Durability of zirconium dioxide ceramic restorations with masticatory simulation

本研究旨在通过对氧化锆（ZrO_2）陶瓷修复体的适合性和抗折性能的研究，评价前牙单牙氧化锆陶瓷冠的适合性和抗折性能。单牙氧化锆陶瓷冠、冠的边缘适合性与其终止线设计无关。在本研究中观察到的边缘和内部适应值均在临床可接受的标准范围内。烧成工艺不影响ZrO_2陶瓷的边缘和内部适应性。结果表明，不同的终止线设计对ZrO_2陶瓷涂层的断裂强度没有影响。在模拟老化过程中，观察到了瓷贴面的碎裂和瓷贴面界面的断裂，并研究了不同的聚合角（6°，12°，20°）和粘结剂间距（10 μm，30 μm，60 μm）对后牙单瓷冠适合性的影响。各组的边缘差异中位数（27-43 μm）和内部间隙宽度中位数（54-70μm）均在临床可接受范围内。对于骨水泥间距60 μm组，会聚角对边缘适应性有显著影响。聚合角20°组的内部空间值明显小于其他组，不同实验设计对氧化锆陶瓷修复体耐久性的影响有待进一步研究。此外，临床评价将是必要的，以验证本研究的结果。

The purpose of the present study was to evaluate the durability of zirconium dioxide (ZrO_2) ceramic restorations by investigations of adaptation and fracture resistance.The first investigation evaluated the adaptation and fracture resistance of anterior single-tooth ZrO_2 ceramic copings or crowns with three different finish line designs (shoulder, rounded shoulder, and chamfer). The finish line design may have no effect on marginal adaptation of single-tooth ZrO_2 ceramic copings and crowns. The marginal and internal adaptation values observed in the present study were all within the range of clinically acceptable standards. The firing procedure did not affect the marginal and internal adaptation of ZrO_2 ceramic restorations. No influence of finish line designs on the fracture strength of ZrO_2 ceramic restorations was demonstrated. Some chipping of veneering porcelain and fracture at the interface between ZrO_2 ceramics and veneering porcelain were observed during the aging simulation.The second investigation examined the influence of different convergence angle (6°, 12°, and 20°) or cement space (10 μm, 30 μm, and 60 μm) on adaptation of posterior single-tooth ZrO_2 ceramic copings. Both the median values of marginal discrepancy (27-43 μm) and internal space width (54-70μm) in all groups were within the clinical acceptable range. For the groups of cement space 60 μm, the convergence angles significantly influenced on the marginal adaptation. The internal space values in the groups of convergence angle 20° was significantly smaller compared to the other groups.Further investigations will be necessary to evaluate the durability of ZrO_2 ceramic restoration with different experimental designs. Furthermore, clinical evaluations would be necessary to validate the results of the present study.