不同核饰厚度比对氧化锆双层瓷结构强度的影响的初步研究

【作者】 卞翠荣； 孔辉；

【机构】 山东大学齐鲁医院口腔修复科；

【摘要】 目的:通过三点弯曲实验测试不同核心瓷/饰面瓷厚度比的氧化锆双层瓷结构的断裂载荷,并根据双层试样弯曲强度计算公式计算各核/饰厚度比双层瓷试件的最大弯曲强度。在此基础上通过三维有限元软件分析探讨不同核/饰厚度比双层瓷在断裂载荷下的应力分布,以此来研究核/饰厚度比对其弯曲强度的影响。方法:义齿加工厂制作不同厚度的泽康氧化锆块共40条并据厚度不同分为B、C、D、E 4个组,各组厚度分别为1.0 mm、1.5 mm、2.0 mm及3.0mm,误差不超过0.05mm。除D组之外,其余各组均由加工厂在氧化锆瓷条上堆塑饰面瓷,并且单独制作厚度为3.0mm的纯饰面瓷条,严格按照厂家推荐程序进行烧结,形成双层瓷结构作为测试样本。顺次用40μm、20μm、9μm氧化铝砂纸研磨瓷面,使各测试样本的最终厚度均为3.0mm,误差不超过0.02mm。按核心瓷/饰面瓷厚度比的不同分为如下3个实验组:B组(1:2)、C组(1:1)、D组(2:1)。A、E组分别为厚度3.0mm的单纯饰面瓷和单纯氧化锆,作为对照组。于Intron多功能试验机上对所有测试样本进行三点弯曲测试。测试时将试件放在三点弯曲夹具(跨距为30 mm,两个支持点及一个加载点的半径均为2.5 mm)上,以0.5 mm/min的加载速度对饰面瓷施加载荷直至样本断裂或分层,收集碎裂的样本碎片并分析断裂模式。根据双层试样三点弯曲强度计算公式和测得的样本的最大断裂载荷值(N)计算出其弯曲强度。所得的数据用SPSS16.0软件做单因素方差分析和SNK组间比较(以α=0.05作为显著性检验水平)。在获得每组最大的断裂载荷的基础上,建立三组不同核/饰厚度比的双层瓷试件二维有限元模型,通过有限元分析,研究试件烧结后的残余应力大小分布和断裂载荷下的拉应力大小分布,为临床判断全瓷修复体可能出现的破坏提供参考依据。结果:处于断裂载荷下,各双层瓷实验组间承受拉应力面弯曲强度值无显著性差异,并且与单纯核心瓷在断裂时测得的强度无明显差异(P>0.05)。各实验组间断裂载荷无显著差异(P>0.05),但均值随着核/饰厚度比的增加而增加,并与单纯核心瓷断裂载荷有显著差异(P<0.05)。有限元分析结果表明,在断裂载荷作用下,试件破坏主要原因的最大拉应力分布在核心瓷的底面,其大小与核心瓷强度基本一致。核/饰比对残余应力大小有影响,随着核/饰比的增加残余应力也随之增加。断裂模式观察显示:A、B、C组均未出现分层,断裂碎片在5片以上。结论:核心瓷/饰面瓷厚度比对氧化锆双层瓷结构强度无明显影响,但对氧化锆双层瓷结构的断裂载荷有一定的影响,表现为随着核/饰厚度比的增加,其断裂载荷的均值有所提高,但均显著低于单纯氧化锆。所以在临床上,在保证满足正常牙合力基础上,为了使修复体更为美观,可以适当增大修饰瓷的厚度。更多还原

【Abstract】 Objective:Examine the fracture load of layered zirconia structure of different core/veneering thickness ratio by three-point bending experiments,and then calculate the flexture strength based on the double-layer formula.On this basis,use the three-dimensional finite element software to analysis the stress distribution of the different core/veneering thickness ratio in order to study the impact of the the core/veneering thickness on its bending strength.Methods:The factory produce40 different thickness Cercon zirconia blocks and the blocks are divided into BCD and E four groups according to different thickness,the thickness of each group were 1.0mm,1.5mm,2.0mm and 3.0mm within 0.05 mm difference.Also a thickness of3.0mm pure veneering porcelain bar is produced as group A.Smooth the surface with 40 urn,20 urn the 9um aluminum oxide sandpaper,so that each test sample thickness are 3.0mm,the error is less than 0.02 mm.All blocksare divided into three experimental groups according tothe different core/veneering thickness ratioas follows:B group(1:2),C group(1:1),D group(2:1).Group A,E,respectively,a thickness of 3.0mm the simplex veneering porcelain and pure zirconia,as a control group.The three-point bending test of all test samples is taken withloading speed of 0.5 mm/min.The load is applied until the veneering porcelain fracture or sample layered,fragments are collected and analysisedfor the fracture mode.According to the three-point bending strength of the blocks,calculate the flexural strength.The data is taken one-way ANOVA analysis and SNK group comparison(α = 0.05 level of significance test) use the SPSS16.0 software.On the basis of the three point bending fracture load of each group,two-dimensional finite element model is established to research specimens sintered residual stress distribution and fracture strength distribution.Results:The tensile stress has no significant difference within experiment groups,and compared with zirconia group has no significant difference(P> 0.05).The fracture load within the experiment groups has no significant differences(P> 0.05),but the mean value increases with increasing the thickness ratio of the core/veneer,and a significant difference(P <0.05)with the zirconia group.The finite element analysis results show that the fracture strength is the same while the core/veneer ratio changes.The residual stress increases with the increase of the ratio of The core/veneer.The fracture mode observed:A,B,C group were not delamination,fracture fragments is more than five.Conclusion:The core/veneer thickness ratio have no significant effect on the flexture strength of double layered zirconia,but have a certain impact on the fracture load,expressed as with the the The core/veneer thickness ratio increases,Mean breaking load increased,but were significantly lower than that of zirconia.So in the clinical,ensure the normal occlusal force,in order to make the prosthesis more beautiful,can appropriately increase the thickness of the modified ceramic guaranteed.更多还原