Objectives: This study aimed to evaluate and compare the settling effect of implant-abutment assembly and the torque loss before and after cyclic loading in three types of abutments.
Methods: Thirty internal hexagon fixtures were randomly divided into three groups (n=10). Group A used original abutments, group B used pre-machined cast abutments, and group C used compatible abutments. In addition, the abutment morse taper angle was measured using an image measuring instrument. Removal torque values (RTVs) were recorded using a digital torque meter before and after cyclic loading. All samples were tested in a universal testing machine with a vertical load between 0 and 250 N for 100 000 cycles of 10 Hz. The settling effect was measured after cyclic loading. Paired t test was performed for intragroup analysis of removal torque loss before and after cycling and one-way ANOVA. Subsequently, Tukey's honestly significant difference test was used for intergroup comparison (α=0.05).
Results: The paired t-test showed signi⁃ficant differences in the intragroup RTVs before and after cycling (P<0.001). ANOVA showed significant differences in the mean of removal torque loss after cycling (P=0.009), the abutment morse taper angle (P<0.001), and the settling values (P=0.01) among different groups. However, no significant difference was found between compatible abutments and pre-machined cast abutments.
Conclusions: The screw removal torque was significantly reduced for all groups in this study after cyclic loading. Differences could be found in the internal accuracy of implant-abutment assembly among different groups. Within the limitations of this study, the results showed the original abutments exhibited lower percentages of torque reduction after cyclic loading than the casting abutments and the compatible abutments.
目的: 本实验旨在探究3种不同修复基台循环加载前后扭矩丧失以及基台沉降。方法: 将30枚内六角种植体随机分为3组，每组10枚种植体，并连接相应修复基台。A组种植体连接原厂成品基台，B组种植体连接铸造基台，C组种植体连接第三方计算机辅助设计/计算机辅助制造（CAD/CAM）基台。通过光学影像测量仪测量3组基台莫氏锥度。使用数显扭矩计测量循环加载前后的移除扭矩。试件在疲劳机上进行循环加载，循环载荷应力振幅范围为0~250 N，以10 Hz的频率施加10万个周期的循环载荷，循环加载后测量基台沉降值。配对t检验用于分析组内循环加载前后扭矩丧失量。方差分析及Tukey HSD检验用于比较基台莫氏锥度、移除扭矩丧失量和基台沉降值的组间差异。结果: 配对t检验显示3组基台循环加载前后扭矩丧失量差异有统计学意义（P<0.001）。方差分析显示基台莫氏锥度（P<0.001）、循环载荷后基台螺丝移除扭矩丧失量（P=0.009）和基台沉降值（P=0.01）在3组之间差异有统计意义，但是铸造基台组和第三方CAD/CAM基台组之间差异无统计学意义（P>0.05）。结论: 所有组中基台经循环加载后螺丝扭矩均有显著下降。不同基台与种植体连接部位之间存在差异。就本实验有限的数据提示成品基台在经过循环加载后对基台螺丝扭矩的维持效果优于铸造基台和第三方CAD/CAM基台。.
Keywords: abutment; cyclic loading; morse taper; removal torque; settling.