Objective:To evaluate the effect of different shoulder width on the compressive strength of full-contour zirconia crowns.Methods:A computer aided design and computer aided manufacturing(CAD/CAM) system was used to prepare 24 full-contour zirconia crowns of the mandible first molar.1 mm occlusal thickness crowns with 4 shoulder width of knife-edge(group A),0.3 mm(group B),0.5 mm(group C) and 1.0 mm(group D) (n =6).The Co-Cr alloy PFM crowns made by the die of group C were used as the controls (n =6).All the full-contour zirconia crowns were bonded to the corresponding die using 3 M glass ionomer cement (GIC) and the compressive strength were measured by an universal testing machine.Based on the statistical analysis,crowns with the shoulder width of 0.5 mm were treated by the thermocycling test under cycling of 10000 times(group C1),20 000 times(group C2) and 30000 times (group C3) respectively(n =6).One-way ANOVA method was used for the statistical analysis.Results:The mean compressive strength(N) of group A,B,C,D and E was 3855.00 ± 305.47,2731.70 ± 261.80,3698.30 ± 276.87,3841.70 ± 544.88 and 2992.17 ± 168.41 respectively.The strength of group B and E were lower than that of group A,C and D(P ＜ 0.05),B vs E P ＞0.05.The compressive strength(N) of group C1,C2 and C3 was 3220.00 ± 504.38 (group C1),3148.33 ± 425.60(C2) and 2992.17 ±168.41 (C3) respectively (P＞0.05).Conclusion:For the full-contour zirconia crowns,both the knife-edge shoulder and the shoulder wider than 0.3 mm can meet the thermoclinical needs.The cycling times used in this study have no influences on the compressive strength.%目的:研究肩台宽度及冷热循环对全锆冠压缩破坏力的影响.方法:制作右下第一磨牙的金属代型4种.肩台宽度分别为刃状(A组)、0.3 mm(B组)、0.5 mm(C组)、1.0 mm(D组),每组6个.通过CAD/CAM技术制作下颌第一磨牙全锆冠;用D组代型制作钴铬烤瓷冠(E组,为对照组).在万能实验机上测量试件的压缩破坏力.统计学分析后制备C组样本18个,进行冷热循环实验.循环次数依次为:10000次(C1组),20000次(C2组),30000次(C3组),每组6个.采用SPSS 13.0统计分析软件对数据进行统计分析.结果:A、B、C、D、E组的压缩破坏力(N)依次为3855.00±305.47、2731.70±261.80、3698.30±276.87、3841.70±544.88、2992.17±168.41.B、E组的压缩破坏力显著低于A、C、D组,P＜0.05.B、E组比较P＞0.05.C、C1、C2、C3组的压缩破坏力(N)依次为3698.30±276.87、3220.00±504.38、3148.33±425.60、3572.00±545.30,各组间比较P＞0.05.结论:4种肩台宽度的全锆冠的压缩破坏力均可满足临床需要,其中0.3 mm肩台宽度的全锆冠的压缩破坏力小于0.5 mm、1.0 mm肩台宽度的全锆冠,但是与对照组(钴铬烤瓷冠组)之间无差异,并且各组压缩破坏力不受冷热循环的影响.
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