Department of Reconstructive Dentistry and Gerodontology, School of Dental Medicine, University of Bern, Bern, Switzerland.
Department of Restorative, Preventive and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland.
J Prosthodont. 2021 Jul;30(6):515-519. doi: 10.1111/jopr.13352. Epub 2021 Mar 27.
The aim of this in vitro study was to evaluate the effect of crown height on the screw stability of screw-retained titanium implant crowns subjected to cyclic loading conditions.
Twenty-one implants with internal hex connections were placed in epoxy resin holders. Mandibular first molar screw-retained titanium implant crowns with UCLA type, crown-abutment connections were CAD/CAM fabricated. Seven crowns of 3 different heights (6 mm, 10 mm, and 14 mm) were made. The crowns were seated onto the implants and screws were tightened to 30 Ncm. The implants were clamped into holders and stepwise cyclic loads were applied to the occlusal surface at 30-degree angles to the long axes of the crowns. The detorque values were measured after each 5 million cycles. Before increasing the applied load, the crowns were secured with new screws and tightened to 30 Ncm. Failure times, survival estimates and detorque values were then analyzed. (alpha = 0.05).
Crown height did not significantly affect detorque values. However, five 14-mm crowns failed with varying fractures during the 475 N loading condition. Overall, a significantly lower survival for 14 mm crowns was found compared to 6 mm and 10 mm crowns (p = 0.004).
Crown heights of one-piece screw-retained titanium implant crowns did not significantly affect detorque values. Screw fracture, however, was greater for crown height of 14 mm than those of 6 mm and 10 mm.
本体外研究旨在评估循环加载条件下冠高对螺丝固位钛种植体冠螺丝稳定性的影响。
将 21 个具有内六角连接的种植体放置在环氧树脂固定器中。制作了具有 UCLA 类型、冠基连接的下颌第一磨牙螺丝固位钛种植体冠。制作了 3 种不同高度（6mm、10mm 和 14mm）的 7 个冠。将冠座安装到种植体上，并将螺丝拧紧至 30 Ncm。将种植体夹入固定器中，以 30 度角逐步向冠的长轴施加循环负载。每 500 万次循环后测量脱扭矩值。在增加施加的负载之前，用新螺丝固定冠并拧紧至 30 Ncm。然后分析失效时间、生存估计和脱扭矩值。（alpha = 0.05）。
冠高对脱扭矩值没有显著影响。然而，在 475 N 加载条件下，五个 14mm 冠出现了不同的断裂失效。总体而言，与 6mm 和 10mm 冠相比，14mm 冠的生存率明显较低（p = 0.004）。
一体式螺丝固位钛种植体冠的冠高对脱扭矩值没有显著影响。然而，对于 14mm 冠高，螺丝断裂的风险高于 6mm 和 10mm 冠高。
