Alsarraf Esra Y, Suprono Montry S, Alnasser Abdullah H, Savignano Roberto, Kattadiyil Mathew T
Assistant Professor, Department of Restorative Sciences, Faculty of Dentistry, Kuwait University, Kuwait City, Kuwait.
Associate Professor and Director, Center for Dental Research, School of Dentistry, Loma Linda University, Loma Linda, Calif.
J Prosthet Dent. 2024 Aug 20. doi: 10.1016/j.prosdent.2024.07.035.
Screw loosening remains one of the most common complications associated with implant-supported restorations. The available literature is scarce regarding the most efficient method of tightening definitive abutment screws for angled screw channel (ASC) abutments.
The purpose of this in vitro study was to identify the optimal screw tightening protocol for ASC abutments by evaluating the influence of different protocols on reverse tightening values (RTVs).
Fifty implants were randomly assigned to 5 groups (n=10). Implants were mounted and received a cover screw and impression coping to simulate the clinical scenario. Each group was allocated to one of the following protocols: tightened once (1×), tightened twice (2×), tightened twice at a 10-minute interval (2× [10 min]), tightened, countertightened, then tightened again (TCT) and tightened, countertightened, tightened, countertightened, then tightened (TCTCT). A monolithic zirconia central incisor implant crown was fabricated by using computer-aided design and computer-aided manufacturing (CAD-CAM) and cemented onto the ASC abutment. The crown-abutment assemblies were secured onto the implants with the Gold-Tite abutment screw by using their assigned tightening protocols. Each screw was tightened to the recommended value of 20 Ncm with a calibrated digital torque measuring device. Specimens were subjected to 250 000 cycles of cyclic loading simulating 3 months of function with a universal testing machine. RTV was measured for each specimen.
The mean RTV for all the groups ranged from 13.5 Ncm to 15.9 Ncm. The highest mean RTV was found with the (1×) protocol. However, the difference was not statistically significant among any of the groups (P>.05).
Multiple retightening and time intervals between tightening events of these ASC abutment screws did not have a significant influence on RTV under simulated function of 3 months. The one time (1×) tightening protocol can be recommended as a suitable method for ASC abutments, thus avoiding unnecessary retightening.
螺钉松动仍然是种植体支持修复体最常见的并发症之一。关于为角度螺钉通道（ASC）基台拧紧最终基台螺钉的最有效方法，现有文献较少。
本体外研究的目的是通过评估不同方案对反向拧紧值（RTV）的影响，确定ASC基台的最佳螺钉拧紧方案。
50颗种植体随机分为5组（n = 10）。种植体安装后安装覆盖螺钉和印模帽以模拟临床情况。每组被分配到以下方案之一：拧紧一次（1×）、拧紧两次（2×）、间隔10分钟拧紧两次（2×[10分钟]）、拧紧、反向拧紧、然后再次拧紧（TCT）以及拧紧、反向拧紧、拧紧、反向拧紧、然后拧紧（TCTCT）。使用计算机辅助设计和计算机辅助制造（CAD-CAM）制作一体式氧化锆中切牙种植体冠，并粘结到ASC基台上。使用Gold-Tite基台螺钉按照指定的拧紧方案将冠-基台组件固定到种植体上。使用校准的数字扭矩测量装置将每个螺钉拧紧至推荐值20 Ncm。使用万能试验机对样本进行250000次循环加载，模拟3个月的功能。测量每个样本的RTV。
所有组的平均RTV在13.5 Ncm至15.9 Ncm之间。（1×）方案的平均RTV最高。然而，各组之间的差异无统计学意义（P>0.05）。
在模拟3个月功能的情况下，这些ASC基台螺钉的多次重新拧紧以及拧紧事件之间的时间间隔对RTV没有显著影响。一次（1×）拧紧方案可推荐为ASC基台的合适方法，从而避免不必要的重新拧紧。
