树脂粘固剂厚度对CAD/CAM长石质陶瓷断裂性能的影响

目的:测试树脂粘固剂不同厚度对CAD/CAM陶瓷断裂韧性值的影响,以期对临床医生提供指导和参考。方法:分别制作12 mm×14 mm×2 mm的CAD/CAM陶瓷和树脂片,用树脂粘固剂进行粘接,分为3组:第1组为空白对照,瓷-树脂片间无粘固剂;第2组的瓷-树脂片间粘固剂厚度约为50μm,第3组的瓷-树脂片间粘固剂厚度100μm。用维氏硬度仪测试硬度和断裂韧性,并进行Weibull分析。结果:3组样本的硬度差异无统计学意义,断裂韧性分别为(1.02±0.11)MN/m3/2,(0.99±0.10)MN/m3/2和(0.97±0.14)MN/m3/2,第3组低于第1组(P<0.05),第2组断裂韧性Weibull分布模数最高,第1～3组的特征断裂韧性值分别为1.08、1.04和1.03MN/m3/2。结论:树脂粘固剂厚度能影响陶瓷的断裂韧性值,提示临床操作应该控制粘固剂的厚度,避免过厚。

Effect of cementation on fracture toughness of chair-side CAD/CAM ceramic

Objective:Chair-side CAD/CAM ceramic restorations are esthetic with a time-saving procedure.However,ceramic restorations often failed due to fracture.This study was to investigate the effect of cement thickness on fracture toughness and hardness of CAD/CAM ceramic.Methods: Machinable ceramic blocks for CAD/CAM(Sirona CEREC Blocs) were cut into 9 slices(12 mm×14 mm×2 mm) using a diamond saw(Leica SP 1600) and polished carefully with sandpaper / diamond pastes to yield a mirror-like surface.LIGHT-CORETM was used to prepare resin slices with dimension of 12 mm×14 mm×2 mm.The polished ceramic slices were then randomly divided into 3 groups and cemented to resin slices using Multilink Automix: Group 1,no cement;Group 2,the thickness of cement was 50 μm;Group 3,the thickness of cement was 100 μm.Hardness(H) was determined by Vickers indentation technique using micro-hardness tester(HMV-2T Shimadzu) with a load of 19.6 N for 15 s.The fracture toughness(KIC) was calculated by KIC = 0.016(E/H)0.5(P/c1.5),where P= applied load,c= crack length,E=elastic modulus,H=(0.47 P/a2),a= half diagonal of the indentation.Results: The fracture toughness for Group 1(no cement) was(1.02±0.11) MN/m3/2,for Group 2 and Group 3 was(0.99±0.10) MN/m3/2 and(0.97±0.14) MN/m3/2.Group 3 showed lower fracture toughness than group 1(P<0.05).The Weibull parameter m of group 2 was the highest and K0 of three groups were 1.08 MN/m3/2,1.04 MN/m3/2 and 1.03 MN/m3/2 respectively.The hardness for Group 1 was(6.68±0.73) GPa,group 2 (6.85±0.64) GPa],group 3 (6.81±0.98) GPa].There was no significant deference in hardness among the 3 groups(P>0.05).Conclusion: Thickness of cementation may affect fracture toughness of machinable ceramic,therefore,a thinner film of cementation is recommended for chair-side CAD/CAM ceramic restorations.