Statement of problem

Displacement of abutments into conical connection implants during screw tightening may also occur during functional loading, creating unsettling forces that may cause loss of preload. A recent conical-hexagon connection with double friction fit (conical-hexagon connection) could prevent this axial displacement.

Purpose

The purpose of this in vitro study was to measure the 3D axial displacement of abutments with a conical-hexagon connection or conical connection in narrow-diameter implants. Removal torque values (RTVs), preload efficiency, and survival after cyclic loading were also compared.

Material and methods

Narrow-diameter implants with a conical connection (Osseospeed EV, 3.0×13 mm-AST) and narrow-diameter implants with a conical-hexagon connection (Eztetic, 3.1×13 mm) were embedded in resin rods (G10) (n=6). Six titanium abutments per system were used, and their spatial relationship to the implant platforms after hand tightening was determined by using 3D digital image correlation. The abutments were tightened to the manufacturers’ specified values, and the abutments’ relative position was recorded again. The displacement of the abutment after tightening was calculated. The implants were subjected to cyclic loading (5×10⁶ cycles at 2 Hz) under 200-N loads at a 30-degree angle. After cyclic loading, the RTVs of screws were measured and compared with those specified by the manufacturers to calculate preload efficiency. ANOVA was used to compare the differences in displacements after tightening and to compare differences in RTVs after cyclic loading across the groups (α=.05).

Results

The mean displacement in the U direction (X-axis) for the AST was −0.7 μm and −4.7 μm for ZIM, with no statistical difference (P=.73). The mean displacement in the V direction (Y-axis) for AST was −37.0 μm, and −150.0 μm for ZIM, with significant statistical difference (P<.001). The mean displacement in the W direction (Z-axis) for AST was −0.9 μm, and −23.0 μm for ZIM, with no statistical difference (P=.35). The survival of groups was similar (P=.058). During cyclic loading, 3 AST specimens fractured. After cyclic loading, mean RTV for AST was −8.77 Ncm, and −14.24 Ncm for ZIM, and these values were significantly different (P=.04). Preload efficiency was 28.1% for AST and 41.5% for ZIM.

Conclusions

Greater abutment displacements were observed with the conical-hexagon connection, which required a higher torque, as specified by its manufacturer. The abutments displaced more in the V-axis in both implants. Only the conical connection implant (Ti Grade 4, commercially pure) had failures during cyclic loading, but the survival of the implants was similar. After cyclic loading, the abutment screws in both systems lost some of their torque value. The abutment screws of the conical-hexagon connection implant maintained preload more efficiently during cyclic loading than those of the conical connection implant.

中文翻译：

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不同内连接的小直径种植体中基台的位移和性能

问题陈述

在螺钉拧紧过程中，基台移位到锥形连接种植体中也可能发生在功能负荷期间，产生可能导致预负荷损失的不稳定力。最近采用双摩擦配合的锥形六角连接（锥形六角连接）可以防止这种轴向位移。

目的

这项体外研究的目的是测量窄直径种植体中具有锥形-六角连接或锥形连接的基台的 3D 轴向位移。还比较了去除扭矩值 (RTV)、预加载效率和循环加载后的存活率。

材料与方法

锥形连接的窄直径种植体（Osseospeed EV，3.0×13 mm-AST）和锥形六边形连接的窄直径种植体（Eztetic，3.1×13 mm）嵌入树脂棒（G10）（n = 6 ）。每个系统使用六个钛基台，并通过使用 3D 数字图像相关性确定手动拧紧后它们与种植体平台的空间关系。将基台拧紧到制造商的规定值，并再次记录基台的相对位置。计算紧固后基台的位移。种植体经受循环载荷（5×10 ⁶在 2 Hz 下循环）在 200-N 负载下以 30 度角。循环加载后，测量螺钉的 RTV，并与制造商规定的值进行比较，以计算预紧效率。ANOVA 用于比较拧紧后位移的差异，并比较各组循环加载后 RTV 的差异 (α=.05)。

结果

AST 的 U 方向（X 轴）平均位移为 -0.7 μm 和 ZIM 的 -4.7 μm，无统计学差异（P =.73）。AST 的 V 方向（Y 轴）平均位移为 -37.0 μm，ZIM 为 -150.0 μm，具有显着统计学差异（P <.001）。AST 的 W 方向（Z 轴）平均位移为 -0.9 μm，ZIM 为 -23.0 μm，无统计学差异（P =.35）。各组的生存率相似（P =.058）。在循环加载过程中，3 个 AST 试样断裂。循环加载后，AST 的平均 RTV 为 -8.77 Ncm，ZIM 的平均 RTV 为 -14.24 Ncm，这些值有显着差异（P =.04）。AST 的预加载效率为 28.1%，ZIM 的预加载效率为 41.5%。

结论

根据制造商的规定，锥形六边形连接需要更高的扭矩，因此观察到更大的基台位移。两种种植体的基台在 V 轴上移位更多。只有锥形连接植入物（Ti 4 级，商业纯）在循环加载过程中出现故障，但植入物的存活率相似。在循环加载后，两个系统中的基台螺钉失去了一些扭矩值。与锥形连接种植体相比，锥形六角连接种植体的基台螺钉在循环加载期间更有效地保持预紧力。