Objective The aim of this study was to evaluate the effect of core thickness on the flexural strength and failure mode of bilayered dental ceramic sheet specimens. Methods Sintered zirconia ceramic blocks(15 mm×5 mm) were cut to 25 sheets, and according to the thickness they were put into group A(0. 3 mm) , B(0. 4 mm) , C(0. 6 mm) , D(0. 8 mm ) , and E ( 1. 0 mm) , respectively ( n = 5). After sand blasting and ultrasonic cleaning, all samples were added 1. 0 mm veneer porcelain and fired. Finally, the thickness of samples were added up to following 1. 3 mm ,1.4 mm ,1.6 mm ,1.8 mm and 2. 0 mm. All specimens were loaded in an universal testing machine for 3 - point flexural test. The dates obtained were submitted to the one - way ANOVA and SNK test. Failure modes of specimens were observed and recorded. Results Mean flexural strength(Mpa) of 5 groups were as follows; group A(352.31 ±10.80) , B(370.93 ±12.05) , C(480. 19 ± 19.14) , D( 681.73 ±6.05) and E( 699. 06 ±29.22). One -way ANOVA and SNK test showed that there was statistically significant difference among the groups. The number of fracture fragments in group A was more than that in others, and of the more sheets occurred delaminations were found in group A but other groups. Conclusion Core thickness changes could significantly influenced the flexural strength and failure mode of bilayered zirconia and veneering porcelain materials, and flexural strength will be enhanced with the increase of core thickness.%目的 分析基底瓷厚度对氧化锆双层瓷结构抗折强度和断裂模式的影响.方法 将规格为15 mm×5mm完全烧结的氧化锆瓷块切割成5组,瓷片共25片,厚度分别为A组(0.3 mm),B组(0.4 mm),C组(0.6 mm),D组(0.8 mm),E组(1.0 mm).经过喷砂和超声清洗后,在所有瓷片上堆塑1.0 mm的饰面瓷并烧结,使各组的样本总厚度分别为1.3 mm,1.4 mm,1.6 mm,1.8 mm,2.0 mm.用电液伺服疲劳试验机对每个样本进行三点弯曲测试,对实验数据进行单因素方差分析及SNK组间比较,观察样本破坏模式.结果 各组抗折强度(MPa)均值分别为A组(352.31±10.80),B组(370.93±12.05),C组(480.19±19.14),D组(681.73±6.05),E组(699.06±29.22).除A组和B组、D组和E组组间外,其他各组组间差异明显(P＜0.05).断裂模式观察显示:A组出现分层,断裂碎片在4片以上；其它各组均无分层,断裂碎片多为2～3片.结论 在饰面瓷厚度不变的前提下,氧化锆双层瓷的抗折强度随基底瓷厚度增加而增强.
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