Zenthöfer Andreas, Fien Dennis, Rossipal Johannes, Ilani Ali, Schmitt Clemens, Hetzler Sebastian, Rammelsberg Peter, Rues Stefan
Department of Prosthodontics, University of Heidelberg, 69120 Heidelberg, Germany.
Materials (Basel). 2024 Apr 30;17(9):2122. doi: 10.3390/ma17092122.
The aim of this paper was to evaluate the fracture resistance of 3D-printed zirconia occlusal veneers (OVs) of different thicknesses and supported by different abutment materials. The standard OV of a natural molar was prepared and digitized using a laboratory 3D scanner. The resulting digital tooth abutment was milled either using cobalt-chromium (CoCr) or a fiber-reinforced composite (FRC). All the abutments were digitized and standardized OVs (30° tilt of all the cusps) designed with 0.4 mm, 0.6 mm, or 0.8 mm wall thicknesses. The OVs were fabricated using either the Programill PM7 milling device (Ivoclar Vivadent, PM) or one of two 3D zirconia printers, Cerafab 7500 (Lithoz, LC) or Zipro-D (AON, ZD). The ZD samples were only tested on CoCr abutments. The completed OVs were luted to their abutments and subjected to artificial aging, consisting of thermocycling and chewing simulation before fracture testing with a steel sphere (d = 8 mm) as an antagonist with three contact points on the occlusal OV surface. Besides the total fracture resistance F, the lowest contact force F leading to the local fracture of a cusp was of interest. The possible effects of the factors fabrication approach, wall thickness, and abutment material were evaluated using ANOVA (α = 0.05; SPSS Ver.28). The total fracture resistance/contact forces leading to failure ranged from F = 416 ± 83 N/F = 140 ± 22 N for the 0.4 mm OVs fabricated using LC placed on the FRC abutments to F = 3309 ± 394 N (ZD)/F = 1206 ± 184 N (PM) for the 0.8 mm thick OVs on the CoCr abutments. All the factors (the fabrication approach, abutment material, and OV wall thickness) had an independent effect on F as well as F ( < 0.032). In pairwise comparisons for F of the OVs luted to the CoCr abutments, the ZD samples statistically outperformed the LC- and PM-fabricated teeth irrespective of the thickness ( < 0.001). Within the limitations of this study, the printed occlusal veneers exhibited comparable fracture resistances to those of the milled variants. However, more resilient abutments (FRC as a simulation of dentine) as well as a thinner wall thickness led to reduced OV fracture resistance, suggesting that 0.4 mm thick zirconia OVs should not be unreservedly used in every clinical situation.
本文旨在评估不同厚度且由不同基台材料支撑的3D打印氧化锆咬合面贴面（OVs）的抗折性。制备天然磨牙的标准OV，并使用实验室3D扫描仪进行数字化处理。所得的数字化牙基台采用钴铬合金（CoCr）或纤维增强复合材料（FRC）进行铣削加工。所有基台均进行数字化处理，并设计了壁厚为0.4mm、0.6mm或0.8mm的标准化OV（所有牙尖倾斜30°）。OVs使用Programill PM7铣削设备（义获嘉伟瓦登特公司，PM）或两台3D氧化锆打印机之一，即Cerafab 7500（Lithoz公司，LC）或Zipro-D（AON公司，ZD）进行制作。ZD样本仅在CoCr基台上进行测试。将完成的OVs粘结到其基台上，并进行人工老化处理，包括热循环和咀嚼模拟，然后使用直径为8mm的钢球作为拮抗剂在OV咬合面表面的三个接触点进行断裂测试。除了总抗折力F外，导致牙尖局部断裂的最低接触力F也受到关注。使用方差分析（α = 0.05；SPSS Ver.28）评估制作方法、壁厚和基台材料这些因素可能产生的影响。导致失效的总抗折力/接触力范围为：放置在FRC基台上使用LC制作的0.4mm OVs为F = 416 ± 83N/F = 140 ± 22N，到CoCr基台上0.8mm厚的OVs为F = 3309 ± 394N（ZD）/F = 1206 ± 184N（PM）。所有因素（制作方法、基台材料和OV壁厚）对F以及F均有独立影响（P < 0.032）。在粘结到CoCr基台的OVs的F的两两比较中，无论厚度如何，ZD样本在统计学上均优于LC和PM制作的牙齿（P < 0.001）。在本研究的局限性范围内，打印的咬合面贴面表现出与铣削变体相当的抗折性。然而，更具弹性的基台（FRC模拟牙本质）以及更薄的壁厚会导致OV抗折性降低，这表明0.4mm厚的氧化锆OVs不应在所有临床情况下不加保留地使用。
