下颌切牙Empress 2瓷贴面与全瓷冠牙预备体及全瓷修复复合体的抗折裂研究

目的比较下颌切牙Empress 2瓷贴面和全瓷冠牙预备体及修复体粘接后复合体的抗折强度。方法选择人离体下颌切牙50颗，随机分为5组。A组为瓷贴面牙体预备组，B组为全瓷冠牙体预备组，C组为瓷贴面修复组，D组为全瓷冠修复组，E组为完整下颌切牙（对照组）。采用标准化牙体预备过程，Empress 2铸瓷系统及树脂粘接技术完成瓷贴面-牙体和全瓷冠-牙体复合体。使用Instron万能试验机测试5组牙齿的抗折裂载荷值，采用方差分析进行统计学分析。结果A、B、C、D、E组的抗折裂载荷值分别为：（576.11±91.53）、（204.13±85.88）、（451.50±116.81）、（386.16±117.75）、（566.05±121.37）N。经统计学分析，B组抗折裂载荷值低于其他组（P<0.01）；A、E组间的差异无统计学意义，其值最高，高于其他组（P<0.05）；C、D组间的差异也无统计学意义，其值低于A、E组，但高于B组（P<0.05）。结论下颌切牙瓷贴面预备后，牙体抗折能力无明显降低。下颌切牙Empress 2瓷贴面与全瓷冠粘接后，2种复合体的抗折裂能力无明显区别。

An in vitro study of the fracture strength of tooth preparations for Empress 2 veneers and crowns and mandibular incisors restored with Empress 2 veneers and crowns

Objective To compare the fracture resistance of mandibular incisors' preparations for veneers and crowns,mandibular incisors restored with Empress 2 veneers and crowns.Methods 50 human mandibular incisors were randomly divided into five groups.Each group consisted of ten teeth and the treatment obtained as follows: A,tooth preparations for veneers;B,tooth preparations for crowns;C,teeth restored with veneers;D,teeth restored with crowns;E,untreated group.The teeth received standardized preparation and the restorations were manufactured with Empress 2 system and cemented with resin luting agent.The fracture resistances of teeth were measured by Instron universal testing machine and statistically analyzed with one-way ANOVA.Results The fracture resistances of A,B,C,D,E were(576.11 ±91.53),(204.13±85.88),(451.50±l 16.81),(386.16±l 17.75)and(566.05±121.37)N,respectively.The statistical analysis demonstrated significant differences between five groups.There were no significant differences between group A and E,group C and D.Conclusion Tooth preparations for veneers did not significantly reduce the fracture resistance of mandibular incisor.The fracture resistance of teeth restored with Empress 2 veneers and crowns did not significantly differ from each other.