodynamic fatigue using a universal testing machine until fracture at a 1 mm/min crosshead speed. Statistical analysis was performed using one-way ANOVA and the significance level was set at α = 0.05.
EmaxCAD and LisiCAD-G groups showed significantly higher mean ceramic weight loss after 100,000 cycles (2 ± 0.3 mg and 1.93 ± 0.2 mg, respectively) than LisiCAD-P group (0.78 ± 0.19 mg). Glazed LiSiCAD specimens demonstrated significantly higher ΔE values from shade A3 compared to polished LiSiCAD. There was no significant difference in ΔE between LiSiCAD-G and EmaxCAD. For fracture resistance, no significant difference was observed between LiSiCAD-G and LiSiCAD-P before or after aging.
The glazed fully crystallized LDS was superior to the partially crystallized one with regard to wear resistance but showed more color changes than the polished fully crystallized one. Furthermore, polishing of fully crystallized LDS could still be considered a better option than glazing when aesthetics is a primary prerequisite.
由于强度和出色的美观性，二硅酸锂（LDS）基玻璃陶瓷是义齿修复领域不可或缺的材料。最近，市场上推出了新型全结晶 LDS 用于铣削加工，交付前仅需椅旁抛光。由于有关对这种材料上釉的资料有限，本研究旨在评估新引入的全结晶 LDS 在上釉后的磨损性能、抗断裂强度和光学性能。
本研究使用全结晶（LiSiCAD）和部分结晶型（EmaxCAD）锂硅玻璃陶瓷（色调 A3）。全结晶试样在炉中进行上釉烧制循环（LiSiCAD-G），并与抛光全结晶对照（LiSiCAD-P，阴性对照）和上釉部分结晶 LDS（EmaxCAD，阳性对照）进行比较。使用专门设计的在德国波恩大学口腔技术系建造的磨损机测试矩形陶瓷试样（n=10，12×6.5×1.5mm）和牙釉质对抗剂的耐磨性。使用源自牙齿磨损前后的微 CT 扫描的重叠虚拟 3D 模型测量对抗剂的釉质磨损量。使用分光光度计测量 100,000 和 200,000 个磨损循环后以毫克为单位的陶瓷试样的重量损失。使用万能试验机在热力学疲劳后评估抗断裂强度，直至以 1mm/min 的十字头速度断裂。使用单向方差分析进行统计分析，显著水平设为α=0.05。
在 100,000 次循环后，EmaxCAD 和 LisiCAD-G 组的陶瓷平均重量损失明显更高（分别为 2±0.3mg 和 1.93±0.2mg），而 LisiCAD-P 组为 0.78±0.19mg。上釉的 LiSiCAD 标本与抛光的 LiSiCAD 相比，从色调 A3 显示出明显更高的ΔE 值。LiSiCAD-G 和 EmaxCAD 之间的ΔE 值没有差异。对于抗断裂强度，在老化前后，LiSiCAD-G 和 LiSiCAD-P 之间没有观察到差异。
在耐磨性方面，上釉的全结晶 LDS 优于部分结晶型，但与抛光的全结晶型相比，颜色变化更大。此外，当美学是主要前提时，对全结晶 LDS 进行抛光仍可被视为比上釉更好的选择。
