Nithyapriya S, Ramesh A S, Kirubakaran A, Mani Jeevitha, Raghunathan J
Department of Prosthodontics, Adhiparasakthi Dental College, Melmaruvathur, Tamil Nadu, India.
J Indian Prosthodont Soc. 2018 Jul-Sep;18(3):189-195. doi: 10.4103/jips.jips_294_17.
Screw loosening is the most common factor associated with dental implant failure. One of the major cause for screw loosening is the "loss of preload". Several factors including screw geometry, material properties particularly stiffness, surface texture and condition of mating surfaces, degree of lubrication, rate of tightening, integrity of joint etc.
This review analyses the factors that are responsible for the loss of preload.
Screw geometry, Implant- Abutment Connection type (external hexagon platform, morse taper), Material properties viz Stiffness, Resilience, Materials viz gold, titanium, titanium alloy, Surface texture of the abutment screw, Condition of mating surfaces, Lubrication, Torque value, Rate of tightening (10, 20, 35N and retorque after 10mins) are taken into consideration in this study. The MEDLINE-PubMed database was searched from September 2016 to 10 years previously. Several journals were hand searched and from cross references. The outcome analysed are the factors that are responsible for loss of preload.
The search yielded 84 articles. After excluding duplicated abstracts and applying the inclusion and exclusion criteria, 36 studies were eligible for analysis. The result shows that loss of preload can occurs depending upon the type of material used, torque method, torque sequences, abutment connection type, influence of lubrication, abutment collar length. However we detected some potential limitations in the studies selected, mainly a minimum number of samples used for the study. Hence we suggest further studies to guarantee an excellence in methodological quality.
Based on the available data it can be summarized that the knowledge of preload loss must be known for the clinicians to avoid such screw loosening and subsequent implant failure.
螺钉松动是与牙种植体失败相关的最常见因素。螺钉松动的主要原因之一是“预紧力丧失”。包括螺钉几何形状、材料特性（特别是刚度）、表面纹理和配合面状况、润滑程度、拧紧速率、接头完整性等在内的几个因素。
本综述分析导致预紧力丧失的因素。
本研究考虑了螺钉几何形状、种植体-基台连接类型（外六角平台、莫氏锥度）、材料特性（即刚度、弹性）、材料（如金、钛、钛合金）、基台螺钉的表面纹理、配合面状况、润滑、扭矩值、拧紧速率（10、20、35N，10分钟后再拧紧）。检索了2016年9月至此前10年的MEDLINE-PubMed数据库。手工检索了几本期刊并查阅了参考文献。分析的结果是导致预紧力丧失的因素。
检索得到84篇文章。排除重复摘要并应用纳入和排除标准后，有36项研究符合分析条件。结果表明，预紧力丧失可能取决于所用材料的类型、扭矩方法、扭矩顺序、基台连接类型、润滑影响、基台颈圈长度。然而，我们在所选研究中发现了一些潜在局限性，主要是研究中使用的样本数量最少。因此，我们建议进一步研究以确保方法学质量的卓越性。
根据现有数据可以总结出，临床医生必须了解预紧力丧失的知识，以避免此类螺钉松动及随后的种植体失败。
