Effects of torque cycles on implant prosthetic screws, a comparative study between hexagonal and square screws

During the rehabilitation procedures with implant supported prosthesis, the prosthesis are installed and removed a few times until the end of the treatment. Thus, the objective of this study was to evaluate the deformations of the square and hexagonal screw fitting, facing the torque cycles. 42 screws (21 hexagonals and 21 squares) were analyzed for external hexagonal implants (4.1 mm of platform), subdivided into 4 groups (n=5), according to the number of torque cycles: GI = 5 cycles; GII = 10 cycles; GIII = 20 cycles; GIV=30 cycles. Then, the screws were photographed (under optical microscope for 5 times) to assess the affected areas using the Image J Software. In addition, images were performed using the Scanning Electron Microscopy (470x). The data were analyzed in the non-parametric statistical analysis, using the Wicolson-Mann-Whitney test, with a significance level of 5%. It was observed that the most common damages were caused by the plastic transformation of the material in the contact region. The square screws showed greater wear in their fitting, compared to the hexagonal screws in all groups. Based on these results, it is recommended for square screws the maximum of 5 cycles and the hexagons, it can reach up to 10 cycles.

在植入支持义齿的康复过程中，义齿需多次安装与拆卸，直至治疗结束。因此，本研究的目的是评估方形和六角形螺钉适配器在面对扭矩循环时的变形情况。对于外部六角形植入物（平台直径为4.1毫米），共分析了42颗螺钉（21颗六角形和21颗方形），并根据扭矩循环次数将其分为四组（每组5颗）：GI组为5次循环；GII组为10次循环；GIII组为20次循环；GIV组为30次循环。随后，使用光学显微镜（拍摄5次）对受影响区域进行拍照，并利用Image J软件进行评估。此外，还运用扫描电子显微镜（放大倍数为470倍）进行了图像采集。数据采用非参数统计方法进行分析，使用Wilcoxon-Mann-Whitney检验，显著性水平为5%。观察结果显示，最常见的损害是由接触区域材料发生塑性变形所致。与所有组别的六角形螺钉相比，方形螺钉在其适配器上的磨损程度更为严重。基于这些结果，建议方形螺钉的最大扭矩循环次数为5次，而六角形螺钉则可达10次。