Sadeqi Haneen A, Baig Mirza Rustum, Al-Shammari Mohammad
Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, P.O. Box 24923,Safat 13110, Kuwait.
Department of Restorative Sciences (Prosthodontics), Faculty of Dentistry, Kuwait University, P.O. Box 24923,Safat 13110, Kuwait.
Materials (Basel). 2021 Oct 23;14(21):6346. doi: 10.3390/ma14216346.
Fit accuracy and fracture strength of milled monolithic zirconia (Zi) and zirconia-reinforced lithium silicate (ZLS) crowns are important parameters determining the success of these restorations. This study aimed to evaluate and compare the marginal and internal fit of monolithic Zi and ZLS crowns, along with the fracture load, with and without mechanical aging. Thirty-two stone dies acquired from a customized master metal molar die were scanned, and ceramic crowns (16 Zi Ceramill Zolid HT and 16 ZLS Vita Suprinity) were designed and milled. Absolute marginal discrepancies (AMD), marginal gaps (MG), and internal gaps (IG) of the crowns, in relation to the master metal die, were evaluated using x-ray nanotomography ( = 16). Next, thirty-two metal dies were fabricated based on the master metal die, and crowns (16 Zi; 16 ZLS) cemented and divided into four groups of eight each; eight Zi with mechanical aging (MA), eight Zi without mechanical aging (WMA), eight ZLS (MA), and eight ZLS (WMA). Two groups of crowns (Zi-MA; ZLS-MA) were subjected to 500,000 mechanical cycles (200 ± 50 N, 10 Hz) followed by axial compressive strength testing of all crowns, until failure, and the values were recorded. Independent sample tests (α = 0.05) revealed no significant differences between Zi and ZLS crowns ( > 0.05); for both internal and marginal gaps, however, there were significant differences in AMD ( < 0.005). Independent samples Mann-Whitney U and Kruskal-Wallis tests revealed significant differences between the two materials, Zi and ZLS, regardless of fatigue loading, and for the individual material groups based on aging (α = 0.05). Multiple comparisons using Bonferroni post-hoc analysis showed significant differences between Zi and ZLS material groups, with or without aging. Within the limitations of this study, the ZLS crown fit was found to be on par with Zi, except for the AMD parameter. As regards fracture resistance, both materials survived the normal range of masticatory forces, but the Zi crowns demonstrated greater resistance to fracture. The monolithic Zi and ZLS crowns seem suitable for clinical application, based on the fit and fracture strength values obtained.
铣削整体式氧化锆（Zi）和氧化锆增强型硅酸锂（ZLS）全冠的贴合精度和断裂强度是决定这些修复体成功与否的重要参数。本研究旨在评估和比较整体式Zi和ZLS全冠的边缘和内部贴合情况，以及有无机械老化时的断裂载荷。从定制的主金属磨牙模型上获取32个石膏模型并进行扫描，设计并铣削陶瓷全冠（16个Zi Ceramill Zolid HT和16个ZLS Vita Suprinity）。使用X射线纳米断层扫描（n = 16）评估全冠相对于主金属模型的绝对边缘差异（AMD）、边缘间隙（MG）和内部间隙（IG）。接下来，基于主金属模型制作32个金属模型，将全冠（16个Zi；16个ZLS）粘结并分成四组，每组八个；八个Zi进行机械老化（MA），八个Zi未进行机械老化（WMA），八个ZLS（MA），八个ZLS（WMA）。两组全冠（Zi-MA；ZLS-MA）进行500,000次机械循环（200±50 N，10 Hz），然后对所有全冠进行轴向抗压强度测试，直至破坏，并记录数值。独立样本t检验（α = 0.05）显示Zi和ZLS全冠之间无显著差异（P>0.05）；然而，对于内部和边缘间隙，AMD存在显著差异（P<0.005）。独立样本曼-惠特尼U检验和克鲁斯卡尔-沃利斯检验显示，无论疲劳加载情况如何，Zi和ZLS这两种材料之间以及基于老化的各个材料组之间均存在显著差异（α = 0.05）。使用Bonferroni事后分析进行的多重比较显示，无论有无老化，Zi和ZLS材料组之间均存在显著差异。在本研究的局限性范围内，发现除AMD参数外，ZLS全冠的贴合度与Zi相当。至于抗断裂性，两种材料在正常咀嚼力范围内均能承受，但Zi全冠表现出更大的抗断裂能力。基于获得的贴合度和断裂强度值，整体式Zi和ZLS全冠似乎适用于临床应用。
