Statement of problem

Cold rolling is widely used for screw thread manufacturing in industry but is less common in implant dentistry, where cutting is the preferred manufacturing method.

Purpose

The purpose of this in vitro study was to compare the surface finish and mechanical performance of a specific model of prosthetic screw used for direct restorations manufactured by thread rolling and cutting.

Material and methods

The thread profiles were measured in an optical measuring machine, the residual stresses in an X-ray diffractometer, the surface finish in a scanning electron microscope, and then fatigue and static load tests were carried out in a direct stress test bench according to the International Organization for Standardization (ISO) 14801. Finally, linear regression models and 95% interval confidence bands were calculated and compared through ANCOVA for fatigue tests while the t test was used for statistical comparisons (α=.05).

Results

The surface finish was smoother, and compressive residual stresses were higher for the roll-threaded screws. Linear regression models showed a fatigue life 9 times higher for roll-threaded screws (P=1) without affecting static behavior, which showed statistically similar static strengths (P=.54). However, the thread profile in the roll-threaded screws was not accurately reproduced, but this should be easily corrected in future prototypes.

Conclusions

Rolling was demonstrated to be a better thread-manufacturing process for prosthetic screws, producing improved surface quality and fatigue behavior.

中文翻译：

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用于牙种植体修复的修复螺钉的疲劳性能：滚压螺纹与切割螺纹

问题陈述

冷轧广泛用于工业中的螺纹制造，但在种植牙科中不太常见，其中切割是首选制造方法。

目的

这项体外研究的目的是比较用于通过滚丝和切割制造的直接修复体的特定假体螺钉模型的表面光洁度和机械性能。

材料与方法

在光学测量机上测量螺纹牙型，在X射线衍射仪上测量残余应力，在扫描电子显微镜上测量表面光洁度，然后在直接应力试验台上按照国际标准进行疲劳和静载荷试验。标准化组织 (ISO) 14801。最后，通过 ANCOVA 计算和比较线性回归模型和 95% 区间置信带进行疲劳测试，而t检验用于统计比较 (α=.05)。

结果

滚压螺纹螺钉的表面光洁度更光滑，压缩残余应力更高。线性回归模型显示，在不影响静态行为的情况下，滚压螺纹螺钉的疲劳寿命提高了 9 倍 ( P = 1)，这显示出统计上相似的静态强度 ( P = .54)。然而，滚螺纹螺钉中的螺纹轮廓没有准确再现，但这应该在未来的原型中很容易纠正。

结论

轧制被证明是一种更好的假肢螺钉螺纹制造工艺，可提高表面质量和疲劳性能。