Objective To investigate the impact of thickness of metal basal crowns on pressure resistance of nano porcelain-fused-to-metal crowns and ordinary porcelain-fused-to-metal crowns. Methods A lathe was used to process a metal die stimulating the premolar preparation, then process five kinds of basal crowns with different thicknesses (respectively 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm andl.O mm) by grinding (10 pieces for each kind). The basal crowns with the same thickness are randomly divided into two groups (5 pieces for each group), which respectively corresponded to A- E nano porcelain groups and A'-E' ordinary porcelain groups. A layer of corresponding porcelain materials was fused onto each group, with the thickness of 1.0 mm. An Instron universal material testing machine was used, and the spherical in denter with a diameter of 6 mm was placed at the center of the occlusal surface of the specimen, then the porcelain layer was pressurized to break at a speed of 1 mm/min. Meanwhile the values were recorded and statistical analysis carried out. Results ①Intra-group comparison: there existed significant differences among each group of A-E groups (P＜0.01); there also existed significant differences among each group of A'-E ' groups (P＜0.01); (2) Inter-group comparison: there was no significant difference between group A and group A' (P＞0.05); however, there were significant differences between group B and group B', group C and group C, group D and group D', group E and group E' (P＜0.01).Conclusion ① With certain porcelain layer thickness, the pressure resistance of nano porcelain groups and ordinary porcelain groups is both enhanced along with the increase of basal crown thickness. The group with a basal crown thickness of 0.2mm has the lowest pressure resistance while the group with a thickness of 1.0mm the highest.②When the basal crown thickness is the same, the pressure resistance of nano porcelain groups is higher than that of ordinary porcelain groups.%目的 探讨金属基底冠厚度对纳米陶瓷金瓷冠和普通陶瓷金瓷冠在耐压力方面的影响.方法 用车床加工一个模拟前磨牙预备体的金属代型,再研磨加工出五种厚度(0.2mm、0.4mm、0.6mm、0.8mm、1.0mm)的基底冠,各10个,将同一厚度的基底冠随机分为两组,每组5个,分别对应A-E的纳米陶瓷组和A′-E′的普通陶瓷组.各组分别熔附相应的陶瓷材料,整个瓷层的厚度为1.0mm.用Instron万能材料实验机,直径6 mm的球状压头置于试件(牙)面中心,以1mm/min的速度加压至瓷层崩裂,记录数值,进行统计分析.结果 ①组内比较结果:A-E各组之间存在显著性差异(P＜0.01)；A′-E′各组之间也存在显著性差异(P＜0.01)；②组间比较结果:A组与A'组无显著差异(P＞0.05),而B组与B′组、C组与C′组、D组与D′组、E组与E′组均有显著性差异(P＜0.01).结论 ①瓷层厚度一定时,随基底冠厚度的增加,纳米陶瓷各组和普通陶瓷各组的耐压力均增高.基底冠厚度为0.2 mm组的耐压力最小,1.0 mm组的耐压力最大.②基底冠厚度相同时,纳米陶瓷各组的耐压力较普通陶瓷各组高.
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