Kohorst Philipp, Dittmer Marc Philipp, Borchers Lothar, Stiesch-Scholz Meike
Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
Acta Biomater. 2008 Sep;4(5):1440-7. doi: 10.1016/j.actbio.2008.04.012. Epub 2008 May 1.
The humid atmosphere and permanent occurrence of chewing forces in the oral environment lead to degradation of ceramics used for prosthetic restorations. The aim of this in vitro study was to evaluate the influence of artificial aging on the load-bearing capacity of four-unit bridges, with both undamaged and predamaged zirconia frameworks. Additionally, different parameters for chewing simulation have been investigated and a finite element analysis was made to predict the location of highest tensile stresses within the bridges. A total of 60 frameworks were milled from presintered zirconia and divided into six homogeneous groups. Prior to veneering, frameworks of two groups were "damaged" by a defined saw cut similar to an accidental flaw generated during shape cutting. After veneering, FPDs were subjected to thermal and mechanical cycling - with the exception of control groups. The load-bearing capacity of tested FPDs was significantly reduced by artificial aging. In comparison to unaged specimens, fracture resistance decreased by about 40%, whereas preliminary damage did not have a significant effect. Increasing number of cycles and increasing upper load limit failed to show any additional effect on fracture force. To predict the progression of degradation under the terms of in vitro simulation for even longer periods, further aging experiments are required.
口腔环境中的潮湿气氛和持续存在的咀嚼力会导致用于修复体的陶瓷材料发生降解。本体外研究的目的是评估人工老化对带有未受损和预受损氧化锆框架的四单位桥承载能力的影响。此外，还研究了咀嚼模拟的不同参数，并进行了有限元分析，以预测桥体内最大拉应力的位置。总共从预烧结氧化锆中铣削出60个框架，并分为六个同质组。在贴面之前，两组框架通过类似形状切割过程中产生的意外缺陷的特定锯切进行“损伤”。贴面后，除对照组外，固定局部义齿进行热循环和机械循环。人工老化显著降低了测试固定局部义齿的承载能力。与未老化的标本相比，抗断裂能力下降了约40%，而初步损伤没有显著影响。增加循环次数和提高上限载荷未能显示出对断裂力的任何额外影响。为了在体外模拟条件下预测更长时间的降解进程，需要进一步的老化实验。
