Fathi Amirhossein, Borhani Sina, Salehi Sepideh, Mosharraf Ramin, Atash Ramin
Dental Prosthodontics Department, School of Dentistry, Dental Materials Research Center, Isfahan University of Medical Sciences, Isfahan, Iran, Isfahan, Iran.
School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran, Isfahan, Iran.
Clin Exp Dent Res. 2025 Aug;11(4):e70162. doi: 10.1002/cre2.70162.
The loosening of abutment screws is a common mechanical complication in dental implants, potentially leading to treatment failure. It is generally believed that dynamic forces may accelerate and facilitate screw loosening. Two approaches exist to address this issue: replacing the screw or re-tightening the existing one. However, there is no consensus on the efficacy of either method in preventing re-loosening.
In this laboratory study, 20 implant-abutment sets with a diameter of 4.5 mm were randomly placed in resin blocks simulating bone tissue. The samples were tightened with a torque of 30 N cm and subjected to 10,000 dynamic cycles in a thermocycler device at temperatures ranging from 5°C to 55°C because it is the usual temperature of the mouth while drinking or eating cold and hot things. After dynamic cycling, the torque required to unscrew the abutment screws was measured using a digital torque meter, and the torque reduction in both groups was calculated.
The results showed a significant reduction in the torque of abutment screws in both implant types after dynamic loading. Additionally, tissue-level implants experienced greater loosening than Bone-level implants, requiring less force to unscrew the abutment in the Tissue-level group. New screws showed less torque reduction compared to previously tightened screws. Opening torque scores in the new bone-level implants after applying the primary thermodynamic cycle (26.7 N cm) were more than in the new tissue-level implants (24.7 N cm). The torque reduction percentage values of the implant after the primary thermodynamic cycle were significantly higher in the tissue-level (17.67 N cm) group than in the bone-level (11 N cm) group.
Overall, dynamic loading can cause loosening of abutment screws in dental implants, with Tissue level implants being more susceptible. It is recommended to periodically replace screws with new ones to prevent torque reduction and related complications.
基台螺丝松动是牙种植体常见的机械并发症，可能导致治疗失败。一般认为动态力可能加速并促使螺丝松动。解决此问题有两种方法：更换螺丝或重新拧紧现有螺丝。然而，对于这两种方法预防再次松动的效果尚无共识。
在本实验室研究中，将20套直径4.5毫米的种植体 - 基台组合随机放置在模拟骨组织的树脂块中。样本以30 N·cm的扭矩拧紧，并在温度范围为5°C至55°C的热循环装置中进行10000次动态循环，因为这是饮用或食用冷热食物时口腔的通常温度。动态循环后，使用数字扭矩计测量拧下基台螺丝所需的扭矩，并计算两组扭矩的降低情况。
结果显示，两种种植体类型的基台螺丝在动态加载后扭矩均显著降低。此外，软组织水平种植体比骨水平种植体松动更明显，在软组织水平组拧下基台所需的力更小。与先前拧紧的螺丝相比，新螺丝扭矩降低较少。在施加初次热力学循环后，新骨水平种植体的开启扭矩得分（26.7 N·cm）高于新软组织水平种植体（24.7 N·cm）。初次热力学循环后，软组织水平组（17.67 N·cm）种植体的扭矩降低百分比值显著高于骨水平组（11 N·cm）。
总体而言，动态加载会导致牙种植体基台螺丝松动，软组织水平种植体更易受影响。建议定期用新螺丝更换，以防止扭矩降低及相关并发症。
