Graduate Program in Dentistry, University of Passo Fundo, BR 285, Km 171, Passo Fundo, São José, RS 99052-900, Brazil.
Department of Biomedical Materials Science, University of Mississippi Medical Center, Jackson, MS, USA.
J Dent. 2022 Aug;123:104181. doi: 10.1016/j.jdent.2022.104181. Epub 2022 Jun 7.
this study aimed to evaluate the adaptation and fatigue behavior of lithium disilicate glass-ceramic (LD) monolithic crowns produced by press (combined with 3D-printing) and CAD/CAM milling (control) techniques.
thirty abutment preparations with a chamfer finish line were produced with a dentin analogue material and scanned with extraoral scanner. Captured images were processed using CAD software to design a premolar. Blocks of LD were milled using CAD/CAM system. For the press technique, crowns were first 3D-printed using a polymeric material and the heat-pressing protocol was performed. Crowns were adhesively cemented to the abutments and scanned using micro-CT. Files were processed and cross-sectional images were analysed in five measuring points: marginal, axial angle, axial, occlusal angle and occlusal. Fatigue test was performed in a MTS universal testing machine (2 Hz, 37°C distilled water) using an anatomic composite piston, following the step-stress method. Failures were detected with an acoustic system and confirmed by transillumination. A cumulative damage-Weibull distribution (95% CI) was used to analyze the fatigue data. Gap thickness data were analyzed using Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05).
CAD/CAM milling resulted in larger gap thickness in the occlusal area and smaller gap thickness in the axial angle and axial area than press (p<0.05). The probability of failure was similar for crowns produced with CAD/CAM milling and press. The most frequent failure mode was radial crack.
LD crowns produced using the combination of 3D-printing/press technique showed similar fatigue behavior than CAD/CAM milled control group, and resulted in smaller gap thickness at the occlusal region.
A more controlled process can be achieved by replacing conventional restoration waxing with 3D printing, which in combination with the press technique produces lithium disilicate glass-ceramic monolithic crowns with good adaptation and high fatigue survival.
本研究旨在评估通过压力成型（联合 3D 打印）和 CAD/CAM 铣削（对照）技术制作的二硅酸锂玻璃陶瓷（LD）整体冠的适应性和疲劳行为。
用牙本质模拟材料制作 30 个带有斜面边缘线的基牙预备体，并使用口外扫描仪进行扫描。采集的图像通过 CAD 软件进行处理，以设计一颗前磨牙。使用 CAD/CAM 系统对 LD 块进行铣削。对于压力成型技术，首先使用聚合材料对冠进行 3D 打印，并执行热压工艺。将冠粘接到基牙上，并用微 CT 进行扫描。对文件进行处理，并在五个测量点分析横截面图像：边缘、轴向角、轴向、咬合角和咬合面。在 MTS 万能试验机（2Hz，37°C 蒸馏水）中，使用解剖复合活塞，采用阶跃应力法进行疲劳试验。使用声发射系统检测失效，并通过透照法确认。使用累积损伤-Weibull 分布（95%置信区间）分析疲劳数据。采用 Kruskal-Wallis 和 Student-Newman-Keuls 检验（α=0.05）分析间隙厚度数据。
CAD/CAM 铣削在咬合区域产生的间隙厚度大于压力成型，而在轴向角和轴向区域产生的间隙厚度小于压力成型（p<0.05）。CAD/CAM 铣削和压力成型制作的冠的失效概率相似。最常见的失效模式是放射状裂纹。
使用 3D 打印/压力成型技术制作的 LD 冠具有与 CAD/CAM 铣削对照组相似的疲劳行为，并且在咬合区域产生的间隙厚度更小。
用 3D 打印代替传统的修复蜡成型，可以实现更可控的过程，与压力成型技术结合，可以制作出具有良好适应性和高疲劳存活率的二硅酸锂玻璃陶瓷整体冠。
