Nawafleh Noor, Bibars Abdel Raheem, Al Twal Elina, Öchsner Andreas
Department of Applied Dental Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan.
Faculty of Mechanical Engineering, Esslingen University of Applied Sciences, Esslingen, Germany.
Eur J Dent. 2020 Mar;14(2):200-205. doi: 10.1055/s-0040-1708228. Epub 2020 Apr 20.
This study investigates the influence of the most commonly used indenter materials on fatigue survival and fracture resistance of zirconia crowns.
A total of 40 zirconia crowns were prepared using computer-aided design (CAD)/computer-aided manufacturing (CAM) technology: 30 crowns were divided into three experimental groups of 10 specimens and the last 10 specimens acted as the control group. The experimental groups were subjected to chewing simulation with simultaneous thermocycling. Three indenter materials (steatite ceramic, stainless steel, and tungsten carbide) with identical diameter were used to load the specimens. All crowns were then subjected to single load to fracture test in universal testing machine. Load was applied vertically with a crosshead speed of 1 mm/min until failure, and fracture load was recorded.
Normal distribution of data was confirmed using the Shapiro-Wilk test. Descriptive statistics including means and standard deviations were determined for all groups. Differences between groups were tested using Dunnett's test and paired sample -test.
Chewing simulation for 1.2 million cycles resulted in 100% survival. The highest mean fracture load was recorded for the control group and the lowest one was for the group fatigued with stainless steel indenter. Chewing simulation statistically significantly ( < 0.05) reduced the mean fracture load of the crowns fatigued with stainless steel and steatite ceramic indenter. However, the mean fracture load for the crowns fatigued with tungsten carbide was not significantly different from that of the control group.
Steatite ceramic and stainless steel indenters produced close results and significantly reduced fracture load of zirconia crowns. However, tungsten carbide indenter caused nonsignificant reduction in the fracture load of zirconia crowns.
本研究调查最常用的压头材料对氧化锆全冠疲劳寿命和抗折性的影响。
采用计算机辅助设计（CAD）/计算机辅助制造（CAM）技术制备40个氧化锆全冠：30个全冠分为三个实验组，每组10个样本，最后10个样本作为对照组。对实验组进行咀嚼模拟并同时进行热循环。使用三种直径相同的压头材料（滑石陶瓷、不锈钢和碳化钨）对样本加载。然后将所有全冠在万能试验机上进行单次加载至断裂试验。以1mm/min的十字头速度垂直施加荷载直至破坏，并记录断裂荷载。
使用Shapiro-Wilk检验确认数据的正态分布。确定所有组的描述性统计量，包括均值和标准差。使用Dunnett检验和配对样本检验对组间差异进行检验。
120万次循环的咀嚼模拟导致100%的存活率。对照组记录到最高的平均断裂荷载，而使用不锈钢压头疲劳处理的组记录到最低的平均断裂荷载。咀嚼模拟在统计学上显著（P<0.05）降低了使用不锈钢和滑石陶瓷压头疲劳处理的全冠的平均断裂荷载。然而，使用碳化钨疲劳处理的全冠的平均断裂荷载与对照组无显著差异。
滑石陶瓷和不锈钢压头产生的结果相近，并显著降低了氧化锆全冠的断裂荷载。然而，碳化钨压头导致氧化锆全冠的断裂荷载降低不显著。
